动态代理（CGLIB 动态代理）

﹏ヽ暗。殇╰゛Y 2022-02-01 08:21 421阅读 0赞

**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>
            
            <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

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dzanp6Y2Jx_size_16_color_FFFFFF_t_70][]

生成的 class 文件

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dzanp6Y2Jx_size_16_color_FFFFFF_t_70 1][]

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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