面试时可能会让你上机写一个基于SpringMVC的小程序

实现简单的登录和注册

步骤：

工程目录：

1.创建一个动态的web工程

2.导入springMvc所需要的jar包（包含mysql驱动包）

3.配置web.xml步骤：

配置唯一的 Servlet

3.1 增加 servlet和 servlet-mapping 标签

3.2 配置 servlet 标签，name 随便起，class 是 DispatcherServlet

3.3 配置 servlet-mapping，name 和上边保持一致，url-pattern 是 /

3.4 在 servlet 标签中增加 init-param 标签设置 spring-mvc 配置文件的路径

3.5 param-name：contextConfigLocation

3.6 param-value：classpath:spring-mvc.xml

代码如下：

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" id="WebApp_ID" version="2.5">
<display-name>Springdemo1</display-name>
<welcome-file-list>
<welcome-file>index.html</welcome-file>
<welcome-file>index.htm</welcome-file>
<welcome-file>index.jsp</welcome-file>
<welcome-file>default.html</welcome-file>
<welcome-file>default.htm</welcome-file>
<welcome-file>default.jsp</welcome-file>
</welcome-file-list>
<!-- The front controller of this Spring Web application, responsible for handling all application requests -->
<servlet>
<servlet-name>springDispatcherServlet</servlet-name>
<servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
<init-param>
<param-name>contextConfigLocation</param-name>
<param-value>classpath:spring-mvc.xml</param-value>
</init-param>
<load-on-startup>1</load-on-startup>
</servlet>

<!-- Map all requests to the DispatcherServlet for handling -->
<servlet-mapping>
<servlet-name>springDispatcherServlet</servlet-name>
<url-pattern>/</url-pattern>
</servlet-mapping>
</web-app>

以上配置web.xml文件的属性过于繁琐，有没有简单的方法？

在原web.xml文件中输入“dispatch“按alt+/会出现提示符，向上按会出现一个“# dispatcherservlet”选中，即可自动添加代码。

注意：把<param-value>location</param-value>修改为<param-value>classpath:spring-mvc.xml</param-value>

           <url-pattern>url</url-pattern>修改为<url-pattern>/</url-pattern>即可。

4.在src目录下建立spring-mvc.xml文件：

4.1复制代码：

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:context="http://www.springframework.org/schema/context"
xmlns:mvc="http://www.springframework.org/schema/mvc"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:task="http://www.springframework.org/schema/task"
xsi:schemaLocation="
http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-4.0.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context-4.0.xsd
http://www.springframework.org/schema/mvc
http://www.springframework.org/schema/mvc/spring-mvc-4.0.xsd
http://www.springframework.org/schema/task
http://www.springframework.org/schema/task/spring-task-4.0.xsd">

</beans>

4.1 增加对注解的支持<context:component-scan base-package="controller"/>

4.2使用默认的 handleMapping 和启用 mvc 中的注解 <mvc:annotation-driven/>

4.3 增加页面解析类 InternalResourceViewResolver

4.3.1 增加 bean 标签

4.3.2 设置 class = 全名 = 包名 + 路径

4.3.3 增加 prefix 和 suffix 设置页面路径的前缀和后缀

设置前缀以后将来所有的 jsp 必须放在 view 文件夹下

<property name="prefix" value="/view/"></property>

<property name="suffix" value=".jsp"></property>

代码如下：

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:context="http://www.springframework.org/schema/context"
xmlns:mvc="http://www.springframework.org/schema/mvc" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:task="http://www.springframework.org/schema/task"
xsi:schemaLocation="
http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-4.0.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context-4.0.xsd
http://www.springframework.org/schema/mvc
http://www.springframework.org/schema/mvc/spring-mvc-4.0.xsd
http://www.springframework.org/schema/task
http://www.springframework.org/schema/task/spring-task-4.0.xsd">
<!-- 启用 mvc 中的注解 -->
<mvc:annotation-driven />
<!-- 启用 自动扫描的包 -->
<context:component-scan base-package="controller" />
<!-- 增加页面解析类 InternalResourceViewResolver -->
<bean
class="org.springframework.web.servlet.view.InternalResourceViewResolver">
<property name="prefix" value="/view/"></property>
<property name="suffix" value=".jsp"></property>
</bean>

</beans>

注意说明的是，启动自动扫描，spring会在指定的包下（例如我这里是controller包），自动扫描标注@Controller的类

prefix指的是返回的值给自动加一个前缀，同理suffix指的就是后缀

5.编写逻辑代码

5.1 建立一个包：controller,包下建立一个LoginControl类

5.2在WebContent下建立一个文件view，在其中新建login.jsp，代码如下：

<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
<form action="login" method="post">
<input type="text" name="username" /><br>
<input type="password" name ="password"/><br>
<input type="submit" value="登录"/><br>
<a href="regist">注册</a>
</form>
</body>
</html>

