CGLIB动态代理底层实现原理
一、前言
最近在探究Spring AOP的性能,发现最后是绕不开JDK动态代理和CGLIB动态代理这两个点。笔者心里大致有这么个概念:对于动态代理来说,CGLIB性能要好于JDK。也知道CGLIB是利用ASM技术基于继承子类实现动态代理,JDK是基于实现接口实现动态代理,但是对于底层实现还是比较模糊。今天就彻底整明白CGLIB动态代理的底层实现。
二、前置准备
(一)测试代码
CGLIB核心的几个概念:
- 被代理对象,本案例【Dog】
- 方法拦截器MethodInterceptor,本案例【CglibMethodInterceptor】
- Enhance代理对象生成工具,本案例【TestMain测试主类中创建】
CglibMethodInterceptor
后面也会将MethodInterceptor
说成Callback
,其实是一个东西,MethodInterceptor
是实现了Callback
接口的。/**
* 方法拦截器,不用依赖被代理业务类的引用
*/
public class CglibMethodInterceptor implements MethodInterceptor {/**
* 功能主要是在调用业务类方法之前 之后添加统计时间的方法逻辑.
* intercept 因为具有 MethodProxy methodProxy 参数的原因,不再需要代理类的引用对象了,直接通过 methodProxy 对象访问被代理对象的方法(这种方式更快)。
* 当然 也可以通过反射机制,通过 method 引用实例Object result = method.invoke(target, args);
形式反射调用被代理类方法,
* target 实例代表被代理类对象引用, 初始化 CglibMethodInterceptor 时候被赋值 。但是Cglib不推荐使用这种方式
*
* @param object代表Cglib 生成的动态代理类 对象本身
* @param method代理类中被拦截的接口方法 Method 实例
* @param args接口方法参数
* @param methodProxy 用于调用父类真正的业务类方法。可以直接调用被代理类接口方法
* @return 被代理类方法执行返回值
* @throws Throwable
*/
@Override
public Object intercept(Object object, Method method, Object[] args, MethodProxy methodProxy) throws Throwable {
System.out.println("before");
MonitorUtil.start();
Object result = methodProxy.invokeSuper(object, args);
//Object result = methodProxy.invoke(object, args);
System.out.println("after");
MonitorUtil.finish(method.getName());
return result;
}
}
2. 被代理类
public class Dog {public String call() {
System.out.println("wang wang wang");
return "Dog ..";
}
}
3. 切面方法
/**
* 方法用时监控类,作为一个切面 ,具有两个方法
*/
public class MonitorUtil {private static final ThreadLocal tl = new ThreadLocal<>();
public static void start() {
tl.set(System.currentTimeMillis());
}/**
* 结束时打印耗时
* @param methodName 监控方法名
*/
public static void finish(String methodName) {
long finishTime = System.currentTimeMillis();
System.out.println(methodName + "方法执行耗时" + (finishTime - tl.get()) + "ms");
}
}
4. 测试主类
public class TestMain {/**
* 用于生成 Cglib 动态代理类工具方法
* @param target 代表需要 被代理的 委托类的 Class 对象
* @return 代理类对象
*/
public static Object cglibProxyGenerator(Class target) {
// 创建加强器,用来创建动态代理类
Enhancer enhancer = new Enhancer();
// 为代理类指定需要代理的类,也即是父类
enhancer.setSuperclass(target);
// 设置方法拦截器回调引用,对于代理类上所有方法的调用,都会调用CallBack,而Callback则需要实现intercept() 方法进行拦截
enhancer.setCallback(new CglibMethodInterceptor());
// 创建cglib 代理类
return enhancer.create();
}public static void main(String[] args) throws ClassNotFoundException {
System.setProperty(DebuggingClassWriter.DEBUG_LOCATION_PROPERTY, "classFiles");
Dog poolDog = (Dog) cglibProxyGenerator(Dog.class);
poolDog.call();
}
}
(二)CGLIB生成的子类
【CGLIB动态代理底层实现原理】?
