【设计模式】代理模式

代理模式就是控制对象的访问，客户访问代理对象，代理对象找真正的对象做事。包括静态代理，动态代理，虚拟代理，远程代理等。这里就简单些下静态代理和动态代理。

1.创建计算器接口

1 package cn.sp.test4;
2 
3 /**
4  * Created by 2YSP on 2017/9/1.
5  */
6 public interface Calculator {
7     int add(int a,int b);
8 }

2.创建实现类（真正做事的）

 1 package cn.sp.test4;
 2 
 3 /**
 4  * Created by 2YSP on 2017/9/1.
 5  * 实现类
 6  */
 7 public class CalculatorImpl implements Calculator {
 8     @Override
 9     public int add(int a, int b) {
10         return a+b;
11     }
12 }

3.创建其代理对象

 1 package cn.sp.test4;
 2 
 3 /**
 4  * Created by 2YSP on 2017/9/1.
 5  * 静态代理类
 6  */
 7 public class CalculatorProxy implements Calculator{
 8     Calculator calculator;
 9 
10     public CalculatorProxy(Calculator calculator){
11         this.calculator = calculator;
12     }
13 
14     @Override
15     public int add(int a, int b) {
16         //具体执行前可以做的工作
17         int result = calculator.add(a, b);
18         //具体执行后可以做的工作
19         return result;
20     }
21 }

4.测试

 1 package cn.sp.test4;
 2 
 3 import jdk.internal.org.objectweb.asm.Handle;
 4 
 5 import java.lang.reflect.Proxy;
 6 
 7 /**
 8  * Created by 2YSP on 2017/9/1.
 9  */
10 public class Test {
11     /**
12      * 动态代理测试
13      */
14     public static  void testDynamicProxy(){
15         Calculator calculator = new CalculatorImpl();
16         LogHandler logHandler = new LogHandler(calculator);
17         //动态生成代理类
18         Calculator proxy = (Calculator)Proxy.newProxyInstance(
19                 calculator.getClass().getClassLoader(), calculator.getClass().getInterfaces(), logHandler);
20         int result = proxy.add(1, 1);
21         System.out.println(result);
22     }
23 
24     public static void main(String[] args) {
25 //        testDynamicProxy();
26         testStaticProxy();
27     }
28 
29     /**
30      * 测试静态代理
31      */
32     public static void testStaticProxy(){
33         Calculator calculator = new CalculatorImpl();
34         CalculatorProxy calculatorProxy = new CalculatorProxy(calculator);
35         int i = calculatorProxy.add(1, 2);
36         System.out.println(i);
37     }
38 }

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动态代理部分：

 1 package cn.sp.test4;
 2 
 3 import java.lang.reflect.InvocationHandler;
 4 import java.lang.reflect.Method;
 5 
 6 /**
 7  * Created by 2YSP on 2017/9/1.
 8  */
 9 public class LogHandler implements InvocationHandler {
10     Object obj;
11 
12     LogHandler(Object obj){
13         this.obj = obj;
14     }
15     @Override
16     public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
17         this.doBefore();
18         Object o = method.invoke(obj, args);
19         this.doAfter();
20         return o;
21     }
22 
23     public void doBefore(){
24         System.out.println("do this before");
25     }
26 
27     public void doAfter(){
28         System.out.println("do this after");
29     }
30 }