javaweb监听器和juery技术

监听servlet创建

java 复制代码

package com.hspedu.listener;

import javax.servlet.ServletContext;
import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;

/**
 * 老韩解读
 * 1. 当一个类实现了 ServletContextListener
 * 2. 该类就是一个监听器
 * 3. 该类可以监听的事件 由该类实现的监听接口决定 ，比如 实现ServletContextListener
 *    , 则该类就可以监听 ServletContext对象的创建和销毁, 以此类推
 * 4. HspServletContextListener 就是一个监听者
 * 5. 当web应用启动时，就会产生 ServletContextEvent 事件, 会调用监听器的对应事件处理方法
 *    contextInitialized, 同时会传递 事件对象
 * 6. 程序员可以通过 ServletContextEvent 事件对象，来获取需要的信息, 然后再进行业务处理
 * 7. tomcat怎么知道这个监听器存在 ? 因为我们需要在web.xml中配置
 */
public class HspServletContextListener implements ServletContextListener {
    @Override
    public void contextInitialized(ServletContextEvent servletContextEvent) {
        ServletContext servletContext = servletContextEvent.getServletContext();
        System.out.println("HspServletContextListener 监听到 " +
                servletContext + " 被创建..");
        //如果我们获取到ServletContext 对象..进行业务处理

    }

    @Override
    public void contextDestroyed(ServletContextEvent servletContextEvent) {
        ServletContext servletContext = servletContextEvent.getServletContext();
        System.out.println("HspServletContextListener 监听到 " +
                servletContext + " 被销毁..");

        //比如可以对servletContext 数据进行处理， 或者日志的管理...
        System.out.println("进行处理工作.....");
    }
}

java 复制代码

HspHttpSessionListener 监听到 session销毁= FAEC215D4C92B5325848CF7438FC7138
用户id=FAEC215D4C92B5325848CF7438FC7138 离线
HspHttpSessionListener 监听到 session销毁= 2785B79C0D9A36C33CA215EA5C23D254
用户id=2785B79C0D9A36C33CA215EA5C23D254 离线

监听文本属性的变化

java 复制代码

package com.hspedu.listener;

import javax.servlet.ServletContextAttributeEvent;
import javax.servlet.ServletContextAttributeListener;

public class HspServletContextAttributeListener implements ServletContextAttributeListener {
    @Override
    public void attributeAdded(ServletContextAttributeEvent servletContextAttributeEvent) {

        System.out.println("HspServletContextAttributeListener 监听到添加属性.."
                + servletContextAttributeEvent.getName() + "=" + servletContextAttributeEvent.getValue() );
    }

    @Override
    public void attributeRemoved(ServletContextAttributeEvent servletContextAttributeEvent) {

        System.out.println("HspServletContextAttributeListener 监听到删除属性.."
                + servletContextAttributeEvent.getName() + "=" + servletContextAttributeEvent.getValue() );
    }

    @Override
    public void attributeReplaced(ServletContextAttributeEvent servletContextAttributeEvent) {

        System.out.println("HspServletContextAttributeListener 监听到修改属性.."
                + servletContextAttributeEvent.getName() + "=" + servletContextAttributeEvent.getValue() );

    }
}

java 复制代码

package com.hspedu.servlet;

import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import java.io.IOException;

public class HiServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        
        //给servletContext 对象操作属性
        ServletContext servletContext = request.getServletContext();
        servletContext.setAttribute("name", "韩顺平教育");
        servletContext.setAttribute("name", "老韩教育");
        servletContext.removeAttribute("name");

        //获取session对象
        //Filter

        HttpSession session = request.getSession();
        session.setAttribute("age", 100);
        session.setAttribute("age", 400);
        session.removeAttribute("age");

        System.out.println("HiServlet 处理完毕....");
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doPost(request, response);
    }
}

java 复制代码

HspHttpSessionListener 监听到 session销毁= FAEC215D4C92B5325848CF7438FC7138
用户id=FAEC215D4C92B5325848CF7438FC7138 离线
HspHttpSessionListener 监听到 session销毁= 2785B79C0D9A36C33CA215EA5C23D254
用户id=2785B79C0D9A36C33CA215EA5C23D254 离线
HspRequestListener 监听到 request对象创建
记录访问日志....
访问IP= 127.0.0.1
访问的资源= http://localhost:8080/filter/hi
HspServletContextAttributeListener 监听到添加属性..name=韩顺平教育
HspServletContextAttributeListener 监听到修改属性..name=韩顺平教育
HspServletContextAttributeListener 监听到删除属性..name=老韩教育
HspHttpSessionListener 监听到 session创建= A8714B2384A7FF7505EA20A456952DAC
用户id=A8714B2384A7FF7505EA20A456952DAC 上线
HspHttpSessionAttributeListener 监听到session添加属性age=100
HspHttpSessionAttributeListener 监听到session修改属性age=100
HspHttpSessionAttributeListener 监听到session删除属性age
HiServlet 处理完毕....
HspRequestListener 监听到 request对象被销毁

