java中getParameter()中的参数 (个人笔记)

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  getParameter()函数括号中的参数是从页面中传过来的,比如 edit.jsp中userid:

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%
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>
    <base href="<%=basePath%>">
    
    <title>My JSP 'index.jsp' starting page</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">
   <!--
   <link rel="stylesheet" type="text/css" href="styles.css">
   -->
  </head>
  
  <body>
    <form action="update.do" method="post">
       <input type="hidden" name="userId" value="$user.id" /> 
       <table>
          <tr>
             <td>用户名:</td>
             <td><input type="text" name="name" value="$user.name"/></td>
          </tr>
          <tr>
             <td>密码:</td>
             <td><input type="text" name="password" value="$user.password"/></td>
          </tr>
          <tr>
             <td colspan="2">
                <input type="submit" value="提交"/>
             </td>
          </tr>
       </table>
    </form>
  </body>
</html>
下面是控制层:

package com.demo.controller;

import java.io.IOException;

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

import com.demo.dao.UserDao;
import com.demo.entity.User;

public class UpdateController extends HttpServlet 
   
   protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException 
      doPost(req, resp);
   

   protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException 
      String ids = req.getParameter("userId").trim();
      Long id = (long) 0;
      if (ids != null) 
         id = Long.parseLong(ids);
      
      String name = req.getParameter("name").trim();
      String password = req.getParameter("password").trim();
      User user = new User();
      user.setId(id);
      user.setName(name);
      user.setPassword(password);
      UserDao userDao = new UserDao();
      userDao.updateUser(user);
      resp.sendRedirect("list.do");
   

其中
String ids = req.getParameter("userId").trim();就是得到了页面中userid的值 备注:trim()方法是为了去掉前后空格

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