5.3form的action指向login，Controller会自动捕获到这个请求，于是在所以LoginControl类需要一个login方法来捕获这个请求

代码如下：

package controller;

import javax.servlet.http.HttpServletRequest;

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 check.CheckLogin;

@Controller
public class LoginControl {
@RequestMapping(value = "login", method = RequestMethod.POST)
public String login(Model model,// 前台页面传的值放入model中
HttpServletRequest request) {// 从前台页面取得的值
String username = request.getParameter("username");
String password = request.getParameter("password");
String user_name = CheckLogin.check(username, password);
if (user_name != null && user_name != "") {

model.addAttribute("USER", user_name);
return "loginsuccess";
}

return "regist";
}
}

5.4 建立check包和LoginCheck类，以及对应的check方法，有check方法，就要用到数据库，先建立一个dao类，代码如下：

package db;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;

public class Dao {
public static Connection getConnection(){
Connection conn = null;
String user="root";
String pass="1234";
String url ="jdbc:mysql://localhost:3306/test?useOldAliasMetadataBehavior=true";
try {
Class.forName("com.mysql.jdbc.Driver");
conn= DriverManager.getConnection(url, user, pass);
} catch (ClassNotFoundException e) {
e.printStackTrace();
System.out.println("数据库驱动有误");
} catch (SQLException e) {
e.printStackTrace();
System.out.println("数据库有误");
}
return conn;
}
public static void closeAll(ResultSet rs,PreparedStatement ps,Connection conn){
try {
if(!rs.isClosed()){
rs.close();
}
if(!ps.isClosed()){
ps.close();
}
if(!conn.isClosed()){
conn.close();
}
} catch (SQLException e) {
e.printStackTrace();
System.out.println("数据库关闭有误");
}
}
public static void close(PreparedStatement p,Connection conn)
{
try
{
if(!p.isClosed()){
p.close();
}
if(!conn.isClosed()){
conn.close();
}
}
catch(SQLException e)
{
e.printStackTrace();
System.out.println("数据关闭出错");
}
}

}

5.5有了dao类就可以编写check方法了：

代码如下：

package check;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;

import db.Dao;

public class CheckLogin {

public static String check(String username, String password) {
try {
String sql = "select * from table_demo where username=? and password=?";
Connection conn = Dao.getConnection();
PreparedStatement ps = conn.prepareStatement(sql);
ps.setString(1, username);
ps.setString(2, password);
ResultSet rs = ps.executeQuery();
if (rs.next()) {
String user_name = rs.getString("username");
return user_name;
}
Dao.closeAll(rs, ps, conn);
} catch (SQLException e) {
e.printStackTrace();
}

return null;
}

}

6.运行项目：

异常;

严重: Servlet /Springdemo1 threw load() exception
java.lang.ClassNotFoundException: org.apache.commons.logging.LogFactory

解决方案;解决办法是在项目中导入commons-logging-1.2.jar（这是我导入的版本，其他版本没有测试）。

7.接下来就是写注册页面的

RegistController类：

package controller;

import javax.servlet.http.HttpServletRequest;

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 check.RegistCheck;

@Controller
public class RegistControl {
@RequestMapping(value = "regist", method = RequestMethod.GET)
public String regist() {
return "regist";
}

@RequestMapping(value = "registSuccess", method = RequestMethod.POST)
public String registSuccess(HttpServletRequest request, Model model) {
String username = request.getParameter("username");
String password = request.getParameter("password");
String age = request.getParameter("age");

if (RegistCheck.registCheck(username, password, age)) {
model.addAttribute("username", username);
return "login";
} else {
return "regist";
}
}

}

8.regist.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
<form action="registSuccess" method="Post">
用户名：<input type="text" name="username"/>
密&nbsp;&nbsp;码<input type="text" name="password"/>
年&nbsp;&nbsp;龄<input type="number" name="age"/>
<input type="submit" value="提交"/>
</form>

</body>
</html>

9.registSuccess.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
注册成功！

</body>
</html>

10:运行效果：

姓名输入1：

数据库中有数据1，可登录成功！

数据库没有1则跳转到注册页面：

点击注册，进入注册页面。如上图，添加对应信息后，点击提交，控制台输出注册成功，回到登录页面，再实现登录！

 简单的小程序，面试时候遇到，总结一下，分享给大家！

java新手，请多指教！哈哈~