监听session创建

java 复制代码

package com.hspedu.listener;

import javax.servlet.http.HttpSession;
import javax.servlet.http.HttpSessionEvent;
import javax.servlet.http.HttpSessionListener;

public class HspHttpSessionListener implements HttpSessionListener {
    @Override
    public void sessionCreated(HttpSessionEvent httpSessionEvent) {
        HttpSession session = httpSessionEvent.getSession();
        //当session创建时，我们给它设置一个生命周期 30s
        session.setMaxInactiveInterval(30);
        System.out.println("HspHttpSessionListener 监听到 session创建= " +
                session.getId());
        System.out.println("用户id=" + session.getId() + " 上线");
    }

    @Override
    public void sessionDestroyed(HttpSessionEvent httpSessionEvent) {
        HttpSession session = httpSessionEvent.getSession();
        System.out.println("HspHttpSessionListener 监听到 session销毁= " +
                session.getId());
        System.out.println("用户id=" + session.getId() + " 离线");
    }
}

监听session属性改变

java 复制代码

package com.hspedu.listener;

import javax.servlet.http.HttpSession;
import javax.servlet.http.HttpSessionAttributeListener;
import javax.servlet.http.HttpSessionBindingEvent;

public class HspHttpSessionAttributeListener implements HttpSessionAttributeListener {
    @Override
    public void attributeAdded(HttpSessionBindingEvent httpSessionBindingEvent) {
        //HttpSession session = httpSessionBindingEvent.getSession();
        System.out.println("HspHttpSessionAttributeListener 监听到session添加属性" +
                httpSessionBindingEvent.getName() + "=" + httpSessionBindingEvent.getValue());
    }

    @Override
    public void attributeRemoved(HttpSessionBindingEvent httpSessionBindingEvent) {
        HttpSession session = httpSessionBindingEvent.getSession();

        System.out.println("HspHttpSessionAttributeListener 监听到session删除属性" +
                httpSessionBindingEvent.getName());
    }

    @Override
    public void attributeReplaced(HttpSessionBindingEvent httpSessionBindingEvent) {

        System.out.println("HspHttpSessionAttributeListener 监听到session修改属性" +
                httpSessionBindingEvent.getName() + "=" + httpSessionBindingEvent.getValue());
    }
}

监听request

java 复制代码

package com.hspedu.listener;

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

public class HspRequestListener implements ServletRequestListener {

    @Override
    public void requestInitialized(ServletRequestEvent servletRequestEvent) {
        System.out.println("HspRequestListener 监听到 request对象创建");
        ServletRequest servletRequest = servletRequestEvent.getServletRequest();
        System.out.println("记录访问日志....");
        System.out.println("访问IP= " + servletRequest.getRemoteAddr());
        System.out.println("访问的资源= " + ((HttpServletRequest)servletRequest).getRequestURL());
    }
    @Override
    public void requestDestroyed(ServletRequestEvent servletRequestEvent) {

        System.out.println("HspRequestListener 监听到 request对象被销毁");
    }


}

filter过滤器的使用

java 复制代码

<%--
  Created by IntelliJ IDEA.
  User: 韩顺平
  Version: 1.0
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>管理后台登录</title>
</head>
<body>
<h1>管理后台登录</h1>
<%
    System.out.println("request=" + request);
%>
<form action="<%=request.getContextPath() %>/login" method="post">
    u：<input type="text" name="username"/> <br/><br/>
    p：<input type="password" name="password"/> <br/><br/>
    <input type="submit" value="用户登录"/></form>
</body>
</html>

java 复制代码

package com.hspedu.servlet;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

public class LoginCheckServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //获取到用户名和密码->DB
        //假设密码是123456, 就可以通过
        String username = request.getParameter("username");
        String password = request.getParameter("password");
        System.out.println("request=" + request);
        if("123456".equals(password)) {

            //合法, 讲用户名，加入session
            request.getSession().setAttribute("username", username);
            //请求转发到admin.jsp
            request.getRequestDispatcher("/manage/admin.jsp")
                    .forward(request,response);
        } else {
            //不合法, 返回登录页面
            request.getRequestDispatcher("/login.jsp")
                    .forward(request,response);

