动态代理 （CGLIB 动态代理）

﹏ヽ暗。殇╰゛Y 2022-02-01 08:21 482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

  1. <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">
  2.   <modelVersion>4.0.0</modelVersion>
  3.   <groupId>com.cglibdynamicproxy</groupId>
  4.   <artifactId>cglibdynamicproxy</artifactId>
  5.   <version>0.0.1-SNAPSHOT</version>
  6.   <name>cglibdynamicproxy</name>
  8.   <dependencies>
  9.         <!-- 引入cglib依赖 -->
  10.         <dependency>
  11.            <groupId>cglib</groupId>
  12.            <artifactId>cglib</artifactId>
  13.            <version>3.2.5</version>
  14.         </dependency>
  15.   </dependencies>
  17.   <build>
  18.      <plugins>
  19.      <plugin>
  20.          <artifactId>maven-compiler-plugin</artifactId>
  21.          <configuration>
  22.              <source>1.8</source>
  23.              <target>1.8</target>
  24.          </configuration>
  25.      </plugin>
  26.      </plugins>
  27.   </build>
  28. </project>

创建被代理类

  1. package com.cglibdynamicproxy.service;
  3. /**
  4.  * 被代理类
  5.  * @author Administrator
  6.  */
  7. public class AgentTarget {
  9.     public void proxyMethod() {
  10.         System.out.println("被代理的方法执行了");;
  11.     }
  12. }

创建 CglibMethodInterceptor 类，实现 MethodInterceptor

  1. package com.cglibdynamicproxy.cglib;
  3. import java.lang.reflect.Method;
  4. import net.sf.cglib.proxy.MethodInterceptor;
  5. import net.sf.cglib.proxy.MethodProxy;
  7. public class CglibMethodInterceptor implements MethodInterceptor{
  9.     /**
  10.      * 拦截父类所有方法的调用
  11.      */
  12.     @Override
  13.     public Object intercept(Object obj, Method method, Object[] args, MethodProxy proxy) throws Throwable {
  14.         //obj  目标类的实例
  15.         //method  目标类方法的反射对象
  16.         //args  方法的动态入参
  17.         //proxy  代理类实例
  18.         System.out.println("before");
  19.                 Object res = null;
  20.                 try{
  21.                     //反射调用目标对象方法
  22.                     res = proxy.invokeSuper(obj, args);
  23.                 }catch (Exception e){
  24.                     System.out.println("e:" + e.getMessage());
  25.                     throw e;
  26.                 }finally {
  27.                     System.out.println("after");
  28.                 }
  29.                 return res;
  30.     }
  31. }

测试类

  1. package com.cglibdynamicproxy;
  3. import com.cglibdynamicproxy.cglib.CglibMethodInterceptor;
  4. import com.cglibdynamicproxy.service.AgentTarget;
  5. import net.sf.cglib.core.DebuggingClassWriter;
  6. import net.sf.cglib.proxy.Enhancer;
  8. public class CglibDynamicProxyMain {
  10.     public static void main(String[] args) {
  11.             //将生成的class文件保存到指定目录，这里是项目目录           
  12.             System.setProperty(DebuggingClassWriter.DEBUG_LOCATION_PROPERTY, "E:\\workspace\\cglibdynamicproxy");
  14.             Enhancer enhancer = new Enhancer();
  15.             //设置父类
  16.             enhancer.setSuperclass(AgentTarget.class);
  17.             //设置回调函数
  18.             enhancer.setCallback(new CglibMethodInterceptor());
  19.             //创建AgentTarget.class的子类
  20.             AgentTarget childAgentTarget = (AgentTarget) enhancer.create();
  21.             //调用方法
  22.             childAgentTarget.proxyMethod();
  23.     }
  24. }

运行如下

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生成的 class 文件

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重点看生成的这个文件 AgentTargetEnhancerByCGLIB303de0ca.class

