java动态代理例子

 1 先看一个简单点动态代理的例子（没有用到factory）
 2 1 定义接口
 3 package com.dynamic.simple;
 4 
 5 import com.dynamic.simple.Subject;
 6 
 7 public interface Subject{   
 8     public void request();   
 9 }  
10 
11 2 实现真实类
12 package com.dynamic.simple;
13 
14 public class RealSubject implements Subject{    
15     public RealSubject(){}    
16     public void request() {
17         System.out.println("From real subject.");    
18     }    
19 }   
20 
21 3 定义动态代理
22 package com.dynamic.simple;
23 
24 import java.lang.reflect.Method;    
25 import java.lang.reflect.InvocationHandler;    
26 public class DynamicSubject implements InvocationHandler {    
27     private Object sub;    
28     
29     public DynamicSubject() {    
30     }    
31     
32     public DynamicSubject(Object obj) {    
33         sub = obj;    
34     }    
35     
36     public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {    
37         System.out.println("before calling " + method);    
38         method.invoke(sub,args);    
39         System.out.println("after calling " + method);    
40         return null;    
41     }    
42 }  
43 
44 4 客户端
45 package com.dynamic.simple;
46 
47 import java.lang.reflect.InvocationHandler;    
48 import java.lang.reflect.Proxy;    
49 
50 public class Client{    
51     static public void main(String[] args) throws Throwable{    
52         RealSubject rs = new RealSubject(); //在这里指定被代理类    
53         InvocationHandler ds = new DynamicSubject(rs); //初始化代理类    
54         Class cls = rs.getClass();    
55         Subject subject = (Subject) Proxy.newProxyInstance(cls.getClassLoader(), cls.getInterfaces(),ds );    
56         subject.request();    
57     }   
58 }

运行客户端结果为：

before calling public abstract void com.dynamic.simple.Subject.request()
From real subject.
after calling public abstract void com.dynamic.simple.Subject.request()

