动态代理 （CGLIB 动态代理）

于 2019-05-13 23:01:57 发布
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本文链接：https://blog.csdn.net/wsjzzcbq/article/details/90182495
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动态代理： 代理类在程序运行时被创建，这种代理方式称为动态代理

动态代理实现有两种方式，JDK 动态代理和 CGlib 动态代理，本文介绍 CGlib 动态代理

CGLib 动态代理：采用底层的字节码技术，可以为一个类创建子类，在子类中采用方法拦截的技术拦截所有父类方法的调用，并在调用中添加横切逻辑

 

CGLib 动态代理示例代码

创建一个普通 maven 工程，引入  CGLib 依赖

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>
  <groupId>com.cglibdynamicproxy</groupId>
  <artifactId>cglibdynamicproxy</artifactId>
  <version>0.0.1-SNAPSHOT</version>
  <name>cglibdynamicproxy</name>
  
  <dependencies>
        <!-- 引入cglib依赖 -->
        <dependency>
           <groupId>cglib</groupId>
           <artifactId>cglib</artifactId>
           <version>3.2.5</version>
        </dependency>
  </dependencies>
  
  <build>
     <plugins>
	 <plugin>
	     <artifactId>maven-compiler-plugin</artifactId>
	     <configuration>
	         <source>1.8</source>
	         <target>1.8</target>
	     </configuration>
	 </plugin>
     </plugins>
  </build>
</project>

创建被代理类

package com.cglibdynamicproxy.service;

/**
 * 被代理类
 * @author Administrator
 */
public class AgentTarget {
	
	public void proxyMethod() {
		System.out.println("被代理的方法执行了");;
	}
}

创建 CglibMethodInterceptor 类，实现 MethodInterceptor

package com.cglibdynamicproxy.cglib;

import java.lang.reflect.Method;
import net.sf.cglib.proxy.MethodInterceptor;
import net.sf.cglib.proxy.MethodProxy;

public class CglibMethodInterceptor implements MethodInterceptor{

	/**
	 * 拦截父类所有方法的调用
	 */
	@Override
	public Object intercept(Object obj, Method method, Object[] args, MethodProxy proxy) throws Throwable {
		//obj  目标类的实例
		//method  目标类方法的反射对象
		//args  方法的动态入参
		//proxy  代理类实例
		System.out.println("before");
                Object res = null;
                try{
        	        //反射调用目标对象方法
                    res = proxy.invokeSuper(obj, args);
                }catch (Exception e){
                    System.out.println("e:" + e.getMessage());
                    throw e;
                }finally {
                    System.out.println("after");
                }
                return res;
	}
}

测试类

package com.cglibdynamicproxy;

import com.cglibdynamicproxy.cglib.CglibMethodInterceptor;
import com.cglibdynamicproxy.service.AgentTarget;
import net.sf.cglib.core.DebuggingClassWriter;
import net.sf.cglib.proxy.Enhancer;

public class CglibDynamicProxyMain {

	public static void main(String[] args) {
            //将生成的class文件保存到指定目录，这里是项目目录           
            System.setProperty(DebuggingClassWriter.DEBUG_LOCATION_PROPERTY, "E:\\workspace\\cglibdynamicproxy");

            Enhancer enhancer = new Enhancer();
            //设置父类
            enhancer.setSuperclass(AgentTarget.class);
            //设置回调函数
            enhancer.setCallback(new CglibMethodInterceptor());
            //创建AgentTarget.class的子类
            AgentTarget childAgentTarget = (AgentTarget) enhancer.create();
            //调用方法
            childAgentTarget.proxyMethod();
	}
}

运行如下

生成的 class 文件

重点看生成的这个文件 AgentTarget$$EnhancerByCGLIB$$303de0ca.class

代码如下

package com.cglibdynamicproxy.service;

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 AgentTarget$$EnhancerByCGLIB$$303de0ca extends AgentTarget 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$proxyMethod$0$Method;
	private static final MethodProxy CGLIB$proxyMethod$0$Proxy;
	private static final Object[] CGLIB$emptyArgs;
	private static final Method CGLIB$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;