Dog$$EnhancerByCGLIB$$beb9d601
//
// Source code recreated from a .class file by IntelliJ IDEA
// (powered by FernFlower decompiler)
//package com.allen.testDynamicProxy.cglibProxy;
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;
// 实现net.sf.cglib.proxy.Factory的目的是提供一些创建代理对象实例的工厂方法,这些方法会比反射创建对象快【clazz.newInstance()】
public class Dog$$EnhancerByCGLIB$$beb9d601 extends Dog 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;
// Dog类call的Method对象
private static final Method CGLIB$call$0$Method;
// Dog类call方法的代理对象
private static final MethodProxy CGLIB$call$0$Proxy;
private static final Object[] CGLIB$emptyArgs;
// Object类equals方法的Method对象
private static final Method CGLIB$equals$1$Method;
private static final MethodProxy CGLIB$equals$1$Proxy;
private static final Method CGLIB$toString$2$Method;
private static final MethodProxy CGLIB$toString$2$Proxy;
private static final Method CGLIB$hashCode$3$Method;
private static final MethodProxy CGLIB$hashCode$3$Proxy;
private static final Method CGLIB$clone$4$Method;
private static final MethodProxy CGLIB$clone$4$Proxy;
/**
* CGLIB$call$0$Method和CGLIB$call$0$Proxy就是MethodInterceptor接口的入参
* MethodProxy 比 Method反射调用方法更快
*/
static void CGLIB$STATICHOOK1() {
CGLIB$THREAD_CALLBACKS = new ThreadLocal();
CGLIB$emptyArgs = new Object[0];
// 加载生成的增强类
Class var0 = Class.forName("com.allen.testDynamicProxy.cglibProxy.Dog$$EnhancerByCGLIB$$beb9d601");
Class var1;
// 通过反射获取Object类的Method对象
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$1$Method = var10000[0];
// 为 Method 创建对应的 MethodProxy 对象
CGLIB$equals$1$Proxy = MethodProxy.create(var1, var0, "(Ljava/lang/Object;
)Z", "equals", "CGLIB$equals$1");
CGLIB$toString$2$Method = var10000[1];
CGLIB$toString$2$Proxy = MethodProxy.create(var1, var0, "()Ljava/lang/String;
", "toString", "CGLIB$toString$2");
CGLIB$hashCode$3$Method = var10000[2];
CGLIB$hashCode$3$Proxy = MethodProxy.create(var1, var0, "()I", "hashCode", "CGLIB$hashCode$3");
CGLIB$clone$4$Method = var10000[3];
CGLIB$clone$4$Proxy = MethodProxy.create(var1, var0, "()Ljava/lang/Object;
", "clone", "CGLIB$clone$4");
// Dog类call方法Method对象
CGLIB$call$0$Method = ReflectUtils.findMethods(new String[]{"call", "()Ljava/lang/String;
"}, (var1 = Class.forName("com.allen.testDynamicProxy.cglibProxy.Dog")).getDeclaredMethods())[0];
CGLIB$call$0$Proxy = MethodProxy.create(var1, var0, "()Ljava/lang/String;
", "call", "CGLIB$call$0");
}final String CGLIB$call$0() {
return super.call();
}
// 重写 Dog类的call方法,添加CallBack回调【即执行MethodInterceptor的intercept方法,即我们自定义的CglibMethodInterceptor的intercept方法】
public final String call() {
// 这边获取MethodInterceptor为null
MethodInterceptor var10000 = this.CGLIB$CALLBACK_0;
if (var10000 == null) {
// 重新绑定MethodInterceptor
CGLIB$BIND_CALLBACKS(this);
// 这边还是null
var10000 = this.CGLIB$CALLBACK_0;
}return var10000 != null ? (String)var10000.intercept(this, CGLIB$call$0$Method, CGLIB$emptyArgs, CGLIB$call$0$Proxy) : super.call();
}final boolean CGLIB$equals$1(Object var1) {
return super.equals(var1);
}public final boolean equals(Object var1) {
MethodInterceptor var10000 = this.CGLIB$CALLBACK_0;
if (var10000 == null) {
CGLIB$BIND_CALLBACKS(this);
var10000 = this.CGLIB$CALLBACK_0;
}if (var10000 != null) {
Object var2 = var10000.intercept(this, CGLIB$equals$1$Method, new Object[]{var1}, CGLIB$equals$1$Proxy);
return var2 == null ? false : (Boolean)var2;
} else {
return super.equals(var1);
}
}final String CGLIB$toString$2() {
return super.toString();
}public final String toString() {
MethodInterceptor var10000 = this.CGLIB$CALLBACK_0;
if (var10000 == null) {
CGLIB$BIND_CALLBACKS(this);