        }
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doPost(request, response);
    }
}

为其添加过滤器

java 复制代码

package com.hspedu.filter;

import javax.servlet.*;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpSession;
import java.io.IOException;

/**
 * 老韩解读
 * 1. filter在web项目启动时, 由tomcat 来创建filter实例, 只会创建一个
 * 2. 会调用filter默认的无参构造器, 同时会调用 init方法, 只会调用一次
 * 3. 在创建filter实例时，同时会创建一个FilterConfig对象,并通过init方法传入
 * 4. 通过FilterConfig对象，程序员可以获取该filter的相关配置信息
 * 5. 当一个http请求和该filter的的url-patter匹配时，就会调用doFilter方法
 * 6. 在调用doFilter方法时,tomcat会同时创建ServletRequest 和 ServletResponse 和 FilterChain对象
 * , 并通过doFilter传入.
 * 7. 如果后面的请求目标资源(jsp,servlet..) 会使用到request，和 response，那么会继续传递
 * 8. 老师的提醒:到javaweb - ssm - springboot , 有 浏览器和 web服务器(tomcat)参与, 而这两个部分不是我们
 *    程序员自己写，所以理解起来比 java se要困难!!!
 */
public class ManageFilter implements Filter {

    private int count = 0;

    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
        //当Tomcat 创建 Filter创建，就会调用该方法，进行初始化
        //老韩提醒：回忆我们自己实现tomcat底层机制+servlet程序， 就会了然
        //
        System.out.println("ManageFilter init被调用...");
    }

    @Override
    public void doFilter(ServletRequest servletRequest,
                         ServletResponse servletResponse,
                         FilterChain filterChain) throws IOException, ServletException {

        System.out.println("ManageFilter doFilter() 被调用=" + (++count));

        //到每次调用该filter时，doFilter就会被调用

        //如果这里，没有调用继续请求的方法，则就停止
        //如果继续访问目标资源-> 等价于放行

        //老师说明：在调用过滤器前，servletRequest对象=request已经被创建并封装
        //所以：我们这里就可以通过servletRequest获取很多信息, 比如访问url , session
        //比如访问的参数 ... 就可以做事务管理，数据获取，日志管理等
        //获取到session
        //可以继续使用 httpServletRequest 方法.
        HttpServletRequest httpServletRequest = (HttpServletRequest) servletRequest;
        System.out.println("输入密码=" + httpServletRequest.getParameter("password"));
        HttpSession session = httpServletRequest.getSession();
        //获取username session对象, 还可以继续使用
        Object username = session.getAttribute("username");
        if (username != null) {
            //老韩解读filterChain.doFilter(servletRequest, servletResponse)
            //1. 继续访问目标资源url
            //2. servletRequest 和 servletResponse 对象会传递给目标资源/文件
            //3. 一定要理解filter传递的两个对象，再后面的servlet/jsp 是同一个对象(指的是在一次http请求)
            System.out.println("servletRequest=" + servletRequest);
            System.out.println("日志信息==");
            System.out.println("访问的用户名=" + username.toString());
            System.out.println("访问的url=" + httpServletRequest.getRequestURL());
            System.out.println("访问的IP=" + httpServletRequest.getRemoteAddr());
            filterChain.doFilter(servletRequest, servletResponse);
        } else {//说明没有登录过..回到登录页面
            servletRequest.getRequestDispatcher("/login.jsp").
                    forward(servletRequest, servletResponse);
        }
    }

    @Override
    public void destroy() {
        //当filter被销毁时，会调用该方法
        System.out.println("ManageFilter destroy()被调用..");
    }
}

最终到达的页面

java 复制代码

<%--
  Created by IntelliJ IDEA.
  User: 韩顺平
  Version: 1.0
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>后台管理</title>
    <base href="<%=request.getContextPath() %>/manage/"/>
</head>
<body>
<h1>后台管理</h1>
<%
    //验证request对象是和前面的filter是一个对象
    System.out.println("request=" + request);
%>
<a href="#">用户列表</a>||<a href="#">添加用户</a>||<a href="#">删除用户</a>
<hr/>
<img src="shunping.jpg" height="300"/>
</body>
</html>

过滤的进一步使用

java 复制代码

package com.hspedu.filter;

import javax.servlet.*;
import java.io.IOException;
import java.util.Enumeration;

