Spring 高级 jdk代理原理-字节码篇
一、利用ASM插件生成 asm生成代理类的字节码代码
1、写好代理类
package com.mangoubiubiu.show.asm; import org.springframework.cglib.proxy.UndeclaredThrowableException; import java.lang.reflect.InvocationHandler; import java.lang.reflect.Method; import java.lang.reflect.Proxy; public class $Proxy0 extends Proxy implements Foo { public $Proxy0(InvocationHandler h) { super(h); } @Override public void foo() { try { h.invoke(this,foo,new Object[0]); } catch (RuntimeException | Error e) { throw e; } catch (Throwable e){ throw new UndeclaredThrowableException(e); } } static Method foo; static { try { foo = Foo.class.getMethod("foo"); } catch (NoSuchMethodException e) { throw new NoSuchMethodError(e.getMessage()); } } }
package com.mangoubiubiu.show.asm; public interface Foo { public void foo(); }
2、反向生成
装下插件
然后右键生成 
下段代码就可以动态生成 $Proxy0 字节码文件
package asm.com.mangoubiubiu.show.asm; import java.util.*; import org.objectweb.asm.*; public class $Proxy0Dump implements Opcodes { public static byte[] dump() throws Exception { ClassWriter cw = new ClassWriter(0); FieldVisitor fv; MethodVisitor mv; AnnotationVisitor av0; cw.visit(52, ACC_PUBLIC + ACC_SUPER, "com/mangoubiubiu/show/asm/$Proxy0", null, "java/lang/reflect/Proxy", new String[]{"com/mangoubiubiu/show/asm/Foo"}); cw.visitSource("$Proxy0.java", null); { fv = cw.visitField(ACC_STATIC, "foo", "Ljava/lang/reflect/Method;", null, null); fv.visitEnd(); } { mv = cw.visitMethod(ACC_PUBLIC, "<init>", "(Ljava/lang/reflect/InvocationHandler;)V", null, null); mv.visitParameter("h", 0); mv.visitCode(); Label l0 = new Label(); mv.visitLabel(l0); mv.visitLineNumber(14, l0); mv.visitVarInsn(ALOAD, 0); mv.visitVarInsn(ALOAD, 1); mv.visitMethodInsn(INVOKESPECIAL, "java/lang/reflect/Proxy", "<init>", "(Ljava/lang/reflect/InvocationHandler;)V", false); Label l1 = new Label(); mv.visitLabel(l1); mv.visitLineNumber(15, l1); mv.visitInsn(RETURN); Label l2 = new Label(); mv.visitLabel(l2); mv.visitLocalVariable("this", "Lcom/mangoubiubiu/show/asm/$Proxy0;", null, l0, l2, 0); mv.visitLocalVariable("h", "Ljava/lang/reflect/InvocationHandler;", null, l0, l2, 1); mv.visitMaxs(2, 2); mv.visitEnd(); } { mv = cw.visitMethod(ACC_PUBLIC, "foo", "()V", null, null); mv.visitCode(); Label l0 = new Label(); Label l1 = new Label(); Label l2 = new Label(); mv.visitTryCatchBlock(l0, l1, l2, "java/lang/RuntimeException"); mv.visitTryCatchBlock(l0, l1, l2, "java/lang/Error"); Label l3 = new Label(); mv.visitTryCatchBlock(l0, l1, l3, "java/lang/Throwable"); mv.visitLabel(l0); mv.visitLineNumber(20, l0); mv.visitVarInsn(ALOAD, 0); mv.visitFieldInsn(GETFIELD, "com/mangoubiubiu/show/asm/$Proxy0", "h", "Ljava/lang/reflect/InvocationHandler;"); mv.visitVarInsn(ALOAD, 0); mv.visitFieldInsn(GETSTATIC, "com/mangoubiubiu/show/asm/$Proxy0", "foo", "Ljava/lang/reflect/Method;"); mv.visitInsn(ICONST_0); mv.visitTypeInsn(ANEWARRAY, "java/lang/Object"); mv.visitMethodInsn(INVOKEINTERFACE, "java/lang/reflect/InvocationHandler", "invoke", "(Ljava/lang/Object;Ljava/lang/reflect/Method;[Ljava/lang/Object;)Ljava/lang/Object;", true); mv.visitInsn(POP); mv.visitLabel(l1); mv.visitLineNumber(25, l1); Label l4 = new Label(); mv.visitJumpInsn(GOTO, l4); mv.visitLabel(l2); mv.visitLineNumber(21, l2); mv.visitFrame(Opcodes.F_SAME1, 0, null, 1, new Object[]{"java/lang/Throwable"}); mv.visitVarInsn(ASTORE, 1); Label l5 = new Label(); mv.visitLabel(l5); mv.visitLineNumber(22, l5); mv.visitVarInsn(ALOAD, 