  1 下面看一个复杂点的动态代理实现（用到了factory）
  2 1 定义接口
  3 package com.proxy;
  4 
  5 import com.proxy.SomeClass;
  6 import com.proxy.SomeClassImpl;
  7 
  8 public interface SomeClass {
  9     public void someMethod();
 10     
 11     public void someOtherMethod(final String text);
 12 }
 13 
 14 2 定义实现类
 15 package com.proxy;
 16 
 17 
 18 public class SomeClassImpl implements SomeClass{
 19     private String name;
 20     
 21     public SomeClassImpl(final String name){
 22         this.name = name;
 23     }
 24     
 25     public void someMethod(){
 26         System.out.println(this.name);
 27     }
 28     
 29     public void someOtherMethod(final String text){
 30         System.out.println(text);
 31     }
 32 }
 33 
 34 3 定义2个代理SomeClassProxy和SomeClassCountingProxy(静态代理时才需要)
 35 /*SomeClassProxy*/
 36 package com.proxy;
 37 
 38 
 39 public class SomeClassProxy implements SomeClass{
 40     
 41     private final SomeClassImpl impl;
 42     
 43     public SomeClassProxy(SomeClassImpl impl){
 44         this.impl = impl;
 45     }
 46     
 47     public void someMethod(){
 48         this.impl.someMethod();
 49     }
 50     
 51     public void someOtherMethod(final String text){
 52         this.impl.someOtherMethod(text);
 53     }
 54 }
 55 
 56 /*SomeClassCountingProxy*/
 57 package com.proxy;
 58 
 59 
 60 public class SomeClassCountingProxy implements SomeClass{
 61     private final SomeClassImpl impl;
 62     
 63     private int invocationCount = 0;
 64     
 65     public SomeClassCountingProxy(SomeClassImpl impl){
 66         this.impl = impl;
 67     }
 68     
 69     public void someMethod(){
 70         this.invocationCount ++;
 71         this.impl.someMethod();
 72     }
 73     
 74     public void someOtherMethod(final String text){
 75         this.invocationCount ++;
 76         this.impl.someOtherMethod(text);
 77     }
 78 
 79     public int getInvocationCount() {
 80         return invocationCount;
 81     }
 82 
 83     public void setInvocationCount(int invocationCount) {
 84         this.invocationCount = invocationCount;
 85     }
 86 }
 87 
 88 4 定义工厂
 89 package com.proxy;
 90 
 91 import java.lang.reflect.InvocationHandler;
 92 import java.lang.reflect.Proxy;
 93 
 94 
 95 public class SomeClassFactory {
 96     /*//static proxy
 97     public static final SomeClass getStaticSomeClassProxy(){
 98         SomeClassImpl impl = new SomeClassImpl(System.getProperty("user.name"));
 99         if (false) {//generally when debuging
100             return new SomeClassCountingProxy(impl);
101         } else {
102             return new SomeClassProxy(impl);
103         }
104     }
105     */
106     
107     //dynamic proxy
108     public static final SomeClass getDynamicSomeClassProxy(){
109         SomeClassImpl impl = new SomeClassImpl(System.getProperty("user.name"));
110         ClassLoader loader = SomeClassImpl.class.getClassLoader();
111         Class[] interfaces = new Class[] {SomeClass.class};
112         InvocationHandler handler = new MethodCountingHandler(impl);
113         SomeClass proxy = (SomeClass)Proxy.newProxyInstance(loader, interfaces, handler);
114         return proxy;
115     }
116 }
117 
118 5 定义InvocationHandler，主要通过这个类实现动态代理功能及其扩展
119 package com.proxy;
120 
121 import java.lang.reflect.InvocationTargetException;
122 import java.lang.reflect.InvocationHandler;
123 import java.lang.reflect.Method;
124 
125 
126 public class MethodCountingHandler implements InvocationHandler{
127 
128     private final Object impl;
129     private int invocationCount = 0;
130     
131     public MethodCountingHandler(final Object impl){
132         this.impl = impl;
133     }
134     
135     public int getInvocationCount(){
136         return invocationCount;
137     }
138     
139     @Override
140     public Object invoke(Object proxy, Method method, Object[] args)
141             throws Throwable {
142         try {
143             this.invocationCount++;
144             Object result = method.invoke(impl, args);
145             return result;
146         } catch (final InvocationTargetException e) {
147             throw e.getTargetException();
148         }
149     }
150 }
151 
152 
153 6 定义客户端
154 package com.proxy;
155 
156 import java.lang.reflect.InvocationHandler;
157 import java.lang.reflect.Proxy;
158 
159 
160 public class DemoDynamic {
161 
162     /**
163      * @param args
164      */
165     public static void main(String[] args) {
166         /*//no use factory
167         SomeClassImpl real = new SomeClassImpl(System.getProperty("user.name"));
168         InvocationHandler dynamic = new MethodCountingHandler(real);
169         Class clz = real.getClass();
170         SomeClass obj = (SomeClass)Proxy.newProxyInstance(clz.getClassLoader(), clz.getInterfaces(), dynamic);
171         obj.someMethod();
172         obj.someOtherMethod("test");
173         */
174         
175         //use factory to get a real object
176         SomeClass obj = (SomeClass)SomeClassFactory.getDynamicSomeClassProxy();
177         obj.someMethod();
178         obj.someOtherMethod("test");
179         
180         //the invocationhandler works as proxy function, extend the function of real object
181         InvocationHandler handler = Proxy.getInvocationHandler(obj);
182         if (handler instanceof MethodCountingHandler) {
183             System.out.println(((MethodCountingHandler)handler).getInvocationCount());
184         }
185     }
186 }

运行结果为：

Administrator
test
2

参照链接：

http://callan.javaeye.com/blog/161806

http://aronlulu.javaeye.com/blog/613461

http://blog.csdn.net/goodluckforlove/archive/2009/10/13/4663079.aspx