JAVA代理源码详解，手把手教你写JAVA代理
一:常用的java代理模式
一般经常做java开发的知道java的代理模式一共有三种，第一种也就是静态代理，这种用法比较简单，没有什么魔法棒，比较好理解，另外两种分别是JDK代理和cglib代理，他们分别是对接口代理和对class类本身进行代理，jdk代理要求类必须实现有一个或者多个接口，对接口进行字节码增强在内存中实现新的class类去反射调用用户target的实现类，这里需要说明的是不管是cglic代理也好还是jdk代理他们在内存中都要占据方法区资源(jdk8 叫原空间)，从而达到代理目的，而cglib代理是对class类本身进行字节码增强配合fastclass来实现代理，关于更多的cglib和jdk代理相关的内容大家可以google搜索一下，网上有很多这里不做再多的说明。下面我们摒弃jdk，和cglib的复杂源码来自己实现一个代理模式，来更深刻的了解一下代理究竟是怎么形成的。
二:JDK代理源码分析
代理模式是指给某一个对象提供一个代理对象，并由代理对象控制对原对象的引用。通俗的来讲代理模式就是我们生活中常见的中介。这种模式有什么用呢？它可以在原对象的基础上增强原对象的功能，比如在原对象调用一个方法的前后进行日志、事务操作等。Spring AOP就使用了代理模式。如何实现代理模式呢？首先来看静态代理。静态代理是指在程序运行前就已经存在的编译好的代理类是为静态代理。实现静态代理有四个步骤：
①定义业务接口；
②被代理类实现业务接口；
③定义代理类并实现业务接口；
④最后便可通过客户端进行调用。（这里可以理解成程序的main方法里的内容）
我们按照这个步骤去实现静态代理。需求：在向数据库添加一个用户时前后打印日志。
②被代理类实现业务接口；
③定义代理类并实现业务接口；
④最后便可通过客户端进行调用。（这里可以理解成程序的main方法里的内容）
我们按照这个步骤去实现静态代理。需求：在向数据库添加一个用户时前后打印日志。
JDK DEMO示例
IUserService.java
public interface IUserService {
void add(String name);
}
UserServiceImpl.java
public class UserServiceImpl implements IUserService{
@Override
public void add(String name) {
System.out.println("数据库中插入： "+name+" 的用户");
}
}
MyInvocationHandler.java
public class MyInvocationHandler implements InvocationHandler {
//被代理对象，Object类型
private Object target;
public MyInvocationHandler(Object target) {
this.target = target;
}
@Override
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
System.out.println("准备向数据库中插入数据");
Object returnvalue = method.invoke(target, args);
System.out.println("插入数据库成功");
return returnvalue;
}
}
测试类
public static void main(String[] args) {
IUserService target = new UserServiceImpl();
MyInvocationHandler handler = new MyInvocationHandler(target);
IUserService proxyObject = (IUserService) Proxy.newProxyInstance(DynamicProxyTest.class.getClassLoader(),
target.getClass().getInterfaces(), handler);
proxyObject.add("张玉龙");
}
使用上非常简单、网上demo也很多，不做充分讲解，对jdk代理用法的小伙伴如果还不熟悉这块代码，就先了解一下jdk代理的使用方式，然后在回来继续看下面的源码分析
JDK代理源码深度分析
这部分如果想要更快更好的理解，建议一边对着源码(本文JDK 1.8)，一边看着博客。毕竟自己亲身实践效果才好嘛。
Proxy.newProxyInstance( ClassLoaderloader, Class[] interfaces, InvocationHandler h)产生了代理对象，所以我们进到newProxyInstance的实现：public static Object newProxyInstance(ClassLoader loader,
Class<?>[] interfaces,
InvocationHandler h)
throws IllegalArgumentException
{
Objects.requireNonNull(h);
final Class<?>[] intfs = interfaces.clone();
final SecurityManager sm = System.getSecurityManager();
if (sm != null) {
checkProxyAccess(Reflection.getCallerClass(), loader, intfs);
}
/*
* Look up or generate the designated proxy class.
*/
Class<?> cl = getProxyClass0(loader, intfs);
/*
* Invoke its constructor with the designated invocation handler.
*/
try {
if (sm != null) {
checkNewProxyPermission(Reflection.getCallerClass(), cl);
}
final Constructor<?> cons = cl.getConstructor(constructorParams);
final InvocationHandler ih = h;
if (!Modifier.isPublic(cl.getModifiers())) {
AccessController.doPrivileged(new PrivilegedAction<Void>() {
public Void run() {
cons.setAccessible(true);
return null;
}
});
}
return cons.newInstance(new Object[]{h});
} catch (IllegalAccessException|InstantiationException e) {
throw new InternalError(e.toString(), e);
} catch (InvocationTargetException e) {
Throwable t = e.getCause();
if (t instanceof RuntimeException) {
throw (RuntimeException) t;
} else {
throw new InternalError(t.toString(), t);
}
} catch (NoSuchMethodException e) {
throw new InternalError(e.toString(), e);
}
}
这段代码核心就是通过
getProxyClass0(loader, intfs)得到代理类的Class对象，然后通过Class对象得到构造方法，进而创建代理对象。下一步看getProxyClass0这个方法。//此方法也是Proxy类下的方法
private static Class<?> getProxyClass0(ClassLoader loader,
Class<?>... interfaces) {
if (interfaces.length > 65535) {
throw new IllegalArgumentException("interface limit exceeded");
}
// If the proxy class defined by the given loader implementing
// the given interfaces exists, this will simply return the cached copy;
// otherwise, it will create the proxy class via the ProxyClassFactory
//意思是：如果代理类被指定的类加载器loader定义了，并实现了给定的接口interfaces，
//那么就返回缓存的代理类对象，否则使用ProxyClassFactory创建代理类。
return proxyClassCache.get(loader, interfaces);
}
这里看到proxyClassCache，有Cache便知道是缓存的意思，正好呼应了前面Look up or generate the designated proxy class。查询（在缓存中已经有）或生成指定的代理类的class对象这段注释。
proxyClassCache是个WeakCache类的对象，调用proxyClassCache.get(loader, interfaces); 可以得到缓存的代理类或创建代理类（没有缓存的情况）。说明WeakCache中有get这个方法。先看下WeakCache类的定义（这里先只给出变量的定义和构造函数）：
//K代表key的类型，P代表参数的类型，V代表value的类型。
// WeakCache<ClassLoader, Class<?>[], Class<?>> proxyClassCache 说明proxyClassCache存的值是Class<?>对象，正是我们需要的代理类对象。
final class WeakCache<K, P, V> {
private final ReferenceQueue<K> refQueue
= new ReferenceQueue<>();
// the key type is Object for supporting null key
private final ConcurrentMap<Object, ConcurrentMap<Object, Supplier<V>>> map
= new ConcurrentHashMap<>();
private final ConcurrentMap<Supplier<V>, Boolean> reverseMap
= new ConcurrentHashMap<>();
private final BiFunction<K, P, ?> subKeyFactory;
private final BiFunction<K, P, V> valueFactory;
public WeakCache(BiFunction<K, P, ?> subKeyFactory,
BiFunction<K, P, V> valueFactory) {
this.subKeyFactory = Objects.requireNonNull(subKeyFactory);
this.valueFactory = Objects.requireNonNull(valueFactory);
}
其中map变量是实现缓存的核心变量，他是一个双重的Map结构:
(key, sub-key) -> value。其中key是传进来的Classloader进行包装后的对象，sub-key是由WeakCache构造函数传人的KeyFactory()生成的。value就是产生代理类的对象，是由WeakCache构造函数传人的ProxyClassFactory()生成的好，大体上说完WeakCache这个类的作用，我们回到刚才
proxyClassCache.get(loader, interfaces);这句代码。get是WeakCache里的方法。源码如下//K和P就是WeakCache定义中的泛型，key是类加载器，parameter是接口类数组
public V get(K key, P parameter) {
//检查parameter不为空
Objects.requireNonNull(parameter);
//清除无效的缓存
expungeStaleEntries();
// cacheKey就是(key, sub-key) -> value里的一级key，
Object cacheKey = CacheKey.valueOf(key, refQueue);
// lazily install the 2nd level valuesMap for the particular cacheKey
//根据一级key得到 ConcurrentMap<Object, Supplier<V>>对象。如果之前不存在，则新建一个ConcurrentMap<Object, Supplier<V>>和cacheKey（一级key）一起放到map中。
ConcurrentMap<Object, Supplier<V>> valuesMap = map.get(cacheKey);
if (valuesMap == null) {
ConcurrentMap<Object, Supplier<V>> oldValuesMap
= map.putIfAbsent(cacheKey,
valuesMap = new ConcurrentHashMap<>());
if (oldValuesMap != null) {
valuesMap = oldValuesMap;
}
}
// create subKey and retrieve the possible Supplier<V> stored by that
// subKey from valuesMap
//这部分就是调用生成sub-key的代码，上面我们已经看过怎么生成的了
Object subKey = Objects.requireNonNull(subKeyFactory.apply(key, parameter));
//通过sub-key得到supplier
Supplier<V> supplier = valuesMap.get(subKey);
//supplier实际上就是这个factory
Factory factory = null;
while (true) {
//如果缓存里有supplier ，那就直接通过get方法，得到代理类对象，返回，就结束了，一会儿分析get方法。
if (supplier != null) {
// supplier might be a Factory or a CacheValue<V> instance
V value = supplier.get();
if (value != null) {
return value;
}
}
// else no supplier in cache
// or a supplier that returned null (could be a cleared CacheValue
// or a Factory that wasn't successful in installing the CacheValue)
// lazily construct a Factory
//下面的所有代码目的就是：如果缓存中没有supplier，则创建一个Factory对象，把factory对象在多线程的环境下安全的赋给supplier。
//因为是在while（true）中，赋值成功后又回到上面去调get方法，返回才结束。
if (factory == null) {
factory = new Factory(key, parameter, subKey, valuesMap);
}
if (supplier == null) {
supplier = valuesMap.putIfAbsent(subKey, factory);
if (supplier == null) {
// successfully installed Factory
supplier = factory;
}
// else retry with winning supplier
} else {
if (valuesMap.replace(subKey, supplier, factory)) {
// successfully replaced
// cleared CacheEntry / unsuccessful Factory
// with our Factory
supplier = factory;
} else {
// retry with current supplier
supplier = valuesMap.get(subKey);
}
}
}
}
所以接下来我们看Factory类中的get方法。
public synchronized V get() { // serialize access
// re-check
Supplier<V> supplier = valuesMap.get(subKey);
//重新检查得到的supplier是不是当前对象
if (supplier != this) {
// something changed while we were waiting:
// might be that we were replaced by a CacheValue
// or were removed because of failure ->
// return null to signal WeakCache.get() to retry
// the loop
return null;
}
// else still us (supplier == this)
// create new value
V value = null;
try {
//代理类就是在这个位置调用valueFactory生成的
//valueFactory就是我们传入的 new ProxyClassFactory()
//一会我们分析ProxyClassFactory()的apply方法
value = Objects.requireNonNull(valueFactory.apply(key, parameter));
} finally {
if (value == null) { // remove us on failure
valuesMap.remove(subKey, this);
}
}
// the only path to reach here is with non-null value
assert value != null;
// wrap value with CacheValue (WeakReference)
//把value包装成弱引用
CacheValue<V> cacheValue = new CacheValue<>(value);
// put into reverseMap
// reverseMap是用来实现缓存的有效性
reverseMap.put(cacheValue, Boolean.TRUE);
// try replacing us with CacheValue (this should always succeed)
if (!valuesMap.replace(subKey, this, cacheValue)) {
throw new AssertionError("Should not reach here");
}
// successfully replaced us with new CacheValue -> return the value
// wrapped by it
return value;
}
}
拨云见日，来到ProxyClassFactory的apply方法，代理类就是在这里生成的。
//这里的BiFunction<T, U, R>是个函数式接口，可以理解为用T，U两种类型做参数，得到R类型的返回值
private static final class ProxyClassFactory
implements BiFunction<ClassLoader, Class<?>[], Class<?>>
{
// prefix for all proxy class names
//所有代理类名字的前缀
private static final String proxyClassNamePrefix = "$Proxy";
// next number to use for generation of unique proxy class names
//用于生成代理类名字的计数器
private static final AtomicLong nextUniqueNumber = new AtomicLong();
@Override
public Class<?> apply(ClassLoader loader, Class<?>[] interfaces) {
Map<Class<?>, Boolean> interfaceSet = new IdentityHashMap<>(interfaces.length);
//验证代理接口，可不看
for (Class<?> intf : interfaces) {
/*
* Verify that the class loader resolves the name of this
* interface to the same Class object.
*/
Class<?> interfaceClass = null;
try {
interfaceClass = Class.forName(intf.getName(), false, loader);
} catch (ClassNotFoundException e) {
}
if (interfaceClass != intf) {
throw new IllegalArgumentException(
intf + " is not visible from class loader");
}
/*
* Verify that the Class object actually represents an
* interface.
*/
if (!interfaceClass.isInterface()) {
throw new IllegalArgumentException(
interfaceClass.getName() + " is not an interface");
}
/*
* Verify that this interface is not a duplicate.
*/
if (interfaceSet.put(interfaceClass, Boolean.TRUE) != null) {
throw new IllegalArgumentException(
"repeated interface: " + interfaceClass.getName());
}
}
//生成的代理类的包名
String proxyPkg = null; // package to define proxy class in
//代理类访问控制符: public ,final
int accessFlags = Modifier.PUBLIC | Modifier.FINAL;
/*
* Record the package of a non-public proxy interface so that the
* proxy class will be defined in the same package. Verify that
* all non-public proxy interfaces are in the same package.