var10000 = this.CGLIB$CALLBACK_0;
}return var10000 != null ? (String)var10000.intercept(this, CGLIB$toString$2$Method, CGLIB$emptyArgs, CGLIB$toString$2$Proxy) : super.toString();
}final int CGLIB$hashCode$3() {
return super.hashCode();
}public final int hashCode() {
MethodInterceptor var10000 = this.CGLIB$CALLBACK_0;
if (var10000 == null) {
CGLIB$BIND_CALLBACKS(this);
var10000 = this.CGLIB$CALLBACK_0;
}if (var10000 != null) {
Object var1 = var10000.intercept(this, CGLIB$hashCode$3$Method, CGLIB$emptyArgs, CGLIB$hashCode$3$Proxy);
return var1 == null ? 0 : ((Number)var1).intValue();
} else {
return super.hashCode();
}
}final Object CGLIB$clone$4() throws CloneNotSupportedException {
return super.clone();
}protected final Object clone() throws CloneNotSupportedException {
MethodInterceptor var10000 = this.CGLIB$CALLBACK_0;
if (var10000 == null) {
CGLIB$BIND_CALLBACKS(this);
var10000 = this.CGLIB$CALLBACK_0;
}return var10000 != null ? var10000.intercept(this, CGLIB$clone$4$Method, CGLIB$emptyArgs, CGLIB$clone$4$Proxy) : super.clone();
}public static MethodProxy CGLIB$findMethodProxy(Signature var0) {
String var10000 = var0.toString();
switch(var10000.hashCode()) {
case -508378822:
if (var10000.equals("clone()Ljava/lang/Object;
")) {
return CGLIB$clone$4$Proxy;
}
break;
case 371634473:
if (var10000.equals("call()Ljava/lang/String;
")) {
return CGLIB$call$0$Proxy;
}
break;
case 1826985398:
if (var10000.equals("equals(Ljava/lang/Object;
)Z")) {
return CGLIB$equals$1$Proxy;
}
break;
case 1913648695:
if (var10000.equals("toString()Ljava/lang/String;
")) {
return CGLIB$toString$2$Proxy;
}
break;
case 1984935277:
if (var10000.equals("hashCode()I")) {
return CGLIB$hashCode$3$Proxy;
}
}return null;
}// 实例化构造方法会绑定CallBacks
public Dog$$EnhancerByCGLIB$$beb9d601() {
CGLIB$BIND_CALLBACKS(this);
}// 设置CallBack到ThreadLocal
public static void CGLIB$SET_THREAD_CALLBACKS(Callback[] var0) {
CGLIB$THREAD_CALLBACKS.set(var0);
}public static void CGLIB$SET_STATIC_CALLBACKS(Callback[] var0) {
CGLIB$STATIC_CALLBACKS = var0;
}
/**
* 判断并绑定CallBack对象【就是MethodInterceptor对象,也即自定义的CglibMethodInterceptor】
*/
private static final void CGLIB$BIND_CALLBACKS(Object var0) {
Dog$$EnhancerByCGLIB$$beb9d601 var1 = (Dog$$EnhancerByCGLIB$$beb9d601)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$CALLBACK_0 = (MethodInterceptor)((Callback[])var10000)[0];
}}
/**
* 使用无参构造方法创建增强后的子类新实例
* @param callbacks 多个MethodInterceptor对象数组
* @return new instance of the same type
*/
public Object newInstance(Callback[] var1) {
CGLIB$SET_THREAD_CALLBACKS(var1);
Dog$$EnhancerByCGLIB$$beb9d601 var10000 = new Dog$$EnhancerByCGLIB$$beb9d601();
// 将ThreadLocal的 CallBacks 至空
CGLIB$SET_THREAD_CALLBACKS((Callback[])null);
return var10000;
}
/**
* 使用无参构造方法创建增强后的子类新实例
* 该对象只能指定一个Callback【MethodInterceptor】
* @param callback 自定义的MethodInterceptor对象
* @return new instance of the same type
*/
public Object newInstance(Callback var1) {
CGLIB$SET_THREAD_CALLBACKS(new Callback[]{var1});
Dog$$EnhancerByCGLIB$$beb9d601 var10000 = new Dog$$EnhancerByCGLIB$$beb9d601();
CGLIB$SET_THREAD_CALLBACKS((Callback[])null);
return var10000;
}
/** 本案例中,实例化增强子类的时候就是调用此方法
* @param types 构造方法参数类型
* @param args 构造方法参数
* @param callbacks 多个CallBack对象数组
* @return new instance of the same type
*/
public Object newInstance(Class[] var1, Object[] var2, Callback[] var3) {
CGLIB$SET_THREAD_CALLBACKS(var3);
Dog$$EnhancerByCGLIB$$beb9d601 var10000 = new Dog$$EnhancerByCGLIB$$beb9d601;
switch(var1.length) {
case 0:
var10000.();
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();
}
}
(三)CGLIB生成的FastClass-1【简称f1】
?