代码如下

  1. package com.cglibdynamicproxy.service;
  3. import java.lang.reflect.Method;
  4. import net.sf.cglib.core.ReflectUtils;
  5. import net.sf.cglib.core.Signature;
  6. import net.sf.cglib.proxy.Callback;
  7. import net.sf.cglib.proxy.Factory;
  8. import net.sf.cglib.proxy.MethodInterceptor;
  9. import net.sf.cglib.proxy.MethodProxy;
  11. public class AgentTarget$$EnhancerByCGLIB$$303de0ca extends AgentTarget implements Factory {
  12.     private boolean CGLIB$BOUND;
  13.     public static Object CGLIB$FACTORY_DATA;
  14.     private static final ThreadLocal CGLIB$THREAD_CALLBACKS;
  15.     private static final Callback[] CGLIB$STATIC_CALLBACKS;
  16.     private MethodInterceptor CGLIB$CALLBACK_0;
  17.     private static Object CGLIB$CALLBACK_FILTER;
  18.     private static final Method CGLIB$proxyMethod$0$Method;
  19.     private static final MethodProxy CGLIB$proxyMethod$0$Proxy;
  20.     private static final Object[] CGLIB$emptyArgs;
  21.     private static final Method CGLIB$equals$1$Method;
  22.     private static final MethodProxy CGLIB$equals$1$Proxy;
  23.     private static final Method CGLIB$toString$2$Method;
  24.     private static final MethodProxy CGLIB$toString$2$Proxy;
  25.     private static final Method CGLIB$hashCode$3$Method;
  26.     private static final MethodProxy CGLIB$hashCode$3$Proxy;
  27.     private static final Method CGLIB$clone$4$Method;
  28.     private static final MethodProxy CGLIB$clone$4$Proxy;
  30.     static void CGLIB$STATICHOOK1() {
  31.         CGLIB$THREAD_CALLBACKS = new ThreadLocal();
  32.         CGLIB$emptyArgs = new Object[0];
  33.         Class var0 = Class.forName("com.cglibdynamicproxy.service.AgentTarget$$EnhancerByCGLIB$$303de0ca");
  34.         Class var1;
  35.         CGLIB$proxyMethod$0$Method = ReflectUtils.findMethods(new String[]{"proxyMethod", "()V"},
  36.                 (var1 = Class.forName("com.cglibdynamicproxy.service.AgentTarget")).getDeclaredMethods())[0];
  37.         CGLIB$proxyMethod$0$Proxy = MethodProxy.create(var1, var0, "()V", "proxyMethod", "CGLIB$proxyMethod$0");
  38.         Method[] var10000 = ReflectUtils.findMethods(
  39.                 new String[]{"equals", "(Ljava/lang/Object;)Z", "toString", "()Ljava/lang/String;", "hashCode", "()I",
  40.                         "clone", "()Ljava/lang/Object;"},
  41.                 (var1 = Class.forName("java.lang.Object")).getDeclaredMethods());
  42.         CGLIB$equals$1$Method = var10000[0];
  43.         CGLIB$equals$1$Proxy = MethodProxy.create(var1, var0, "(Ljava/lang/Object;)Z", "equals", "CGLIB$equals$1");
  44.         CGLIB$toString$2$Method = var10000[1];
  45.         CGLIB$toString$2$Proxy = MethodProxy.create(var1, var0, "()Ljava/lang/String;", "toString", "CGLIB$toString$2");
  46.         CGLIB$hashCode$3$Method = var10000[2];
  47.         CGLIB$hashCode$3$Proxy = MethodProxy.create(var1, var0, "()I", "hashCode", "CGLIB$hashCode$3");
  48.         CGLIB$clone$4$Method = var10000[3];
  49.         CGLIB$clone$4$Proxy = MethodProxy.create(var1, var0, "()Ljava/lang/Object;", "clone", "CGLIB$clone$4");
  50.     }
  52.     final void CGLIB$proxyMethod$0() {
  53.         super.proxyMethod();
  54.     }
  56.     public final void proxyMethod() {
  57.         MethodInterceptor var10000 = this.CGLIB$CALLBACK_0;
  58.         if (this.CGLIB$CALLBACK_0 == null) {
  59.             CGLIB$BIND_CALLBACKS(this);
  60.             var10000 = this.CGLIB$CALLBACK_0;
  61.         }
  63.         if (var10000 != null) {
  64.             var10000.intercept(this, CGLIB$proxyMethod$0$Method, CGLIB$emptyArgs, CGLIB$proxyMethod$0$Proxy);
  65.         } else {
  66.             super.proxyMethod();
  67.         }
  68.     }
  70.     final boolean CGLIB$equals$1(Object var1) {
  71.         return super.equals(var1);
  72.     }
  74.     public final boolean equals(Object var1) {