*/
//验证所有非公共的接口在同一个包内；公共的就无需处理
//生成包名和类名的逻辑，包名默认是com.sun.proxy，类名默认是$Proxy 加上一个自增的整数值
//如果被代理类是 non-public proxy interface ，则用和被代理类接口一样的包名
for (Class<?> intf : interfaces) {
int flags = intf.getModifiers();
if (!Modifier.isPublic(flags)) {
accessFlags = Modifier.FINAL;
String name = intf.getName();
int n = name.lastIndexOf('.');
String pkg = ((n == -1) ? "" : name.substring(0, n + 1));
if (proxyPkg == null) {
proxyPkg = pkg;
} else if (!pkg.equals(proxyPkg)) {
throw new IllegalArgumentException(
"non-public interfaces from different packages");
}
}
}
if (proxyPkg == null) {
// if no non-public proxy interfaces, use com.sun.proxy package
proxyPkg = ReflectUtil.PROXY_PACKAGE + ".";
}
/*
* Choose a name for the proxy class to generate.
*/
long num = nextUniqueNumber.getAndIncrement();
//代理类的完全限定名，如com.sun.proxy.$Proxy0.calss
String proxyName = proxyPkg + proxyClassNamePrefix + num;
/*
* Generate the specified proxy class.
*/
//核心部分，生成代理类的字节码
byte[] proxyClassFile = ProxyGenerator.generateProxyClass(
proxyName, interfaces, accessFlags);
try {
//把代理类加载到JVM中，至此动态代理过程基本结束了
return defineClass0(loader, proxyName,
proxyClassFile, 0, proxyClassFile.length);
} catch (ClassFormatError e) {
/*
* A ClassFormatError here means that (barring bugs in the
* proxy class generation code) there was some other
* invalid aspect of the arguments supplied to the proxy
* class creation (such as virtual machine limitations
* exceeded).
*/
throw new IllegalArgumentException(e.toString());
}
}
}
到这里其实已经分析完了，但是本着深究的态度，决定看看JDK生成的动态代理字节码是什么，于是我们将字节码保存到磁盘上的class文件中。代码如下：
public static void main(String[] args) {
IUserService target = new UserServiceImpl();
MyInvocationHandler handler = new MyInvocationHandler(target);
//第一个参数是指定代理类的类加载器（我们传入当前测试类的类加载器）
//第二个参数是代理类需要实现的接口（我们传入被代理类实现的接口，这样生成的代理类和被代理类就实现了相同的接口）
//第三个参数是invocation handler，用来处理方法的调用。这里传入我们自己实现的handler
IUserService proxyObject = (IUserService) Proxy.newProxyInstance(DynamicProxyTest.class.getClassLoader(),
target.getClass().getInterfaces(), handler);
proxyObject.add("张玉龙");
String path = "D:/$Proxy0.class";
byte[] classFile = ProxyGenerator.generateProxyClass("$Proxy0", HelloworldImpl.class.getInterfaces());
FileOutputStream out = null;
try {
out = new FileOutputStream(path);
out.write(classFile);
out.flush();
} catch (Exception e) {
e.printStackTrace();
} finally {
try {
out.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
运行这段代码，会在D盘生成一个名为$Proxy0.class的文件。通过反编译工具,得到JDK为我们生成的代理类是这样的：
// Decompiled by Jad v1.5.8e2. Copyright 2001 Pavel Kouznetsov.
// Jad home page: http://kpdus.tripod.com/jad.html
// Decompiler options: packimports(3) fieldsfirst ansi space
import com.zhb.jdk.proxy.IUserService;
import java.lang.reflect.*;
public final class $Proxy0 extends Proxy
implements IUserService
{
private static Method m1;
private static Method m2;
private static Method m3;
private static Method m0;
//代理类的构造函数，其参数正是是InvocationHandler实例，
//Proxy.newInstance方法就是通过通过这个构造函数来创建代理实例的
public $Proxy0(InvocationHandler invocationhandler)
{
super(invocationhandler);
}
// Object类中的三个方法，equals，toString， hashCode
public final boolean equals(Object obj)
{
try
{
return ((Boolean)super.h.invoke(this, m1, new Object[] {
obj
})).booleanValue();
}
catch (Error ) { }
catch (Throwable throwable)
{
throw new UndeclaredThrowableException(throwable);
}
}
public final String toString()
{
try
{
return (String)super.h.invoke(this, m2, null);
}
catch (Error ) { }
catch (Throwable throwable)
{
throw new UndeclaredThrowableException(throwable);
}
}
//接口代理方法
public final void add(String s)
{
try
{
// invocation handler的 invoke方法在这里被调用
super.h.invoke(this, m3, new Object[] {
s
});
return;
}
catch (Error ) { }
catch (Throwable throwable)
{
throw new UndeclaredThrowableException(throwable);
}
}
public final int hashCode()
{
try
{
// 在这里调用了invoke方法。
return ((Integer)super.h.invoke(this, m0, null)).intValue();
}
catch (Error ) { }
catch (Throwable throwable)
{
throw new UndeclaredThrowableException(throwable);
}
}
// 静态代码块对变量进行一些初始化工作
static
{
try
{
m1 = Class.forName("java.lang.Object").getMethod("equals", new Class[] {
Class.forName("java.lang.Object")
});
m2 = Class.forName("java.lang.Object").getMethod("toString", new Class[0]);
m3 = Class.forName("com.zhb.jdk.proxy.IUserService").getMethod("add", new Class[] {
Class.forName("java.lang.String")
});
m0 = Class.forName("java.lang.Object").getMethod("hashCode", new Class[0]);
}
catch (NoSuchMethodException nosuchmethodexception)
{
throw new NoSuchMethodError(nosuchmethodexception.getMessage());
}
catch (ClassNotFoundException classnotfoundexception)
{
throw new NoClassDefFoundError(classnotfoundexception.getMessage());
}
}
}
生成了Object类的三个方法：toString，hashCode，equals。还有我们需要被代理的方法。
JDK代理类的cache clear机制
大家都知道、在项目中被代理的class越来越多，所以jdk会搞一个cache的方式来防止相同的代理接口重复生成class，影响性能不说，实现也不是很优雅，那么现在就会有一个问题了，当classloader已经在内存中没有依赖的时候，被代理的proxy class其实也没有什么意义了，这样就需要清空无用的cache，java Proxy采用了非常巧妙的“弱引用机制”，我们来看下面的代码
我们还是继续看get方法的源码
public V get(K key, P parameter) {
Objects.requireNonNull(parameter);
expungeStaleEntries();
Object cacheKey = CacheKey.valueOf(key, refQueue);
// lazily install the 2nd level valuesMap for the particular cacheKey
ConcurrentMap<Object, Supplier<V>> valuesMap = map.get(cacheKey);
if (valuesMap == null) {
ConcurrentMap<Object, Supplier<V>> oldValuesMap
= map.putIfAbsent(cacheKey,
valuesMap = new ConcurrentHashMap<>());
if (oldValuesMap != null) {
valuesMap = oldValuesMap;
}
}
.......
}
其中源码中有一个方法expungeStaleEntries、我们进去这个方法一窥究竟
private void expungeStaleEntries() {
CacheKey<K> cacheKey;
while ((cacheKey = (CacheKey<K>)refQueue.poll()) != null) {
cacheKey.expungeFrom(map, reverseMap);
}
}
在看看expungeFrom方法源码干了些什么
void expungeFrom(ConcurrentMap<?, ? extends ConcurrentMap<?, ?>> map,
ConcurrentMap<?, Boolean> reverseMap) {
// removing just by key is always safe here because after a CacheKey
// is cleared and enqueue-ed it is only equal to itself
// (see equals method)...
ConcurrentMap<?, ?> valuesMap = map.remove(this);
// remove also from reverseMap if needed
if (valuesMap != null) {
for (Object cacheValue : valuesMap.values()) {
reverseMap.remove(cacheValue);
}
}
}
代码很清晰了，清空被代理的对象。现在的关键就是refQueue对象是怎么来的。我们继续找一下跟refQueue相关的源码、在get中还有一段代码是这样的
Object cacheKey = CacheKey.valueOf(key, refQueue);
private static final class CacheKey<K> extends WeakReference<K> {
// a replacement for null keys
private static final Object NULL_KEY = new Object();
static <K> Object valueOf(K key, ReferenceQueue<K> refQueue) {
return key == null
// null key means we can't weakly reference it,
// so we use a NULL_KEY singleton as cache key
? NULL_KEY
// non-null key requires wrapping with a WeakReference
: new CacheKey<>(key, refQueue);
}
private final int hash;
private CacheKey(K key, ReferenceQueue<K> refQueue) {
super(key, refQueue);
this.hash = System.identityHashCode(key); // compare by identity
}
.....
}
这样看就非常清晰了、原来是CacheKey继承了WeakReference弱引用机制，当弱引用依赖的key没有引用的时候，当前失效的对象就会进入ReferenceQueue中来实现清空cache的功能、这种实现思路和ThreadLocal的实现原理是一样的、大家有兴趣可以去阅读以下相关源码。
三:cglib代理源码分析
有了上面的源码分析经验，聪明的小伙伴一定知道cglib代理实际上也差不多，只不过是基于Class类生成的，可以对类进行代理，无需接口，但是内部的实验逻辑也比较复杂，先上一个简单的demo
package cglib;
import net.sf.cglib.core.DebuggingClassWriter;
import net.sf.cglib.proxy.Enhancer;
import net.sf.cglib.proxy.MethodInterceptor;
import net.sf.cglib.proxy.MethodProxy;
import java.lang.reflect.Method;
public class CglibTest implements MethodInterceptor {
@Override
public Object intercept(Object obj, Method method, Object[] args, MethodProxy proxy) throws Throwable {
System.out.println ("我被代理了");
return proxy.invokeSuper ( obj,args );
}
public String hello(String name){
return "你好" + name;
}
public static void main(String[] args) {
System.setProperty ( DebuggingClassWriter.DEBUG_LOCATION_PROPERTY,"/Users/zhangyulong/Downloads" );
Enhancer enhancer = new Enhancer();
enhancer.setSuperclass (CglibTest.class);
enhancer.setCallback(new CglibTest());
CglibTest cglibTest = (CglibTest) enhancer.create ();
String result = cglibTest.hello ( "张玉龙" );
System.out.println (result);
}
}
执行结果
CGLIB debugging enabled, writing to '/Users/zhangyulong/Downloads' 我被代理了 你好张玉龙
”耳熟能详“的生成结果，那么接下来我们看看它到底是怎么生成的，实现原理和Jdk代理有什么不同？
我们一层一层的翻源码来看看
public Object create() {
classOnly = false;
argumentTypes = null;
return createHelper();
}
classOnly代码是否只生成class，不生成代理对象，默认是false，说明要生成对象。argumentType是构造器参数类型，由于我们使用无参构造器，这些参数暂时可以忽略掉。
private Object createHelper() {
preValidate();
Object key = KEY_FACTORY.newInstance((superclass != null) ? superclass.getName() : null,
ReflectUtils.getNames(interfaces),
filter == ALL_ZERO ? null : new WeakCacheKey<CallbackFilter>(filter),
callbackTypes,
useFactory,
interceptDuringConstruction,
serialVersionUID);
this.currentKey = key;
Object result = super.create(key);
return result;
}
preValidate 首先验证一下参数类型以及基础校验，cglib支持CallbackFilter，由于我们callBack只有一个，enhancer.setCallback(new CglibTest()); 所以这里默认没有filter，看下cglib的处理
private void preValidate() {
if (callbackTypes == null) {
callbackTypes = CallbackInfo.determineTypes(callbacks, false);
validateCallbackTypes = true;
}
if (filter == null) {
if (callbackTypes.length > 1) {
throw new IllegalStateException("Multiple callback types possible but no filter specified");
}
filter = ALL_ZERO;
}
}
private static final CallbackFilter ALL_ZERO = new CallbackFilter(){
public int accept(Method method) {
return 0;
}
};
默认返回0，就是我们传入的new CglibTest()。重新返回主流程，我们看一下
Object key = KEY_FACTORY.newInstance((superclass != null) ? superclass.getName() : null,
ReflectUtils.getNames(interfaces),
filter == ALL_ZERO ? null : new WeakCacheKey<CallbackFilter>(filter),
callbackTypes,
useFactory,
interceptDuringConstruction,
serialVersionUID);
this.currentKey = key;
Object result = super.create(key);
首先根据代理类生成了一个key。这个key的主要作用就是对生成的代理类进行缓存，生成代码在KeyFactory.create方法。这里不是主线流程，感兴趣的小伙伴自己深入一下即可
public static KeyFactory create(ClassLoader loader, Class keyInterface, KeyFactoryCustomizer customizer,
List<KeyFactoryCustomizer> next) {
Generator gen = new Generator();
gen.setInterface(keyInterface);
if (customizer != null) {
gen.addCustomizer(customizer);
}
if (next != null && !next.isEmpty()) {
for (KeyFactoryCustomizer keyFactoryCustomizer : next) {
gen.addCustomizer(keyFactoryCustomizer);
}
}
gen.setClassLoader(loader);
return gen.create();
}
我们主要看一下AbstractClassGenerator.create方法，这里也是我们生成代理代码的主流程
protected Object create(Object key) {
try {
ClassLoader loader = getClassLoader();
Map<ClassLoader, ClassLoaderData> cache = CACHE;
ClassLoaderData data = cache.get(loader);
if (data == null) {
synchronized (AbstractClassGenerator.class) {
cache = CACHE;
data = cache.get(loader);
if (data == null) {
Map<ClassLoader, ClassLoaderData> newCache = new WeakHashMap<ClassLoader, ClassLoaderData>(cache);
data = new ClassLoaderData(loader);
newCache.put(loader, data);
CACHE = newCache;
}
}
}
this.key = key;
Object obj = data.get(this, getUseCache());
if (obj instanceof Class) {
return firstInstance((Class) obj);
}
return nextInstance(obj);
} catch (RuntimeException e) {
throw e;
} catch (Error e) {
throw e;
} catch (Exception e) {
throw new CodeGenerationException(e);
}
}
聪明的小伙伴已经发现了，cglib代理以及jdk代理的缓存结构大同小异。
private static volatile Map<ClassLoader, ClassLoaderData> CACHE = new WeakHashMap<ClassLoader, ClassLoaderData>();
1级缓存， ClassLoader以及我们cglib的代理缓存对象ClassLoaderData，在ClassLoaderData里维护了一个弱引用的classloader对象，以及代理类的缓存对偶性 LoadingCache。这和JDK代理弱引用classloader几乎是完全一样的
public ClassLoaderData(ClassLoader classLoader) {
if (classLoader == null) {
throw new IllegalArgumentException("classLoader == null is not yet supported");
}
this.classLoader = new WeakReference<ClassLoader>(classLoader);
Function<AbstractClassGenerator, Object> load =
new Function<AbstractClassGenerator, Object>() {
public Object apply(AbstractClassGenerator gen) {
Class klass = gen.generate(ClassLoaderData.this);
return gen.wrapCachedClass(klass);
}
};
generatedClasses = new LoadingCache<AbstractClassGenerator, Object, Object>(GET_KEY, load);
}
public ClassLoader getClassLoader() {
return classLoader.get();
}
上面我们讲了JDK代理的缓存清空的逻辑，那么我们看下cglib代理对象时，classloader失效后如何处理的，毕竟是弱引用classloader，那么一定要做缓存清空处理的。
ClassLoader classLoader = data.getClassLoader();
if (classLoader == null) {
throw new IllegalStateException("ClassLoader is null while trying to define class " +
getClassName() + ". It seems that the loader has been expired from a weak reference somehow. " +
"Please file an issue at cglib's issue tracker.");
}
cglib的处理还是比较暴力的，直接抛出异常。接下来我们看下二级缓存以及生成字节码的处理
public Object get(AbstractClassGenerator gen, boolean useCache) {
if (!useCache) {
return gen.generate(ClassLoaderData.this);
} else {
Object cachedValue = generatedClasses.get(gen);
return gen.unwrapCachedValue(cachedValue);
}
}
useCache来决定是否生成字节码后，每次都缓存。 我们手动设置就可以了。
/**
* Whether use and update the static cache of generated classes
* for a class with the same properties. Default is <code>true</code>.
