Struts2拦截器的底层实现(AOP思想)

1.目标类接口：

package com.interceptor;

public interface TargetInterface 
{
    public void doSomething();
}

2.目标类实现：

package com.interceptor;

public class Target implements TargetInterface
{
    public void doSomething() 
    {
        System.out.println("doSomething");
    }
}

3.自定义拦截器：

package com.interceptor;

public class Interceptor 
{

        public void before()
        {
            System.out.println("before");
        }
        
        public void after()
        {
            System.out.println("after");
        }
}

4.将拦截器类和目标代码类结合在一起的处理类：

package com.interceptor;

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

public class MyHandler implements InvocationHandler 
{

    private Object object;
    private Interceptor interceptor=new Interceptor();
    
    public void setObject(Object object)
    {
        this.object=object;
    }
    
    public Object invoke(Object proxy, Method method, Object[] args)
            throws Throwable {
        
        Object result=null;
        interceptor.before();
        result=method.invoke(object, args);
        interceptor.after();
        return result;
    }
}

5.将目标类进行包装后的代理类：

package com.interceptor;
import java.lang.reflect.Proxy;

public class MyProxy 
{
    public Object getProxy(Object object)
    {
        MyHandler myHandler=new MyHandler();
        myHandler.setObject(object);
        return Proxy.newProxyInstance(Target.class.getClassLoader(),object.getClass().getInterfaces(),myHandler);
    }
}

6.客户端程序测试类：

package com.interceptor;

public class Client 
{
    public static void main(String[] args) {
        TargetInterface target=new Target();
        MyProxy myProxy=new MyProxy();
        TargetInterface proxy=(TargetInterface)myProxy.getProxy(target);
        proxy.doSomething();
    }

}

最后运行结果是：