SERVLETJSP Unit08： 过滤器、监听器

一.过滤器

1.过滤器的作用

• 用来处理项目中的公共的业务

• 记录日志,过滤敏感词,登录检查

公共业务:很多请求都需要进行处理的业务

2.使用步骤

• 创建一个类,实现Filter接口

• 在web.xml中配置此类

3.小案例

4.登录检查

5.参数说明

二.监听器

1.什么是监听器

• 监听器用来监听事件,当某事件发生时,它会通知服务器

• 它监听的目标是一些对象

2.监听器的分类(接口)

1) request

• 创建与销毁:ServletRequestListener

• 数据的变化:ServletRequestAttributeListener

2) session

• 创建与销毁:HttpSessionListener

• 数据的变化:HttpSessionAttributeListener

3) context

• 创建与销毁:ServletContextListener

• 数据的变化:ServletContextAttributeListener

3.开发步骤

• 创建一个类,实现对应的监听器接口

• 在web.xml中声明此类

---

案例

AddCostServlet.java

package web;import java.io.IOException;import javax.servlet.ServletException;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;public class AddCostServlet extends HttpServlet {    @Override    protected void service(        HttpServletRequest req,         HttpServletResponse res) throws ServletException, IOException {        System.out.println("增加资费");    }}

FindCostServlet.java

package web;import java.io.IOException;import javax.servlet.ServletException;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;public class FindCostServlet extends HttpServlet {    @Override    protected void service(        HttpServletRequest req,         HttpServletResponse res) throws ServletException, IOException {        System.out.println("查询资费");        req.setAttribute("name", "zhangsan");    }}

GuolvFilter.java

package web;import java.io.IOException;import javax.servlet.Filter;import javax.servlet.FilterChain;import javax.servlet.FilterConfig;import javax.servlet.ServletException;import javax.servlet.ServletRequest;import javax.servlet.ServletResponse;public class GuolvFilter implements Filter {    public void destroy() {        System.out.println("销毁GuolvFilter");    }    public void doFilter(        ServletRequest req,         ServletResponse res,         FilterChain chain)        throws IOException, ServletException {        System.out.println("在前面过滤敏感词");        chain.doFilter(req, res);        System.out.println("在后面过滤敏感词");    }    String words;    public void init(FilterConfig cfg) throws ServletException {        System.out.println("初始化GuolvFilter");        words = cfg.getInitParameter("words");        System.out.println("words:"+words);    }}

LogFilter.java

package web;import java.io.IOException;import javax.servlet.Filter;import javax.servlet.FilterChain;import javax.servlet.FilterConfig;import javax.servlet.ServletException;import javax.servlet.ServletRequest;import javax.servlet.ServletResponse;public class LogFilter implements Filter {    public void destroy() {        System.out.println("销毁LogFilter");    }    public void doFilter(        ServletRequest req,         ServletResponse res,         FilterChain chain)        throws IOException, ServletException {        System.out.println("在前面记日志");        //请求继续,向下执行        chain.doFilter(req, res);        System.out.println("在后面记日志");    }    public void init(FilterConfig arg0) throws ServletException {        System.out.println("初始化LogFilter");    }}

MyListener.java

package web;import javax.servlet.ServletRequestAttributeEvent;import javax.servlet.ServletRequestAttributeListener;import javax.servlet.ServletRequestEvent;import javax.servlet.ServletRequestListener;public class MyListener     implements ServletRequestListener,    ServletRequestAttributeListener {    public void requestDestroyed(ServletRequestEvent e) {        //request销毁时调用        System.out.println("销毁request");        System.out.println(e.getServletRequest());    }    public void requestInitialized(ServletRequestEvent arg0) {        //request创建时调用        System.out.println("创建request");    }    public void attributeAdded(ServletRequestAttributeEvent arg0) {        System.out.println("向request添加数据");    }    public void attributeRemoved(ServletRequestAttributeEvent arg0) {        // TODO Auto-generated method stub    }    public void attributeReplaced(ServletRequestAttributeEvent arg0) {        // TODO Auto-generated method stub    }}

web.xml

<?xml version="1.0" encoding="UTF-8"?><web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" version="2.5">  <display-name>jsp5</display-name>  <welcome-file-list>    <welcome-file>index.html</welcome-file>    <welcome-file>index.htm</welcome-file>    <welcome-file>index.jsp</welcome-file>    <welcome-file>default.html</welcome-file>    <welcome-file>default.htm</welcome-file>    <welcome-file>default.jsp</welcome-file>  </welcome-file-list>  <servlet>      <servlet-name>findCost</servlet-name>      <servlet-class>web.FindCostServlet</servlet-class>  </servlet>  <servlet-mapping>      <servlet-name>findCost</servlet-name>      <url-pattern>/findCost</url-pattern>  </servlet-mapping>  <servlet>      <servlet-name>addCost</servlet-name>      <servlet-class>web.AddCostServlet</servlet-class>  </servlet>  <servlet-mapping>      <servlet-name>addCost</servlet-name>      <url-pattern>/addCost</url-pattern>  </servlet-mapping>  <filter>      <filter-name>log</filter-name>      <filter-class>web.LogFilter</filter-class>  </filter>  <filter-mapping>      <filter-name>log</filter-name>      <!-- 声明Filter对哪些请求路径有效,即          用户在访问哪些路径时Tomcat调用此Filter. -->      <url-pattern>/*</url-pattern>  </filter-mapping>  <!-- 多个Filter其顺序以mapping的配置顺序为准 -->  <filter>      <filter-name>guolv</filter-name>      <filter-class>web.GuolvFilter</filter-class>      <init-param>          <param-name>words</param-name>          <param-value>              靠,TMD,NND          </param-value>      </init-param>  </filter>  <filter-mapping>      <filter-name>guolv</filter-name>      <url-pattern>/*</url-pattern>  </filter-mapping>  <!-- 注册监听器,Tomcat会在相应事件发生时,          自动调用此监听器的对应的方法. -->  <listener>      <listener-class>          web.MyListener      </listener-class>  </listener></web-app>