动态代理的实现过程

定义被代理对象的接口和接口实现：

1 package com.xl;
2 public interface Book {
3     
4     public void addBooks();
5 }

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 1 package com.xl;
 2 
 3 public class BookImpl implements Book {
 4 
 5     @Override
 6     public void addBooks() {
 7         // TODO Auto-generated method stub
 8         System.out.println("the books add successfully!");
 9 
10     }
11 
12 }

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定义代理器，实现InvocationHandler接口，定义私有变量和相应的构造函数，重写invoke方法，调用method对象的invoke方法，返回被代理对象：

 1 package com.xl;
 2 import java.lang.reflect.InvocationHandler;
 3 import java.lang.reflect.Method;
 4 
 5 
 6 public class bookproxy implements InvocationHandler {
 7 
 8     private Object o;
 9     
10     //构造函数
11     public bookproxy(Object o){
12         this.o = o;
13     }
14     @Override
15     public Object invoke(Object proxy, Method method, Object[] args)
16             throws Throwable {
17         
18         Object rs;
19         
20         System.out.println("方法调用前！");
21         
22         rs = method.invoke(o);
23         
24         System.out.println("方法调用后！");
25         
26         return rs;
27     }
28 
29 }

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客户端的调用，创建被代理对象的实例给其接口来引用，创建代理器并将被代理对象传进去，给InvocationHandler来引用，创建代理对象实例，强制转换成被代理接口，最后调用代理对象实例的方法：

 1 package com.xl;
 2 
 3 import java.lang.reflect.InvocationHandler;
 4 import java.lang.reflect.Proxy;
 5 
 6 public class ProxyTest {
 7 
 8     /**
 9      * @param args
10      */
11     public static void main(String[] args) {
12         // TODO Auto-generated method stub
13 
14         Book b = new BookImpl();
15         
16         InvocationHandler ih = new bookproxy(b);
17         
18         Book bproxy = (Book) Proxy.newProxyInstance(b.getClass().getClassLoader(),
19                 b.getClass().getInterfaces(), 
20                 ih);
21         
22         bproxy.addBooks();
23     }
24 
25 }

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转载于:https://www.cnblogs.com/NoEndForLearning/p/3862382.html