手把手逐步解析Javaweb登录实例
一、编写前端界面
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
<style>
* {
margin: 0;
padding: 0;
}
html {
height: 100%;
}
body {
height: 100%;
}
.container {
height: 100%;
background-image: linear-gradient(to right, #fbc2eb, #a6c1ee);
}
.login-wrapper {
background-color: #fff;
width: 358px;
height: 588px;
border-radius: 15px;
padding: 0 50px;
position: relative;
left: 50%;
top: 50%;
transform: translate(-50%, -50%);
}
.header {
font-size: 38px;
font-weight: bold;
text-align: center;
line-height: 200px;
}
.input-item {
display: block;
width: 100%;
margin-bottom: 20px;
border: 0;
padding: 10px;
border-bottom: 1px solid rgb(128, 125, 125);
font-size: 15px;
outline: none;
}
.input-item:placeholder {
text-transform: uppercase;
}
.btn {
text-align: center;
padding: 10px;
width: 100%;
margin-top: 40px;
background-image: linear-gradient(to right, #a6c1ee, #fbc2eb);
color: #fff;
border-style:none;
}
.msg {
text-align: center;
line-height: 88px;
}
a {
text-decoration-line: none;
color: #abc1ee;
}
</style>
</head>
<body>
<div class="container">
<div class="login-wrapper">
<div class="header">Login</div>
<div class="form-wrapper">
<form action="" id="form">
<input type="text" name="username" placeholder="username" class="input-item">
<input type="password" name="password" placeholder="password" class="input-item">
<input type="submit" class="btn" value="Ligin">
</form>
</div>
<div class="msg">
Don't have account?
<a href="index1.html">Sign up</a>
</div>
</div>
</div>
</body>
</html>
二、创建数据库数据表
CREATE TABLE tb_user(
id INT PRIMARY KEY AUTO_INCREMENT,
username VARCHAR(20) UNIQUE,
PASSWORD VARCHAR(32)
);
INSERT INTO tb_user(username,PASSWORD) VALUES('zhangsan','123'),('lisi','234');
SELECT * FROM tb_user;
三、创建项目，编写实体类
package com.itheima.pojo;
public class User {
private Integer id;
private String username;
private String password;
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getUsername() {
return username;
}
public void setUsername(String username) {
this.username = username;
}
public String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}
@Override
public String toString() {
return "User{" +
"id=" + id +
", username='" + username + '\'' +
", password='" + password + '\'' +
'}';
}
}
四、导入mybatis，mysql驱动坐标
<dependency>
<groupId>org.mybatis</groupId>
<artifactId>mybatis</artifactId>
<version>3.5.5</version>
</dependency>
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>5.1.38</version>
</dependency>
五、创建mybatis-config.xml核心配置文件，UserMapper.xml映射文件，UserMapper接口
resource目录下的核心配置文件
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configuration
PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
"https://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
<!-- 起别名 -->
<typeAliases>
<package name="com.itheima.pojo"/>
</typeAliases>
<environments default="development">
<environment id="development">
<transactionManager type="JDBC"/>
<dataSource type="POOLED">
<property name="driver" value="com.mysql.jdbc.Driver"/>
<property name="url" value="jdbc:mysql:///db1?useSSL=false&useServerPreStmts=true"/>
<property name="username" value="root"/>
<property name="password" value="123456"/>
</dataSource>
</environment>
</environments>
<mappers>
<!-- 包扫描，扫描mapper -->
<package name="com.itheima.mapper"/>
</mappers>
</configuration>
创建itheima目录下的mapper包的UserMapper接口
创建resource目录下的itheima目录下的mapper包的UserMapper.xml映射文件
六、补全代码
- UserMapper接口（此处用了注解的方式，所以没写映射文件）
package com.itheima.mapper;
import com.itheima.pojo.User;
import org.apache.ibatis.annotations.Param;
import org.apache.ibatis.annotations.Select;
public interface UserMapper {
/**
* 根据用户名和密码查询对象
* @param username
* @param password
* @return
*/
@Select("select * from tb_user where username = #{username} and password = #{password}")
User Select(@Param("username") String username, @Param("password") String password);
}
- html代码（补全表单跳转的servlet）
<form action="/tomcat-demo2/loginServlet" method="post" id="form">
- 编写servlet
package com.itheima.web;
import com.itheima.mapper.UserMapper;
import com.itheima.pojo.User;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
@WebServlet("/loginServlet")
public class LoginServlet extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
this.doGet(request, response);
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// 1. 接收用户名和密码
String username = request.getParameter("username");
String password = request.getParameter("password");
// 2. 调用mybatis完成查询
// 2.1 获取sqlSessionFactory对象
String resource = "mybatis-config.xml";
InputStream inputStream = Resources.getResourceAsStream(resource);
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
// 2.2 获取SqlSession对象
SqlSession sqlSession = sqlSessionFactory.openSession();
// 2.3 获取Mapper
UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
// 2.4 调用方法
User user = userMapper.Select(username, password);
// 2.5 释放资源
sqlSession.close();
//获取字符输出流，并设置content type
response.setContentType("text/html;charset=utf-8");
PrintWriter writer = response.getWriter();
// 3. 判断uer是否为null
if (user != null){
//登录成功
writer.write("登录成功");
}else {
//登录失败
writer.write("登录失败");
}
}
}
此时代码就可以正常运行了，需要注意的是，pom文件中一定要注意mysql的驱动是自己下载的驱动，如果是maven导入的驱动会报错。我在此处犯了两次错误，浪费了许多时间！
4.26日补：
如果我们写多个功能的话，servlet代码中会获取多个SQLSessionFactory对象，这个对象是一个数据池，如果创建多个会浪费许多资源，所以我们创建一个工具类，使用静态代码块的方式来解决这个问题。
package com.itheima.util;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import java.io.IOException;
import java.io.InputStream;
public class SqlSessionFactoryUtils {
private static SqlSessionFactory sqlSessionFactory;
static {
//静态代码块会随着类的加载而自动执行，且只执行一次
try {
String resource = "mybatis-config.xml";
InputStream inputStream = Resources.getResourceAsStream(resource);
sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
} catch (IOException e) {
e.printStackTrace();
}
}
public static SqlSessionFactory getSqlSessionFactory(){
return sqlSessionFactory;
}
}
