servlet中Filter的使用

这是我自己编写JSP页面

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%@taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    <title>我的JSP页面</title>
    <meta http-equiv="pragma" content="no-cache">
    <meta http-equiv="cache-control" content="no-cache">
    <meta http-equiv="expires" content="0">    
    <meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
    <meta http-equiv="description" content="This is my page">
  </head>
  <style type="text/css">
      body{
          padding:0px;margin:auto;
      }
      .form{
          margin:auto;width:300px;height:auto;
      }
      h1{
          color:green;text-align:center;
      }
      .color{
          color:red;font-size:24px;
      }
  </style>
  <body>
  <h1>my form</h1>
  <div class="form">
    <form action="Servlet_1" method="post">
        <label class="color">${sessionScope.warning }</label>
           <p><label>name: </label><input type="text" name="name" required placeholder="name">
           <p><label>sex:  </label><input type="radio" name="sex" value="man"><label>man</label>
               <input type="radio" name="sex" value="woman"><label>woman</label>
           <p><label>comment:</label>
               <br><textarea rows="10" cols="30" required placeholder="comments" name="comment"></textarea>
           <p><input type="submit" name="submit" value="submit">
               <input type="reset" name="reset" value="reset">
       </form>  
  </div>
  </body>
</html>

代码说明：

${sessionScope.warning }是利用jstl标签获取session的值 warning是从Filter中传过来的session的key值

详细的知识可以百度，这里不多说

接下来要写的是Filter 过滤器要实现Filter接口

package com.servlet.Filter;

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 Myfilter implements Filter {

    @Override
    public void destroy() {

    }

    @Override
    public void doFilter(ServletRequest req, ServletResponse res,
            FilterChain chain) throws IOException, ServletException {
        HttpServletRequest request = (HttpServletRequest)req;
        HttpServletResponse response = (HttpServletResponse)res;
        String sex = request.getParameter("sex");
        if(sex == "" || sex == null){
            HttpSession session = request.getSession();
            session.setAttribute("warning", "sex is not allowed null !");
            response.sendRedirect("index.jsp");
        }else{
            chain.doFilter(req, res);
        }
        
    }

    @Override
    public void init(FilterConfig arg0) throws ServletException {
        
    }

}

 当sex选中时，request.getParameter("sex") != null ;这样就可以执行chain.doFilter(req,res);接下来如果还有其他过滤器的话就执行其他过滤器，如果没有就从服务器上获取相关资源，我们这儿没有过滤器了，接下来我们编写一个servlet，由servlet获取数据

package com.servlet.main;

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class Servlet_1 extends HttpServlet {

    private static final long serialVersionUID = 1L;

    public Servlet_1() {
        super();
    }

    public void destroy() {
        super.destroy(); 
    }
    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        this.doPost(request, response);
    }

    public void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        request.setCharacterEncoding("UTF-8");
        response.setCharacterEncoding("UTF-8");
        response.setContentType("text/html");
        PrintWriter out = response.getWriter(); 
        String name = request.getParameter("name");
        String sex = request.getParameter("sex");
        String comment = request.getParameter("comment");
        out.print("<html><head><title></title></head><body>");
        out.print("name:<br>"+name+"<P>sex:<br>"+sex+"<P>comment:<br>"+comment);
        out.print("</body></html>");
    }
    public void init() throws ServletException {
    }

}

servlet的相关问题就不多叙述了

最后我们看看运行结果：

sex不选：

sex选择man：

 

posted @ 2015-11-13 15:47  流氓公子  阅读(418)  评论(0)  编辑  收藏  举报