1.mybatis入门

• 目录结构

  
  image.png

• 准备pom.xml文件

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>

  <groupId>com.mc</groupId>
  <artifactId>mcMybatis</artifactId>
  <version>0.0.1-SNAPSHOT</version>
  <packaging>war</packaging>

  <properties>
    <java.version>1.6</java.version>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
  </properties>

  <dependencies>
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>4.12</version>
      <scope>test</scope>
    </dependency>
    <dependency>
      <groupId>org.mybatis</groupId>
      <artifactId>mybatis</artifactId>
      <version>3.3.0</version>
    </dependency>
    <dependency>
      <groupId>mysql</groupId>
      <artifactId>mysql-connector-java</artifactId>
      <version>5.1.38</version>
    </dependency>
    <dependency>
      <groupId>org.slf4j</groupId>
      <artifactId>slf4j-api</artifactId>
      <version>1.7.12</version>
    </dependency>
    <dependency>
      <groupId>org.slf4j</groupId>
      <artifactId>slf4j-log4j12</artifactId>
      <version>1.7.12</version>
    </dependency>
    <dependency>
      <groupId>log4j</groupId>
      <artifactId>log4j</artifactId>
      <version>1.2.17</version>
    </dependency>
  </dependencies>

  <build>
    <plugins>
      <plugin>
        <artifactId>maven-compiler-plugin</artifactId>
        <configuration>
          <source>${java.version}</source>
          <target>${java.version}</target>
        </configuration>
      </plugin>
    </plugins>
  </build>
</project>

• 创建mybatis-config .xml

<!DOCTYPE configuration
        PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
    <settings>
        <setting name="logImpl" value="LOG4J"/>
    </settings>
    
     <typeAliases>
        <package name="com.mc.model"/>
    </typeAliases>

    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC">
                <property name="" value=""/>
            </transactionManager>
            <dataSource type="UNPOOLED">
                <property name="driver" value="com.mysql.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql://***.**.**.146:3306/test"/>
                <property name="username" value="root"/>
                <property name="password" value="fumengchao"/>
            </dataSource>
        </environment>
    </environments>
    <mappers>
        <!--<mapper resource="com/mc/mapper/CountryMapper.xml"/>-->
        <package name="com.mc.mapper"/>
    </mappers>
</configuration>

简单介绍下这个配置：

1. <setting name="logImpl" value="LOG4J"/>中的logImpl属性指定使用log4j输出日志。
2. <typeAliases>设置一个包的别名别名，配置过后在具体的xml中可以只写类名就可以。
3. <environments＞环境 配置中 主要 配置了数据库连接。
4. </mappers>中可以配置具体的mapper路径（通过resource），也可以通过包来配置（package）

import java.io.Serializable;
import java.util.Date;
import java.util.List;

/**
 * 用户表
 */
public class SysUser implements Serializable {
    private static final long serialVersionUID = -328602757171077630L;
    /**
     * 用户ID
     */
    private Long id;
    /**
     * 用户名
     */
    private String userName;
}

• 在src/main/resources下添加log4j.properies,<mapper namespace="com.mc.mapper.UserMapper">

log4j.rootLogger=ERROR, stdout

#MyBatis \u65E5\u5FD7\u914D\u7F6E
注意此包名必须和namesapce下面的包名一致
log4j.logger.com.mc.mapper=TRACE

##\u5168\u5C40\u914D\u7F6E
log4j.rootLogger=ERROR, stdout

#MyBatis \u65E5\u5FD7\u914D\u7F6E
#注意此包名必须和namesapce下面的包名一致
log4j.logger.com.mc.mapper=TRACE

#\u63A7\u5236\u53F0\u8F93\u51FA\u914D\u7F6E
log4j.appender.stdout=org.apache.log4j.ConsoleAppender
log4j.appender.stdout.layout=org.apache.log4j.PatternLayout
log4j.appender.stdout.layout.ConversionPattern=%5p [%t] - %m%n

• 创建userMapper.java

public interface UserMapper {

    SysUser selectById(Long id);