Dog$$FastClassByCGLIB$$7ac19ed7
//
// Source code recreated from a .class file by IntelliJ IDEA
// (powered by FernFlower decompiler)
//package com.allen.testDynamicProxy.cglibProxy;
import java.lang.reflect.InvocationTargetException;
import net.sf.cglib.core.Signature;
import net.sf.cglib.reflect.FastClass;
public class Dog$$FastClassByCGLIB$$7ac19ed7 extends FastClass {
public Dog$$FastClassByCGLIB$$7ac19ed7(Class var1) {
super(var1);
}public int getIndex(Signature var1) {
String var10000 = var1.toString();
switch(var10000.hashCode()) {
case 371634473:
if (var10000.equals("call()Ljava/lang/String;
")) {
return 0;
}
break;
case 1826985398:
if (var10000.equals("equals(Ljava/lang/Object;
)Z")) {
return 1;
}
break;
case 1913648695:
if (var10000.equals("toString()Ljava/lang/String;
")) {
return 2;
}
break;
case 1984935277:
if (var10000.equals("hashCode()I")) {
return 3;
}
}return -1;
}public int getIndex(String var1, Class[] var2) {
switch(var1.hashCode()) {
case -1776922004:
if (var1.equals("toString")) {
switch(var2.length) {
case 0:
return 2;
}
}
break;
case -1295482945:
if (var1.equals("equals")) {
switch(var2.length) {
case 1:
if (var2[0].getName().equals("java.lang.Object")) {
return 1;
}
}
}
break;
case 3045982:
if (var1.equals("call")) {
switch(var2.length) {
case 0:
return 0;
}
}
break;
case 147696667:
if (var1.equals("hashCode")) {
switch(var2.length) {
case 0:
return 3;
}
}
}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 {
Dog var10000 = (Dog)var2;
int var10001 = var1;
try {
switch(var10001) {
case 0:
return var10000.call();
case 1:
return new Boolean(var10000.equals(var3[0]));
case 2:
return var10000.toString();
case 3:
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 {
Dog var10000 = new Dog;
Dog var10001 = var10000;
int var10002 = var1;
try {
switch(var10002) {
case 0:
var10001.();
return var10000;
}
} catch (Throwable var3) {
throw new InvocationTargetException(var3);
}throw new IllegalArgumentException("Cannot find matching method/constructor");
}public int getMaxIndex() {
return 3;
}
}
(四)CGLIB生成的FastClass-2【简称f2】
?
Dog$$EnhancerByCGLIB$$beb9d601$$FastClassByCGLIB$$916924fc
//
// Source code recreated from a .class file by IntelliJ IDEA
// (powered by FernFlower decompiler)
//package com.allen.testDynamicProxy.cglibProxy;
import com.allen.testDynamicProxy.cglibProxy.Dog..EnhancerByCGLIB..beb9d601;
import java.lang.reflect.InvocationTargetException;
import net.sf.cglib.core.Signature;
import net.sf.cglib.proxy.Callback;
import net.sf.cglib.reflect.FastClass;
public class Dog$$EnhancerByCGLIB$$beb9d601$$FastClassByCGLIB$$916924fc extends FastClass {
public Dog$$EnhancerByCGLIB$$beb9d601$$FastClassByCGLIB$$916924fc(Class var1) {
super(var1);
}public int getIndex(Signature var1) {
String var10000 = var1.toString();
switch(var10000.hashCode()) {
case -2055565910:
if (var10000.equals("CGLIB$SET_THREAD_CALLBACKS([Lnet/sf/cglib/proxy/Callback;
)V")) {
return 1;
}
break;
case -1882565338:
if (var10000.equals("CGLIB$equals$1(Ljava/lang/Object;
)Z")) {
return 4;
}
break;
case -1457535688:
if (var10000.equals("CGLIB$STATICHOOK1()V")) {
return 8;
}
break;
case -1411842725:
if (var10000.equals("CGLIB$hashCode$3()I")) {
return 6;
}
break;
case -1212270792:
if (var10000.equals("CGLIB$call$0()Ljava/lang/String;
")) {
return 5;
}
break;
case -894172689:
if (var10000.equals("newInstance(Lnet/sf/cglib/proxy/Callback;
)Ljava/lang/Object;
")) {
return 20;
}
break;
case -623122092:
if (var10000.equals("CGLIB$findMethodProxy(Lnet/sf/cglib/core/Signature;
)Lnet/sf/cglib/proxy/MethodProxy;
")) {
return 13;
}
break;
case -508378822:
if (var10000.equals("clone()Ljava/lang/Object;
")) {
return 17;
}
break;
case -419626537:
if (var10000.equals("setCallbacks([Lnet/sf/cglib/proxy/Callback;
)V")) {
return 9;
}
break;
case 371634473:
if (var10000.equals("call()Ljava/lang/String;
")) {
return 2;
}
break;
case 560567118:
if (var10000.equals("setCallback(ILnet/sf/cglib/proxy/Callback;
)V")) {
return 12;
}
break;
case 811063227:
if (var10000.equals("newInstance([Ljava/lang/Class;
[Ljava/lang/Object;
[Lnet/sf/cglib/proxy/Callback;
)Ljava/lang/Object;
")) {
return 19;
}
break;
case 973717575:
if (var10000.equals("getCallbacks()[Lnet/sf/cglib/proxy/Callback;
")) {
return 11;
}
break;
case 1221173700:
if (var10000.equals("newInstance([Lnet/sf/cglib/proxy/Callback;
)Ljava/lang/Object;
")) {
return 18;
}
break;
case 1230699260:
if (var10000.equals("getCallback(I)Lnet/sf/cglib/proxy/Callback;
")) {
return 10;
}
break;
case 1306468936:
if (var10000.equals("CGLIB$toString$2()Ljava/lang/String;
")) {
return 3;
}
break;
case 1584330438:
if (var10000.equals("CGLIB$SET_STATIC_CALLBACKS([Lnet/sf/cglib/proxy/Callback;
)V")) {
return 0;
}
break;
case 1800494055:
if (var10000.equals("CGLIB$clone$4()Ljava/lang/Object;
")) {
return 7;
}
break;
case 1826985398:
if (var10000.equals("equals(Ljava/lang/Object;
)Z")) {
return 14;
}
break;
case 1913648695:
if (var10000.equals("toString()Ljava/lang/String;
")) {
return 15;
}
break;
case 1984935277:
if (var10000.equals("hashCode()I")) {
return 16;
}
}return -1;
}public int getIndex(String var1, Class[] var2) {
switch(var1.hashCode()) {
case -1776922004:
if (var1.equals("toString")) {
switch(var2.length) {
case 0:
return 15;
}
}
break;
case -1295482945:
if (var1.equals("equals")) {
switch(var2.length) {
case 1:
if (var2[0].getName().equals("java.lang.Object")) {
return 14;
}
}
}
break;
case -1053468136:
if (var1.equals("getCallbacks")) {
switch(var2.length) {
case 0:
return 11;
}
}
break;
case -124978609:
if (var1.equals("CGLIB$equals$1")) {
switch(var2.length) {
case 1:
if (var2[0].getName().equals("java.lang.Object")) {
return 4;
}
}
}
break;
case -60403779:
if (var1.equals("CGLIB$SET_STATIC_CALLBACKS")) {
switch(var2.length) {
case 1:
if (var2[0].getName().equals("[Lnet.sf.cglib.proxy.Callback;
")) {
return 0;
}
}
}
break;
case -29025555:
if (var1.equals("CGLIB$hashCode$3")) {
switch(var2.length) {
case 0:
return 6;
}
}
break;
case 3045982:
if (var1.equals("call")) {
switch(var2.length) {
case 0:
return 2;
}
}
break;
case 52714989:
if (var1.equals("CGLIB$call$0")) {
switch(var2.length) {
case 0:
return 5;
}
}
break;
case 85179481:
if (var1.equals("CGLIB$SET_THREAD_CALLBACKS")) {
switch(var2.length) {
case 1:
if (var2[0].getName().equals("[Lnet.sf.cglib.proxy.Callback;
")) {
return 1;
}
}
}
break;
case 94756189:
if (var1.equals("clone")) {
switch(var2.length) {
case 0:
return 17;
}
}
break;
case 147696667:
if (var1.equals("hashCode")) {
switch(var2.length) {
case 0:
return 16;
}
}
break;
case 161998109:
if (var1.equals("CGLIB$STATICHOOK1")) {
switch(var2.length) {
case 0:
return 8;
}
}
break;
case 495524492:
if (var1.equals("setCallbacks")) {
switch(var2.length) {
case 1:
if (var2[0].getName().equals("[Lnet.sf.cglib.proxy.Callback;
")) {
return 9;
}
}
}
break;
case 1154623345:
if (var1.equals("CGLIB$findMethodProxy")) {
switch(var2.length) {
case 1:
if (var2[0].getName().equals("net.sf.cglib.core.Signature")) {
return 13;
}
}
}
break;
case 1543336189:
if (var1.equals("CGLIB$toString$2")) {
switch(var2.length) {
case 0:
return 3;
}
}
break;
case 1811874389:
if (var1.equals("newInstance")) {
switch(var2.length) {
case 1:
String var10001 = var2[0].getName();
switch(var10001.hashCode()) {
case -845341380:
if (var10001.equals("net.sf.cglib.proxy.Callback")) {
return 20;
}
break;
case 1730110032:
if (var10001.equals("[Lnet.sf.cglib.proxy.Callback;
")) {
return 18;
}
}
case 2:
default:
break;
case 3:
if (var2[0].getName().equals("[Ljava.lang.Class;
") && var2[1].getName().equals("[Ljava.lang.Object;
") && var2[2].getName().equals("[Lnet.sf.cglib.proxy.Callback;
")) {
return 19;
}
}
}
break;
case 1817099975:
if (var1.equals("setCallback")) {
switch(var2.length) {
case 2:
if (var2[0].getName().equals("int") && var2[1].getName().equals("net.sf.cglib.proxy.Callback")) {
return 12;
}
}
}
break;
case 1905679803:
if (var1.equals("getCallback")) {
switch(var2.length) {
case 1:
if (var2[0].getName().equals("int")) {
return 10;
}
}
}
break;
case 1951977610:
if (var1.equals("CGLIB$clone$4")) {
switch(var2.length) {
case 0:
return 7;
}
}
}return -1;
}public int getIndex(Class[] var1) {
switch(var1.length) {
case 0:
return 0;
default:
return -1;
}
}public Object invoke(int var1, Object var2, Object[] var3) throws InvocationTargetException {
beb9d601 var10000 = (beb9d601)var2;
