• day16学习总结

    一、监听器

    简介：

            监听器属于java web中的三大组件之一

            监听器用于监听内置对象创建 监听内置对象作用域的值 监听容器(spring)的初始化操作

    分类：

            监听内置对象的创建与销毁

            监听内置对象的作用域的值

            监听session中对象的绑定

    监听内置对象的创建与销毁：

            ServletContextListener

    1. package com.qf.listenter;
    2.  
    3. import javax.servlet.ServletContextEvent;
    4. import javax.servlet.ServletContextListener;
    5. import javax.servlet.annotation.WebListener;
    6.  
    7. /*@WebListener*/
    8. public class MyServletContextListener implements ServletContextListener {
    9.     @Override
    10.     public void contextInitialized(ServletContextEvent servletContextEvent) {
    11.         System.out.println("创建");
    12.     }
    13.  
    14.     @Override
    15.     public void contextDestroyed(ServletContextEvent servletContextEvent) {
    16.         System.out.println("销毁");
    17.     }
    18. }

            

    ServletRequestListener 

    1. package com.qf.listenter;
    2.  
    3. import javax.servlet.ServletRequestEvent;
    4. import javax.servlet.ServletRequestListener;
    5. import javax.servlet.annotation.WebListener;
    6.  
    7. /*@WebListener*/
    8. public class MyServletRequestListener implements ServletRequestListener {
    9.     @Override
    10.     public void requestDestroyed(ServletRequestEvent servletRequestEvent) {
    11.         System.out.println("创建");
    12.     }
    13.  
    14.     @Override
    15.     public void requestInitialized(ServletRequestEvent servletRequestEvent) {
    16.         System.out.println("销毁");
    17.     }
    18. }
    1. package com.qf.servlet;
    2.  
    3. import javax.servlet.ServletException;
    4. import javax.servlet.annotation.WebServlet;
    5. import javax.servlet.http.HttpServlet;
    6. import javax.servlet.http.HttpServletRequest;
    7. import javax.servlet.http.HttpServletResponse;
    8. import javax.servlet.http.HttpSession;
    9. import java.io.IOException;
    10. @WebServlet(name = "servlet01",urlPatterns = "/servlet01")
    11. public class Servlet01 extends HttpServlet {
    12.     @Override
    13.     protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    14.         System.out.println("发送了请求");
    15.         /*HttpSession session = req.getSession();
    16.         //手动销毁
    17.         session.invalidate();*/
    18.     }
    19. }

            

    HttpSessionListener

    1. package com.qf.listenter;
    2.  
    3. import javax.servlet.annotation.WebListener;
    4. import javax.servlet.http.HttpSessionEvent;
    5. import javax.servlet.http.HttpSessionListener;
    6. /*@WebListener*/
    7. public class MyHttpSessionListener implements HttpSessionListener {
    8.     @Override
    9.     public void sessionCreated(HttpSessionEvent httpSessionEvent) {
    10.         System.out.println("创建");
    11.     }
    12.  
    13.     @Override
    14.     public void sessionDestroyed(HttpSessionEvent httpSessionEvent) {
    15.         System.out.println("销毁");
    16.     }
    17. }
    1. package com.qf.servlet;
    2.  
    3. import javax.servlet.ServletException;
    4. import javax.servlet.annotation.WebServlet;
    5. import javax.servlet.http.HttpServlet;
    6. import javax.servlet.http.HttpServletRequest;
    7. import javax.servlet.http.HttpServletResponse;
    8. import javax.servlet.http.HttpSession;
    9. import java.io.IOException;
    10. @WebServlet(name = "servlet01",urlPatterns = "/servlet01")
    11. public class Servlet01 extends HttpServlet {
    12.     @Override
    13.     protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    14.         System.out.println("发送了请求");
    15.         HttpSession session = req.getSession();
    16.         //手动销毁
    17.         session.invalidate();
    18.     }
    19. }