*/
public void setUseCache(boolean useCache) {
this.useCache = useCache;
}
/**
* @see #setUseCache
*/
public boolean getUseCache() {
return useCache;
}
Object cachedValue = generatedClasses.get(gen); 缓存的逻辑分支，我们接着跟下去。
public V get(K key) {
final KK cacheKey = keyMapper.apply(key);
Object v = map.get(cacheKey);
if (v != null && !(v instanceof FutureTask)) {
return (V) v;
}
return createEntry(key, cacheKey, v);
}
逻辑非常清晰了，先看map中是否有cache对象。有直接拿出来，没有通过createEntry(key, cacheKey, v)来生成即可。keyMapper.apply(key)是什么呢，我们看看
private static final Function<AbstractClassGenerator, Object> GET_KEY = new Function<AbstractClassGenerator, Object>() {
public Object apply(AbstractClassGenerator gen) {
return gen.key;
}
};
gen.key就是我们上面提到的KeyFactory生成的key。生成代理对象，并且缓存下来
protected V createEntry(final K key, KK cacheKey, Object v) {
FutureTask<V> task;
boolean creator = false;
if (v != null) {
// Another thread is already loading an instance
task = (FutureTask<V>) v;
} else {
task = new FutureTask<V>(new Callable<V>() {
public V call() throws Exception {
return loader.apply(key);
}
});
Object prevTask = map.putIfAbsent(cacheKey, task);
if (prevTask == null) {
// creator does the load
creator = true;
task.run();
} else if (prevTask instanceof FutureTask) {
task = (FutureTask<V>) prevTask;
} else {
return (V) prevTask;
}
}
V result;
try {
result = task.get();
} catch (InterruptedException e) {
throw new IllegalStateException("Interrupted while loading cache item", e);
} catch (ExecutionException e) {
Throwable cause = e.getCause();
if (cause instanceof RuntimeException) {
throw ((RuntimeException) cause);
}
throw new IllegalStateException("Unable to load cache item", cause);
}
if (creator) {
map.put(cacheKey, result);
}
return result;
}
到目前为止，我们缓存相关的逻辑都已经讲解完毕了，我们把精力放到生成字节码部分，最终生成字节码的方法如下
protected Class generate(ClassLoaderData data) {
Class gen;
Object save = CURRENT.get();
CURRENT.set(this);
try {
ClassLoader classLoader = data.getClassLoader();
if (classLoader == null) {
throw new IllegalStateException("ClassLoader is null while trying to define class " +
getClassName() + ". It seems that the loader has been expired from a weak reference somehow. " +
"Please file an issue at cglib's issue tracker.");
}
synchronized (classLoader) {
String name = generateClassName(data.getUniqueNamePredicate());
data.reserveName(name);
this.setClassName(name);
}
if (attemptLoad) {
try {
gen = classLoader.loadClass(getClassName());
return gen;
} catch (ClassNotFoundException e) {
// ignore
}
}
byte[] b = strategy.generate(this);
String className = ClassNameReader.getClassName(new ClassReader(b));
ProtectionDomain protectionDomain = getProtectionDomain();
synchronized (classLoader) { // just in case
if (protectionDomain == null) {
gen = ReflectUtils.defineClass(className, b, classLoader);
} else {
gen = ReflectUtils.defineClass(className, b, classLoader, protectionDomain);
}
}
return gen;
} catch (RuntimeException e) {
throw e;
} catch (Error e) {
throw e;
} catch (Exception e) {
throw new CodeGenerationException(e);
} finally {
CURRENT.set(save);
}
}
先使用generateClassName生成代理类的名字，这里就是我们debug Spring Aop源码以及其他源码中 带$符号以及cglib很长的名称。
private String generateClassName(Predicate nameTestPredicate) {
return namingPolicy.getClassName(namePrefix, source.name, key, nameTestPredicate);
}
最关键的生成字节码的部分
byte[] b = strategy.generate(this);
public byte[] generate(ClassGenerator cg) throws Exception {
DebuggingClassWriter cw = getClassVisitor();
transform(cg).generateClass(cw);
return transform(cw.toByteArray());
}
protected DebuggingClassWriter getClassVisitor() throws Exception {
return new DebuggingClassWriter(ClassWriter.COMPUTE_FRAMES);
}
public byte[] toByteArray() {
return (byte[]) java.security.AccessController.doPrivileged(
new java.security.PrivilegedAction() {
public Object run() {
byte[] b = ((ClassWriter) DebuggingClassWriter.super.cv).toByteArray();
if (debugLocation != null) {
String dirs = className.replace('.', File.separatorChar);
try {
new File(debugLocation + File.separatorChar + dirs).getParentFile().mkdirs();
File file = new File(new File(debugLocation), dirs + ".class");
OutputStream out = new BufferedOutputStream(new FileOutputStream(file));
try {
out.write(b);
} finally {
out.close();
}
if (traceCtor != null) {
file = new File(new File(debugLocation), dirs + ".asm");
out = new BufferedOutputStream(new FileOutputStream(file));
try {
ClassReader cr = new ClassReader(b);
PrintWriter pw = new PrintWriter(new OutputStreamWriter(out));
ClassVisitor tcv = (ClassVisitor)traceCtor.newInstance(new Object[]{null, pw});
cr.accept(tcv, 0);
pw.flush();
} finally {
out.close();
}
}
} catch (Exception e) {
throw new CodeGenerationException(e);
}
}
return b;
}
});
}
}
我们看到这里可以将生成的代码放到指定的位置来方便查看。这也就是我们demo中设置代码生成位置的原因，我们要看看它到底生成了什么。
System.setProperty ( DebuggingClassWriter.DEBUG_LOCATION_PROPERTY,"/Users/zhangyulong/Downloads" );
生成字节码的方法在Enhancer中
public void generateClass(ClassVisitor v)
底层是通过asm工具来生成的字节码，然后通过构造器反射来生成的代码逻辑。由于代码生成部分比较复杂，我们忽略这一部分，只关注一下和CallBackFilter相关的内容。
private void emitMethods(final ClassEmitter ce, List methods, List actualMethods) { ........... MethodInfo method = (MethodInfo)it1.next(); Method actualMethod = (it2 != null) ? (Method)it2.next() : null; int index = filter.accept(actualMethod); if (index >= callbackTypes.length) { throw new IllegalArgumentException("Callback filter returned an index that is too large: " + index); } originalModifiers.put(method, new Integer((actualMethod != null) ? actualMethod.getModifiers() : method.getModifiers())); indexes.put(method, new Integer(index)); List group = (List)groups.get(generators[index]); if (group == null) { groups.put(generators[index], group = new ArrayList(methods.size())); } group.add(method); ................ }
这里我们可以看到生成代理类字节码时，根据我们传入的CallbackFilter来决定使用哪个Callback。
看一下到底生成了哪些文件。
CglibTest$$EnhancerByCGLIB$$fc037646.class CglibTest$$EnhancerByCGLIB$$fc037646$$FastClassByCGLIB$$ec49b181.class CglibTest$$FastClassByCGLIB$$ef5535a6.class
在目录中我们发现生成了三个文件。首先第一个是根据CglibTest原生类来生成的代理类，第二个是原生类的FastClass，第三个是代理类的FastClass
代理类
//
// Source code recreated from a .class file by IntelliJ IDEA
// (powered by FernFlower decompiler)
//
package cglib;
import java.lang.reflect.Method;
import net.sf.cglib.core.ReflectUtils;
import net.sf.cglib.core.Signature;
import net.sf.cglib.proxy.Callback;
import net.sf.cglib.proxy.Factory;
import net.sf.cglib.proxy.MethodInterceptor;
import net.sf.cglib.proxy.MethodProxy;
public class CglibTest$$EnhancerByCGLIB$$fc037646 extends CglibTest implements Factory {
private boolean CGLIB$BOUND;
public static Object CGLIB$FACTORY_DATA;
private static final ThreadLocal CGLIB$THREAD_CALLBACKS;
private static final Callback[] CGLIB$STATIC_CALLBACKS;
private MethodInterceptor CGLIB$CALLBACK_0;
private static Object CGLIB$CALLBACK_FILTER;
private static final Method CGLIB$hello$0$Method;
private static final MethodProxy CGLIB$hello$0$Proxy;
private static final Object[] CGLIB$emptyArgs;
private static final Method CGLIB$intercept$1$Method;
private static final MethodProxy CGLIB$intercept$1$Proxy;
private static final Method CGLIB$equals$2$Method;
private static final MethodProxy CGLIB$equals$2$Proxy;
private static final Method CGLIB$toString$3$Method;
private static final MethodProxy CGLIB$toString$3$Proxy;
private static final Method CGLIB$hashCode$4$Method;
private static final MethodProxy CGLIB$hashCode$4$Proxy;
private static final Method CGLIB$clone$5$Method;
private static final MethodProxy CGLIB$clone$5$Proxy;
static void CGLIB$STATICHOOK1() {
CGLIB$THREAD_CALLBACKS = new ThreadLocal();
CGLIB$emptyArgs = new Object[0];
Class var0 = Class.forName("cglib.CglibTest$$EnhancerByCGLIB$$fc037646");
Class var1;
Method[] var10000 = ReflectUtils.findMethods(new String[]{"equals", "(Ljava/lang/Object;)Z", "toString", "()Ljava/lang/String;", "hashCode", "()I", "clone", "()Ljava/lang/Object;"}, (var1 = Class.forName("java.lang.Object")).getDeclaredMethods());
CGLIB$equals$2$Method = var10000[0];
CGLIB$equals$2$Proxy = MethodProxy.create(var1, var0, "(Ljava/lang/Object;)Z", "equals", "CGLIB$equals$2");
CGLIB$toString$3$Method = var10000[1];
CGLIB$toString$3$Proxy = MethodProxy.create(var1, var0, "()Ljava/lang/String;", "toString", "CGLIB$toString$3");
CGLIB$hashCode$4$Method = var10000[2];
CGLIB$hashCode$4$Proxy = MethodProxy.create(var1, var0, "()I", "hashCode", "CGLIB$hashCode$4");
CGLIB$clone$5$Method = var10000[3];
CGLIB$clone$5$Proxy = MethodProxy.create(var1, var0, "()Ljava/lang/Object;", "clone", "CGLIB$clone$5");
var10000 = ReflectUtils.findMethods(new String[]{"hello", "(Ljava/lang/String;)Ljava/lang/String;", "intercept", "(Ljava/lang/Object;Ljava/lang/reflect/Method;[Ljava/lang/Object;Lnet/sf/cglib/proxy/MethodProxy;)Ljava/lang/Object;"}, (var1 = Class.forName("cglib.CglibTest")).getDeclaredMethods());
CGLIB$hello$0$Method = var10000[0];
CGLIB$hello$0$Proxy = MethodProxy.create(var1, var0, "(Ljava/lang/String;)Ljava/lang/String;", "hello", "CGLIB$hello$0");
CGLIB$intercept$1$Method = var10000[1];
CGLIB$intercept$1$Proxy = MethodProxy.create(var1, var0, "(Ljava/lang/Object;Ljava/lang/reflect/Method;[Ljava/lang/Object;Lnet/sf/cglib/proxy/MethodProxy;)Ljava/lang/Object;", "intercept", "CGLIB$intercept$1");
}
final String CGLIB$hello$0(String var1) {
return super.hello(var1);
}
public final String hello(String var1) {
MethodInterceptor var10000 = this.CGLIB$CALLBACK_0;
if (var10000 == null) {
CGLIB$BIND_CALLBACKS(this);
var10000 = this.CGLIB$CALLBACK_0;
}
return var10000 != null ? (String)var10000.intercept(this, CGLIB$hello$0$Method, new Object[]{var1}, CGLIB$hello$0$Proxy) : super.hello(var1);
}
final Object CGLIB$intercept$1(Object var1, Method var2, Object[] var3, MethodProxy var4) throws Throwable {
return super.intercept(var1, var2, var3, var4);
}
public final Object intercept(Object var1, Method var2, Object[] var3, MethodProxy var4) throws Throwable {
MethodInterceptor var10000 = this.CGLIB$CALLBACK_0;
if (var10000 == null) {
CGLIB$BIND_CALLBACKS(this);