int var10001 = var1;
try {
switch(var10001) {
case 0:
beb9d601.CGLIB$SET_STATIC_CALLBACKS((Callback[])var3[0]);
return null;
case 1:
beb9d601.CGLIB$SET_THREAD_CALLBACKS((Callback[])var3[0]);
return null;
case 2:
return var10000.call();
case 3:
return var10000.CGLIB$toString$2();
case 4:
return new Boolean(var10000.CGLIB$equals$1(var3[0]));
case 5:
return var10000.CGLIB$call$0();
case 6:
return new Integer(var10000.CGLIB$hashCode$3());
case 7:
return var10000.CGLIB$clone$4();
case 8:
beb9d601.CGLIB$STATICHOOK1();
return null;
case 9:
var10000.setCallbacks((Callback[])var3[0]);
return null;
case 10:
return var10000.getCallback(((Number)var3[0]).intValue());
case 11:
return var10000.getCallbacks();
case 12:
var10000.setCallback(((Number)var3[0]).intValue(), (Callback)var3[1]);
return null;
case 13:
return beb9d601.CGLIB$findMethodProxy((Signature)var3[0]);
case 14:
return new Boolean(var10000.equals(var3[0]));
case 15:
return var10000.toString();
case 16:
return new Integer(var10000.hashCode());
case 17:
return var10000.clone();
case 18:
return var10000.newInstance((Callback[])var3[0]);
case 19:
return var10000.newInstance((Class[])var3[0], (Object[])var3[1], (Callback[])var3[2]);
case 20:
return var10000.newInstance((Callback)var3[0]);
}
} catch (Throwable var4) {
throw new InvocationTargetException(var4);
}throw new IllegalArgumentException("Cannot find matching method/constructor");
}public Object newInstance(int var1, Object[] var2) throws InvocationTargetException {
beb9d601 var10000 = new beb9d601;
beb9d601 var10001 = var10000;
int var10002 = var1;
try {
switch(var10002) {
case 0:
var10001.();
return var10000;
}
} catch (Throwable var3) {
throw new InvocationTargetException(var3);
}throw new IllegalArgumentException("Cannot find matching method/constructor");
}public int getMaxIndex() {
return 20;
}
}
三、CGLIB代理类创建流程 ? 代理类的创建主要是在enhancer.create()方法调用后进行的,大致流程如下:
文章图片
(一)代理类的创建
? 首先看下在实例化代理类期间绑定
Callback
的过程「即自定义的MethodInterceptor
」,核心源码【net.sf.cglib.proxy.Enhancer.EnhancerFactoryData#newInstance】:文章图片
注意这边的
setThreadCallbacks
是个final类型的变量,会在EnhancerFactoryData
的构造方法中赋值为代理类Dog$$EnhancerByCGLIB$$beb9d601
的SET_THREAD_CALLBACKS
方法对象,对应的SET_THREAD_CALLBACKS
源码如下:// 设置CallBack到ThreadLocal
public static void CGLIB$SET_THREAD_CALLBACKS(Callback[] var0) {
// CGLIB$THREAD_CALLBACKS是个final static变量,在代理类的静态代码块中赋值为ThreadLocal()
// 代理类的静态代码块下面会讲到
CGLIB$THREAD_CALLBACKS.set(var0);
}
? 最后通过反射实例化代理类
Dog$$EnhancerByCGLIB$$beb9d601
的时候,会执行代理对象的静态方法块,期间会给每个被代理类Dog
的成员方法创建一个MethdProxy
代理方法对象。(二)创建MethodProxy
?
MethodProxy
封装了原始Dog类的方法签名【sig1】,对应代理类方法的签名【sig2】以及代理类的一些创建信息【原始类和代理类的名称、类生成策略等等】。对应的代理类的静态代码块内容如下:// CGLIB$call$0$Method和CGLIB$call$0$Proxy就是MethodInterceptor接口的入参
static void CGLIB$STATICHOOK1() {
CGLIB$THREAD_CALLBACKS = new ThreadLocal();
CGLIB$emptyArgs = new Object[0];
// 加载生成的增强类
Class var0 = Class.forName("com.allen.testDynamicProxy.cglibProxy.Dog$$EnhancerByCGLIB$$beb9d601");
Class var1;
// 通过反射获取Object类的Method对象
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$1$Method = var10000[0];
// 为 Method 创建对应的 MethodProxy 对象
CGLIB$equals$1$Proxy = MethodProxy.create(var1, var0, "(Ljava/lang/Object;
)Z", "equals", "CGLIB$equals$1");
CGLIB$toString$2$Method = var10000[1];
CGLIB$toString$2$Proxy = MethodProxy.create(var1, var0, "()Ljava/lang/String;
", "toString", "CGLIB$toString$2");
CGLIB$hashCode$3$Method = var10000[2];
CGLIB$hashCode$3$Proxy = MethodProxy.create(var1, var0, "()I", "hashCode", "CGLIB$hashCode$3");
CGLIB$clone$4$Method = var10000[3];
CGLIB$clone$4$Proxy = MethodProxy.create(var1, var0, "()Ljava/lang/Object;
", "clone", "CGLIB$clone$4");
// Dog类call方法Method对象
CGLIB$call$0$Method = ReflectUtils.findMethods(new String[]{"call", "()Ljava/lang/String;
"}, (var1 = Class.forName("com.allen.testDynamicProxy.cglibProxy.Dog")).getDeclaredMethods())[0];
// var1: 被代理类var0:代理类
CGLIB$call$0$Proxy = MethodProxy.create(var1, var0, "()Ljava/lang/String;
", "call", "CGLIB$call$0");
}
? 对应
MethodProxy.create()
【net.sf.cglib.proxy.MethodProxy#creat()】方法:/**
* For internal use by {@link Enhancer} only;
see the {@link net.sf.cglib.reflect.FastMethod} class
* for similar functionality.
