CGLIB动态代理--实例/原理

Myth丶恋晨 2023-10-01 18:21 53阅读 0赞

原文网址：[CGLIB动态代理--实例/原理\_IT利刃出鞘的博客-CSDN博客][CGLIB_--_IT_-CSDN]

## 简介 ##

**说明**

本文用示例介绍CGLIB动态代理的用法**。**

**原理**

CGLIB是针对类来实现代理的。

原理是对指定的目标类生成一个子类，并覆盖其中方法实现增强，但因为采用的是继承，所以不能对final修饰的类进行代理。

**限制**

JDK的动态代理机制只能代理实现了接口的类，而不能实现接口的类就不能实现JDK的动态代理。

## 实例：统计执行时间 ##

**依赖**

<dependency>
                <groupId>cglib</groupId>
                <artifactId>cglib</artifactId>
                <version>3.2.5</version>
            </dependency>

较低版本的cglib可能需要此依赖：

**代码**

package org.example.a;
    
    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;
    
    //被代理类
    class ExecutionTimeReality {
        //这里打印出任务名，并休眠500ms模拟任务执行了很长时间
        public void dealTask(String taskName) {
            System.out.println("Task is running: " + taskName);
            try {
                Thread.sleep(500);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    
        //这里打印出任务名，并休眠500ms模拟任务执行了很长时间
        public void sayHello(String name) {
            System.out.println("hello: " + name);
        }
    }
    
    //代理类
    class ExecutionTimeProxy implements MethodInterceptor {
    
        @Override
        public Object intercept(Object obj, Method method, Object[] args,
                                MethodProxy proxy) throws Throwable {
            long startTime = System.currentTimeMillis();
            proxy.invokeSuper(obj, args);
            long endTime = System.currentTimeMillis();
            System.out.println("Elapsed time: " + (endTime - startTime) + " ms");
    
            return null;
        }
    }
    
    //工厂方法获得代理对象
    class DynamicProxyFactory {
        public static Object getInstance() {
            Object target = new ExecutionTimeReality();
            ExecutionTimeProxy proxySubject = new ExecutionTimeProxy();
            Enhancer enhancer = new Enhancer();
            enhancer.setSuperclass(target.getClass());
            enhancer.setCallback(proxySubject);
            return enhancer.create();
        }
    }
    
    public class Demo {
        public static void main(String[] args) {
            System.setProperty(DebuggingClassWriter.DEBUG_LOCATION_PROPERTY, "E:\\CglibProxyClass");
            ExecutionTimeReality subject = (ExecutionTimeReality) DynamicProxyFactory.getInstance();
            subject.dealTask("TestTask");
        }
    }

执行结果

Task is running: TestTask
    Elapsed time: 524 ms

## 原理 ##

### **流程概述** ###

本部分应该放到最后作为结论。但本处为了快速体会总体流程，放到最前边。

实例化Enhancer并设置要代理的类及回调（MethodInterceptor接口的实现类对象）  
创建代理类（继承自被代理类）  
被代理类的dealTask方法（已被代理类覆写，实际调用代理类的dealTask方法）  
回调的intercept方法（ExecutionTimeProxy.intercept） //回调是在第一步中传进来的  
proxy.invokeSuper(obj, args); //调用父类 （invokeSuper方法是MethodProxy声明的）  
this.init(); //若不存在FastClass，则生成  
this.fastClassInfo.f2.invoke(fci.i2, obj, args);  
FastClass的invoke方法  
将第一个参数与数字比对，执行对应的方法

### 手动生成代理类源码 ###

分析源码，就要看生成的代理类源码，生成方法：在main最开始写此代码：

System.setProperty(DebuggingClassWriter.DEBUG_LOCATION_PROPERTY, "E:\\CglibProxyClass");

运行后，会生成E:/CglibProxyClass文件夹，其结构如下

E:\CGLIBPROXYCLASS
    ├─net
    │  └─sf
    │      └─cglib
    │          ├─core
    │          │      MethodWrapper$MethodWrapperKey$$KeyFactoryByCGLIB$$d45e49f7.class
    │          │
    │          └─proxy
    │                  Enhancer$EnhancerKey$$KeyFactoryByCGLIB$$7fb24d72.class
    │
    └─org
        └─example
            └─a
                    ExecutionTimeReality$$EnhancerByCGLIB$$5a92c386$$FastClassByCGLIB$$bebee033.class
                    ExecutionTimeReality$$EnhancerByCGLIB$$5a92c386.class
                    ExecutionTimeReality$$FastClassByCGLIB$$81389d66.class

分析如下：

1.快速类

ExecutionTimeReality$$EnhancerByCGLIB$$5a92c386$$FastClassByCGLIB$$bebee033.class

快速类1。此类暂不讨论。代码中没分析到。

2.代理类

ExecutionTimeReality$$EnhancerByCGLIB$$5a92c386.class

代理类，会调用到ExecutionTimeReality$EnhancerByCGLIB$5a92c386.class

3.另一个快速类

ExecutionTimeReality$$FastClassByCGLIB$$81389d66.class

快速类2。被代理类调用到。FastClass并不是跟代理类一块生成的，而是在第一次执行MethodProxy invoke/invokeSuper时生成的并放在了缓存中。