var10000 = this.CGLIB$CALLBACK_0;
}
return var10000 != null ? var10000.intercept(this, CGLIB$intercept$1$Method, new Object[]{var1, var2, var3, var4}, CGLIB$intercept$1$Proxy) : super.intercept(var1, var2, var3, var4);
}
final boolean CGLIB$equals$2(Object var1) {
return super.equals(var1);
}
public final boolean equals(Object var1) {
MethodInterceptor var10000 = this.CGLIB$CALLBACK_0;
if (var10000 == null) {
CGLIB$BIND_CALLBACKS(this);
var10000 = this.CGLIB$CALLBACK_0;
}
if (var10000 != null) {
Object var2 = var10000.intercept(this, CGLIB$equals$2$Method, new Object[]{var1}, CGLIB$equals$2$Proxy);
return var2 == null ? false : (Boolean)var2;
} else {
return super.equals(var1);
}
}
final String CGLIB$toString$3() {
return super.toString();
}
public final String toString() {
MethodInterceptor var10000 = this.CGLIB$CALLBACK_0;
if (var10000 == null) {
CGLIB$BIND_CALLBACKS(this);
var10000 = this.CGLIB$CALLBACK_0;
}
return var10000 != null ? (String)var10000.intercept(this, CGLIB$toString$3$Method, CGLIB$emptyArgs, CGLIB$toString$3$Proxy) : super.toString();
}
final int CGLIB$hashCode$4() {
return super.hashCode();
}
public final int hashCode() {
MethodInterceptor var10000 = this.CGLIB$CALLBACK_0;
if (var10000 == null) {
CGLIB$BIND_CALLBACKS(this);
var10000 = this.CGLIB$CALLBACK_0;
}
if (var10000 != null) {
Object var1 = var10000.intercept(this, CGLIB$hashCode$4$Method, CGLIB$emptyArgs, CGLIB$hashCode$4$Proxy);
return var1 == null ? 0 : ((Number)var1).intValue();
} else {
return super.hashCode();
}
}
final Object CGLIB$clone$5() throws CloneNotSupportedException {
return super.clone();
}
protected final Object clone() throws CloneNotSupportedException {
MethodInterceptor var10000 = this.CGLIB$CALLBACK_0;
if (var10000 == null) {
CGLIB$BIND_CALLBACKS(this);
var10000 = this.CGLIB$CALLBACK_0;
}
return var10000 != null ? var10000.intercept(this, CGLIB$clone$5$Method, CGLIB$emptyArgs, CGLIB$clone$5$Proxy) : super.clone();
}
public static MethodProxy CGLIB$findMethodProxy(Signature var0) {
String var10000 = var0.toString();
switch(var10000.hashCode()) {
case -1249666147:
if (var10000.equals("intercept(Ljava/lang/Object;Ljava/lang/reflect/Method;[Ljava/lang/Object;Lnet/sf/cglib/proxy/MethodProxy;)Ljava/lang/Object;")) {
return CGLIB$intercept$1$Proxy;
}
break;
case -508378822:
if (var10000.equals("clone()Ljava/lang/Object;")) {
return CGLIB$clone$5$Proxy;
}
break;
case 848333779:
if (var10000.equals("hello(Ljava/lang/String;)Ljava/lang/String;")) {
return CGLIB$hello$0$Proxy;
}
break;
case 1826985398:
if (var10000.equals("equals(Ljava/lang/Object;)Z")) {
return CGLIB$equals$2$Proxy;
}
break;
case 1913648695:
if (var10000.equals("toString()Ljava/lang/String;")) {
return CGLIB$toString$3$Proxy;
}
break;
case 1984935277:
if (var10000.equals("hashCode()I")) {
return CGLIB$hashCode$4$Proxy;
}
}
return null;
}
public CglibTest$$EnhancerByCGLIB$$fc037646() {
CGLIB$BIND_CALLBACKS(this);
}
public static void CGLIB$SET_THREAD_CALLBACKS(Callback[] var0) {
CGLIB$THREAD_CALLBACKS.set(var0);
}
public static void CGLIB$SET_STATIC_CALLBACKS(Callback[] var0) {
CGLIB$STATIC_CALLBACKS = var0;
}
private static final void CGLIB$BIND_CALLBACKS(Object var0) {
CglibTest$$EnhancerByCGLIB$$fc037646 var1 = (CglibTest$$EnhancerByCGLIB$$fc037646)var0;
if (!var1.CGLIB$BOUND) {
var1.CGLIB$BOUND = true;
Object var10000 = CGLIB$THREAD_CALLBACKS.get();
if (var10000 == null) {
var10000 = CGLIB$STATIC_CALLBACKS;
if (var10000 == null) {
return;
}
}
var1.CGLIB$CALLBACK_0 = (MethodInterceptor)((Callback[])var10000)[0];
}
}
public Object newInstance(Callback[] var1) {
CGLIB$SET_THREAD_CALLBACKS(var1);
CglibTest$$EnhancerByCGLIB$$fc037646 var10000 = new CglibTest$$EnhancerByCGLIB$$fc037646();
CGLIB$SET_THREAD_CALLBACKS((Callback[])null);
return var10000;
}
public Object newInstance(Callback var1) {
CGLIB$SET_THREAD_CALLBACKS(new Callback[]{var1});
CglibTest$$EnhancerByCGLIB$$fc037646 var10000 = new CglibTest$$EnhancerByCGLIB$$fc037646();
CGLIB$SET_THREAD_CALLBACKS((Callback[])null);
return var10000;
}
public Object newInstance(Class[] var1, Object[] var2, Callback[] var3) {
CGLIB$SET_THREAD_CALLBACKS(var3);
CglibTest$$EnhancerByCGLIB$$fc037646 var10000 = new CglibTest$$EnhancerByCGLIB$$fc037646;
switch(var1.length) {
case 0:
var10000.<init>();
CGLIB$SET_THREAD_CALLBACKS((Callback[])null);
return var10000;
default:
throw new IllegalArgumentException("Constructor not found");
}
}
public Callback getCallback(int var1) {
CGLIB$BIND_CALLBACKS(this);
MethodInterceptor var10000;
switch(var1) {
case 0:
var10000 = this.CGLIB$CALLBACK_0;
break;
default:
var10000 = null;
}
return var10000;
}
public void setCallback(int var1, Callback var2) {
switch(var1) {
case 0:
this.CGLIB$CALLBACK_0 = (MethodInterceptor)var2;
default:
}
}
public Callback[] getCallbacks() {
CGLIB$BIND_CALLBACKS(this);
return new Callback[]{this.CGLIB$CALLBACK_0};
}
public void setCallbacks(Callback[] var1) {
this.CGLIB$CALLBACK_0 = (MethodInterceptor)var1[0];
}
static {
CGLIB$STATICHOOK1();
}
}
代理类的FastClass
//
// Source code recreated from a .class file by IntelliJ IDEA
// (powered by FernFlower decompiler)
//
package cglib;
import cglib.CglibTest..EnhancerByCGLIB..fc037646;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import net.sf.cglib.core.Signature;
import net.sf.cglib.proxy.Callback;
import net.sf.cglib.proxy.MethodProxy;
import net.sf.cglib.reflect.FastClass;
public class CglibTest$$EnhancerByCGLIB$$fc037646$$FastClassByCGLIB$$ec49b181 extends FastClass {
public CglibTest$$EnhancerByCGLIB$$fc037646$$FastClassByCGLIB$$ec49b181(Class var1) {
super(var1);
}
public int getIndex(Signature var1) {
String var10000 = var1.toString();
switch(var10000.hashCode()) {
case -2055565910:
if (var10000.equals("CGLIB$SET_THREAD_CALLBACKS([Lnet/sf/cglib/proxy/Callback;)V")) {
return 3;
}
break;
case -1457535688:
if (var10000.equals("CGLIB$STATICHOOK1()V")) {
return 16;
}
break;
case -1411812934:
if (var10000.equals("CGLIB$hashCode$4()I")) {
return 21;
}
break;
case -1249666147:
if (var10000.equals("intercept(Ljava/lang/Object;Ljava/lang/reflect/Method;[Ljava/lang/Object;Lnet/sf/cglib/proxy/MethodProxy;)Ljava/lang/Object;")) {
return 14;
}
break;
case -894172689:
if (var10000.equals("newInstance(Lnet/sf/cglib/proxy/Callback;)Ljava/lang/Object;")) {
return 11;
}
break;
case -879968516:
if (var10000.equals("CGLIB$hello$0(Ljava/lang/String;)Ljava/lang/String;")) {
return 17;
}
break;
case -623122092:
if (var10000.equals("CGLIB$findMethodProxy(Lnet/sf/cglib/core/Signature;)Lnet/sf/cglib/proxy/MethodProxy;")) {
return 0;
}
break;
case -508378822:
if (var10000.equals("clone()Ljava/lang/Object;")) {
return 9;
}
break;
case -419626537:
if (var10000.equals("setCallbacks([Lnet/sf/cglib/proxy/Callback;)V")) {
return 1;
}
break;
case 374345669:
if (var10000.equals("CGLIB$equals$2(Ljava/lang/Object;)Z")) {
return 19;
}
break;
case 560567118:
if (var10000.equals("setCallback(ILnet/sf/cglib/proxy/Callback;)V")) {
return 15;
}
break;
case 811063227:
if (var10000.equals("newInstance([Ljava/lang/Class;[Ljava/lang/Object;[Lnet/sf/cglib/proxy/Callback;)Ljava/lang/Object;")) {
return 12;
}
break;
case 848333779:
if (var10000.equals("hello(Ljava/lang/String;)Ljava/lang/String;")) {
return 13;
}
break;
case 973717575:
if (var10000.equals("getCallbacks()[Lnet/sf/cglib/proxy/Callback;")) {
return 5;
}
break;
case 1115619315:
if (var10000.equals("CGLIB$intercept$1(Ljava/lang/Object;Ljava/lang/reflect/Method;[Ljava/lang/Object;Lnet/sf/cglib/proxy/MethodProxy;)Ljava/lang/Object;")) {
return 18;
}
break;
case 1221173700:
if (var10000.equals("newInstance([Lnet/sf/cglib/proxy/Callback;)Ljava/lang/Object;")) {
return 10;
}
break;
case 1230699260:
if (var10000.equals("getCallback(I)Lnet/sf/cglib/proxy/Callback;")) {
return 4;
}
break;
case 1341835395:
if (var10000.equals("main([Ljava/lang/String;)V")) {
return 23;
}
break;
case 1517819849:
if (var10000.equals("CGLIB$toString$3()Ljava/lang/String;")) {
return 20;
}
break;
case 1584330438:
if (var10000.equals("CGLIB$SET_STATIC_CALLBACKS([Lnet/sf/cglib/proxy/Callback;)V")) {
return 2;
}
break;
case 1826985398:
if (var10000.equals("equals(Ljava/lang/Object;)Z")) {
return 6;
}
break;
case 1913648695:
if (var10000.equals("toString()Ljava/lang/String;")) {
return 7;
}
break;
case 1984935277:
if (var10000.equals("hashCode()I")) {
return 8;
}
break;
case 2011844968:
if (var10000.equals("CGLIB$clone$5()Ljava/lang/Object;")) {
return 22;
}
}
return -1;
}
public int getIndex(String var1, Class[] var2) {
switch(var1.hashCode()) {
case -1776922004:
if (var1.equals("toString")) {
switch(var2.length) {
case 0:
return 7;
}
}
break;
case -1295482945:
if (var1.equals("equals")) {
switch(var2.length) {
case 1:
if (var2[0].getName().equals("java.lang.Object")) {
return 6;
}
}
}
break;
case -1053468136:
if (var1.equals("getCallbacks")) {
switch(var2.length) {
case 0:
return 5;
}
}
break;
case -981624788:
if (var1.equals("CGLIB$intercept$1")) {
switch(var2.length) {
case 4:
if (var2[0].getName().equals("java.lang.Object") && var2[1].getName().equals("java.lang.reflect.Method") && var2[2].getName().equals("[Ljava.lang.Object;") && var2[3].getName().equals("net.sf.cglib.proxy.MethodProxy")) {
return 18;
}
}
}
break;
case -124978608:
if (var1.equals("CGLIB$equals$2")) {
switch(var2.length) {
case 1:
if (var2[0].getName().equals("java.lang.Object")) {
return 19;
}
}
}
break;
case -60403779:
if (var1.equals("CGLIB$SET_STATIC_CALLBACKS")) {
switch(var2.length) {
case 1:
if (var2[0].getName().equals("[Lnet.sf.cglib.proxy.Callback;")) {
return 2;
}
}
}
break;
case -29025554:
if (var1.equals("CGLIB$hashCode$4")) {
switch(var2.length) {
case 0:
return 21;
}
}
break;
case 3343801:
if (var1.equals("main")) {
switch(var2.length) {
case 1:
if (var2[0].getName().equals("[Ljava.lang.String;")) {
return 23;
}
}
}
break;
case 85179481:
if (var1.equals("CGLIB$SET_THREAD_CALLBACKS")) {
switch(var2.length) {
case 1:
if (var2[0].getName().equals("[Lnet.sf.cglib.proxy.Callback;")) {
return 3;
}
}
}
break;
case 94756189:
if (var1.equals("clone")) {
