servlet中配置登录过滤器

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servlet中配置登录过滤器

实现登录过滤主要依靠实现Filter接口，重写dofilter（）方法实现。
话不多说，直接上代码

1、在WebContent中建立登录login.jsp和主页面main.jsp，

login.jsp:

<%@ page language="java" contentType="text/html; charset=UTF-8"    pageEncoding="UTF-8"%><!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"><html><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8"><title>Insert title here</title></head><body><form action="login_action" method="post">    id:<input type="text" name = "id" ><br/>    password:<input type="text" name = "password"><br/>    <input type="submit" value="提交" ></form></body></htAml>

main.jsp:

<%@ page language="java" contentType="text/html; charset=UTF-8"    pageEncoding="UTF-8"%><!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"><html><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8"><title>Insert title here</title></head><body>main</body></html>

2、在src中建立filter_demo包，并在包中建立建立servlet类，login.action：

package filter_demo;import java.io.IOException;import java.io.PrintWriter;import java.util.List;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 org.apache.catalina.Session;public class login_action extends HttpServlet{    @Override    protected void doGet(HttpServletRequest req, HttpServletResponse resp)            throws ServletException, IOException {        // TODO Auto-generated method stub        super.doGet(req, resp);    }    @Override    protected void doPost(HttpServletRequest req, HttpServletResponse resp)            throws ServletException, IOException {        // TODO Auto-generated method stub          String id = req.getParameter("id");          HttpSession session = req.getSession();//取得session对象         session.setAttribute("id", id);         String path = req.getContextPath();         resp.sendRedirect(path+"/main.jsp");     }}

3、在包中建立过滤器类，login_filter.java：

package filter_demo;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;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import javax.servlet.http.HttpSession;public class login_filter implements Filter{    @Override    public void destroy() {        // TODO Auto-generated method stub    }    @Override    public void doFilter(ServletRequest arg0, ServletResponse arg1,            FilterChain arg2) throws IOException, ServletException {        // TODO Auto-generated method stub        System.out.println("我是拦截器");         HttpServletRequest servletRequest = (HttpServletRequest) arg0;           HttpServletResponse servletResponse = (HttpServletResponse) arg1;           HttpSession session = servletRequest.getSession();           String path = servletRequest.getServletPath();          if(path.equals("/login.jsp")||path.equals("/login_action")){                arg2.doFilter(arg0,arg1);                            System.out.println("通过1");         }         else{             String id = (String) session.getAttribute("id");             if(id == null)             {                 System.out.println("拦截");                 arg0.getRequestDispatcher("/login.jsp").forward(arg0, arg1);             }else {                    arg2.doFilter(arg0,arg1);                        }         }    }    @Override    public void init(FilterConfig arg0) throws ServletException {        // TODO Auto-generated method stub    }}

4、配置web.xml，添加相应的映射：

<?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_3_0.xsd" id="WebApp_ID" version="3.0">  <display-name>filter_demo</display-name>    <filter>          <filter-name>login_filter</filter-name>          <filter-class>filter_demo.login_filter</filter-class>      </filter>      <filter-mapping>          <filter-name>login_filter</filter-name>          <url-pattern>/*</url-pattern>      </filter-mapping>       <servlet>        <servlet-name>login_action</servlet-name>        <servlet-class>filter_demo.login_action</servlet-class>    </servlet>    <servlet-mapping>        <servlet-name>login_action</servlet-name>        <url-pattern>/login_action</url-pattern>     <welcome-file-list>          <welcome-file>login.jsp</welcome-file>    </welcome-file-list>  </web-app>

以上是代码是web.xml中全部代码，其中有关filter的配置信息如下：

    <filter>          <filter-name>login_filter</filter-name>          <filter-class>filter_demo.login_filter</filter-class>      </filter>      <filter-mapping>          <filter-name>login_filter</filter-name>          <url-pattern>/*</url-pattern>      </filter-mapping>

到此全部的代码就已经全部写好，启动tomcat，在浏览器中直接输入http://localhost:8080/filter_demo/main.jsp，会发现页面回调到login.jsp而不是main.jsp，这就说明我们的过滤器起作用了。工作机制是在web页面向服务器发送请求之后，请求会先到到过滤器，先触发filter的dofilter函数，对请求的地址和类型和地址进行过滤，选择是否放行或者重定向。若符合要求，选择放行，对浏览器返回main.jsp，若不符合要求则执行重定向方法，对浏览器返回login.jsp

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