spring mvc 模拟数据库实现注册 登录
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spring mvc 模拟数据库实现注册 登录
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model層代碼，用戶
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層，幾個簡單的注冊 登錄 歡迎頁面,分別如下： <%@ 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>注冊頁面<form action="reg" method="post">賬戶：<input type="text" name="username"/><br/>密碼：<input type="password" name="pwd"/><br/><input type="submit" value="注冊"/></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>用戶登錄<form action="login" method="post">賬戶：<input type="text" name="username"/><br/>密碼：<input type="password" name="pwd"/><br/><input type="submit" value="登錄"/></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>用戶： ${user.username }<br/>密碼:${user.pwd }</body> </html>
控制器代碼，其中很多代碼還可以繼續(xù)簡化 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; //注解該類是一個控制器，可以同時接受多個請求動作; @Controller public class UserController {//靜態(tài)List<User>集合，用來代替數(shù)據(jù)庫來保存注冊的用戶信息;private static List<User>userList;//UserController類的構(gòu)造器，初始化List<User>集合public UserController() {super();userList=new ArrayList<User>();}//靜態(tài)的日志類;logFactory//該方法，請求.../reg,該方法支持Post請求@RequestMapping(value="/reg",method=RequestMethod.GET)public String regForm(){//跳轉(zhuǎn)到注冊頁面;return "zhuce";}//該方法映射的請求為.../reg,支持Post請求@RequestMapping(value="/reg",method=RequestMethod.POST)public String register(@RequestParam("username")String username,@RequestParam("pwd")String pwd ){//創(chuàng)建User對象;User u=new User();u.setUsername(username);u.setPwd(pwd);//模擬數(shù)據(jù)存儲到數(shù)據(jù)庫user里面userList.add(u);//跳轉(zhuǎn)到登錄頁面return "login";}//該方法映射的請求是.../login@RequestMapping("/login")public ModelAndView login(@RequestParam("username")String username,@RequestParam("pwd")String pwd,ModelAndView mv){//RequestParam將請求中的username和pwd參數(shù)賦值給username，pwd變量。//到集合中去查找下用戶是否存在，此處用來模擬數(shù)據(jù)庫驗證。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傳遞的是requestScopereturn mv;}}return mv;}}配置文件，web.xml代碼 <?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代碼 <?xml version="1.0" encoding="UTF-8"?> <beansxmlns="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.xsdhttp://www.springframework.org/schema/contexthttp://www.springframework.org/schema/context/spring-context-3.0.xsdhttp://www.springframework.org/schema/mvchttp://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>
在后續(xù)講課中添加了刪除 修改 查詢功能，針對刪除報錯如下：java.util.ConcurrentModificationException異常.
對Vector、ArrayList在迭代的時候如果同時對其進行修改就會拋出java.util.ConcurrentModificationException異常。下面我們就來討論以下這個異常出現(xiàn)的原因以及解決辦法。
單線程環(huán)境下的解決辦法
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();?? //注意這個地方 ????????} ????} }在多線程環(huán)境下的解決方法
1）在使用iterator迭代的時候使用synchronized或者Lock進行同步；
2）使用并發(fā)容器CopyOnWriteArrayList代替ArrayList和Vector。
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