switch(var2.length) {
case 0:
return 9;
}
}
break;
case 99162322:
if (var1.equals("hello")) {
switch(var2.length) {
case 1:
if (var2[0].getName().equals("java.lang.String")) {
return 13;
}
}
}
break;
case 147696667:
if (var1.equals("hashCode")) {
switch(var2.length) {
case 0:
return 8;
}
}
break;
case 161998109:
if (var1.equals("CGLIB$STATICHOOK1")) {
switch(var2.length) {
case 0:
return 16;
}
}
break;
case 495524492:
if (var1.equals("setCallbacks")) {
switch(var2.length) {
case 1:
if (var2[0].getName().equals("[Lnet.sf.cglib.proxy.Callback;")) {
return 1;
}
}
}
break;
case 502538434:
if (var1.equals("intercept")) {
switch(var2.length) {
case 4:
if (var2[0].getName().equals("java.lang.Object") && var2[1].getName().equals("java.lang.reflect.Method") && var2[2].getName().equals("[Ljava.lang.Object;") && var2[3].getName().equals("net.sf.cglib.proxy.MethodProxy")) {
return 14;
}
}
}
break;
case 1154623345:
if (var1.equals("CGLIB$findMethodProxy")) {
switch(var2.length) {
case 1:
if (var2[0].getName().equals("net.sf.cglib.core.Signature")) {
return 0;
}
}
}
break;
case 1543336190:
if (var1.equals("CGLIB$toString$3")) {
switch(var2.length) {
case 0:
return 20;
}
}
break;
case 1811874389:
if (var1.equals("newInstance")) {
switch(var2.length) {
case 1:
String var10001 = var2[0].getName();
switch(var10001.hashCode()) {
case -845341380:
if (var10001.equals("net.sf.cglib.proxy.Callback")) {
return 11;
}
break;
case 1730110032:
if (var10001.equals("[Lnet.sf.cglib.proxy.Callback;")) {
return 10;
}
}
case 2:
default:
break;
case 3:
if (var2[0].getName().equals("[Ljava.lang.Class;") && var2[1].getName().equals("[Ljava.lang.Object;") && var2[2].getName().equals("[Lnet.sf.cglib.proxy.Callback;")) {
return 12;
}
}
}
break;
case 1817099975:
if (var1.equals("setCallback")) {
switch(var2.length) {
case 2:
if (var2[0].getName().equals("int") && var2[1].getName().equals("net.sf.cglib.proxy.Callback")) {
return 15;
}
}
}
break;
case 1891304123:
if (var1.equals("CGLIB$hello$0")) {
switch(var2.length) {
case 1:
if (var2[0].getName().equals("java.lang.String")) {
return 17;
}
}
}
break;
case 1905679803:
if (var1.equals("getCallback")) {
switch(var2.length) {
case 1:
if (var2[0].getName().equals("int")) {
return 4;
}
}
}
break;
case 1951977611:
if (var1.equals("CGLIB$clone$5")) {
switch(var2.length) {
case 0:
return 22;
}
}
}
return -1;
}
public int getIndex(Class[] var1) {
switch(var1.length) {
case 0:
return 0;
default:
return -1;
}
}
public Object invoke(int var1, Object var2, Object[] var3) throws InvocationTargetException {
fc037646 var10000 = (fc037646)var2;
int var10001 = var1;
try {
switch(var10001) {
case 0:
return fc037646.CGLIB$findMethodProxy((Signature)var3[0]);
case 1:
var10000.setCallbacks((Callback[])var3[0]);
return null;
case 2:
fc037646.CGLIB$SET_STATIC_CALLBACKS((Callback[])var3[0]);
return null;
case 3:
fc037646.CGLIB$SET_THREAD_CALLBACKS((Callback[])var3[0]);
return null;
case 4:
return var10000.getCallback(((Number)var3[0]).intValue());
case 5:
return var10000.getCallbacks();
case 6:
return new Boolean(var10000.equals(var3[0]));
case 7:
return var10000.toString();
case 8:
return new Integer(var10000.hashCode());
case 9:
return var10000.clone();
case 10:
return var10000.newInstance((Callback[])var3[0]);
case 11:
return var10000.newInstance((Callback)var3[0]);
case 12:
return var10000.newInstance((Class[])var3[0], (Object[])var3[1], (Callback[])var3[2]);
case 13:
return var10000.hello((String)var3[0]);
case 14:
return var10000.intercept(var3[0], (Method)var3[1], (Object[])var3[2], (MethodProxy)var3[3]);
case 15:
var10000.setCallback(((Number)var3[0]).intValue(), (Callback)var3[1]);
return null;
case 16:
fc037646.CGLIB$STATICHOOK1();
return null;
case 17:
return var10000.CGLIB$hello$0((String)var3[0]);
case 18:
return var10000.CGLIB$intercept$1(var3[0], (Method)var3[1], (Object[])var3[2], (MethodProxy)var3[3]);
case 19:
return new Boolean(var10000.CGLIB$equals$2(var3[0]));
case 20:
return var10000.CGLIB$toString$3();
case 21:
return new Integer(var10000.CGLIB$hashCode$4());
case 22:
return var10000.CGLIB$clone$5();
case 23:
CglibTest.main((String[])var3[0]);
return null;
}
} catch (Throwable var4) {
throw new InvocationTargetException(var4);
}
throw new IllegalArgumentException("Cannot find matching method/constructor");
}
public Object newInstance(int var1, Object[] var2) throws InvocationTargetException {
fc037646 var10000 = new fc037646;
fc037646 var10001 = var10000;
int var10002 = var1;
try {
switch(var10002) {
case 0:
var10001.<init>();
return var10000;
}
} catch (Throwable var3) {
throw new InvocationTargetException(var3);
}
throw new IllegalArgumentException("Cannot find matching method/constructor");
}
public int getMaxIndex() {
return 23;
}
}
原生类的FastClass
//
// Source code recreated from a .class file by IntelliJ IDEA
// (powered by FernFlower decompiler)
//
package cglib;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import net.sf.cglib.core.Signature;
import net.sf.cglib.proxy.MethodProxy;
import net.sf.cglib.reflect.FastClass;
public class CglibTest$$FastClassByCGLIB$$ef5535a6 extends FastClass {
public CglibTest$$FastClassByCGLIB$$ef5535a6(Class var1) {
super(var1);
}
public int getIndex(Signature var1) {
String var10000 = var1.toString();
switch(var10000.hashCode()) {
case -1249666147:
if (var10000.equals("intercept(Ljava/lang/Object;Ljava/lang/reflect/Method;[Ljava/lang/Object;Lnet/sf/cglib/proxy/MethodProxy;)Ljava/lang/Object;")) {
return 2;
}
break;
case 848333779:
if (var10000.equals("hello(Ljava/lang/String;)Ljava/lang/String;")) {
return 1;
}
break;
case 1341835395:
if (var10000.equals("main([Ljava/lang/String;)V")) {
return 0;
}
break;
case 1826985398:
if (var10000.equals("equals(Ljava/lang/Object;)Z")) {
return 3;
}
break;
case 1913648695:
if (var10000.equals("toString()Ljava/lang/String;")) {
return 4;
}
break;
case 1984935277:
if (var10000.equals("hashCode()I")) {
return 5;
}
}
return -1;
}
public int getIndex(String var1, Class[] var2) {
switch(var1.hashCode()) {
case -1776922004:
if (var1.equals("toString")) {
switch(var2.length) {
case 0:
return 4;
}
}
break;
case -1295482945:
if (var1.equals("equals")) {
switch(var2.length) {
case 1:
if (var2[0].getName().equals("java.lang.Object")) {
return 3;
}
}
}
break;
case 3343801:
if (var1.equals("main")) {
switch(var2.length) {
case 1:
if (var2[0].getName().equals("[Ljava.lang.String;")) {
return 0;
}
}
}
break;
case 99162322:
if (var1.equals("hello")) {
switch(var2.length) {
case 1:
if (var2[0].getName().equals("java.lang.String")) {
return 1;
}
}
}
break;
case 147696667:
if (var1.equals("hashCode")) {
switch(var2.length) {
case 0:
return 5;
}
}
break;
case 502538434:
if (var1.equals("intercept")) {
switch(var2.length) {
case 4:
if (var2[0].getName().equals("java.lang.Object") && var2[1].getName().equals("java.lang.reflect.Method") && var2[2].getName().equals("[Ljava.lang.Object;") && var2[3].getName().equals("net.sf.cglib.proxy.MethodProxy")) {
return 2;
}
}
}
}
return -1;
}
public int getIndex(Class[] var1) {
switch(var1.length) {
case 0:
return 0;
default:
return -1;
}
}
public Object invoke(int var1, Object var2, Object[] var3) throws InvocationTargetException {
CglibTest var10000 = (CglibTest)var2;
int var10001 = var1;
try {
switch(var10001) {
case 0:
CglibTest.main((String[])var3[0]);
return null;
case 1:
return var10000.hello((String)var3[0]);
case 2:
return var10000.intercept(var3[0], (Method)var3[1], (Object[])var3[2], (MethodProxy)var3[3]);
case 3:
return new Boolean(var10000.equals(var3[0]));
case 4:
return var10000.toString();
case 5:
return new Integer(var10000.hashCode());
}
} catch (Throwable var4) {
throw new InvocationTargetException(var4);
}
throw new IllegalArgumentException("Cannot find matching method/constructor");
}
public Object newInstance(int var1, Object[] var2) throws InvocationTargetException {
CglibTest var10000 = new CglibTest;
CglibTest var10001 = var10000;
int var10002 = var1;
try {
switch(var10002) {
case 0:
var10001.<init>();
return var10000;
}
} catch (Throwable var3) {
throw new InvocationTargetException(var3);
}
throw new IllegalArgumentException("Cannot find matching method/constructor");
}
public int getMaxIndex() {
return 5;
}
}
我们看下代理类的hello方法
public final String hello(String var1) {
MethodInterceptor var10000 = this.CGLIB$CALLBACK_0;
if (var10000 == null) {
CGLIB$BIND_CALLBACKS(this);
var10000 = this.CGLIB$CALLBACK_0;
}
return var10000 != null ? (String)var10000.intercept(this, CGLIB$hello$0$Method, new Object[]{var1}, CGLIB$hello$0$Proxy) : super.hello(var1);
}
最终调用了 var10000.intercept(this, CGLIB$hello$0$Method, new Object[]{var1}, CGLIB$hello$0$Proxy)方法，也就是我们的
@Override
public Object intercept(Object obj, Method method, Object[] args, MethodProxy proxy) throws Throwable {
System.out.println ("我被代理了");
return proxy.invokeSuper ( obj,args );
}
proxy.invokeSuper ( obj,args ) 是怎么实现的呢，接下来我们重点看看 CGLIB$hello$0$Proxy的生成逻辑。
CGLIB$hello$0$Proxy = MethodProxy.create(var1, var0, "(Ljava/lang/String;)Ljava/lang/String;", "hello", "CGLIB$hello$0");
public static MethodProxy create(Class c1, Class c2, String desc, String name1, String name2) {
MethodProxy proxy = new MethodProxy();
proxy.sig1 = new Signature(name1, desc);
proxy.sig2 = new Signature(name2, desc);
proxy.createInfo = new CreateInfo(c1, c2);
return proxy;
}
这里根据代理类以及原生类的hello方法生成了方法签名 Signature。
5个参数分别是 Class c1 目标类Class，Class c2 代理类Class，String desc 代理方法的描述，String name1 被代理方法名，String name2 代理方法名
接下来
public Object invokeSuper(Object obj, Object[] args) throws Throwable {
try {
init();
FastClassInfo fci = fastClassInfo;
return fci.f2.invoke(fci.i2, obj, args);
} catch (InvocationTargetException e) {
throw e.getTargetException();
}
}
private void init()
{
/*
* Using a volatile invariant allows us to initialize the FastClass and
* method index pairs atomically.
*
* Double-checked locking is safe with volatile in Java 5. Before 1.5 this
* code could allow fastClassInfo to be instantiated more than once, which
* appears to be benign.
