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>