1); mv.visitInsn(ATHROW); mv.visitLabel(l3); mv.visitLineNumber(23, l3); mv.visitFrame(Opcodes.F_SAME1, 0, null, 1, new Object[]{"java/lang/Throwable"}); mv.visitVarInsn(ASTORE, 1); Label l6 = new Label(); mv.visitLabel(l6); mv.visitLineNumber(24, l6); mv.visitTypeInsn(NEW, "org/springframework/cglib/proxy/UndeclaredThrowableException"); mv.visitInsn(DUP); mv.visitVarInsn(ALOAD, 1); mv.visitMethodInsn(INVOKESPECIAL, "org/springframework/cglib/proxy/UndeclaredThrowableException", "<init>", "(Ljava/lang/Throwable;)V", false); mv.visitInsn(ATHROW); mv.visitLabel(l4); mv.visitLineNumber(26, l4); mv.visitFrame(Opcodes.F_SAME, 0, null, 0, null); mv.visitInsn(RETURN); Label l7 = new Label(); mv.visitLabel(l7); mv.visitLocalVariable("e", "Ljava/lang/Throwable;", null, l5, l3, 1); mv.visitLocalVariable("e", "Ljava/lang/Throwable;", null, l6, l4, 1); mv.visitLocalVariable("this", "Lcom/mangoubiubiu/show/asm/$Proxy0;", null, l0, l7, 0); mv.visitMaxs(4, 2); mv.visitEnd(); } { mv = cw.visitMethod(ACC_STATIC, "<clinit>", "()V", null, null); mv.visitCode(); Label l0 = new Label(); Label l1 = new Label(); Label l2 = new Label(); mv.visitTryCatchBlock(l0, l1, l2, "java/lang/NoSuchMethodException"); mv.visitLabel(l0); mv.visitLineNumber(32, l0); mv.visitLdcInsn(Type.getType("Lcom/mangoubiubiu/show/asm/Foo;")); mv.visitLdcInsn("foo"); mv.visitInsn(ICONST_0); mv.visitTypeInsn(ANEWARRAY, "java/lang/Class"); mv.visitMethodInsn(INVOKEVIRTUAL, "java/lang/Class", "getMethod", "(Ljava/lang/String;[Ljava/lang/Class;)Ljava/lang/reflect/Method;", false); mv.visitFieldInsn(PUTSTATIC, "com/mangoubiubiu/show/asm/$Proxy0", "foo", "Ljava/lang/reflect/Method;"); mv.visitLabel(l1); mv.visitLineNumber(35, l1); Label l3 = new Label(); mv.visitJumpInsn(GOTO, l3); mv.visitLabel(l2); mv.visitLineNumber(33, l2); mv.visitFrame(Opcodes.F_SAME1, 0, null, 1, new Object[]{"java/lang/NoSuchMethodException"}); mv.visitVarInsn(ASTORE, 0); Label l4 = new Label(); mv.visitLabel(l4); mv.visitLineNumber(34, l4); mv.visitTypeInsn(NEW, "java/lang/NoSuchMethodError"); mv.visitInsn(DUP); mv.visitVarInsn(ALOAD, 0); mv.visitMethodInsn(INVOKEVIRTUAL, "java/lang/NoSuchMethodException", "getMessage", "()Ljava/lang/String;", false); mv.visitMethodInsn(INVOKESPECIAL, "java/lang/NoSuchMethodError", "<init>", "(Ljava/lang/String;)V", false); mv.visitInsn(ATHROW); mv.visitLabel(l3); mv.visitLineNumber(36, l3); mv.visitFrame(Opcodes.F_SAME, 0, null, 0, null); mv.visitInsn(RETURN); mv.visitLocalVariable("e", "Ljava/lang/NoSuchMethodException;", null, l4, l3, 0); mv.visitMaxs(3, 1); mv.visitEnd(); } cw.visitEnd(); return cw.toByteArray(); } }
二、生成$Proxy0.class 文件
1 将asm插件生成的代码拿过来，导好包
package com.mangoubiubiu.show.asm; import jdk.internal.org.objectweb.asm.*; import org.springframework.asm.AnnotationVisitor; import static org.springframework.asm.Opcodes.*; public class $Proxy0Dump { public static byte[] dump() throws Exception { ClassWriter cw = new ClassWriter(0); FieldVisitor fv; MethodVisitor mv; AnnotationVisitor av0; cw.visit(52, ACC_PUBLIC + ACC_SUPER, "com/mangoubiubiu/show/asm/$Proxy0", null, "java/lang/reflect/Proxy", new String[]{"com/mangoubiubiu/show/asm/Foo"}); cw.visitSource("$Proxy0.java", null); { fv = cw.visitField(ACC_STATIC, "foo", "Ljava/lang/reflect/Method;", null, null); fv.visitEnd(); } { mv = cw.visitMethod(ACC_PUBLIC, "<init>", "(Ljava/lang/reflect/InvocationHandler;)V", null, null); mv.visitParameter("h", 0); mv.visitCode(); Label l0 = new