  75.         MethodInterceptor var10000 = this.CGLIB$CALLBACK_0;
  76.         if (this.CGLIB$CALLBACK_0 == null) {
  77.             CGLIB$BIND_CALLBACKS(this);
  78.             var10000 = this.CGLIB$CALLBACK_0;
  79.         }
  81.         if (var10000 != null) {
  82.             Object var2 = var10000.intercept(this, CGLIB$equals$1$Method, new Object[]{var1}, CGLIB$equals$1$Proxy);
  83.             return var2 == null ? false : (Boolean) var2;
  84.         } else {
  85.             return super.equals(var1);
  86.         }
  87.     }
  89.     final String CGLIB$toString$2() {
  90.         return super.toString();
  91.     }
  93.     public final String toString() {
  94.         MethodInterceptor var10000 = this.CGLIB$CALLBACK_0;
  95.         if (this.CGLIB$CALLBACK_0 == null) {
  96.             CGLIB$BIND_CALLBACKS(this);
  97.             var10000 = this.CGLIB$CALLBACK_0;
  98.         }
  100.         return var10000 != null
  101.                 ? (String) var10000.intercept(this, CGLIB$toString$2$Method, CGLIB$emptyArgs, CGLIB$toString$2$Proxy)
  102.                 : super.toString();
  103.     }
  105.     final int CGLIB$hashCode$3() {
  106.         return super.hashCode();
  107.     }
  109.     public final int hashCode() {
  110.         MethodInterceptor var10000 = this.CGLIB$CALLBACK_0;
  111.         if (this.CGLIB$CALLBACK_0 == null) {
  112.             CGLIB$BIND_CALLBACKS(this);
  113.             var10000 = this.CGLIB$CALLBACK_0;
  114.         }
  116.         if (var10000 != null) {
  117.             Object var1 = var10000.intercept(this, CGLIB$hashCode$3$Method, CGLIB$emptyArgs, CGLIB$hashCode$3$Proxy);
  118.             return var1 == null ? 0 : ((Number) var1).intValue();
  119.         } else {
  120.             return super.hashCode();
  121.         }
  122.     }
  124.     final Object CGLIB$clone$4() throws CloneNotSupportedException {
  125.         return super.clone();
  126.     }
  128.     protected final Object clone() throws CloneNotSupportedException {
  129.         MethodInterceptor var10000 = this.CGLIB$CALLBACK_0;
  130.         if (this.CGLIB$CALLBACK_0 == null) {
  131.             CGLIB$BIND_CALLBACKS(this);
  132.             var10000 = this.CGLIB$CALLBACK_0;
  133.         }
  135.         return var10000 != null
  136.                 ? var10000.intercept(this, CGLIB$clone$4$Method, CGLIB$emptyArgs, CGLIB$clone$4$Proxy)
  137.                 : super.clone();
  138.     }
  140.     public static MethodProxy CGLIB$findMethodProxy(Signature var0) {
  141.         String var10000 = var0.toString();
  142.         switch (var10000.hashCode()) {
  143.             case -508378822 :
  144.                 if (var10000.equals("clone()Ljava/lang/Object;")) {
  145.                     return CGLIB$clone$4$Proxy;
  146.                 }
  147.                 break;
  148.             case -472693722 :
  149.                 if (var10000.equals("proxyMethod()V")) {
  150.                     return CGLIB$proxyMethod$0$Proxy;
  151.                 }
  152.                 break;
  153.             case 1826985398 :
  154.                 if (var10000.equals("equals(Ljava/lang/Object;)Z")) {
  155.                     return CGLIB$equals$1$Proxy;
  156.                 }
  157.                 break;
  158.             case 1913648695 :
  159.                 if (var10000.equals("toString()Ljava/lang/String;")) {
  160.                     return CGLIB$toString$2$Proxy;
  161.                 }
  162.                 break;
  163.             case 1984935277 :
  164.                 if (var10000.equals("hashCode()I")) {
  165.                     return CGLIB$hashCode$3$Proxy;
  166.                 }
  167.         }
  169.         return null;
  170.     }
  172.     public AgentTarget$$EnhancerByCGLIB$$303de0ca() {