    监听内置对象作用域的值：

            ServletContextAttributeListener

    1. package com.qf.listenter;
    2.  
    3. import javax.servlet.ServletContextAttributeEvent;
    4. import javax.servlet.ServletContextAttributeListener;
    5. import javax.servlet.annotation.WebListener;
    6.  
    7. /*@WebListener*/
    8. public class MyServletContextAttributeListener implements ServletContextAttributeListener {
    9.     @Override
    10.     public void attributeAdded(ServletContextAttributeEvent servletContextAttributeEvent) {
    11.         System.out.println(servletContextAttributeEvent.getServletContext().getAttribute("uname"));
    12.         System.out.println("执行了添加");
    13.     }
    14.  
    15.     @Override
    16.     public void attributeRemoved(ServletContextAttributeEvent servletContextAttributeEvent) {
    17.         System.out.println(servletContextAttributeEvent.getServletContext().getAttribute("uname"));
    18.         System.out.println("执行了删除");
    19.     }
    20.  
    21.     @Override
    22.     public void attributeReplaced(ServletContextAttributeEvent servletContextAttributeEvent) {
    23.         System.out.println(servletContextAttributeEvent.getServletContext().getAttribute("uname"));
    24.         System.out.println("执行了修改");
    25.  
    26.     }
    27. }
    1. package com.qf.servlet;
    2.  
    3. import javax.servlet.ServletContext;
    4. import javax.servlet.ServletException;
    5. import javax.servlet.annotation.WebServlet;
    6. import javax.servlet.http.HttpServlet;
    7. import javax.servlet.http.HttpServletRequest;
    8. import javax.servlet.http.HttpServletResponse;
    9. import java.io.IOException;
    10.  
    11. @WebServlet(name = "servlet02",urlPatterns = "/servlet02")
    12. public class Servlet02 extends HttpServlet {
    13.  
    14.     @Override
    15.     protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    16.         ServletContext servletContext = req.getServletContext();
    17.         servletContext.setAttribute("uname","班长");
    18.         servletContext.setAttribute("uname","肥男");
    19.         servletContext.removeAttribute("uname");
    20.     }
    21. }

            

            ServletRequestAttributeListener

    1. package com.qf.listenter;
    2.  
    3. import javax.servlet.ServletRequestAttributeEvent;
    4. import javax.servlet.ServletRequestAttributeListener;
    5. import javax.servlet.annotation.WebListener;
    6.  
    7. /*@WebListener*/
    8. public class MyServletRequestAttributeListener implements ServletRequestAttributeListener {
    9.     @Override
    10.     public void attributeAdded(ServletRequestAttributeEvent servletRequestAttributeEvent) {
    11.         System.out.println(servletRequestAttributeEvent.getServletRequest().getAttribute("uname"));
    12.         System.out.println("执行了添加");
    13.     }
    14.  
    15.     @Override
    16.     public void attributeRemoved(ServletRequestAttributeEvent servletRequestAttributeEvent) {
    17.         System.out.println(servletRequestAttributeEvent.getServletRequest().getAttribute("uname"));
    18.         System.out.println("执行了删除");
    19.     }
    20.  
    21.     @Override
    22.     public void attributeReplaced(ServletRequestAttributeEvent servletRequestAttributeEvent) {System.out.println(servletRequestAttributeEvent.getServletRequest().getAttribute("uname"));
    23.         System.out.println("执行了修改");
    24.  
    25.     }
    26. }
    1. package com.qf.servlet;
    2.  
    3. import javax.servlet.ServletException;
    4. import javax.servlet.annotation.WebServlet;
    5. import javax.servlet.http.HttpServlet;
    6. import javax.servlet.http.HttpServletRequest;
    7. import javax.servlet.http.HttpServletResponse;
    8. import java.io.IOException;
    9.  
    10. @WebServlet(name = "servlet03",urlPatterns = "/servlet03")
    11. public class Servlet03 extends HttpServlet {
    12.     @Override
    13.     protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    14.         req.setAttribute("uname","班长");
    15.         req.setAttribute("uname","肥男");
    16.         req.removeAttribute("uname");
    17.     }
    18. }

