简述spring中常有的几种advice？
在Spring中，Advice都是通过Interceptor来实现的，主要有以下几种：
1. 环绕Advice：
//例子摘自Spring reference public interface MethodInterceptor extends Interceptor { Object invoke(MethodInvocation invocation) throws Throwable; } public class DebugInterceptor implements MethodInterceptor { public Object invoke(MethodInvocation invocation) throws Throwable { System.out.println("Before: invocation=[" + invocation + "]"); //(1) Object rval = invocation.proceed(); System.out.println("Invocation returned"); //(2) return rval; } }
环绕advice类似一个拦截器链，这个拦截器链的中心就是被拦截的方法。在程序(1)(2)我们可以加入我们自己的代码，以表示在方法执行前后我们需要干什么。invocation.proceed()方法运行指向连接点的拦截器链并返回proceed()的结果。
2. Before Advice
public interface MethodBeforeAdvice extends BeforeAdvice { void before(Method m, Object[] args, Object target) throws Throwable; }
一个更简单的通知类型是before 通知。它不需要 MethodInvocation对象，因为它只是在进入方法之前被调用。before advice的一个主要优点是它不需要调用proceed()方法，因此就不会发生 无意间运行拦截器链失败的情况。
3. After advice
public interface AfterReturningAdvice extends Advice { void afterReturning(Object returnValue, Method m, Object[] args, Object target) throws Throwable; } ！
一个After advice可以访问返回值（但不能进行修改），被调用方法，方法参数以及目标对象。
4.Throws Advice
//ThrowsAdvice 是一个空接口，起标识作用 public interface ThrowsAdvice extends Advice { } //所给对象必须实现一个或者多个针对特定类型的异常通知方法，格式如下 afterThrowing([Method], [args], [target], subclassOfThrowable) //只有最后一个参数是必须的。因此异常通知方法对方法及参数的需求，方法的签名将从一到四个参数之间变化。
最后还有一个是introduction advice，这个我想什么时候自己单独做个例子理解一下。
做了个例子如下，想像一个用户登录场景：在登录之前，我们对其输入的用户名进行有效性检查；登录成功后，我们记上用户登录次数；如果登录失败，则进行异常处理。实现代码如下：
package com.learn.spring.test.advisor; //登录的业务代码 public interface LoginService { void login(String name, String password) throws UnauthorityException; } public class LoginServiceImpl implements LoginService { public void login(String name, String password) throws UnauthorityException { check(name, password); System.err.println(name + " is logining system..."); } private void check(String name, String password) throws UnauthorityException { if("myyate".equals(name) && "pass".equals(password) ) { System.err.println(name + " passed check...."); } else { throw new UnauthorityException("invalid password"); } } }
//用户名检查 拦截器 public class LoginNameCheckInterceptor implements MethodBeforeAdvice { public void before(Method method, Object[] args, Object target) throws Throwable { System.err.println("check user's name is valid?"); if(args[0] == null || "".equals(args[0].toString().trim())) { throw new IllegalArgumentException(); } } }
//用户登录次数统计拦截器 public class LoginCountInterceptor implements AfterReturningAdvice ...{ public void afterReturning(Object returnValue, Method method, Object[] args, Object target) throws Throwable ...{ System.err.println("Counting the login counts of " + args[0]); } }
//异常处理拦截器 public class ExceptionThrowInterceptor implements ThrowsAdvice { public void afterThrowing(Method m, Object[] args, Object target, IllegalArgumentException ex) throws Throwable { System.err.println("Login name is wrong, exception: " + ex); } public void afterThrowing(Method m, Object[] args, Object target, UnauthorityException ex) { System.err.println(target.getClass() + "." + m.getName() + "() throw a exception: " + ex.getMessage()); } }
配置文件如下：
<?xml version="1.0" encoding="UTF-8"?> <beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:aop="http://www.springframework.org/schema/aop" xmlns:tx="http://www.springframework.org/schema/tx" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-2.0.xsd http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-2.0.xsd http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-2.0.xsd"> <bean id="loginServiceTarget" class="com.learn.spring.test.advisor.LoginServiceImpl"/> <bean id="loginNameCheckInterceptor" class="com.learn.spring.test.advisor.LoginNameCheckInterceptor"/> <!-- <bean id="loginCheckInterceptor" class="com.learn.spring.test.advisor.LoginCheckInterceptor"/> --> <bean id="loginCountInterceptor" class="com.learn.spring.test.advisor.LoginCountInterceptor"/> <bean id="exceptionThrowInterceptor" class="com.learn.spring.test.advisor.ExceptionThrowInterceptor"/> <bean id="loginService" class="org.springframework.aop.framework.ProxyFactoryBean"> <property name="target"><ref local="loginServiceTarget"/></property> <property name="proxyInterfaces"> <list> <value>com.learn.spring.test.advisor.LoginService</value> </list> </property> <property name="interceptorNames"> <list> <value>loginNameCheckInterceptor</value> <value>loginCountInterceptor</value> <value>exceptionThrowInterceptor</value> </list> </property> </bean> </beans>
测试代码运行：
public class Test { public static void main(String[] args) throws Exception { BeanFactory bf = BeanFactoryFactory.getBeanFactory("beans.xml", Test.class); LoginService ls = (LoginService) bf.getBean("loginService"); ls.login("myyate", "pass"); } }
输出结果：
check user's name is valid?
myyate passed check....
myyate is logining system...
Counting the login counts of myyate
转载：https://blog.csdn.net/caolaosanahnu/article/details/7914595