/**
 * 老师解读： 演示FilterConfig使用
 *
 */
public class HspFilterConfig implements Filter {

    private String ip; //从配置获取的ip

    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
        System.out.println("HspFilterConfig init() 被调用..");
        //通过filterConfig 获取相关的参数
        String filterName = filterConfig.getFilterName();
        ip = filterConfig.getInitParameter("ip");
        ServletContext servletContext = filterConfig.getServletContext();
        //可以获取到该filter所有的配置参数名
        Enumeration<String> initParameterNames =
                filterConfig.getInitParameterNames();

        //遍历枚举
        while (initParameterNames.hasMoreElements()) {
            System.out.println("名字=" + initParameterNames.nextElement());
        }

        System.out.println("filterName= " + filterName);
        System.out.println("ip= " + ip);
        System.out.println("servletContext= " + servletContext);


    }

    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {

        //通过forbidden ip 来进行控制
        //先获取到访问ip
        String remoteAddr = servletRequest.getRemoteAddr();
        if(remoteAddr.contains(ip)) {
            System.out.println("封杀该网段..");
            servletRequest.getRequestDispatcher("/login.jsp").
                    forward(servletRequest,servletResponse);
            return; //直接返回
        }

        //继续访问目标资源
        filterChain.doFilter(servletRequest,servletResponse);
    }

    @Override
    public void destroy() {

    }
}

java 复制代码

<filter>
        <filter-name>config</filter-name>
        <filter-class>
            com.hspedu.filter.HspFilterConfig
        </filter-class>
        <init-param>
            <param-name>ip</param-name>
            <param-value>127.0</param-value>
        </init-param>
        <init-param>
            <param-name>port</param-name>
            <param-value>8888</param-value>
        </init-param>
    </filter>
    <filter-mapping>
        <filter-name>config</filter-name>
        <url-pattern>/abc/*</url-pattern>
    </filter-mapping>

过滤器作业、

java 复制代码

<%--
  Created by IntelliJ IDEA.
  User: 韩顺平
  Version: 1.0
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java"%>
<html>
<head>
    <title>Title</title>
</head>
<body>
<h1>发表对阿凡达电影评论</h1>
过滤词: 苹果, 香蕉 ${errorInfo}
<form method="post" action="<%=request.getContextPath()%>/topic/showTopic.jsp">
    用户: <input type="text" name="username"><br/>
    评论: <textarea rows="10" name="content" cols="20"></textarea><br/>
    <input type="submit" value="发表评论">
</form>
</body>
</html>

java 复制代码

package com.hspedu.filter;

import javax.servlet.*;
import java.io.IOException;

public class TopicFilter implements Filter {

    //属性-> 存放禁用词
    private String[] forbiddenWords = null;

    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
        //获取禁用词
        String forbiddenword = filterConfig.getInitParameter("forbid");
        forbiddenWords = forbiddenword.split(",");
    }

    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {

        //解决从topic.jsp 提交的中文乱码问题
        servletRequest.setCharacterEncoding("utf-8");

        //判断评论是不是有禁用词
        String content = servletRequest.getParameter("content");
        //循环遍历一把，看看有没有禁用词
        for (String forbiddenWord : forbiddenWords) {//java基础
            if (content.contains(forbiddenWord)) {
                //返回topic.jsp
                servletRequest.setAttribute("errorInfo", "你输入的有禁用词");
                servletRequest.getRequestDispatcher("/topic.jsp")
                        .forward(servletRequest, servletResponse);
                return;//返回
            }
        }

        //继续到目标
        filterChain.doFilter(servletRequest, servletResponse);
    }

    @Override
    public void destroy() {

    }
}

过滤链

java 复制代码

package com.hspedu.filter;

import javax.servlet.*;
import java.io.IOException;

public class AFilter implements Filter {
    @Override
    public void init(FilterConfig filterConfig) throws ServletException {

    }

    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {

        System.out.println("AFilter---> 线程id=" +
                Thread.currentThread().getId());

        System.out.println("AFilter doFilter 的前置代码...");
        System.out.println("执行 AFilter doFilter()");
        filterChain.doFilter(servletRequest, servletResponse);
        System.out.println("AFilter doFilter 的后置代码...");
    }

    @Override
    public void destroy() {

    }
}

java 复制代码

package com.hspedu.filter;

import javax.servlet.*;
import java.io.IOException;

public class BFilter implements Filter {
    @Override
    public void init(FilterConfig filterConfig) throws ServletException {

    }

    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {

        System.out.println("BFilter---> 线程id=" +
                Thread.currentThread().getId());

        System.out.println("BFilter doFilter 的前置代码...");

        System.out.println("执行 BFilter doFilter()");
        filterChain.doFilter(servletRequest, servletResponse);
        System.out.println("BFilter doFilter 的后置代码...");
    }

    @Override
    public void destroy() {

    }
}