struts2模拟拦截器实现的小例子

　　1.拦截器接口

public interface Interceptor {
    void interceptor(ActionInvocation invocation);
}

　　2.给接口做3个实现

public class FirstInterceptor implements Interceptor {
    public void interceptor(ActionInvocation invocation) {
        System.out.println(1);
        invocation.invoke();
        System.out.println(-1);
    }
}

public class SecondInterceptor implements Interceptor{
    public void interceptor(ActionInvocation invocation) {
        System.out.println(2);
        invocation.invoke();
        System.out.println(-2);
    }
}

public class ThirdInterceptor implements Interceptor{
    public void interceptor(ActionInvocation invocation) {
        System.out.println(3);
        invocation.invoke();
        System.out.println(-3);
    }
}

　　3.一个Action对象

public class Action {
    public void execute(){
        System.out.println("execute执行了！！！");
    }
}

　　4.ActionInvocation在初始化的时候，把3个拦截器的实现初始化到List里，模拟拦截器栈

public class ActionInvocation {
    List<Interceptor> interceptors = new ArrayList<Interceptor>();
    int index = -1;
    Action a = new Action();
    
    public ActionInvocation(){
        this.interceptors.add(new FirstInterceptor());
        this.interceptors.add(new SecondInterceptor());
        this.interceptors.add(new ThirdInterceptor());
    }
    public void invoke() {
        index++;
        
        if (index >= this.interceptors.size()) {
            a.execute();
        } else {
            this.interceptors.get(index).interceptor(this);
        }
    }
}

　　5.运行

public class Main {
    public static void main(String[] args) {
        new ActionInvocation().invoke();
    }
}

　　6.结果

1
2
3
execute执行了！！！
-3
-2
-1