Label(); mv.visitLabel(l0); mv.visitLineNumber(14, l0); mv.visitVarInsn(ALOAD, 0); mv.visitVarInsn(ALOAD, 1); mv.visitMethodInsn(INVOKESPECIAL, "java/lang/reflect/Proxy", "<init>", "(Ljava/lang/reflect/InvocationHandler;)V", false); Label l1 = new Label(); mv.visitLabel(l1); mv.visitLineNumber(15, l1); mv.visitInsn(RETURN); Label l2 = new Label(); mv.visitLabel(l2); mv.visitLocalVariable("this", "Lcom/mangoubiubiu/show/asm/$Proxy0;", null, l0, l2, 0); mv.visitLocalVariable("h", "Ljava/lang/reflect/InvocationHandler;", null, l0, l2, 1); mv.visitMaxs(2, 2); mv.visitEnd(); } { mv = cw.visitMethod(ACC_PUBLIC, "foo", "()V", null, null); mv.visitCode(); Label l0 = new Label(); Label l1 = new Label(); Label l2 = new Label(); mv.visitTryCatchBlock(l0, l1, l2, "java/lang/RuntimeException"); mv.visitTryCatchBlock(l0, l1, l2, "java/lang/Error"); Label l3 = new Label(); mv.visitTryCatchBlock(l0, l1, l3, "java/lang/Throwable"); mv.visitLabel(l0); mv.visitLineNumber(20, l0); mv.visitVarInsn(ALOAD, 0); mv.visitFieldInsn(GETFIELD, "com/mangoubiubiu/show/asm/$Proxy0", "h", "Ljava/lang/reflect/InvocationHandler;"); mv.visitVarInsn(ALOAD, 0); mv.visitFieldInsn(GETSTATIC, "com/mangoubiubiu/show/asm/$Proxy0", "foo", "Ljava/lang/reflect/Method;"); mv.visitInsn(ICONST_0); mv.visitTypeInsn(ANEWARRAY, "java/lang/Object"); mv.visitMethodInsn(INVOKEINTERFACE, "java/lang/reflect/InvocationHandler", "invoke", "(Ljava/lang/Object;Ljava/lang/reflect/Method;[Ljava/lang/Object;)Ljava/lang/Object;", true); mv.visitInsn(POP); mv.visitLabel(l1); mv.visitLineNumber(25, l1); Label l4 = new Label(); mv.visitJumpInsn(GOTO, l4); mv.visitLabel(l2); mv.visitLineNumber(21, l2); mv.visitFrame(Opcodes.F_SAME1, 0, null, 1, new Object[]{"java/lang/Throwable"}); mv.visitVarInsn(ASTORE, 1); Label l5 = new Label(); mv.visitLabel(l5); mv.visitLineNumber(22, l5); mv.visitVarInsn(ALOAD, 1); mv.visitInsn(ATHROW); mv.visitLabel(l3); mv.visitLineNumber(23, l3); mv.visitFrame(Opcodes.F_SAME1, 0, null, 1, new Object[]{"java/lang/Throwable"}); mv.visitVarInsn(ASTORE, 1); Label l6 = new Label(); mv.visitLabel(l6); mv.visitLineNumber(24, l6); mv.visitTypeInsn(NEW, "org/springframework/cglib/proxy/UndeclaredThrowableException"); mv.visitInsn(DUP); mv.visitVarInsn(ALOAD, 1); mv.visitMethodInsn(INVOKESPECIAL, "org/springframework/cglib/proxy/UndeclaredThrowableException", "<init>", "(Ljava/lang/Throwable;)V", false); mv.visitInsn(ATHROW); mv.visitLabel(l4); mv.visitLineNumber(26, l4); mv.visitFrame(Opcodes.F_SAME, 0, null, 0, null); mv.visitInsn(RETURN); Label l7 = new Label(); mv.visitLabel(l7); mv.visitLocalVariable("e", "Ljava/lang/Throwable;", null, l5, l3, 1); mv.visitLocalVariable("e", "Ljava/lang/Throwable;", null, l6, l4, 1); mv.visitLocalVariable("this", "Lcom/mangoubiubiu/show/asm/$Proxy0;", null, l0, l7, 0); mv.visitMaxs(4, 2); mv.visitEnd(); } { mv = cw.visitMethod(ACC_STATIC, "<clinit>", "()V", null, null); mv.visitCode(); Label l0 = new Label(); Label l1 = new Label(); Label l2 = new Label(); mv.visitTryCatchBlock(l0, l1, l2, "java/lang/NoSuchMethodException"); mv.visitLabel(l0); mv.visitLineNumber(32, l0); mv.visitLdcInsn(Type.getType("Lcom/mangoubiubiu/show/asm/Foo;")); mv.visitLdcInsn("foo"); mv.visitInsn(ICONST_0); mv.visitTypeInsn(ANEWARRAY, "java/lang/Class"); mv.visitMethodInsn(INVOKEVIRTUAL, "java/lang/Class", "getMethod", "(Ljava/lang/String;[Ljava/lang/Class;)Ljava/lang/reflect/Method;", false); mv.visitFieldInsn(PUTSTATIC, "com/mangoubiubiu/show/asm/$Proxy0", "foo", "Ljava/lang/reflect/Method;"); mv.visitLabel(l1); mv.visitLineNumber(35, l1); Label