黑马程序员_java学习笔记之代理类

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张孝祥老师代理类讲解之总结 ?

package com.itheima; import java.lang.reflect.Constructor; import java.lang.reflect.InvocationHandler; import java.lang.reflect.Method; import java.lang.reflect.Proxy; import java.util.ArrayList; import java.util.Collection; public class ProxyReview { public static void main(String[] args)throws Exception{ //public static Class<?> getProxyClass(ClassLoader loader,Class<?>... interfaces)  throws IllegalArgumentException Class clazzProxy1=Proxy.getProxyClass(Collection. class .getClassLoader(), Collection. class ); //注在这里接口.class 文件是可变参数的，不是一个集合 //获取动态类的.class文件的名字 System. out .println(clazzProxy1.getName()); System. out .println( "" ); //利用反射获取clazzProxy1中的非私有构造方法的数组 Constructor[] constructors=clazzProxy1.getConstructors(); //对构造函数进行遍历 for (Constructor  constructor : constructors){ //创建一个字符串缓冲区 StringBuilder sb= new StringBuilder(); String name=constructor.getName(); sb.append(name); sb.append( "(" ); //对构造方法的参数列表进行遍历 Class[] clazzParams = constructor.getParameterTypes(); for (Class clazzParam : clazzParams ){ sb.append(clazzParam.getName()); } //因为添加到最后一个参数时也会有,所以在添加时需要删除最后一个, if (clazzParams!= null &&clazzParams.length!=0){ sb.deleteCharAt(clazzParams.length-1); } sb.append( ")" ); System. out .println(sb.toString()); } System. out .println( "" ); //利用反射获取clazzProxy1中的非私有方法的数组 Method[] methods=clazzProxy1.getMethods(); //对方法进行遍历 for (Method  method : methods){ //创建一个字符串缓冲区 StringBuilder sb= new StringBuilder(); String name=method.getName(); sb.append(name); sb.append( "(" ); //对非私有方法的参数列表进行遍历 //特别注意 在下面方法中 如果方法的没有参数则返回长度为0的数组  在遍历不会报空指针异常  Class[] clazzParams = method.getParameterTypes(); for (Class clazzParam : clazzParams ){ sb.append(clazzParam.getName()); } //因为添加到最后一个参数时也会有,所以在添加时需要删除最后一个, if (clazzParams!= null &&clazzParams.length!=0){ sb.deleteCharAt(clazzParams.length-1); } sb.append( ")" ); System. out .println(sb.toString()); } //根据class文件创建一个动态类的对象 // //首先得到生成对象的构造函数，通过构造函数创建对象 class myInvocationHandler implements InvocationHandler{ //复写invoke方法 @Override public Object invoke(Object proxy, Method method, Object[] args) throws Throwable { // TODO Auto-generated method stub return null ; } } Constructor constructor=clazzProxy1.getConstructor(InvocationHandler. class ); Collection collection = (Collection)constructor.newInstance( new myInvocationHandler()); //Proxy没有不带参数的构造方法所以给其穿个参数，参数类型为InvocationHandler是个借口，自己new一个myInvocationHandlerd对象 Collection colletion2 = (Collection)constructor.newInstance( new InvocationHandler(){ @Override public Object invoke(Object proxy, Method method, Object[] args) throws Throwable { // TODO Auto-generated method stub return null ; } } ); Collection collection4 = (Collection)Proxy.newProxyInstance(Collection. class .getClassLoader(), new Class[]{Collection. class }, new InvocationHandler(){ //定义一个目标类 ArrayList target= new ArrayList(); @Override public Object invoke(Object proxy, Method method, Object[] args) throws Throwable { // TODO Auto-generated method stub Object retVal=method.invoke(target, args); return null ; } } ); //调用动态类collection3的add方法 会报空指针异常，调用有返回值类型的方法都会报错 collection4.add( "123" ); System. out .println(collection4.size()); System. out .println(collection4); Collection collection3 = (Collection)Proxy.newProxyInstance(Collection. class .getClassLoader(), new Class[]{Collection. class }, new InvocationHandler(){ //定义一个目标类 ArrayList target= new ArrayList(); @Override public Object invoke(Object proxy, Method method, Object[] args) throws Throwable { // TODO Auto-generated method stub //调用目标类的方法，并传参 Object retVal=method.invoke(target, args); return null ; } } ); //调用动态类collection3的add方法 会报空指针异常，调用有返回值类型的方法都会报错 collection4.add( "123" ); System. out .println(collection4.size()); System. out .println(collection4); //下面是用myeclipse完整的一段代码其中有用到公告 final ArrayList target= new ArrayList(); Collection collection5 = getProxy(target, new MyAdvice()); collection5.add( "abc" ); collection5.add( "bcd" ); collection5.add( "bxd" ); System. out .println(collection5.size()); } //利用myeclipse将这两个对象抽成一个方法 private static Collection getProxy(final ArrayList target,final Advice advice) { Collection collection5 = (Collection)Proxy.newProxyInstance(Collection. class .getClassLoader(), new Class[]{Collection. class }, new InvocationHandler(){ //定义一个目标类 @Override public Object invoke(Object proxy, Method method, Object[] args) throws Throwable { // TODO Auto-generated method stub //调用目标类的方法，并传参 advice.beforeMethod(method); Object retVal=method.invoke(target, args); advice.afterMethod(method); return null ; } } ); return collection5; } } class MyAdvice implements Advice { long startTime=0; @Override public void beforeMethod(Method method) { // TODO Auto-generated method stub System. out .println( "我这是要开始" ); startTime=System.currentTimeMillis(); } @Override public void afterMethod(Method method) { // TODO Auto-generated method stub System. out .println( "我结束了" ); long endTime=System.currentTimeMillis(); System. out .println(method.getName()+ " running time is " +(startTime-endTime)); } } interface Advice { public abstract void beforeMethod(Method method); public abstract void afterMethod(Method method); }