使用Servlet对复杂表单进行服务器端验证
一个form表单的jsp页面
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%><html> <head> <title></title> </head> <body> <form action="TestListServlet"> username:<input type="text" name="username"><br> password:<input type="password" name="password"><br> interests:<input type="checkbox" name="interests" value="篮球">篮球 <input type="checkbox" name="interests" value="football">足球 <input type="checkbox" name="interests" value="swimg">游泳<br> address:<input type="text" name="address">地址<br> <input type="submit" value="submit"> </form> </body></html>
一个用户进行服务器验证的Servlet类
package com.mison;import java.io.IOException;import java.util.ArrayList;import java.util.List;import javax.servlet.RequestDispatcher;import javax.servlet.ServletException;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;public class TestListServlet extends HttpServlet { @Override protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { this.process(req, resp); } @Override protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { this.process(req, resp); } protected void process(HttpServletRequest req, HttpServletResponse resp)throws ServletException, IOException { String username=req.getParameter("username"); String password=req.getParameter("password"); String interests[]=req.getParameterValues("interests"); String address=req.getParameter("address"); List<String>array=new ArrayList(); if(""==username){ array.add("用户名不能为空"); } else if(username.length()<4||username.length()>12){ array.add("用户长度必须在4-6个字母之间"); } if(""==password){ array.add("密码不能为空"); } else if(password.length()<4||password.length()>12){ array.add("密码长度必须在4-6个字母之间"); } if(null==interests){ array.add("兴趣至少选一个"); } else if(interests.length==3){ array.add("兴趣最多选2个"); } if(""==address){ array.add("地址不能为空"); } if(array.isEmpty()){ RequestDispatcher rd=req.getRequestDispatcher("result.jsp"); rd.forward(req, resp); }else{ req.setAttribute("array", array); RequestDispatcher rd =req.getRequestDispatcher("error.jsp"); rd.forward(req, resp); } }}一个显示正确结果的jsp页面
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%><html> <head> <title>My JSP 'result.jsp' starting page</title> </head> <body> username:<%=request.getParameter("username")%><br> password:<%=request.getParameter("password") %><br> interests:<%String []interests=(String [])request.getParameterValues("interests"); for(int i=0;i<interests.length;i++){ String str =interests[i]; %> <%=str.toString() %> <%} %> <br> address:<%=request.getParameter("address")%> </body></html>一个显示错误结果并答应出错误消息的jsp页面
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%><html> <head> <title>My JSP 'error.jsp' starting page</title> </head> <body> <%List <String>array=(List)request.getAttribute("array"); Iterator<String> it =array.iterator(); while(it.hasNext()){ out.println("*"+it.next());%><br> <%}%> </body></html>不过还有一个问题有待解决:1. 就是checkbox 的value值为中文的时候 会在结果显示出乱码 ，为何？ 等有空再解决吧！
2.null==username 与""==username 有何差别呢？