l3 = new Label(); mv.visitJumpInsn(GOTO, l3); mv.visitLabel(l2); mv.visitLineNumber(33, l2); mv.visitFrame(Opcodes.F_SAME1, 0, null, 1, new Object[]{"java/lang/NoSuchMethodException"}); mv.visitVarInsn(ASTORE, 0); Label l4 = new Label(); mv.visitLabel(l4); mv.visitLineNumber(34, l4); mv.visitTypeInsn(NEW, "java/lang/NoSuchMethodError"); mv.visitInsn(DUP); mv.visitVarInsn(ALOAD, 0); mv.visitMethodInsn(INVOKEVIRTUAL, "java/lang/NoSuchMethodException", "getMessage", "()Ljava/lang/String;", false); mv.visitMethodInsn(INVOKESPECIAL, "java/lang/NoSuchMethodError", "<init>", "(Ljava/lang/String;)V", false); mv.visitInsn(ATHROW); mv.visitLabel(l3); mv.visitLineNumber(36, l3); mv.visitFrame(Opcodes.F_SAME, 0, null, 0, null); mv.visitInsn(RETURN); mv.visitLocalVariable("e", "Ljava/lang/NoSuchMethodException;", null, l4, l3, 0); mv.visitMaxs(3, 1); mv.visitEnd(); } cw.visitEnd(); return cw.toByteArray(); } }
2 编写测试类
package com.mangoubiubiu.show.asm; import java.io.File; import java.io.FileOutputStream; public class TestProxy { public static void main(String[] args) throws Exception { byte[] dump = $Proxy0Dump.dump(); File file = new File(""); String filePath = file.getAbsolutePath()+"\\$Proxy0.class"; System.out.println(file.getAbsolutePath()); FileOutputStream outputStream = new FileOutputStream(new File(filePath)); outputStream.write(dump,0,dump.length); } }
查看源码 发现和我们自己写的代理类一样
// // Source code recreated from a .class file by IntelliJ IDEA // (powered by Fernflower decompiler) // package com.mangoubiubiu.show.asm; import java.lang.reflect.InvocationHandler; import java.lang.reflect.Method; import java.lang.reflect.Proxy; import org.springframework.cglib.proxy.UndeclaredThrowableException; public class $Proxy0 extends Proxy implements Foo { static Method foo; public $Proxy0(InvocationHandler h) { super(h); } public void foo() { try { this.h.invoke(this, foo, new Object[0]); } catch (Error | RuntimeException var2) { throw var2; } catch (Throwable var3) { throw new UndeclaredThrowableException(var3); } } static { try { foo = Foo.class.getMethod("foo"); } catch (NoSuchMethodException var1) { throw new NoSuchMethodError(var1.getMessage()); } } }
三、加载二进制字节码到内存中
package com.mangoubiubiu.show.asm; import java.io.File; import java.io.FileOutputStream; import java.lang.reflect.Constructor; import java.lang.reflect.InvocationHandler; import java.lang.reflect.Method; public class TestProxy { public static void main(String[] args) throws Exception { byte[] dump = $Proxy0Dump.dump(); // File file = new File(""); // String filePath = file.getAbsolutePath()+"\\$Proxy0.class"; // System.out.println(file.getAbsolutePath()); // FileOutputStream outputStream = new FileOutputStream(new File(filePath)); // outputStream.write(dump,0,dump.length); ClassLoader loader = new ClassLoader() { @Override protected Class<?> findClass(String name) throws ClassNotFoundException { return super.defineClass(name,dump,0,dump.length); } }; //拿到类对象 Class<?> proxyClass = loader.loadClass("com.mangoubiubiu.show.asm.$Proxy0"); Constructor<?> constructor = proxyClass.getConstructor(InvocationHandler.class); Foo fooProxy = (Foo) constructor.newInstance(new InvocationHandler() { @Override public Object invoke(Object proxy, Method method, Object[] args) throws Throwable { System.out.println("before"); System.out.println("调用目标"); return null; } }); fooProxy.foo(); } }