	static void CGLIB$STATICHOOK1() {
		CGLIB$THREAD_CALLBACKS = new ThreadLocal();
		CGLIB$emptyArgs = new Object[0];
		Class var0 = Class.forName("com.cglibdynamicproxy.service.AgentTarget$$EnhancerByCGLIB$$303de0ca");
		Class var1;
		CGLIB$proxyMethod$0$Method = ReflectUtils.findMethods(new String[]{"proxyMethod", "()V"},
				(var1 = Class.forName("com.cglibdynamicproxy.service.AgentTarget")).getDeclaredMethods())[0];
		CGLIB$proxyMethod$0$Proxy = MethodProxy.create(var1, var0, "()V", "proxyMethod", "CGLIB$proxyMethod$0");
		Method[] var10000 = ReflectUtils.findMethods(
				new String[]{"equals", "(Ljava/lang/Object;)Z", "toString", "()Ljava/lang/String;", "hashCode", "()I",
						"clone", "()Ljava/lang/Object;"},
				(var1 = Class.forName("java.lang.Object")).getDeclaredMethods());
		CGLIB$equals$1$Method = var10000[0];
		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");
	}

	final void CGLIB$proxyMethod$0() {
		super.proxyMethod();
	}

	public final void proxyMethod() {
		MethodInterceptor var10000 = this.CGLIB$CALLBACK_0;
		if (this.CGLIB$CALLBACK_0 == null) {
			CGLIB$BIND_CALLBACKS(this);
			var10000 = this.CGLIB$CALLBACK_0;
		}

		if (var10000 != null) {
			var10000.intercept(this, CGLIB$proxyMethod$0$Method, CGLIB$emptyArgs, CGLIB$proxyMethod$0$Proxy);
		} else {
			super.proxyMethod();
		}
	}

	final boolean CGLIB$equals$1(Object var1) {
		return super.equals(var1);
	}

	public final boolean equals(Object var1) {
		MethodInterceptor var10000 = this.CGLIB$CALLBACK_0;
		if (this.CGLIB$CALLBACK_0 == 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$CALLBACK_0;
		if (this.CGLIB$CALLBACK_0 == 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$CALLBACK_0;
		if (this.CGLIB$CALLBACK_0 == 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$CALLBACK_0;
		if (this.CGLIB$CALLBACK_0 == 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 -472693722 :
				if (var10000.equals("proxyMethod()V")) {
					return CGLIB$proxyMethod$0$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;
	}

	public AgentTarget$$EnhancerByCGLIB$$303de0ca() {
		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) {
		AgentTarget$$EnhancerByCGLIB$$303de0ca var1 = (AgentTarget$$EnhancerByCGLIB$$303de0ca) var0;
		if (!var1.CGLIB$BOUND) {
			var1.CGLIB$BOUND = true;
			Object var10000 = CGLIB$THREAD_CALLBACKS.get();
			if (var10000 == null) {
				var10000 = CGLIB$STATIC_CALLBACKS;
				if (CGLIB$STATIC_CALLBACKS == null) {
					return;
				}
			}

			var1.CGLIB$CALLBACK_0 = (MethodInterceptor) ((Callback[]) var10000)[0];
		}

	}

	public Object newInstance(Callback[] var1) {
		CGLIB$SET_THREAD_CALLBACKS(var1);
		AgentTarget$$EnhancerByCGLIB$$303de0ca var10000 = new AgentTarget$$EnhancerByCGLIB$$303de0ca();
		CGLIB$SET_THREAD_CALLBACKS((Callback[]) null);
		return var10000;
	}

	public Object newInstance(Callback var1) {
		CGLIB$SET_THREAD_CALLBACKS(new Callback[]{var1});
		AgentTarget$$EnhancerByCGLIB$$303de0ca var10000 = new AgentTarget$$EnhancerByCGLIB$$303de0ca();
		CGLIB$SET_THREAD_CALLBACKS((Callback[]) null);
		return var10000;
	}

	public Object newInstance(Class[] var1, Object[] var2, Callback[] var3) {
      CGLIB$SET_THREAD_CALLBACKS(var3);
      AgentTarget$$EnhancerByCGLIB$$303de0ca var10000 = new AgentTarget$$EnhancerByCGLIB$$303de0ca;
      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();
	}
}

其中，这段代码为核心内容

public final void proxyMethod() {
		MethodInterceptor var10000 = this.CGLIB$CALLBACK_0;
		if (this.CGLIB$CALLBACK_0 == null) {
			CGLIB$BIND_CALLBACKS(this);
			var10000 = this.CGLIB$CALLBACK_0;
		}

		if (var10000 != null) {
			var10000.intercept(this, CGLIB$proxyMethod$0$Method, CGLIB$emptyArgs, CGLIB$proxyMethod$0$Proxy);
		} else {
			super.proxyMethod();
		}
	}

程序运行流程：代理对象继承父类 AgentTarget，重写 proxyMethod 方法，拦截器调用 intercept 方法，intercept 方法由自定义的 CglibMethodInterceptor 实现，当调用 MyMethodInterceptor 中的 intercept 方法时，通过反射调用目标对象方法，从而完成了由代理对象访问到目标对象的动态代理

 

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