思路： 搭建环境–>导入Mybatis–>编写代码–>测试！

第一部分是整体搭建+查询数据库中所有用户

1.搭建环境

搭建数据库

CREATE DATABASE `mybatis`; USE `mybatis`; CREATE TABLE `user`( `id` INT(20) NOT NULL PRIMARY KEY, `name` VARCHAR(30) DEFAULT NULL, `pwd` VARCHAR(30) DEFAULT NULL )ENGINE=INNODB DEFAULT CHARSET=utf8; INSERT INTO `user`(`id`,`name`,`pwd`) VALUES (1,'狂神','123456'), (2,'张三','123456'), (3,'李四','123890')

新建项目

新建一个普通的maven项目删除src目录导入maven依赖 <!--导入依赖--> <dependencies> <!--mysql驱动--> <dependency> <groupId>mysql</groupId> <artifactId>mysql-connector-java</artifactId> <version>5.1.47</version> </dependency> <!--mybatis--> <!-- https://mvnrepository.com/artifact/org.mybatis/mybatis --> <dependency> <groupId>org.mybatis</groupId> <artifactId>mybatis</artifactId> <version>3.5.2</version> </dependency> <!--junit--> <dependency> <groupId>junit</groupId> <artifactId>junit</artifactId> <version>4.12</version> </dependency> </dependencies>

2.创建一个子模块

编写Mybatis的核心配置文件 （在resources下，通常名命mybatis-config.xml） <?xml version="1.0" encoding="UTF-8" ?> <!DOCTYPE configuration PUBLIC "-//mybatis.org//DTD Config 3.0//EN" "http://mybatis.org/dtd/mybatis-3-config.dtd"> <!--configuration核心配置文件--> <configuration> <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://localhost:3306/mybatis?useSSL=true&useUnicode=true&characterEncoding=UTF-8"/> <property name="username" value="root"/> <property name="password" value="123456"/> </dataSource> </environment> </environments> </configuration>

编写mybatis工具类 //sqlSessionFactory --> sqlSession public class MybatisUtils { private static SqlSessionFactory sqlSessionFactory; static{ try { //使用Mybatis第一步：获取sqlSessionFactory对象 String resource = "mybatis-config.xml"; InputStream inputStream = Resources.getResourceAsStream(resource); sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream); } catch (IOException e) { e.printStackTrace(); } } //既然有了 SqlSessionFactory，顾名思义，我们就可以从中获得 SqlSession 的实例了。 // SqlSession 完全包含了面向数据库执行 SQL 命令所需的所有方法。 public static SqlSession getSqlSession(){ return sqlSessionFactory.openSession(); } }

3.编写代码

实体类 package com.peach.pojo; public class User { private int id; private String name; private String pwd; public User() { } public User(int id, String name, String pwd) { this.id = id; this.name = name; this.pwd = pwd; } public int getId() { return id; } public void setId(int id) { this.id = id; } public String getName() { return name; } public void setName(String name) { this.name = name; } public String getPwd() { return pwd; } public void setPwd(String pwd) { this.pwd = pwd; } @Override public String toString() { return "User{" + "id=" + id + ", name='" + name + '\'' + ", pwd='" + pwd + '\'' + '}'; } } DAO接口，相当于Mybatis中的Mapper public interface UserDao { List<User> getUserList(); } 接口实现类由原来的UserDaoImpl转为一个 Mapper配置文件. <?xml version="1.0" encoding="UTF-8" ?> <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd"> <!--namespace=绑定一个对应的Dao/Mapper接口--> <mapper namespace="com.kuang.dao.UserDao"> <!--select查询语句--> <select id="getUserList" resultType="com.kuang.pojo.User"> select * from mybatis.user </select> </mapper>

4.测试

在test中编写测试类，而且包名与main中尽量对应一致 都是固定步骤：

public class UserDaoTest { @Test public void test(){ //第一步：获得SqlSession对象 SqlSession sqlSession = MybatisUtils.getSqlSession(); //方式一：getMapper //通过它获得接口 UserMapper userDao = sqlSession.getMapper(UserMapper.class); List<User> userList = userDao.getUserList(); for (User user : userList){ System.out.println(user); } //关闭SqlSession sqlSession.close(); } }

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第二部分，在第一部分搭建的基础上进行增删改查

只需对下面这三个文件按图片表号顺序修改

1.select

编写接口（Mapper） //根据ID查询用户 User getUserById(int id); 编写对应的mapper中的SQL语句 在之前学习的JDBC中，实现类需要写SQL一系列语句，而mybatis中只需写一个标签 <select id="getUserById" parameterType="int" resultType="com.kuang.pojo.User"> select * from mybatis.user where id = #{id} </select> 测试 @Test public void getUserById() { SqlSession sqlSession = MybatisUtils.getSqlSession(); UserMapper mapper = sqlSession.getMapper(UserMapper.class); User user = mapper.getUserById(1); System.out.println(user); sqlSession.close(); }

2.Insert

<!--对象中的属性，可以直接取出来--> <insert id="addUser" parameterType="com.kuang.pojo.User"> insert into mybatis.user (id, name, pwd) values (#{id},#{name},#{pwd}); </insert>

3.update

<update id="updateUser" parameterType="com.kuang.pojo.User"> update mybatis.user set name=#{name},pwd=#{pwd} where id = #{id} ; </update>

4.delete

<delete id="deleteUser" parameterType="int"> delete from mybatis.user where id = #{id}; </delete>