* @param c1 被代理类
* @param c2 代理类
* @param desc 方法描述【"()Ljava/lang/String;
"】
* @param name1 方法1名称【"call"】
* @param name2 方法2名称【"CGLIB$call$0"】
*/
public static MethodProxy create(Class c1, Class c2, String desc, String name1, String name2) {
MethodProxy proxy = new MethodProxy();
// 构建方法签名
proxy.sig1 = new Signature(name1, desc);
proxy.sig2 = new Signature(name2, desc);
proxy.createInfo = new CreateInfo(c1, c2);
return proxy;
}
关于方法签名的debug信息【后面会用这个方法签名在Fastclass中查询对应的index索引】:
文章图片
(三)创建CreateInfo
?
CreateInfo
是MethodProxy
的一个内部类,主要保存代理类的一些创建信息。private static class CreateInfo
{
// 对应Dog原始类
Class c1;
// 代理类Dog$$EnhancerByCGLIB$$beb9d601
Class c2;
// 代理类命名策略
NamingPolicy namingPolicy;
// 代理类生成策略
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();
}
}
}
四、CGLIB动态代理调用流程 ? 当执行目标方法时,代理对象调用流程如下:
文章图片
相信看完上面的流程图,基本就对CGLIB的底层实现有了大致的概念。当然下面我还会进行详细分析。
(一)重写父类方法
? 基于一开始的demo,笔者从调用目标方法一步步分析。??
main
方法调用poolDog.call();
时,实际上执行的是代理对象的call()
方法,代理对象的生成已经在上一节分析过了。那我们直接看代理对象的call()
方法,源码如下:/**
* 重写 Dog类的call方法,添加CallBack回调
* 【即执行MethodInterceptor的intercept方法,即我们自定义的CglibMethodInterceptor的intercept方法】
*/
public final String call() {
// 从成员属性CGLIB$CALLBACK_0获取MethodInterceptor
// 第一次调用是null,进入下面的if逻辑
MethodInterceptor var10000 = this.CGLIB$CALLBACK_0;
if (var10000 == null) {
// 重新绑定MethodInterceptor,并赋值给成员属性CGLIB$CALLBACK_0
CGLIB$BIND_CALLBACKS(this);
var10000 = this.CGLIB$CALLBACK_0;
}
// @param this 代理对象本身
// @param CGLIB$call$0$Method Dog类call方法Method对象【静态代码块已赋值】
// @param CGLIB$emptyArgs Dog类call方法参数【我这边是void,所以没有】
// @param CGLIB$call$0$Proxy Dog类call方法的代理方法对象【静态代码块已赋值】
return var10000 != null ? (String)var10000.intercept(this, CGLIB$call$0$Method, CGLIB$emptyArgs, CGLIB$call$0$Proxy) : super.call();
}/**
* 判断并绑定CallBack对象【就是MethodInterceptor对象,也即自定义的CglibMethodInterceptor】
*/
private static final void CGLIB$BIND_CALLBACKS(Object var0) {
// var0即代理类当前对象,将其对象的引用指向var1
Dog$$EnhancerByCGLIB$$beb9d601 var1 = (Dog$$EnhancerByCGLIB$$beb9d601)var0;
// 这边判断是true,创建代理类的时候通过反射已将对应的Callback设置到ThreadLocal
if (!var1.CGLIB$BOUND) {
var1.CGLIB$BOUND = true;
// 将ThreadLocal中的Callback赋值给var10000
Object var10000 = CGLIB$THREAD_CALLBACKS.get();
if (var10000 == null) {
var10000 = CGLIB$STATIC_CALLBACKS;
if (var10000 == null) {
return;
}
}
// 将Callback赋值给成员属性CGLIB$CALLBACK_0
var1.CGLIB$CALLBACK_0 = (MethodInterceptor)((Callback[])var10000)[0];
}}
当调用代理对象重写过的
call()
方法时,会执行对应的方法拦截器,即我们自定义的MethodInterceptor
中intercept
方法的逻辑【本案例中对应自定义拦截器类CglibMethodInterceptor
】,对应intercept
方法的传参和含义在上面的代码注释中已说明。(二)原始父类方法的匹配调用
? 接下来,在
MethodInterceptor
的intercept
方法中调用的methodProxy.invokeSuper(object, args);
时,最终就会执行父类Dog
的call()
方法。具体怎么调用执行的,先看MethodProxy.invokeSuper(object, args);
的执行逻辑,源码如下:/**
* 调用CGLIB增强的父类目标方法
* @param obj the enhanced object, must be the object passed as the first