**详细分析**

ExecutionTimeReality$$EnhancerByCGLIB$$5a92c386.class

此类代码如下：

//
    // Source code recreated from a .class file by IntelliJ IDEA
    // (powered by Fernflower decompiler)
    //
    
    package org.example.a;
    
    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 ExecutionTimeReality$$EnhancerByCGLIB$$5a92c386 extends ExecutionTimeReality 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$dealTask$0$Method;
        private static final MethodProxy CGLIB$dealTask$0$Proxy;
        private static final Object[] CGLIB$emptyArgs;
        private static final Method CGLIB$sayHello$1$Method;
        private static final MethodProxy CGLIB$sayHello$1$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("org.example.a.ExecutionTimeReality$$EnhancerByCGLIB$$5a92c386");
            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$5");
            var10000 = ReflectUtils.findMethods(new String[]{"dealTask", "(Ljava/lang/String;)V", "sayHello", "(Ljava/lang/String;)V"}, (var1 = Class.forName("org.example.a.ExecutionTimeReality")).getDeclaredMethods());
            CGLIB$dealTask$0$Method = var10000[0];
            CGLIB$dealTask$0$Proxy = MethodProxy.create(var1, var0, "(Ljava/lang/String;)V", "dealTask", "CGLIB$dealTask$0");
            CGLIB$sayHello$1$Method = var10000[1];
            CGLIB$sayHello$1$Proxy = MethodProxy.create(var1, var0, "(Ljava/lang/String;)V", "sayHello", "CGLIB$sayHello$1");
        }
    
        final void CGLIB$dealTask$0(String var1) {
            super.dealTask(var1);
        }
    
        public final void dealTask(String var1) {
            MethodInterceptor var10000 = this.CGLIB$CALLBACK_0;
            if (var10000 == null) {
                CGLIB$BIND_CALLBACKS(this);
                var10000 = this.CGLIB$CALLBACK_0;
            }
    
            if (var10000 != null) {
                var10000.intercept(this, CGLIB$dealTask$0$Method, new Object[]{var1}, CGLIB$dealTask$0$Proxy);
            } else {
                super.dealTask(var1);
            }
        }
    
        final void CGLIB$sayHello$1(String var1) {
            super.sayHello(var1);
        }
    
        public final void sayHello(String var1) {
            MethodInterceptor var10000 = this.CGLIB$CALLBACK_0;
            if (var10000 == null) {
                CGLIB$BIND_CALLBACKS(this);
                var10000 = this.CGLIB$CALLBACK_0;
            }
    
            if (var10000 != null) {
                var10000.intercept(this, CGLIB$sayHello$1$Method, new Object[]{var1}, CGLIB$sayHello$1$Proxy);
            } else {
                super.sayHello(var1);
            }
        }
    
        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$findMethodProxy(Signature var0) {
            String var10000 = var0.toString();
            switch(var10000.hashCode()) {
            case -1165719922:
                if (var10000.equals("dealTask(Ljava/lang/String;)V")) {
                    return CGLIB$dealTask$0$Proxy;
                }
                break;
            case -508378822:
                if (var10000.equals("clone()Ljava/lang/Object;")) {
                    return CGLIB$clone$5$Proxy;
                }
                break;
            case 771401912:
                if (var10000.equals("sayHello(Ljava/lang/String;)V")) {
                    return CGLIB$sayHello$1$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 ExecutionTimeReality$$EnhancerByCGLIB$$5a92c386() {
            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) {
            ExecutionTimeReality$$EnhancerByCGLIB$$5a92c386 var1 = (ExecutionTimeReality$$EnhancerByCGLIB$$5a92c386)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);
            ExecutionTimeReality$$EnhancerByCGLIB$$5a92c386 var10000 = new ExecutionTimeReality$$EnhancerByCGLIB$$5a92c386();
            CGLIB$SET_THREAD_CALLBACKS((Callback[])null);
            return var10000;
        }
    
        public Object newInstance(Callback var1) {
            CGLIB$SET_THREAD_CALLBACKS(new Callback[]{var1});
            ExecutionTimeReality$$EnhancerByCGLIB$$5a92c386 var10000 = new ExecutionTimeReality$$EnhancerByCGLIB$$5a92c386();
            CGLIB$SET_THREAD_CALLBACKS((Callback[])null);
            return var10000;
        }
    
        public Object newInstance(Class[] var1, Object[] var2, Callback[] var3) {
            CGLIB$SET_THREAD_CALLBACKS(var3);
            ExecutionTimeReality$$EnhancerByCGLIB$$5a92c386 var10000 = new ExecutionTimeReality$$EnhancerByCGLIB$$5a92c386;
            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();
        }
    }

通过代理类的源码可以看到，代理类会获得所有在父类继承来的方法，并且会有MethodProxy与之对应，比如：

private static final Method CGLIB$dealTask$0$Method;
    private static final MethodProxy CGLIB$dealTask$0$Proxy;
    private static final Method CGLIB$sayHello$1$Method;
    private static final MethodProxy CGLIB$sayHello$1$Proxy;