  173.         CGLIB$BIND_CALLBACKS(this);
  174.     }
  176.     public static void CGLIB$SET_THREAD_CALLBACKS(Callback[] var0) {
  177.         CGLIB$THREAD_CALLBACKS.set(var0);
  178.     }
  180.     public static void CGLIB$SET_STATIC_CALLBACKS(Callback[] var0) {
  181.         CGLIB$STATIC_CALLBACKS = var0;
  182.     }
  184.     private static final void CGLIB$BIND_CALLBACKS(Object var0) {
  185.         AgentTarget$$EnhancerByCGLIB$$303de0ca var1 = (AgentTarget$$EnhancerByCGLIB$$303de0ca) var0;
  186.         if (!var1.CGLIB$BOUND) {
  187.             var1.CGLIB$BOUND = true;
  188.             Object var10000 = CGLIB$THREAD_CALLBACKS.get();
  189.             if (var10000 == null) {
  190.                 var10000 = CGLIB$STATIC_CALLBACKS;
  191.                 if (CGLIB$STATIC_CALLBACKS == null) {
  192.                     return;
  193.                 }
  194.             }
  196.             var1.CGLIB$CALLBACK_0 = (MethodInterceptor) ((Callback[]) var10000)[0];
  197.         }
  199.     }
  201.     public Object newInstance(Callback[] var1) {
  202.         CGLIB$SET_THREAD_CALLBACKS(var1);
  203.         AgentTarget$$EnhancerByCGLIB$$303de0ca var10000 = new AgentTarget$$EnhancerByCGLIB$$303de0ca();
  204.         CGLIB$SET_THREAD_CALLBACKS((Callback[]) null);
  205.         return var10000;
  206.     }
  208.     public Object newInstance(Callback var1) {
  209.         CGLIB$SET_THREAD_CALLBACKS(new Callback[]{var1});
  210.         AgentTarget$$EnhancerByCGLIB$$303de0ca var10000 = new AgentTarget$$EnhancerByCGLIB$$303de0ca();
  211.         CGLIB$SET_THREAD_CALLBACKS((Callback[]) null);
  212.         return var10000;
  213.     }
  215.     public Object newInstance(Class[] var1, Object[] var2, Callback[] var3) {
  216.       CGLIB$SET_THREAD_CALLBACKS(var3);
  217.       AgentTarget$$EnhancerByCGLIB$$303de0ca var10000 = new AgentTarget$$EnhancerByCGLIB$$303de0ca;
  218.       switch(var1.length) {
  219.       case 0:
  220.          var10000.<init>();
  221.          CGLIB$SET_THREAD_CALLBACKS((Callback[])null);
  222.          return var10000;
  223.       default:
  224.          throw new IllegalArgumentException("Constructor not found");
  225.       }
  226.    }
  228.     public Callback getCallback(int var1) {
  229.         CGLIB$BIND_CALLBACKS(this);
  230.         MethodInterceptor var10000;
  231.         switch (var1) {
  232.             case 0 :
  233.                 var10000 = this.CGLIB$CALLBACK_0;
  234.                 break;
  235.             default :
  236.                 var10000 = null;
  237.         }
  239.         return var10000;
  240.     }
  242.     public void setCallback(int var1, Callback var2) {
  243.         switch (var1) {
  244.             case 0 :
  245.                 this.CGLIB$CALLBACK_0 = (MethodInterceptor) var2;
  246.             default :
  247.         }
  248.     }
  250.     public Callback[] getCallbacks() {
  251.         CGLIB$BIND_CALLBACKS(this);
  252.         return new Callback[]{this.CGLIB$CALLBACK_0};
  253.     }
  255.     public void setCallbacks(Callback[] var1) {
  256.         this.CGLIB$CALLBACK_0 = (MethodInterceptor) var1[0];
  257.     }
  259.     static {
  260.         CGLIB$STATICHOOK1();
  261.     }
  262. }

其中，这段代码为核心内容

  1. public final void proxyMethod() {
  2.         MethodInterceptor var10000 = this.CGLIB$CALLBACK_0;
  3.         if (this.CGLIB$CALLBACK_0 == null) {
  4.             CGLIB$BIND_CALLBACKS(this);
  5.             var10000 = this.CGLIB$CALLBACK_0;
  6.         }
  8.         if (var10000 != null) {
  9.             var10000.intercept(this, CGLIB$proxyMethod$0$Method, CGLIB$emptyArgs, CGLIB$proxyMethod$0$Proxy);
  10.         } else {
  11.             super.proxyMethod();
  12.         }
  13.     }

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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