* argument to the MethodInterceptor
* @param args the arguments passed to the intercepted method;
you may substitute a different
* argument array as long as the types are compatible
* @see MethodInterceptor#intercept
* @throws Throwable the bare exceptions thrown by the called method are passed through
* without wrapping in an InvocationTargetException
*/
public Object invokeSuper(Object obj, Object[] args) throws Throwable {
try {
// 初始化辅助数据
init();
FastClassInfo fci = fastClassInfo;
return fci.f2.invoke(fci.i2, obj, args);
} catch (InvocationTargetException e) {
throw e.getTargetException();
}
}
1. init()方法 ? 在上面的流程图中我们也大致能看到init()方法干了些什么事。主要是在处理
FastClass
,FastClass
是什么?简单理解,
FastClass
是代理对象方法 到 被代理对象方法的映射【对应FastClass的源码已在前置准备中贴出】。1)先看下
init()
方法源码:
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)
{
// 获取代理类的创建信息【上面有提过】
CreateInfo ci = createInfo;
// 新建FastClassInfo对象
FastClassInfo fci = new FastClassInfo();
// 生成FastClass f1,并赋值给FastClassInfo的成员属性
fci.f1 = helper(ci, ci.c1);
fci.f2 = helper(ci, ci.c2);
// 根据方法签名,获取代理类中对应call方法在f1中的索引
fci.i1 = fci.f1.getIndex(sig1);
// 根据方法签名,获取代理类中对应call方法在f2中的索引
fci.i2 = fci.f2.getIndex(sig2);
fastClassInfo = fci;
createInfo = null;
}
}
}
}/*
* FastClassInfo也是MethodProxy的一个内部类
*/
private static class FastClassInfo
{
// 对应前置准备中的f1
FastClass f1;
// 对应前置准备中的f2
FastClass f2;
int i1;
int i2;
}
init()
方法其实就是创建了两个FastClass
,然后建立FastClass 到 代理对象 关于 目标方法 的 索引。2)fci.f2.invoke(fci.i2, obj, args); ? invoke的传参说明:
- i2: 获取代理类中对应call方法在f2中的索引
- obj: 代理对象本身
- args: 目标方法的传参
文章图片
接下就会调用代理对象对应的方法:
文章图片
看到这是不是有点明了了,最后这不就是执行了我们父类
Dog
的call()
方法吗。那整个核心的实现逻辑和调用流程大致就是这样的。(三)CGLIB死循环了
? 上面一小节关于目标方法的调用是通过
net.sf.cglib.proxy.MethodProxy#invokeSuper
完成的,CGLIB中还有一个net.sf.cglib.proxy.MethodProxy#invoke
。在自定义的MethodProxy中,将invokeSuper改成invoke,运行一下,报错了,无限递归导致栈溢出。? 在解释原因之前,有没有发现一个问题,前面不是生成了两个FastClass吗,截止现在我们只用到了一个。你的猜想正确,
invoke
方法就是用的f1中的索引。? 死循话的问题我这边不详细解释,以一张图说明【其中的元素信息完全基于前置准备的代码,同学们可以自己本地写个demo尝试】:
文章图片
五、性能:CGLIB vs JDK ? 其实说实话,工作中并没有说单单就因为将动态代理模式从JDK换成CGLIB,性能就有明显提升的情况,大部分情况性能相差不多。但是明显CGLIB适用性更广,SpringBoot将AOP的动态代理默认设置成了CGLIB,我想估计也不是性能使然。
? 理论上说,针对JDK动态代理的
Method.invoke()
和CGLIB的MethodProxy.invokeSuper()
这两个invoke来说,CGLIB感觉更加优雅些,但是刚开始第一次调用CGLIB是比较慢的,还记得上面提到的init()
吗。非要钻牛角尖说CGLIB性能更好的话,可能是MethodAccessor
的锅。关于JDK代理的细节,可以参考我之前的文章:https://www.heapdump.cn/artic...Method.invoke(target,params)
,实际是MethodAccessor
实例真正完成反射调用。Java 版本的MethodAccessorImpl
调用效率比Native
版本要快 20 倍以上,但是 Java 版本加载时要比 Native 多消耗 3-4 倍资源,所以默认会调用 Native 版本,如果调用次数超过 15 次以后,就会选择运行效率更高的 Java 版本。但是??:存放method的reflectionData
是SoftReference
的,即在某些内存比较苛刻的情况下是可能被回收的【通过-XX:SoftRefLRUPolicyMSPerMB
这个参数来控制回收的时机】。一旦回收,就需要调用getDeclaredMethods0
进行遍历查找,重新缓存。
? over,希望这篇吐血肝货,可以帮你理解CGLIB底层实现原理。继续肝·····
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