动态代理例子

最新推荐文章于 2025-03-19 19:35:48 发布

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最新推荐文章于 2025-03-19 19:35:48 发布

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动态代理实现例子2：　　

 
    
  
import java.util.List;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import java.util.Vector;

public class VectorProxy implements InvocationHandler
{
    private Object proxyObj;

    public VectorProxy(Object obj)
    {
        this.proxyObj = obj;
    }

    public static Object factory(Object obj)
    {
        Class<?> classType = obj.getClass();

        return Proxy.newProxyInstance(classType.getClassLoader(), //类加载器随便指定一个就可以
                classType.getInterfaces(), new VectorProxy(obj));
    }

    @Override
    public Object invoke(Object proxy, Method method, Object[] args)
            throws Throwable
    {
        System.out.println("Before calling: " + method);

        // 打印出方法参数
        if (args != null)
        {
            for (Object obj : args)
            {
                System.out.println(obj);
            }
        }

        // 调用方法
        Object object = method.invoke(proxyObj, args);

        System.out.println("After calling: " + method);

        return object;
    }

    public static void main(String[] args)
    {
        List v = (List) factory(new Vector());
        
        System.out.println(v.getClass().getName());
        
        v.add("New");
        v.add("York");
        
        System.out.println(v);
        
        v.remove(0);
        System.out.println(v);

    }

} 
    
  

动态代理实现例子3：

　　这个例子中定义了一个接口：　

public interface Foo
{
    public void doAction();
}

　　这个接口有两个实现类：

public class FooImpl1 implements Foo
{
    @Override
    public void doAction()
    {
        System.out.println("From Implement 1 !");
    }
}

public class FooImpl2 implements Foo
{
    @Override
    public void doAction()
    {
        System.out.println("From Implement 2 !");
    }
}

　　定义invocation handler，其中的set方法使得实际对象是可更换的:

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

public class CommonInvocationHandler implements InvocationHandler
{
    private Object target;

    public CommonInvocationHandler()
    {

    }

    public CommonInvocationHandler(Object obj)
    {
        this.target = obj;
    }

    public void setTarget(Object target)
    {
        this.target = target;
    }

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

}

　　使用：

import java.lang.reflect.Proxy;

public class Demo
{
    public static void main(String[] args)
    {
        CommonInvocationHandler handler = new CommonInvocationHandler();

        Foo f = null;

        handler.setTarget(new FooImpl1());

        f = (Foo) Proxy.newProxyInstance(Foo.class.getClassLoader(),
                new Class[] { Foo.class }, handler);
        
        f.doAction();
        System.out.println("----------------------------");
        handler.setTarget(new FooImpl2());    
        f.doAction();

    }

}