2. MyBatis快速入门

<dependency>
    <groupId>mysql</groupId>
    <artifactId>mysql-connector-java</artifactId>
    <version>5.1.38</version>
</dependency>
<dependency>
    <groupId>org.mybatis</groupId>
    <artifactId>mybatis</artifactId>
    <version>3.2.8</version>
</dependency>

<?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">
<!-- 根标签 -->
<configuration>
<properties>
    <property name="driver" value="com.mysql.jdbc.Driver"/>
    <property name="url" value="jdbc:mysql://127.0.0.1:3306/ssmdemo?useUnicode=true&amp;characterEncoding=utf-8&amp;allowMultiQueries=true"/>
    <property name="username" value="root"/>
        <property name="password" value="123456"/>
   </properties>

   <!-- 环境，可以配置多个，default：指定采用哪个环境 -->
   <environments default="test">
      <!-- id：唯一标识 -->
      <environment id="test">
         <!-- 事务管理器，JDBC类型的事务管理器 -->
         <transactionManager type="JDBC" />
         <!-- 数据源，池类型的数据源 -->
         <dataSource type="POOLED">
            <property name="driver" value="com.mysql.jdbc.Driver" />
            <property name="url" value="jdbc:mysql://127.0.0.1:3306/ssmdemo"/>
            <property name="username" value="root" />
            <property name="password" value="123456" />
         </dataSource>
      </environment>
      <environment id="development">
         <!-- 事务管理器，JDBC类型的事务管理器 -->
         <transactionManager type="JDBC" />
         <!-- 数据源，池类型的数据源 -->
         <dataSource type="POOLED">
            <property name="driver" value="${driver}" /> <!-- 配置了properties，所以可以直接引用 -->
            <property name="url" value="${url}" />
            <property name="username" value="${username}" />
            <property name="password" value="${password}" />
         </dataSource>
      </environment>
   </environments>
</configuration>

<?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">
<!-- mapper:根标签，namespace：命名空间，随便写，一般保证命名空间唯一 -->
<mapper namespace="MyMapper">
   <!-- statement，内容：sql语句。id：唯一标识，随便写，在同一个命名空间下保持唯一
      resultType：sql语句查询结果集的封装类型,tb_user即为数据库中的表
    -->
   <select id="selectUser" resultType="com.zpc.mybatis.User">
      select * from tb_user where id = #{id}
   </select>
</mapper>

<?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">
<!-- 根标签 -->
<configuration>
   <mappers>
     <mapper resource="mappers/MyMapper.xml" />
   </mappers>
</configuration>

// 指定全局配置文件
String resource = "mybatis-config.xml";
// 读取配置文件
InputStream inputStream = Resources.getResourceAsStream(resource);
// 构建sqlSessionFactory
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);

// 获取sqlSession
SqlSession sqlSession = sqlSessionFactory.openSession();
// 操作CRUD，第一个参数：指定statement，规则：命名空间+“.”+statementId
// 第二个参数：指定传入sql的参数：这里是用户id
User user = sqlSession.selectOne("MyMapper.selectUser", 1);
System.out.println(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 java.io.InputStream;

public class MybatisTest {
   public static void main(String[] args) throws Exception {
      // 指定全局配置文件
      String resource = "mybatis-config.xml";
      // 读取配置文件
      InputStream inputStream = Resources.getResourceAsStream(resource);
      // 构建sqlSessionFactory
      SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
      // 获取sqlSession
      SqlSession sqlSession = sqlSessionFactory.openSession();
      try {
         // 操作CRUD，第一个参数：指定statement，规则：命名空间+“.”+statementId
         // 第二个参数：指定传入sql的参数：这里是用户id
         User user = sqlSession.selectOne("MyMapper.selectUser", 1);
         System.out.println(user);
      } finally {
         sqlSession.close();
      }
   }
}

import lombok.Data;
import java.util.Date;
@Data
public class User {
    private String id;
    private String userName;
    private String password;
    private String name;
    private Integer age;
    private Integer sex;
    private Date birthday;
    private String created;
    private String updated;
}

<select id="queryUserById" resultType="com.zpc.mybatis.pojo.User">
select
tuser.id as id,
tuser.user_name as userName,
tuser.password as password,
tuser.name as name,
tuser.age as age,
tuser.birthday as birthday,
tuser.sex as sex,
tuser.created as created,
tuser.updated as updated
from
tb_user tuser
where tuser.id = #{id};
</select>

#注意放置位置
<settings>
    <setting name="mapUnderscoreToCamelCase" value="true"/>
</settings>