            HttpSessionAttributeListener

    1. package com.qf.listenter;
    2.  
    3. import javax.servlet.annotation.WebListener;
    4. import javax.servlet.http.HttpSessionAttributeListener;
    5. import javax.servlet.http.HttpSessionBindingEvent;
    6. /*@WebListener*/
    7. public class MyHttpSessionAttributeListener implements HttpSessionAttributeListener {
    8.     @Override
    9.     public void attributeAdded(HttpSessionBindingEvent httpSessionBindingEvent) {
    10.         System.out.println(httpSessionBindingEvent.getSession().getAttribute("uname"));
    11.         System.out.println("执行了添加");
    12.     }
    13.  
    14.     @Override
    15.     public void attributeRemoved(HttpSessionBindingEvent httpSessionBindingEvent) {
    16.         System.out.println(httpSessionBindingEvent.getSession().getAttribute("uname"));
    17.         System.out.println("执行了删除");
    18.     }
    19.  
    20.     @Override
    21.     public void attributeReplaced(HttpSessionBindingEvent httpSessionBindingEvent) {
    22.         System.out.println(httpSessionBindingEvent.getSession().getAttribute("uname"));
    23.         System.out.println("执行了修改");
    24.  
    25.     }
    26. }
    1. package com.qf.servlet;
    2.  
    3. import javax.servlet.ServletException;
    4. import javax.servlet.annotation.WebServlet;
    5. import javax.servlet.http.HttpServlet;
    6. import javax.servlet.http.HttpServletRequest;
    7. import javax.servlet.http.HttpServletResponse;
    8. import javax.servlet.http.HttpSession;
    9. import java.io.IOException;
    10.  
    11. @WebServlet(name = "servlet04",urlPatterns = "/servlet04")
    12. public class Servlet04 extends HttpServlet {
    13.     @Override
    14.     protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    15.         HttpSession session = req.getSession();
    16.         session.setAttribute("uname","班长");
    17.         session.setAttribute("uname","肥男");
    18.         session.removeAttribute("uname");
    19.     }
    20. }

    监听session中对象的绑定：

            

    1. package com.qf.entity;
    2.  
    3. import javax.servlet.http.HttpSessionBindingEvent;
    4. import javax.servlet.http.HttpSessionBindingListener;
    5.  
    6. public class STest implements HttpSessionBindingListener {
    7.     @Override
    8.     public void valueBound(HttpSessionBindingEvent httpSessionBindingEvent) {
    9.         System.out.println(httpSessionBindingEvent.getSession().getAttribute("uname"));
    10.         System.out.println("绑定");
    11.     }
    12.  
    13.     @Override
    14.     public void valueUnbound(HttpSessionBindingEvent httpSessionBindingEvent) {
    15.         System.out.println(httpSessionBindingEvent.getSession().getAttribute("uname"));
    16.         System.out.println("解绑");
    17.  
    18.     }
    19. }
    1. package com.qf.servlet;
    2.  
    3. import com.qf.entity.STest;
    4.  
    5. import javax.servlet.ServletException;
    6. import javax.servlet.annotation.WebServlet;
    7. import javax.servlet.http.HttpServlet;
    8. import javax.servlet.http.HttpServletRequest;
    9. import javax.servlet.http.HttpServletResponse;
    10. import javax.servlet.http.HttpSession;
    11. import java.io.IOException;
    12.  
    13. @WebServlet(name = "servlet05",urlPatterns = "/servlet05")
    14. public class Servlet05 extends HttpServlet {
    15.     @Override
    16.     protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    17.         STest s = new STest();
    18.         HttpSession session = req.getSession();
    19.         session.setAttribute("STest",s);
    20.         session.removeAttribute("STest");
    21.  
    22.     }
    23. }

    二、过滤器

    简介：

            开发中过滤器是对请求路径以及数据进行过滤

    基本使用：

            新建一个类 实现Filter接口

    1. package com.qf.filter;
    2.  
    3. import javax.servlet.*;
    4. import javax.servlet.annotation.WebFilter;
    5. import java.io.IOException;
    6. @WebFilter(urlPatterns = "/*")
    7. public class MyFilter implements Filter {
    8.  
    9.     //初始化
    10.     @Override
    11.     public void init(FilterConfig filterConfig) throws ServletException {
    12.  
    13.     }
    14.     //过滤方法
    15.     @Override
    16.     public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
    17.         System.out.println("执行");
    18.         //放行
    19.         filterChain.doFilter(servletRequest, servletResponse);
    20.         System.out.println("哈哈哈");
    21.     }
    22.     //销毁
    23.     @Override
    24.     public void destroy() {
    25.  
    26.     }
    27. }

            使用注解配置过滤的路径

            或者使用web.xml配置过滤路径

    1. <filter>
    2. <filter-name>myFilterfilter-name>
    3. <filter-class>filter.MyFilterfilter-class>
    4. filter>
    5. <filter-mapping>
    6. <filter-name>myFilterfilter-name>
    7. <url-pattern>/*url-pattern>
    8. filter-mapping>

    执行流程:

            

    案例：

            

