搭建项目框架

第一步：创建Maven项目

• 添加依赖

  <dependency>
    <groupId>junit</groupId>
    <artifactId>junit</artifactId>
    <version>4.12</version>
    <scope>test</scope>
</dependency>
<dependency>
    <groupId>org.projectlombok</groupId>
    <artifactId>lombok</artifactId>
    <version>1.18.10</version>
</dependency>
<dependency>
    <groupId>mysql</groupId>
    <artifactId>mysql-connector-java</artifactId>
    <version>8.0.11</version>
</dependency>
<dependency>
    <groupId>org.mybatis</groupId>
    <artifactId>mybatis</artifactId>
    <version>3.5.4</version>
</dependency>

• 指定映射文件位置

<resources>
    <resource>
        <directory>src/main/java</directory>
        <includes>
            <include>**/*.xml</include>
        </includes>
    </resource>
</resources>

创建MySQL配置文件mysql.properties

driver=com.mysql.cj.jdbc.Driver
url=jdbc:mysql://127.0.0.1/test?useSSL=false&serverTimezone=CST
username=root
password=root

第三步：创建MyBatis配置文件mybatis-cfg.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>
    <!--引入外部properties文件  -->
    <properties resource="mysql.properties"></properties>
    <settings>
        <!-- 打印查询语句 -->
        <setting name="logImpl" value="STDOUT_LOGGING" />
    </settings>
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC" />
            <dataSource type="POOLED">  <!-- 数据源的配置，连接到数据库 -->
                <property name="driver" value="${driver}" />
                <property name="url" value="${url}"/>
                <property name="username" value="${username}" />
                <property name="password" value="${password}" />
            </dataSource>
        </environment>
    </environments>
    <mappers>
        <mapper resource="com/hc/dao/mapping/DeptDao.xml"/>
    </mappers>
</configuration>

第四步：创建MyBatis工具类

public class MyBatisUtil {
	private static String CONFIG_FILE_LOCATION = "mybatis-cfg.xml";
	private static final ThreadLocal<SqlSession> threadLocal = new 
													ThreadLocal<SqlSession>();
    private static SqlSessionFactory sessionFactory;
    
    static {
    		try {
			Reader reader=Resources.getResourceAsReader(CONFIG_FILE_LOCATION);
			SqlSessionFactoryBuilder builder=new SqlSessionFactoryBuilder();
			sessionFactory=builder.build(reader);
		} catch (Exception e) {
			e.printStackTrace();
		}
    }
    
    public static SqlSession getSession() {
    		SqlSession  session = threadLocal.get();
		if (session == null) {
			session = (sessionFactory!=null) ? sessionFactory.openSession() : null;
			threadLocal.set(session);
		}
        return session;
    }
    public static void closeSession()  {
    	   SqlSession session = threadLocal.get();
        if (session != null) {
            session.close();
  		   threadLocal.set(null);
        }
    }
}

具体代码

第一步：创建实体类

@Getter
@Setter
@Builder
@NoArgsConstructor
@AllArgsConstructor
@ToString(callSuper = true)
public class Dept {
    /**
     * 部门编号
     */
    private Byte deptno;

    /**
     * 部门名称
     */
    private String dname;

    /**
     * 部门地址
     */
    private String loc;
}

第二步：创建DeptDao.java

public interface DeptDao {
    int deleteByPrimaryKey(Byte deptno);

    int insert(Dept record);

    int insertSelective(Dept record);

    Dept selectByPrimaryKey(Byte deptno);

    int updateByPrimaryKeySelective(Dept record);

    int updateByPrimaryKey(Dept record);
}

第三步：创建DeptDao.xml

<?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 namespace="com.hc.dao.DeptDao">
    <resultMap id="BaseResultMap" type="com.hc.bean.Dept">
        <id column="deptno" jdbcType="TINYINT" property="deptno"/>
        <result column="dname" jdbcType="VARCHAR" property="dname"/>
        <result column="loc" jdbcType="VARCHAR" property="loc"/>
    </resultMap>
    
