java静态代理和动态代理

先看静态代理的代码：

package com.reflect;

public interface HelloWorld {
public void sayHi();
}

package com.reflect;

public class HelloWorldImpl implements HelloWorld {

@Override
public void sayHi() {
System.out.println("Hi");
}

}

package com.reflect;

public class HelloWorldStaticProxy implements HelloWorld {
private HelloWorld helloWorld;

public HelloWorldStaticProxy(HelloWorld helloWorld) {
this.helloWorld = helloWorld;
}

@Override
public void sayHi() {
helloWorld.sayHi();
}

}

package com.reflect;

public interface Welcome {

public void welcome();
}

package com.reflect;

public class WelcomeImpl implements Welcome {

@Override
public void welcome() {
System.out.println("welcome");
}

}

package com.reflect;

public class WelcomeStaticProxy implements Welcome {
private Welcome welcome;

public WelcomeStaticProxy(Welcome welcome) {
this.welcome = welcome;
}

@Override
public void welcome() {
welcome.welcome();
}

}

测试代码

package com.reflect;

import junit.framework.TestCase;

public class TestProxy extends TestCase {

public void testStaticProxy() {
HelloWorld helloWorld = new HelloWorldStaticProxy(new HelloWorldImpl());
helloWorld.sayHi();

Welcome welcomeProxy = new WelcomeStaticProxy(new WelcomeImpl());
welcomeProxy.welcome();
}

public void testDynamicProxy() {
HelloWorldInvocationHandler handler = new HelloWorldInvocationHandler();

HelloWorld helloWorld = (HelloWorld) handler.bind(new HelloWorldImpl());
helloWorld.sayHi();

Welcome welcome = (Welcome) handler.bind(new WelcomeImpl());
welcome.welcome();
}
}

测试一下静态代理

运行testStaticProxy，输出：

Hi
welcome

看看代码，发现一个静态代理类对应一个接口，有多少个接口，就需要多少个静态代理类。

现在看动态代理的代码：

package com.reflect;

import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;

public class HelloWorldInvocationHandler implements InvocationHandler {
private Object target;

public Object bind(Object target) {
this.target = target;
return Proxy.newProxyInstance(target.getClass().getClassLoader(), target.getClass().getInterfaces(), this);
}

@Override
public Object invoke(Object proxy, Method method, Object[] args)
throws Throwable {
return method.invoke(target, args);
}

}

运行testDynamicProxy：

输出

Hi
welcome

看到代码，一个动态代理类，可以对应多个接口，因为参数是Object。这样，多个接口，只要一个代理类就行了。