            代码：

                    jsp

    1. <%--
    2.   Created by IntelliJ IDEA.
    3.   User: 86182
    4.   Date: 2022/9/7
    5.   Time: 13:38
    6.   To change this template use File | Settings | File Templates.
    7. --%>
    8. <%@ page contentType="text/html;charset=UTF-8" language="java" %>
    9. <html>
    10. <head>
    11.     <title>Titletitle>
    12. head>
    13. <body>
    14. <form action="${pageContext.request.contextPath}/servlet06" method="post">
    15.     <p style="color: red">
    16.         ${msg}
    17.     p>
    18.     <p>
    19.         用户名：<input type="text" name="uname">
    20.     p>
    21.     <p>
    22.         密码:<input type="password" name="upwd">
    23.     p>
    24.     <p>
    25.         <input type="submit" value="登录">
    26.     p>
    27. form>
    28. body>
    29. html>
    30.  
    31.  
    32.  
    33.  
    34.  
    35. <%--
    36.   Created by IntelliJ IDEA.
    37.   User: 86182
    38.   Date: 2022/9/7
    39.   Time: 13:40
    40.   To change this template use File | Settings | File Templates.
    41. --%>
    42. <%@ page contentType="text/html;charset=UTF-8" language="java" %>
    43. <html>
    44. <head>
    45.     <title>Titletitle>
    46. head>
    47. <body>
    48. <h1>登录成功h1>
    49. body>
    50. html>

                    servlet

    1. package com.qf.servlet;
    2.  
    3. import javax.servlet.ServletException;
    4. import javax.servlet.annotation.WebServlet;
    5. import javax.servlet.http.HttpServlet;
    6. import javax.servlet.http.HttpServletRequest;
    7. import javax.servlet.http.HttpServletResponse;
    8. import java.io.IOException;
    9.  
    10. @WebServlet(name = "servlet06",urlPatterns = "/servlet06")
    11. public class Servlet06 extends HttpServlet {
    12.     @Override
    13.     protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    14.         //获取前端传递的参数
    15.         String uname = req.getParameter("uname");
    16.         String upwd = req.getParameter("upwd");
    17.         //验证登录
    18.         if ("admin".equals(uname)&&"123456".equals(upwd)){
    19.             //将用户名添加到sess作用域中
    20.             req.getSession().setAttribute("uname",uname);
    21.             //跳转到登录成功页面
    22.             resp.sendRedirect("success.jsp");
    23.         }else {
    24.             req.setAttribute("msg","登录失败");
    25.             req.getRequestDispatcher("login.jsp").forward(req,resp);
    26.         }
    27.     }
    28. }

     

             过滤器：

    1. package com.qf.filter;
    2.  
    3. import javax.servlet.*;
    4. import javax.servlet.annotation.WebFilter;
    5. import javax.servlet.http.HttpServletRequest;
    6. import javax.servlet.http.HttpServletResponse;
    7. import java.io.IOException;
    8. @WebFilter(urlPatterns = "/*")
    9. public class LoginFilter implements Filter {
    10.     @Override
    11.     public void init(FilterConfig filterConfig) throws ServletException {
    12.  
    13.     }
    14.  
    15.     @Override
    16.     public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
    17.         HttpServletRequest request = (HttpServletRequest) servletRequest;
    18.         HttpServletResponse response = (HttpServletResponse) servletResponse;
    19.         //获取请求路径
    20.         String uri = request.getRequestURI();
    21.         //判断路径中是否包含登录页面或者servlet06路径
    22.         if (uri.contains("login.jsp")||uri.contains("servlet06")){
    23.             //放行
    24.             filterChain.doFilter(servletRequest, servletResponse);
    25.         }else {
    26.             //获取session中的值
    27.             Object uname = request.getSession().getAttribute("uname");
    28.             //判断
    29.             if (uname==null||"".equals(uname)){
    30.                 request.setAttribute("msg","非法登录");
    31.                 request.getRequestDispatcher("login.jsp").forward(request,response);
    32.             }else {
    33.                 //uname存在
    34.                 //放行
    35.                 filterChain.doFilter(servletRequest, servletResponse);
    36.             }
    37.         }
    38.  
    39.     }
    40.  
    41.     @Override
    42.     public void destroy() {
    43.  
    44.     }
    45. }

            修改tomcat默认访问的路径：

     

     

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  • 原文地址：https://blog.csdn.net/qq_53884348/article/details/126744642