另外，从代理类的类型来看，它直接继承要代理的类，所以可以代理的没有接口的类。其实，它跟接口没关系了，有接口也不会用到。

public class ExecutionTimeReality$$EnhancerByCGLIB$$5a92c386 extends ExecutionTimeReality implements Factory

**方法的调用**

final void CGLIB$dealTask$0(String var1) {
        super.dealTask(var1);
    }
    
    public final void dealTask(String var1) {
        MethodInterceptor var10000 = this.CGLIB$CALLBACK_0;
        if (var10000 == null) {
            CGLIB$BIND_CALLBACKS(this);
            var10000 = this.CGLIB$CALLBACK_0;
        }
    
        if (var10000 != null) {
            var10000.intercept(this, CGLIB$dealTask$0$Method, new Object[]{var1}, CGLIB$dealTask$0$Proxy);
        } else {
            super.dealTask(var1);
        }
    }

### FastClass机制 ###

Cglib动态代理执行代理方法效率之所以比JDK的高是因为Cglib采用了FastClass机制，它的原理简单来说就是：为代理类和被代理类各生成一个Class，这个Class会为代理类或被代理类的方法分配一个index(int类型)。这个index当做一个入参，FastClass就可以直接定位要调用的方法直接进行调用，这样省去了反射调用，所以调用效率比JDK动态代理通过反射调用高。

ExecutionTimeReality$FastClassByCGLIB$81389d66

//
    // Source code recreated from a .class file by IntelliJ IDEA
    // (powered by Fernflower decompiler)
    //
    
    package org.example.a;
    
    import java.lang.reflect.InvocationTargetException;
    import net.sf.cglib.core.Signature;
    import net.sf.cglib.reflect.FastClass;
    
    public class ExecutionTimeReality$$FastClassByCGLIB$$81389d66 extends FastClass {
        public ExecutionTimeReality$$FastClassByCGLIB$$81389d66(Class var1) {
            super(var1);
        }
    
        public int getIndex(Signature var1) {
            String var10000 = var1.toString();
            switch(var10000.hashCode()) {
            case -1165719922:
                if (var10000.equals("dealTask(Ljava/lang/String;)V")) {
                    return 0;
                }
                break;
            case 771401912:
                if (var10000.equals("sayHello(Ljava/lang/String;)V")) {
                    return 1;
                }
                break;
            case 1826985398:
                if (var10000.equals("equals(Ljava/lang/Object;)Z")) {
                    return 2;
                }
                break;
            case 1913648695:
                if (var10000.equals("toString()Ljava/lang/String;")) {
                    return 3;
                }
                break;
            case 1984935277:
                if (var10000.equals("hashCode()I")) {
                    return 4;
                }
            }
    
            return -1;
        }
    
        public int getIndex(String var1, Class[] var2) {
            switch(var1.hashCode()) {
            case -2012993625:
                if (var1.equals("sayHello")) {
                    switch(var2.length) {
                    case 1:
                        if (var2[0].getName().equals("java.lang.String")) {
                            return 1;
                        }
                    }
                }
                break;
            case -1776922004:
                if (var1.equals("toString")) {
                    switch(var2.length) {
                    case 0:
                        return 3;
                    }
                }
                break;
            case -1295482945:
                if (var1.equals("equals")) {
                    switch(var2.length) {
                    case 1:
                        if (var2[0].getName().equals("java.lang.Object")) {
                            return 2;
                        }
                    }
                }
                break;
            case 147696667:
                if (var1.equals("hashCode")) {
                    switch(var2.length) {
                    case 0:
                        return 4;
                    }
                }
                break;
            case 510300177:
                if (var1.equals("dealTask")) {
                    switch(var2.length) {
                    case 1:
                        if (var2[0].getName().equals("java.lang.String")) {
                            return 0;
                        }
                    }
                }
            }
    
            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 {
            ExecutionTimeReality var10000 = (ExecutionTimeReality)var2;
            int var10001 = var1;
    
            try {
                switch(var10001) {
                case 0:
                    var10000.dealTask((String)var3[0]);
                    return null;
                case 1:
                    var10000.sayHello((String)var3[0]);
                    return null;
                case 2:
                    return new Boolean(var10000.equals(var3[0]));
                case 3:
                    return var10000.toString();
                case 4:
                    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 {
            ExecutionTimeReality var10000 = new ExecutionTimeReality;
            ExecutionTimeReality 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 4;
        }
    }

## **其他网址** ##

[JDK动态代理和CGLIB代理的区别\_学无止境! 无休无止! -CSDN博客][JDK_CGLIB_ _ -CSDN]

[Cglib动态代理实现原理 - 糖豆包子 - 博客园][Cglib_ - _ -]

[CGLIB_--_IT_-CSDN]: https://knife.blog.csdn.net/article/details/122913170
[JDK_CGLIB_ _ -CSDN]: https://blog.csdn.net/samrtian/article/details/50596288
[Cglib_ - _ -]: https://www.cnblogs.com/monkey0307/p/8328821.html