*/
if (fastClassInfo == null)
{
synchronized (initLock)
{
if (fastClassInfo == null)
{
CreateInfo ci = createInfo;
FastClassInfo fci = new FastClassInfo();
fci.f1 = helper(ci, ci.c1);
fci.f2 = helper(ci, ci.c2);
fci.i1 = fci.f1.getIndex(sig1);
fci.i2 = fci.f2.getIndex(sig2);
fastClassInfo = fci;
}
}
}
}
private static class FastClassInfo
{
FastClass f1;
FastClass f2;
int i1;
int i2;
}
private static class CreateInfo
{
Class c1;
Class c2;
NamingPolicy namingPolicy;
GeneratorStrategy strategy;
boolean attemptLoad;
public CreateInfo(Class c1, Class c2)
{
this.c1 = c1;
this.c2 = c2;
AbstractClassGenerator fromEnhancer = AbstractClassGenerator.getCurrent();
if (fromEnhancer != null) {
namingPolicy = fromEnhancer.getNamingPolicy();
strategy = fromEnhancer.getStrategy();
attemptLoad = fromEnhancer.getAttemptLoad();
}
}
}
private static FastClass helper(CreateInfo ci, Class type) {
FastClass.Generator g = new FastClass.Generator();
g.setType(type);
g.setClassLoader(ci.c2.getClassLoader());
g.setNamingPolicy(ci.namingPolicy);
g.setStrategy(ci.strategy);
g.setAttemptLoad(ci.attemptLoad);
return g.create();
}
其实这里最主要的就是生成代理类和普通类的FastClass，以及hello方法的index，然后去调用，我们看一下简单的例子来看看FastClass底层倒底是什么
public class FastClass1 {
public void hello(String name) {
System.out.println("hello, " + name);
}
public void hi(String msg) {
System.out.println("hi, " + msg);
}
}
public class FastClass2 {
public Object invoke(Object obj, int methodIndex, Object[] parameters) {
FastClass1 target = (FastClass1)obj;
Object result = null;
switch (methodIndex) {
case 1:
target.hello((String)parameters[0]);
break;
case 2:
target.hi((String)parameters[0]);
break;
}
return result;
}
public int getIndex(String methodDescriptor) {
switch (methodDescriptor.hashCode()) {
case -2084786067:
return 1;
case -70025314:
return 2;
}
return -1;
}
}
public class FastClassTest {
public static void main(String[] args) {
FastClass1 fastClass1 = new FastClass1();
FastClass2 fastClass2 = new FastClass2();
int helloIndex = fastClass2.getIndex("hello(Ljava/lang/String;)V");//方法名(参数类型;...)返回类型
fastClass2.invoke(fastClass1, helloIndex, new Object[]{"张三"});
int hiIndex = fastClass2.getIndex("hi(Ljava/lang/String;)V");
fastClass2.invoke(fastClass1, hiIndex, new Object[]{"cglib动态代理"});
}
}
上例中，FastClass2是FastClass1的Fastclass，在FastClass2中有两个方法getIndex和invoke。在getIndex方法中对FastClass1的每个方法建立索引，并根据入参(方法名+方法的描述符)来返回相应的索引。invoke根据指定的索引，以parameters为入参调用对象obj的方法。这样就避免了反射调用，提高了效率。我们生成的CglibTest$$EnhancerByCGLIB$$fc037646$$FastClassByCGLIB$$ec49b181.class以及CglibTest$$FastClassByCGLIB$$ef5535a6.class 原理也是类似。
MethodProxy中invokeSuper 和MethodProxy中invoke的区别是什么 我们来看看
public Object invoke(Object obj, Object[] args) throws Throwable {
try {
init();
FastClassInfo fci = fastClassInfo;
return fci.f1.invoke(fci.i1, obj, args);
} catch (InvocationTargetException e) {
throw e.getTargetException();
} catch (IllegalArgumentException e) {
if (fastClassInfo.i1 < 0)
throw new IllegalArgumentException("Protected method: " + sig1);
throw e;
}
}
public Object invokeSuper(Object obj, Object[] args) throws Throwable {
try {
init();
FastClassInfo fci = fastClassInfo;
return fci.f2.invoke(fci.i2, obj, args);
} catch (InvocationTargetException e) {
throw e.getTargetException();
}
}
fci.f1.invoke(fci.i1, obj, args);执行原生类Fastclass的hello方法
fci.f2.invoke(fci.i2, obj, args);执行代理类FastClass的hello方法
经常有小伙伴不小心用错的逻辑，导致死循环。
@Override
public Object intercept(Object obj, Method method, Object[] args, MethodProxy proxy) throws Throwable {
System.out.println ("我被代理了");
return proxy.invoke ( obj,args );
}
.........
我被代理了
我被代理了
我被代理了
Exception in thread "main" java.lang.StackOverflowError
at sun.nio.cs.UTF_8.updatePositions(UTF_8.java:77)
at sun.nio.cs.UTF_8.access$200(UTF_8.java:57)
at sun.nio.cs.UTF_8$Encoder.encodeArrayLoop(UTF_8.java:636)
at sun.nio.cs.UTF_8$Encoder.encodeLoop(UTF_8.java:691)
at java.nio.charset.CharsetEncoder.encode(CharsetEncoder.java:579)
at sun.nio.cs.StreamEncoder.implWrite(StreamEncoder.java:271)
at sun.nio.cs.StreamEncoder.write(StreamEncoder.java:125)
at java.io.OutputStreamWriter.write(OutputStreamWriter.java:207)
at java.io.BufferedWriter.flushBuffer(BufferedWriter.java:129)
at java.io.PrintStream.write(PrintStream.java:526)
at java.io.PrintStream.print(PrintStream.java:669)
at java.io.PrintStream.println(PrintStream.java:806)
at cglib.CglibTest.intercept(CglibTest.java:13)
at cglib.CglibTest$$EnhancerByCGLIB$$fc037646.hello(<generated>)
at cglib.CglibTest$$FastClassByCGLIB$$ef5535a6.invoke(<generated>)
at net.sf.cglib.proxy.MethodProxy.invoke(MethodProxy.java:204)
at cglib.CglibTest.intercept(CglibTest.java:14)
at cglib.CglibTest$$EnhancerByCGLIB$$fc037646.hello(<generated>)
at cglib.CglibTest$$FastClassByCGLIB$$ef5535a6.invoke(<generated>)
at net.sf.cglib.proxy.MethodProxy.invoke(MethodProxy.java:204)
at cglib.CglibTest.intercept(CglibTest.java:14)
at cglib.CglibTest$$EnhancerByCGLIB$$fc037646.hello(<generated>)
at cglib.CglibTest$$FastClassByCGLIB$$ef5535a6.invoke(<generated>)
at net.sf.cglib.proxy.MethodProxy.invoke(MethodProxy.java:204)
at cglib.CglibTest.intercept(CglibTest.java:14)
at cglib.CglibTest$$EnhancerByCGLIB$$fc037646.hello(<generated>)
at cglib.CglibTest$$FastClassByCGLIB$$ef5535a6.invoke(<generated>)
at net.sf.cglib.proxy.MethodProxy.invoke(MethodProxy.java:204)
at cglib.CglibTest.intercept(CglibTest.java:14)
at cglib.CglibTest$$EnhancerByCGLIB$$fc037646.hello(<generated>)
at cglib.CglibTest$$FastClassByCGLIB$$ef5535a6.invoke(<generated>)
at net.sf.cglib.proxy.MethodProxy.invoke(MethodProxy.java:204)
at cglib.CglibTest.intercept(CglibTest.java:14)
at cglib.CglibTest$$EnhancerByCGLIB$$fc037646.hello(<generated>)
at cglib.CglibTest$$FastClassByCGLIB$$ef5535a6.invoke(<generated>)
at net.sf.cglib.proxy.MethodProxy.invoke(MethodProxy.java:204)
at cglib.CglibTest.intercept(CglibTest.java:14)
at cglib.CglibTest$$EnhancerByCGLIB$$fc037646.hello(<generated>)
at cglib.CglibTest$$FastClassByCGLIB$$ef5535a6.invoke(<generated>)
.........
为什么会这样，因为invokeSuper执行的是代理类的FastClass的方法，invoke是执行的原生类的FastClass的方法，
CGLIB$hello$0$Proxy = MethodProxy.create(var1, var0, "(Ljava/lang/String;)Ljava/lang/String;", "hello", "CGLIB$hello$0");
最终执行的方法不一样，分别是hello以及CGLIB$hello$0
final String CGLIB$hello$1(String var1) {
return super.hello(var1);
}
public final String hello(String var1) {
MethodInterceptor var10000 = this.CGLIB$CALLBACK_0;
if (var10000 == null) {
CGLIB$BIND_CALLBACKS(this);
var10000 = this.CGLIB$CALLBACK_0;
}
return var10000 != null ? (String)var10000.intercept(this, CGLIB$hello$1$Method, new Object[]{var1}, CGLIB$hello$1$Proxy) : super.hello(var1);
}
执行CGLIB$hello$1方法最终调用原生方法，执行hello方法会一直执行MethodInterceptor的intercept方法导致死循环，最后还有一点拦截器在cglib中可以实现很多类型，这个也是在字节码生成代码中来实现的,Spring等框架常用的就MethodInterceptor
class CallbackInfo
{
private static final CallbackInfo[] CALLBACKS = {
new CallbackInfo(NoOp.class, NoOpGenerator.INSTANCE),
new CallbackInfo(MethodInterceptor.class, MethodInterceptorGenerator.INSTANCE),
new CallbackInfo(InvocationHandler.class, InvocationHandlerGenerator.INSTANCE),
new CallbackInfo(LazyLoader.class, LazyLoaderGenerator.INSTANCE),
new CallbackInfo(Dispatcher.class, DispatcherGenerator.INSTANCE),
new CallbackInfo(FixedValue.class, FixedValueGenerator.INSTANCE),
new CallbackInfo(ProxyRefDispatcher.class, DispatcherGenerator.PROXY_REF_INSTANCE),
};
}
我们常用的callBack就是MethodInterceptor，但是其他的可能不太常用，他们的区别是什么呢，来看下面的代码
package cglib.callback;
import net.sf.cglib.core.DebuggingClassWriter;
import net.sf.cglib.proxy.*;
import java.lang.reflect.Method;
public class CglibTestCallBack {
public String hello0(String name){
return "你好0" + name;
}
public String hello1(String name){
return "你好1" + name;
}
public String hello2(String name){
return "你好2" + name;
}
public String hello3(String name){
return "你好3" + name;
}
public String hello4(String name){
return "你好4" + name;
}
public String hello5(String name){
return "你好5" + name;
}
public String hello6(String name){
return "你好6" + name;
}
public static void main(String[] args) {
System.setProperty ( DebuggingClassWriter.DEBUG_LOCATION_PROPERTY,"/Users/zhangyulong/Downloads" );
Enhancer enhancer = new Enhancer();
enhancer.setSuperclass ( CglibTestCallBack.class);
enhancer.setCallbacks(
new Callback[]{
new DispatcherCallBack(),
new FixedValueCallBack(),
new InvocationHandlerCallback(),
new LazyLoaderCallBack(),
new MethodInterceptorCallBack(),
new NoOpCallBack(),
new ProxyRefDispatcherCallBack()
}
);
enhancer.setCallbackFilter ( new CallbackFilter () {
@Override
public int accept(Method method) {
String name = method.getName ();
if(!name.startsWith ( "hello" )) return 0;
String num = name.substring ( "hello".length () );
return Integer.parseInt ( num );
}
} );
CglibTestCallBack cglibTest = (CglibTestCallBack) enhancer.create ();
String result = cglibTest.hello1 ( "张玉龙" );
System.out.println (result);
}
}
public class DispatcherCallBack implements Dispatcher {
@Override
public Object loadObject() throws Exception {
return null;
}
}
public class FixedValueCallBack implements FixedValue {
@Override
public Object loadObject() throws Exception {
return null;
}
}
public class InvocationHandlerCallback implements InvocationHandler {
@Override
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
return null;
}
}
public class LazyLoaderCallBack implements LazyLoader {
@Override
public Object loadObject() throws Exception {
return null;
}
}
public class NoOpCallBack implements NoOp {
}
public class ProxyRefDispatcherCallBack implements ProxyRefDispatcher {
@Override
public Object loadObject(Object proxy) throws Exception {
return null;
}
}
我们设置了六个callBack，对应了六个方法 hello0-6, 我们来看看他们生成的代理类的方法是什么样的，下面是代理类的部分代码
public final String hello0(String var1) {
Dispatcher var10000 = this.CGLIB$CALLBACK_0;
if (var10000 == null) {
CGLIB$BIND_CALLBACKS(this);
var10000 = this.CGLIB$CALLBACK_0;
}
return ((CglibTestCallBack)var10000.loadObject()).hello0(var1);
}
public final String hello1(String var1) {
FixedValue var10000 = this.CGLIB$CALLBACK_1;
if (var10000 == null) {
CGLIB$BIND_CALLBACKS(this);
var10000 = this.CGLIB$CALLBACK_1;
}
return (String)var10000.loadObject();
}
public final String hello2(String var1) {
try {
InvocationHandler var10000 = this.CGLIB$CALLBACK_2;
if (var10000 == null) {
CGLIB$BIND_CALLBACKS(this);
var10000 = this.CGLIB$CALLBACK_2;
}
return (String)var10000.invoke(this, CGLIB$hello2$1, new Object[]{var1});
} catch (Error | RuntimeException var2) {
throw var2;
} catch (Throwable var3) {
throw new UndeclaredThrowableException(var3);
}
}
public final String hello3(String var1) {
return ((CglibTestCallBack)this.CGLIB$LOAD_PRIVATE_3()).hello3(var1);
}
private final synchronized Object CGLIB$LOAD_PRIVATE_3() {
Object var10000 = this.CGLIB$LAZY_LOADER_3;
if (var10000 == null) {
LazyLoader var10001 = this.CGLIB$CALLBACK_3;
if (var10001 == null) {
CGLIB$BIND_CALLBACKS(this);
var10001 = this.CGLIB$CALLBACK_3;
}
var10000 = this.CGLIB$LAZY_LOADER_3 = var10001.loadObject();
}
return var10000;
}
public final String hello4(String var1) {
MethodInterceptor var10000 = this.CGLIB$CALLBACK_4;
