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标题:
JDK Dynamic Proxy模式的简单范例
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作者:
sesutough
时间:
2007-06-06 09:37
标题:
JDK Dynamic Proxy模式的简单范例
JDK Dynamic Proxy模式的简单范例
在JDK1.3版本中引入了Dynamic Proxy的代理机制，通过实现java.lang.reflect.InvocationHandler接口，可以实现拦截需要改写的方法。下面是一个简单范例。
有下面一个接口TestInterface和它的一个实现TestImpl：
package sample.proxy;
/**//**
* Title:
*
* Description:
*
* Copyright: Copyright (c) 2005
*
* Company:
*
* @author George Hill
* @version 1.0
*/
public interface TestInterface
{
public String print();
}
package sample.proxy;
/**//**
* Title:
*
* Description:
*
* Copyright: Copyright (c) 2005
*
* Company:
*
* @author George Hill
* @version 1.0
*/
public class TestImpl implements TestInterface
{
public String print()
{
return "Hello, it's from TestImpl class";
}
}
下面拦截print方法，调用自己的实现，这需要实现java.lang.reflect.InvocationHandler接口。
package sample.proxy;
import java.lang.reflect.*;
/**//**
* Title:
*
* Description:
*
* Copyright: Copyright (c) 2005
*
* Company:
*
* @author George Hill
* @version 1.0
*/
public class TestHandler implements InvocationHandler
{
TestInterface test;
/**//**
* 将动态代理绑定到指定的TestInterface
* @param test TestInterface
* @return TestInterface 绑定代理后的TestInterface
*/
public TestInterface bind(TestInterface test)
{
this.test = test;
TestInterface proxyTest = (TestInterface) Proxy.newProxyInstance(
test.getClass().getClassLoader(), test.getClass().getInterfaces(), this);
return proxyTest;
}
/**//**
* 方法调用拦截器，拦截print方法
* @param proxy Object
* @param method Method
* @param args Object[]
* @return Object
* @throws Throwable
*/
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable
{
// 如果调用的是print方法，则替换掉
if ("print".equals(method.getName()))
{
return "HaHa, It's come from TestHandler";
} else
{
return method.invoke(this.test, args);
}
}
}
下面是测试用例：
package sample.test;
import junit.framework.*;
import sample.proxy.*;
/**//**
* Title:
*
* Description:
*
* Copyright: Copyright (c) 2005
*
* Company:
*
* @author George Hill
* @version 1.0
*/
public class TestDynamicProxy extends TestCase
{
private TestInterface test = null;
protected void setUp() throws Exception
{
super.setUp();
TestHandler handler = new TestHandler();
// 用handler去生成实例
test = handler.bind(new TestImpl());
}
protected void tearDown() throws Exception
{
test = null;
super.tearDown();
}
public void testPrint()
{
System.out.println(test.print());
}
}
运行测试用例，可以看到输出的是“HaHa, It's come from TestHandler”。
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