    List<SysUser> selectAll();

    /**
     * 通过用户ID查询角色
     * @param userId
     * @return
     */
    List<SysRoleExtend> selectRolesByUserId(Long userId);
}

• 创建userMapper.xml

<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd" >
<mapper namespace="com.mc.mapper.UserMapper">
    <resultMap id="userMap" type="SysUser">
        <id property="id" column="id"/>
        <result property="userName" column="user_name"/>
        <result property="userPassword" column="user_password"/>
        <result property="userEmail" column="user_email"/>
        <result property="userInfo" column="user_info"/>
        <result property="headImg" column="head_img" jdbcType="BLOB"/>
        <result property="createTime" column="create_time" jdbcType="TIMESTAMP"/>
    </resultMap>
    <select id="selectById" resultMap="userMap">
        select * from sys_user where id=#{id}
    </select>

    <select id="selectAll" resultType="SysUser">
        select * from sys_user
    </select>

    <!--方式1:在sysRole中增加一个SysUser类，通过类名.字段名的方式拿到-->

    <!--<select id="selectRolesByUserId" resultType="SysRole">-->
        <!--SELECT-->
          <!--a.id,-->
          <!--a.role_name roleName,-->
          <!--a.enabled,-->
          <!--a.create_by createBy,-->
          <!--a.create_time createTime,-->
          <!--c.user_name as "user.userName",-->
          <!--c.id as "user.id"-->
        <!--FROM-->
          <!--sys_user_role b-->
        <!--INNER JOIN sys_role a ON a.id = b.role_id-->
        <!--INNER JOIN sys_user c ON c.id = b.user_id-->
        <!--WHERE c.id=#{userId}-->
    <!--</select>-->
    <!--方式2：写一个类继承SysRole 扩展里面的字段要和数据库保持一致-->
    <select id="selectRolesByUserId" resultType="SysRoleExtend">
        SELECT
          a.id,
          a.role_name roleName,
          a.enabled,
          a.create_by createBy,
          a.create_time createTime,
          c.user_name userName,
          c.id as userId

        FROM
          sys_user_role b
        INNER JOIN sys_role a ON a.id = b.role_id
        INNER JOIN sys_user c ON c.id = b.user_id
        WHERE c.id=#{userId}
    </select>

</mapper>```
- 让mybatis跑起来(必须和xml路径一致，xml创建包的时候必须一层一层创建，不然会有问题)
```/***
 * @ClassName BaseMapperTest
 * @Description todo
 * @Author CC
 * @Date: 2019/8/714:01
 * @Version 1.0
 */
public class BaseMapperTest {
    private static SqlSessionFactory sqlSessionFactory;

    @BeforeClass
    public static void init() {
        try {
            Reader reader = Resources.getResourceAsReader("mybatis-config.xml");
            sqlSessionFactory = new SqlSessionFactoryBuilder().build(reader);
            reader.close();
        } catch (IOException ignore) {
            ignore.printStackTrace();
        }
    }

    public SqlSession getSqlSession() {
        return sqlSessionFactory.openSession();
    }
}

 * @ClassName UserMapperTest
 * @Description todo
 * @Author CC
 * @Date: 2019/8/714:09
 * @Version 1.0
 */
public class UserMapperTest extends BaseMapperTest {

    @Test
    public void testSelectById() {
        SqlSession sqlSession = getSqlSession();
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        SysUser sysUser = mapper.selectById(1L);
        Assert.assertNotNull(sysUser);
    }

    @Test
    public void testSelectAll() {
        SqlSession sqlSession = getSqlSession();
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        List<SysUser> sysUsers = mapper.selectAll();
        Assert.assertNotNull(sysUsers);
        sqlSession.close();
    }

    @Test
    public void testSelectRolesByUserId() {
        SqlSession sqlSession = getSqlSession();
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        List<SysRoleExtend> sysRoles = mapper.selectRolesByUserId(1L);
        Assert.assertNotNull(sysRoles);
        sqlSession.close();
    }
}