if (var10000 == null) {
CGLIB$BIND_CALLBACKS(this);
var10000 = this.CGLIB$CALLBACK_4;
}
return var10000 != null ? (String)var10000.intercept(this, CGLIB$hello4$3$Method, new Object[]{var1}, CGLIB$hello4$3$Proxy) : super.hello4(var1);
}
public final String hello6(String var1) {
ProxyRefDispatcher var10000 = this.CGLIB$CALLBACK_6;
if (var10000 == null) {
CGLIB$BIND_CALLBACKS(this);
var10000 = this.CGLIB$CALLBACK_6;
}
return ((CglibTestCallBack)var10000.loadObject(this)).hello6(var1);
}
无需多解释，生成的代码非常清晰了，由于hello5是实现了NoOp，代理类忽略这个方法，直接调用原生类的hello5。值得注意的是CGLIB$BIND_CALLBACKS(this);这个方法是这些代理方法中统一的设置callback的方法，我们看看它到底干了些什么。
private static final void CGLIB$BIND_CALLBACKS(Object var0) {
CglibTestCallBack$$EnhancerByCGLIB$$58712cb6 var1 = (CglibTestCallBack$$EnhancerByCGLIB$$58712cb6)var0;
if (!var1.CGLIB$BOUND) {
var1.CGLIB$BOUND = true;
Object var10000 = CGLIB$THREAD_CALLBACKS.get();
if (var10000 == null) {
var10000 = CGLIB$STATIC_CALLBACKS;
if (var10000 == null) {
return;
}
}
Callback[] var10001 = (Callback[])var10000;
var1.CGLIB$CALLBACK_6 = (ProxyRefDispatcher)((Callback[])var10000)[6];
var1.CGLIB$CALLBACK_5 = (NoOp)var10001[5];
var1.CGLIB$CALLBACK_4 = (MethodInterceptor)var10001[4];
var1.CGLIB$CALLBACK_3 = (LazyLoader)var10001[3];
var1.CGLIB$CALLBACK_2 = (InvocationHandler)var10001[2];
var1.CGLIB$CALLBACK_1 = (FixedValue)var10001[1];
var1.CGLIB$CALLBACK_0 = (Dispatcher)var10001[0];
}
}
代码非常简单，就是从CGLIB$THREAD_CALLBACKS 或者CGLIB$STATIC_CALLBACKS中获取callBack数组，那么这个数组我们什么时候设置的呢？看下面代码 net.sf.cglib.proxy.Enhancer#firstInstance
protected Object firstInstance(Class type) throws Exception {
if (classOnly) {
return type;
} else {
return createUsingReflection(type);
}
}
private Object createUsingReflection(Class type) {
setThreadCallbacks(type, callbacks);
try{
if (argumentTypes != null) {
return ReflectUtils.newInstance(type, argumentTypes, arguments);
} else {
return ReflectUtils.newInstance(type);
}
}finally{
// clear thread callbacks to allow them to be gc'd
setThreadCallbacks(type, null);
}
}
private static final String SET_THREAD_CALLBACKS_NAME = "CGLIB$SET_THREAD_CALLBACKS";
private static void setThreadCallbacks(Class type, Callback[] callbacks) {
setCallbacksHelper(type, callbacks, SET_THREAD_CALLBACKS_NAME);
}
特别明显在初始化时，将我们设置的callBack数组设置到代理类中，并且在代理类生成实例之后，再清空，方便gc回收，到此cglib的源码解析就已经完成了。这里有一个细节就是上面的代码 只有hello4方法才会生成FastClass，所以我们生成的代理类只有1个，没有生成原生类和代理的FsstClass，这是因为fastclass的生成只有首次调用方法的时候，才会去触发。
public Object invokeSuper(Object obj, Object[] args) throws Throwable {
try {
init();
FastClassInfo fci = fastClassInfo;
return fci.f2.invoke(fci.i2, obj, args);
} catch (InvocationTargetException e) {
throw e.getTargetException();
}
}
所以当我们调用hello4方法时，首次调用就会生成代理类了。这也就是为什么cglib代理首次调用的时候速度会慢一些，因为要先生成字节码。
四:手把手写基于接口的java代理
上面我们分析了jdk动态代理源码、cglib代理源码、那我们是不是可以自己用自己的方式去写一个属于自己的jdk代理呢，答案是可以的
首先我们写一个基类，当然我并没有在基类里面写什么东西，只是模拟java中的proxy类而已，当然我们也可以丰富的去拓展一下这个类的方法，来实现更多的功能，读者可以通过读完这篇文章之后自己去考虑一下如何来拓展。
1 package meituan.zylproxy.handlder; 2 public class ZylProxy { 3 public ZylProxy(){ 4 } 5 }
代理的核心接口，我们去做代理的时候一定是通过反射去调用的，不管jdk也好还是cglib也好，永远也无法脱离反射，我们照猫画虎，自己写一个代理接口核心类，这并不是什么难题，看起来和jdk的核心类接口也没有什么区别。
1 package meituan.zylproxy.handlder; 2 3 import java.lang.reflect.Method; 4 5 public interface ZYLInvocationHandler { 6 7 public Object invoke(Object proxy, Method method, Object[] args) 8 throws Exception; 9 }
说明一下 第一个参数proxy是代表代理类，而不是用户自己写的原生类实现。参数Method是接口的方法,args是运行时参数列表，在运行时传递过来的实际上就是实现类的参数，好了，下面让我们去深入核心。
我们自定义两个接口和接口的实现Idto，Idto2，和Dtoimpl如下：
1 package meituan.zylproxy.test.i; 2 3 public interface Idto { 4 5 public void add(); 6 7 public String get(); 8 9 }
package meituan.zylproxy.test.i; public interface Idto2 { public void adda(); public String geta(); }
package meituan.zylproxy.test.i.impl; import meituan.zylproxy.test.i.Idto; import meituan.zylproxy.test.i.Idto2; public class DtoImpl implements Idto,Idto2{ @Override public void add() { System.out.println("add"); } @Override public String get() { System.out.println("get"); return "return get"; } @Override public void adda() { System.out.println("adda"); } @Override public String geta() { System.out.println("geta"); return "return geta"; } }
这是几个再简单不过的接口和实现类了，也没有什么可说的。接下来我们想对接口进行代理，无非是我们动态将接口进行实现，从而达到对使用者进行自定义handle接口暴露而已，下面看一下我们需要生成一个什么样的代理类。
import java.lang.reflect.Method; import meituan.zylproxy.handlder.ZylProxy; import meituan.zylproxy.handlder.ZYLInvocationHandler; import meituan.zylproxy.test.i.Idto; import meituan.zylproxy.test.i.Idto2; public class IdtoPorxy extends ZylProxy implements Idto, Idto2 { public ZYLInvocationHandler zYLInvocationHandler; public static Method add1; public static Method get2; public static Method adda3; public static Method geta4; static { try { add1 = Class.forName ( "meituan.zylproxy.test.i.Idto" ).getMethod ( "add", new Class[0] ); get2 = Class.forName ( "meituan.zylproxy.test.i.Idto" ).getMethod ( "get", new Class[0] ); adda3 = Class.forName ( "meituan.zylproxy.test.i.Idto2" ).getMethod ( "adda", new Class[0] ); geta4 = Class.forName ( "meituan.zylproxy.test.i.Idto2" ).getMethod ( "geta", new Class[0] ); } catch (Exception e) { } } public IdtoPorxy(ZYLInvocationHandler zYLInvocationHandler) { this.zYLInvocationHandler = zYLInvocationHandler; } public void add() { Object[] o = {}; try { this.zYLInvocationHandler.invoke ( this, add1, o ); return; } catch (Throwable e) { e.printStackTrace (); } } public java.lang.String get() { Object[] o = {}; try { return (java.lang.String) this.zYLInvocationHandler.invoke ( this, get2, o ); } catch (Exception e) { e.printStackTrace (); } return null; } public void adda() { Object[] o = {}; try { this.zYLInvocationHandler.invoke ( this, adda3, o ); return; } catch (Throwable e) { e.printStackTrace (); } } public java.lang.String geta() { Object[] o = {}; try { return (java.lang.String) this.zYLInvocationHandler.invoke ( this, geta4, o ); } catch (Exception e) { e.printStackTrace (); } return null; } }
这个类不是由用户写的，而是我们动态生成的，对于jdk来说是生成了字节码，对cglib来说是通过字节码增强，其实实现的方式有多种，后面为了更方便大家理解我用字符串的形式来动态生成这么一个"家伙"，先看看这个类干了些什么吧，也很简单。
public class IdtoPorxy extends ZylProxy implements Idto, Idto2
首先是继承了刚才我们所说的ZylProxy，留着今后拓展，可以参照java的Proxy，然后并且动态的实现了这两个接口。很简单
public ZYLInvocationHandler zYLInvocationHandler;
public IdtoPorxy(ZYLInvocationHandler zYLInvocationHandler) {
this.zYLInvocationHandler = zYLInvocationHandler;
}
这个是通过构造函数传进来一个handler对象，对实现类的操作都靠它了。
public static Method add1; public static Method get2; public static Method adda3; public static Method geta4; static { try { add1 = Class.forName ( "meituan.zylproxy.test.i.Idto" ).getMethod ( "add", new Class[0] ); get2 = Class.forName ( "meituan.zylproxy.test.i.Idto" ).getMethod ( "get", new Class[0] ); adda3 = Class.forName ( "meituan.zylproxy.test.i.Idto2" ).getMethod ( "adda", new Class[0] ); geta4 = Class.forName ( "meituan.zylproxy.test.i.Idto2" ).getMethod ( "geta", new Class[0] ); } catch (Exception e) { } }
枚举出来所有的接口的方法，通过class.forname来获取到Method元数据。备用
public void add() { Object[] o = {}; try { this.zYLInvocationHandler.invoke ( this, add1, o ); return; } catch (Throwable e) { e.printStackTrace (); } } public java.lang.String get() { Object[] o = {}; try { return (java.lang.String) this.zYLInvocationHandler.invoke ( this, get2, o ); } catch (Exception e) { e.printStackTrace (); } return null; } public void adda() { Object[] o = {}; try { this.zYLInvocationHandler.invoke ( this, adda3, o ); return; } catch (Throwable e) { e.printStackTrace (); } } public java.lang.String geta() { Object[] o = {}; try { return (java.lang.String) this.zYLInvocationHandler.invoke ( this, geta4, o ); } catch (Exception e) { e.printStackTrace (); } return null; }
上面是要枚举出来所有的方法的实现，很简单都一个模样，把实现交给handler去做就可以了。至于怎么实现靠handler，我们动态生成的这个类只负责委托，不做任何事情。看到这里大家一定急不可待的想知道这个类怎么生成的了，我把我写的源码给大家贴出来看一下。
package meituan.zylproxy.util; import java.lang.reflect.Method; import java.lang.reflect.Modifier; import meituan.zylproxy.test.i.Idto; import meituan.zylproxy.test.i.Idto2; public class ClassUtil { public static String mackProxyClass(Class<?> c) throws Exception{ if(!c.isInterface()){ throw new Exception("代理的类必须是接口"); } StringBuffer importsp = new StringBuffer(); importsp.append("import java.lang.reflect.Method;\n"); importsp.append("import meituan.zylproxy.handlder.ZylProxy;\n"); importsp.append("import meituan.zylproxy.handlder.ZYLInvocationHandler;\n"); importsp.append("import " +c.getName() + ";\n"); StringBuilder publicStaticMethods = new StringBuilder(); //public static Method add; StringBuilder publicMethods = new StringBuilder(); publicMethods.append("public ZYLInvocationHandler zYLInvocationHandler;\n"); StringBuilder constructorsp = new StringBuilder(); String interFaceName = c.getName().substring(c.getName().lastIndexOf(".")+1); constructorsp.append("public ").append("" + interFaceName + "Porxy"). append("(ZYLInvocationHandler zYLInvocationHandler) { " + "this.zYLInvocationHandler = zYLInvocationHandler;" + "}"); publicStaticMethods.append(" static { try { "); StringBuilder classsp = new StringBuilder(); classsp.append("public class").append(" " + interFaceName + "Porxy").append(" extends ZylProxy implements ").append(interFaceName).append("{"); StringBuilder allMethods = new StringBuilder(); Method[] Methods = c.getMethods(); int curr=0; for (Method m_:Methods) { curr++; publicMethods.append("public static Method ").append(m_.getName() + String.valueOf(curr)).append(";\n"); publicStaticMethods.append("").append(m_.getName() + String.valueOf(curr)).append("="); publicStaticMethods.append("Class.forName(\"" + c.getName() + "\")" + ".getMethod(\""+ m_.getName() +"\", "); StringBuilder sp =new StringBuilder(); StringBuilder spArgs = new StringBuilder(); spArgs.append("Object[] o ={"); //public sp.append(Modifier.toString(m_.getModifiers()).replace("abstract", "")).append(" "); //void | java.lang.String sp.append(m_.getReturnType().getName()).append(" "); //add()|get() sp.append(m_.getName().concat("(")); StringBuilder methodCLass = new StringBuilder(); if(m_.getParameterTypes().length>0){ Class<?>[] claszz = m_.getParameterTypes(); int methodOffset = 0; methodCLass.append("new Class[] { "); for (Class<?> c_ : claszz) { String paramStr = "obj" + String.valueOf(++methodOffset); spArgs.append(paramStr.concat(",")); sp.append(c_.getName().toString().concat(" ").concat(paramStr)).append(","); methodCLass.append("Class.forName(\"" + c_.getName()).append("\"),"); } sp = new StringBuilder(sp.substring(0, sp.length()-1)); spArgs = new StringBuilder(spArgs.substring(0, spArgs.length()-1)); methodCLass = new StringBuilder(methodCLass.substring(0, methodCLass.length()-1)); } if(methodCLass.length()>0){ methodCLass.append("}"); } else{ methodCLass.append("new Class[0]"); } sp.append("){\n"); spArgs.append("}"); sp.append(spArgs+";\n"); if(sp.toString().contains("void")){ sp.append("try {\n this.zYLInvocationHandler.invoke(this,").append(m_.getName() + String.valueOf(curr)).append(",").append("o);\n return;\n"); sp.append("} catch (Throwable e) {e.printStackTrace();}}"); } else{ sp.append("try {return " + "(" + m_.getReturnType().getName() + ")" + "this.zYLInvocationHandler.invoke(this,").append(m_.getName() + String.valueOf(curr)).append(",").append("o);\n"); sp.append("} catch (Exception e) {e.printStackTrace();} return null;"); } publicStaticMethods.append(methodCLass).append(");\n"); allMethods.append(sp); } publicStaticMethods.append("} catch(Exception e){}}"); classsp.append(publicMethods) .append(publicStaticMethods) .append(constructorsp).append(allMethods).append("}"); classsp.append("}"); importsp.append(classsp); return importsp.toString(); } public static String mackMultiProxyClass(Class<?