spring mvc 模拟数据库实现注册登录

用户9184480

发布于 2024-12-17 11:14:30

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代码可运行

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代码可运行

model层代码，用户

package com.entity;
import java.io.Serializable;

public class User implements Serializable {
  //私有字段;
  private String username;
  private String pwd;
  public String getUsername() {
    return username;
  }
  public void setUsername(String username) {
    this.username = username;
  }
  public String getPwd() {
    return pwd;
  }
  public void setPwd(String pwd) {
    this.pwd = pwd;
  }


}

view层，几个简单的注册登录欢迎页面,分别如下：

<%@ 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 'zhuce.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">
  </head>

  <body>
  注册页面
    <form action="reg" method="post">
      账户：<input type="text" name="username"/><br/>
      密码：<input type="password" name="pwd"/><br/>
      <input type="submit" value="注册"/>
    </form>
  </body>
</html>

<%@ 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 'login.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">
  </head>

  <body>
  用户登录
    <form action="login" method="post">
      账户：<input type="text" name="username"/><br/>
      密码：<input type="password" name="pwd"/><br/>
      <input type="submit" value="登录"/>
    </form>
  </body>
</html>

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%@ page isELIgnored="false" %>
<%
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 'welcome.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">
  </head>

  <body>
  用户：  ${user.username }<br/>
  密码:${user.pwd }
  </body>
</html>

控制器代码，其中很多代码还可以继续简化

package com.controller;
import java.util.ArrayList;
import java.util.List;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.springframework.stereotype.Controller;
//import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.servlet.ModelAndView;

import com.entity.User;
//注解该类是一个控制器，可以同时接受多个请求动作;
@Controller
public class UserController {
  //静态List<User>集合，用来代替数据库来保存注册的用户信息;
  private static List<User>userList;
  //UserController类的构造器，初始化List<User>集合
  public UserController() {
    super();
    userList=new ArrayList<User>();
  }
  //静态的日志类;logFactory
  //该方法，请求.../reg,该方法支持Post请求
  @RequestMapping(value="/reg",method=RequestMethod.GET)
  public String regForm(){
    //跳转到注册页面;
    return "zhuce";
  }
  //该方法映射的请求为.../reg,支持Post请求
  @RequestMapping(value="/reg",method=RequestMethod.POST)
  public String register(
      @RequestParam("username")String username,
      @RequestParam("pwd")String pwd  ){
    //创建User对象;
    User u=new User();
    u.setUsername(username);
    u.setPwd(pwd);
    //模拟数据存储到数据库user里面
    userList.add(u);
    //跳转到登录页面
    return "login";
  }
  //该方法映射的请求是.../login
  @RequestMapping("/login")
  public ModelAndView login(@RequestParam("username")String username,
                  @RequestParam("pwd")String pwd,ModelAndView mv){
    //RequestParam将请求中的username和pwd参数赋值给username，pwd变量。
    //到集合中去查找下用户是否存在，此处用来模拟数据库验证。
    for(User user:userList){
      if(user.getUsername().equals(username)&&user.getPwd().equals(pwd)){
        mv.addObject("user",user);
        mv.setViewName("welcome");
        //mv.addAttribute("user",user);model传递的是requestScope
        return mv;
      }
    }
    return mv;
  }

}

配置文件，web.xml代码

<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.5" 
  xmlns="http://java.sun.com/xml/ns/javaee" 
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
  xsi:schemaLocation="http://java.sun.com/xml/ns/javaee 
  http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">
  <welcome-file-list>
    <welcome-file>index.jsp</welcome-file>
  </welcome-file-list>
  <servlet>
    <servlet-name>hello</servlet-name>
    <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
    <init-param>
      <param-name>contextConfigLocation</param-name>
      <param-value>WEB-INF/spring-servlet.xml</param-value>
    </init-param>
    <load-on-startup>1</load-on-startup>
  </servlet>
  <servlet-mapping>
    <servlet-name>hello</servlet-name>
    <url-pattern>/</url-pattern>
  </servlet-mapping>

  <filter>  
        <filter-name>encodingFilter</filter-name>  
        <filter-class>org.springframework.web.filter.CharacterEncodingFilter</filter-class>  
        <init-param>  
            <param-name>encoding</param-name>  
            <param-value>UTF-8</param-value>  
        </init-param>  
    </filter>  
    <filter-mapping>  
        <filter-name>encodingFilter</filter-name>  
        <url-pattern>/*</url-pattern>  
    </filter-mapping>  
</web-app>

spring-servlet.xml代码

<?xml version="1.0" encoding="UTF-8"?>
<beans
  xmlns="http://www.springframework.org/schema/beans"
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xmlns:p="http://www.springframework.org/schema/p"
  xmlns:context="http://www.springframework.org/schema/context"
  xmlns:mvc="http://www.springframework.org/schema/mvc"
  xsi:schemaLocation="http://www.springframework.org/schema/beans 
  http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
  http://www.springframework.org/schema/context
  http://www.springframework.org/schema/context/spring-context-3.0.xsd
  http://www.springframework.org/schema/mvc
  http://www.springframework.org/schema/mvc/spring-mvc.xsd">
  <context:annotation-config></context:annotation-config>
  <context:component-scan base-package="com"></context:component-scan>
  <!-- ViewResolver -->
  <bean class="org.springframework.web.servlet.view.InternalResourceViewResolver">
    <property name="viewClass" value="org.springframework.web.servlet.view.JstlView"></property>
    <property name="prefix" value="/"></property>
    <property name="suffix" value=".jsp"></property>
  </bean>

<!--  <bean name="/hello" class="com.controller.HelloController"></bean>-->
</beans>

在后续讲课中添加了删除修改查询功能，针对删除报错如下：java.util.ConcurrentModificationException异常.

对Vector、ArrayList在迭代的时候如果同时对其进行修改就会抛出java.util.ConcurrentModificationException异常。下面我们就来讨论以下这个异常出现的原因以及解决办法。

单线程环境下的解决办法

public  class  Test {
     public  static  void  main(String[] args)  {
         ArrayList<Integer> list =  new  ArrayList<Integer>();
         list.add( 2 );
         Iterator<Integer> iterator = list.iterator();
         while (iterator.hasNext()){
             Integer integer = iterator.next();
             if (integer== 2 )
                 iterator.remove();    //注意这个地方
         }
     }
}