    <sql id="Base_Column_List">
   		deptno, dname, loc
    </sql>
    
    <select id="selectByPrimaryKey" parameterType="java.lang.Byte" resultMap="BaseResultMap">
        select
        <include refid="Base_Column_List"/>
        from tb_dept
        where deptno = #{deptno,jdbcType=TINYINT}
    </select>
    
    <delete id="deleteByPrimaryKey" parameterType="java.lang.Byte">
	    delete from tb_dept
	    where deptno = #{deptno,jdbcType=TINYINT}
  	</delete>
  
    <insert id="insert" parameterType="com.hc.bean.Dept">
	    insert into tb_dept (deptno, dname, loc )
	    values (#{deptno,jdbcType=TINYINT}, #{dname,jdbcType=VARCHAR}, #{loc,jdbcType=VARCHAR} )
	  </insert>
  
    <insert id="insertSelective" parameterType="com.hc.bean.Dept">
        insert into tb_dept
        <trim prefix="(" suffix=")" suffixOverrides=",">
            <if test="deptno != null">
                deptno,
            </if>
            <if test="dname != null">
                dname,
            </if>
            <if test="loc != null">
                loc,
            </if>
        </trim>
        <trim prefix="values (" suffix=")" suffixOverrides=",">
            <if test="deptno != null">
                #{deptno,jdbcType=TINYINT},
            </if>
            <if test="dname != null">
                #{dname,jdbcType=VARCHAR},
            </if>
            <if test="loc != null">
                #{loc,jdbcType=VARCHAR},
            </if>
        </trim>
    </insert>
    
    <update id="updateByPrimaryKeySelective" parameterType="com.hc.bean.Dept">
        update tb_dept
        <set>
            <if test="dname != null">
                dname = #{dname,jdbcType=VARCHAR},
            </if>
            <if test="loc != null">
                loc = #{loc,jdbcType=VARCHAR},
            </if>
        </set>
        where deptno = #{deptno,jdbcType=TINYINT}
    </update>
    
    <update id="updateByPrimaryKey" parameterType="com.hc.bean.Dept">
	    update tb_dept
	    set dname = #{dname,jdbcType=VARCHAR},
	      loc = #{loc,jdbcType=VARCHAR}
	    where deptno = #{deptno,jdbcType=TINYINT}
	  </update>
  
</mapper>

第四步：测试代码

public class DeptMapperTest {

    private SqlSession session;
    private  DeptDao mapper;
    @Before
    public void before(){
          session = MyBatisUtil.getSession();
          mapper = session.getMapper(DeptDao.class);
    }
    @After
    public void after(){
        session.commit();
    }
    @Test
    public void deleteByPrimaryKey() {
        int res = mapper.deleteByPrimaryKey((byte) 46);
        System.out.println(res);
    }

    @Test
    public void insert() {
        Dept dept = new Dept((byte)1,"aa","aaaaaaaaaaa");
        int res = mapper.insert(dept);
        System.out.println(res);
    }

    @Test
    public void insertSelective() {
        Dept dept = new Dept();
        dept.setDname("abcd");
        int res = mapper.insertSelective(dept);
        System.out.println(res);
    }

    @Test
    public void selectByPrimaryKey() {
        Dept dept = mapper.selectByPrimaryKey((byte) 10);
        System.out.println(dept);
    }

    @Test
    public void updateByPrimaryKeySelective() {
        Dept dept = new Dept();
        dept.setDeptno((byte)40);
        dept.setDname("abc");
        int res = mapper.updateByPrimaryKeySelective(dept);
        System.out.println(res);
    }

    @Test
    public void updateByPrimaryKey() {
//        Dept dept = new Dept();
//        dept.setDeptno((byte)47);
//        dept.setDname("asdf");
//        int res = mapper.updateByPrimaryKey(dept);
        System.out.println(3/0);
    }
}