>[] cs) throws Exception{ StringBuffer importsp = new StringBuffer(); importsp.append("import java.lang.reflect.Method;\n"); importsp.append("import meituan.zylproxy.handlder.ZylProxy;\n"); importsp.append("import meituan.zylproxy.handlder.ZYLInvocationHandler;\n"); StringBuilder publicStaticMethods = new StringBuilder(); publicStaticMethods.append(" static { try { "); //public static Method add; StringBuilder publicMethods = new StringBuilder(); publicMethods.append("public ZYLInvocationHandler zYLInvocationHandler;\n"); int curr=0; StringBuilder constructorsp = new StringBuilder(); String interFaceName = cs[0].getName().substring(cs[0].getName().lastIndexOf(".")+1); constructorsp.append("public ").append("" + interFaceName + "Porxy"). append("(ZYLInvocationHandler zYLInvocationHandler) { " + "this.zYLInvocationHandler = zYLInvocationHandler;" + "}"); StringBuilder allMethods = new StringBuilder(); StringBuilder classsp = new StringBuilder(); classsp.append("public class").append(" " + interFaceName + "Porxy").append(" extends ZylProxy implements "); for (Class<?> c:cs) { if(!c.isInterface()){ throw new Exception("代理的类必须是接口"); } classsp.append(c.getName().substring(c.getName().lastIndexOf(".")+1)).append(","); importsp.append("import " +c.getName() + ";\n"); Method[] Methods = c.getMethods(); for (Method m_:Methods) { curr++; publicMethods.append("public static Method ").append(m_.getName() + String.valueOf(curr)).append(";\n"); publicStaticMethods.append("").append(m_.getName() + String.valueOf(curr)).append("="); publicStaticMethods.append("Class.forName(\"" + c.getName() + "\")" + ".getMethod(\""+ m_.getName() +"\", "); StringBuilder sp =new StringBuilder(); StringBuilder spArgs = new StringBuilder(); spArgs.append("Object[] o ={"); //public sp.append(Modifier.toString(m_.getModifiers()).replace("abstract", "")).append(" "); //void | java.lang.String sp.append(m_.getReturnType().getName()).append(" "); //add()|get() sp.append(m_.getName().concat("(")); StringBuilder methodCLass = new StringBuilder(); if(m_.getParameterTypes().length>0){ Class<?>[] claszz = m_.getParameterTypes(); int methodOffset = 0; methodCLass.append("new Class[] { "); for (Class<?> c_ : claszz) { String paramStr = "obj" + String.valueOf(++methodOffset); spArgs.append(paramStr.concat(",")); sp.append(c_.getName().toString().concat(" ").concat(paramStr)).append(","); methodCLass.append("Class.forName(\"" + c_.getName()).append("\"),"); } sp = new StringBuilder(sp.substring(0, sp.length()-1)); spArgs = new StringBuilder(spArgs.substring(0, spArgs.length()-1)); methodCLass = new StringBuilder(methodCLass.substring(0, methodCLass.length()-1)); } if(methodCLass.length()>0){ methodCLass.append("}"); } else{ methodCLass.append("new Class[0]"); } sp.append("){\n"); spArgs.append("}"); sp.append(spArgs+";\n"); if(sp.toString().contains("void")){ sp.append("try {\n this.zYLInvocationHandler.invoke(this,").append(m_.getName() + String.valueOf(curr)).append(",").append("o);\n return;\n"); sp.append("} catch (Throwable e) {e.printStackTrace();}}"); } else{ sp.append("try {return " + "(" + m_.getReturnType().getName() + ")" + "this.zYLInvocationHandler.invoke(this,").append(m_.getName() + String.valueOf(curr)).append(",").append("o);\n"); sp.append("} catch (Exception e) {e.printStackTrace();} return null;}"); } publicStaticMethods.append(methodCLass).append(");\n"); allMethods.append(sp); } } classsp = new StringBuilder(classsp.substring(0, classsp.length()-1)).append("{"); publicStaticMethods.append("} catch(Exception e){}}"); classsp.append(publicMethods) .append(publicStaticMethods) .append(constructorsp).append(allMethods).append(""); classsp.append("}"); importsp.append(classsp); return importsp.toString(); } public static void main(String[] args) throws Exception { System.out.println(mackMultiProxyClass(new Class<?>[]{Idto.class})); } }
看起来很复杂，仔细看一下就看了那么几个事情，把一个接口class或者多个接口class变成纯字符串的过程，一共两个方法，一个是单接口的实现，很早之前写的，第二个方法是多接口的实现支持多接口，只需要传一个class对象就会生成代理类的字符串，这里仅仅是字符串，需要编译成class使用。那么如何编译成class呢。通过java中的工具类 JavaCompiler很简单的就可以生成了。我们来看两个工具类实现
package meituan.zylproxy; import java.io.ByteArrayOutputStream; import java.io.File; import java.io.FilterOutputStream; import java.io.IOException; import java.io.OutputStream; import java.io.Reader; import java.io.StringReader; import java.net.URI; import java.nio.CharBuffer; import java.nio.file.WatchEvent.Kind; import java.util.HashMap; import java.util.Map; import javax.tools.FileObject; import javax.tools.ForwardingJavaFileManager; import javax.tools.JavaFileManager; import javax.tools.JavaFileObject; import javax.tools.SimpleJavaFileObject; @SuppressWarnings("unchecked") final class MemoryJavaFileManager extends ForwardingJavaFileManager { private final static String EXT = ".java"; private Map<String, byte[]> classBytes; public MemoryJavaFileManager(JavaFileManager fileManager) { super(fileManager); classBytes = new HashMap<String, byte[]>(); } public Map<String, byte[]> getClassBytes() { return classBytes; } public void close() throws IOException { classBytes = new HashMap<String, byte[]>(); } public void flush() throws IOException { } private static class StringInputBuffer extends SimpleJavaFileObject { final String code; StringInputBuffer(String name, String code) { super(toURI(name), Kind.SOURCE); this.code = code; } public CharBuffer getCharContent(boolean ignoreEncodingErrors) { return CharBuffer.wrap(code); } public Reader openReader() { return new StringReader(code); } } private class ClassOutputBuffer extends SimpleJavaFileObject { private String name; ClassOutputBuffer(String name) { super(toURI(name), Kind.CLASS); this.name = name; } public OutputStream openOutputStream() { return new FilterOutputStream(new ByteArrayOutputStream()) { public void close() throws IOException { out.close(); ByteArrayOutputStream bos = (ByteArrayOutputStream) out; classBytes.put(name, bos.toByteArray()); } }; } } public JavaFileObject getJavaFileForOutput(JavaFileManager.Location location, String className, JavaFileObject.Kind kind, FileObject sibling) throws IOException { if (kind == JavaFileObject.Kind.CLASS) { return new ClassOutputBuffer(className); } else { return super.getJavaFileForOutput(location, className, kind, sibling); } } static JavaFileObject makeStringSource(String name, String code) { return new StringInputBuffer(name, code); } static URI toURI(String name) { File file = new File(name); if (file.exists()) { return file.toURI(); } else { try { final StringBuilder newUri = new StringBuilder(); newUri.append("mfm:///"); newUri.append(name.replace('.', '/')); if (name.endsWith(EXT)) newUri.replace(newUri.length() - EXT.length(), newUri.length(), EXT); return URI.create(newUri.toString()); } catch (Exception exp) { return URI.create("mfm:///com/sun/script/java/java_source"); } } } }
package meituan.zylproxy; import java.io.IOException; import java.net.URL; import java.net.URLClassLoader; import java.util.Arrays; import java.util.HashMap; import java.util.Map; import java.util.regex.Matcher; import java.util.regex.Pattern; import javax.tools.JavaCompiler; import javax.tools.JavaFileObject; import javax.tools.StandardJavaFileManager; import javax.tools.ToolProvider; public class DynamicLoader { public static Map<String, byte[]> compile(String javaSrc) { Pattern pattern = Pattern.compile("public\\s+class\\s+(\\w+)"); Matcher matcher = pattern.matcher(javaSrc); if (matcher.find()) return compile(matcher.group(1) + ".java", javaSrc); return null; } public static Map<String, byte[]> compile(String javaName, String javaSrc) { JavaCompiler compiler = ToolProvider.getSystemJavaCompiler(); StandardJavaFileManager stdManager = compiler.getStandardFileManager(null, null, null); try (MemoryJavaFileManager manager = new MemoryJavaFileManager(stdManager)) { JavaFileObject javaFileObject = manager.makeStringSource(javaName, javaSrc); JavaCompiler.CompilationTask task = compiler.getTask(null, manager, null, null, null, Arrays.asList(javaFileObject)); if (task.call()) return manager.getClassBytes(); } catch (IOException e) { e.printStackTrace(); } return null; } public static class MemoryClassLoader extends URLClassLoader { Map<String, byte[]> classBytes = new HashMap<String, byte[]>(); public MemoryClassLoader(Map<String, byte[]> classBytes) { super(new URL[0], MemoryClassLoader.class.getClassLoader()); this.classBytes.putAll(classBytes); } @Override protected Class<?> findClass(String name) throws ClassNotFoundException { byte[] buf = classBytes.get(name); if (buf == null) { return super.findClass(name); } classBytes.remove(name); return defineClass(name, buf, 0, buf.length); } } }
通过DynamicLoader的compile方法可以把纯字符串的str转成byte[]数组，有了byte[]数组就可以很方便的获取到class对象了，自定义一个MemoryClassLoader通过defineClass方法来获取到class对象。这样基本所有的事情都做完了。下面我们写一个工厂类来获取代理类。
package meituan.zylproxy.util; import java.util.Map; import meituan.zylproxy.DynamicLoader; import meituan.zylproxy.handlder.ZYLInvocationHandler; public class PorxyFactory { //单interface的时候用 public static Object newProxyInstance(Class<?> c,ZYLInvocationHandler h) throws Exception{ String classStr = ClassUtil.mackProxyClass(c); Map<String, byte[]> m = DynamicLoader.compile(classStr); DynamicLoader.MemoryClassLoader classLoader = new DynamicLoader.MemoryClassLoader(m); Class<?> proxy =classLoader.loadClass(m.keySet().toArray(new String[0])[0]); return proxy.getConstructor(ZYLInvocationHandler.class).newInstance(h); } //多interface的时候用 public static Object newProxyInstancewWithMultiClass(Class<?>[] c,ZYLInvocationHandler h) throws Exception{ String classStr = ClassUtil.mackMultiProxyClass(c); System.out.println (classStr); Map<String, byte[]> m = DynamicLoader.compile(classStr); DynamicLoader.MemoryClassLoader classLoader = new DynamicLoader.MemoryClassLoader(m); Class<?> proxy =classLoader.loadClass(m.keySet().toArray(new String[0])[0]); return proxy.getConstructor(ZYLInvocationHandler.class).newInstance(h); } }
最后一步我们测试一下结果吧，写一个测试类
package meituan.zylproxy.test; import meituan.zylproxy.handlder.Hander; import meituan.zylproxy.test.i.Idto; import meituan.zylproxy.test.i.impl.DtoImpl; import meituan.zylproxy.util.PorxyFactory; public class ZylPorxyTest { public static void main(String[] args) throws Exception { Idto d = (Idto) PorxyFactory.newProxyInstancewWithMultiClass(DtoImpl.class.getInterfaces(), new Hander(new DtoImpl())); d.add(); } }
很简单，第一个参数是所有的接口，第二个是handler实现。最后我们看看结果。
大功告成。
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