數據表
項目框架搭建
第一步:創建Maven項目
- 添加Maven依賴:
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.12</version>
<scope>test</scope>
</dependency>
<dependency>
<groupId>log4j</groupId>
<artifactId>log4j</artifactId>
<version>1.2.17</version>
</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>8.0.18</version>
</dependency>
<dependency>
<groupId>org.mybatis</groupId>
<artifactId>mybatis</artifactId>
<version>3.5.4</version>
</dependency>
- 指定Mapper XML文件在mybatis-config.xml中的配置有效,強制部署resources目錄到classes
<resources>
<resource>
<directory>src/main/resources</directory>
<includes>
<include>**/*.xml</include>
</includes>
</resource>
<resource>
<directory>${basedir}/src/main/resources</directory>
</resource>
</resources>
第二步:配置文件
- log4j.properties
log4j.rootLogger=DEBUG, Console
#Console
log4j.appender.Console=org.apache.log4j.ConsoleAppender
log4j.appender.Console.layout=org.apache.log4j.PatternLayout
log4j.appender.Console.layout.ConversionPattern=%d [%t] %-5p [%c] - %m%n
log4j.logger.java.sql.ResultSet=INFO
log4j.logger.org.apache=INFO
log4j.logger.java.sql.Connection=DEBUG
log4j.logger.java.sql.Statement=DEBUG
log4j.logger.java.sql.PreparedStatement=DEBUG
- mysql.properties
driver=com.mysql.cj.jdbc.Driver
url=jdbc:mysql://127.0.0.1/db_test?useSSL=false&serverTimezone=CST
username=root
password=root
第三步:工具類MyBatisUtil
public class MyBatisUtil {
private static String CONFIG_FILE_LOCATION = "mybatis-config.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);
}
}
}
第四步:實體類
- Dept
@Data
@ToString
@AllArgsConstructor
@NoArgsConstructor
public class Dept implements Serializable {
private static final long serialVersionUID = -4186854135138751084L;
private Integer deptno;
private String dname;
private String loc;
}
- Emp
@Data
@ToString(exclude = "dept") //設置toString輸出字段中不包含emps字段
@AllArgsConstructor
@NoArgsConstructor
public class Emp implements Serializable {
private static final long serialVersionUID = 4976291764719306570L;
private Integer empno; //封裝數據類型
private String ename;
private String job;
private Integer mgr; //封裝數據類型
private LocalDate hiredate;
private Double sal;
private Double comm;
private Integer deptno;
////////////////////////////////////////
private Dept dept;
}
XML方式
第一步:創建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>
<!--引入外部properties文件 -->
<properties resource="mysql.properties"></properties>
<settings>
<!-- 打印查詢語句 -->
<setting name="logImpl" value="STDOUT_LOGGING"/>
</settings>
<environments default="development">
<environment id="development">
<transactionManager type="JDBC"/>
<dataSource type="POOLED"> <!-- 數據源的配置,連接到數據庫 -->
<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/EmpMapper.xml"/>
</mappers>
</configuration>
注意:mappers標籤中使用的是resouce
第二步:DeptDao
public interface EmpDao {
Emp selectEmpWithDeptByEmpno(int Empno);
}
第三步:DeptMapper.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.EmpDao">
<resultMap type="com.hc.bean.Emp" id="empDept">
<id property="empno" column="empno" />
<result property="ename" column="ename" />
<result property="job" column="job" />
<result property="mgr" column="mgr" />
<result property="hiredate" column="hiredate" />
<result property="sal" column="sal" />
<result property="comm" column="comm" />
<association property="dept" javaType="com.hc.bean.Dept">
<id property="deptno" column="deptno" />
<result property="dname" column="dname" />
<result property="loc" column="loc" />
</association>
</resultMap>
<select id="selectEmpWithDeptByEmpno" parameterType="int" resultMap="empDept">
select * from tb_emp
inner join tb_dept
on tb_emp.deptno = tb_dept.deptno
WHERE empno = #{empno};
</select>
</mapper>
測試代碼
public class EmpDaoTest {
@Test
public void getEmpWithDeptByEmpno() {
SqlSession session = MyBatisUtil.getSession();
EmpDao empDao= session.getMapper(EmpDao.class);
Emp emp = empDao.selectEmpWithDeptByEmpno(7788);
System.out.println(emp);
System.out.println(emp.getDept());
}
}
註解方式
第一步:創建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>
<!--引入外部properties文件 -->
<properties resource="mysql.properties"></properties>
<settings>
<!-- 打印查詢語句 -->
<setting name="logImpl" value="STDOUT_LOGGING"/>
</settings>
<environments default="development">
<environment id="development">
<transactionManager type="JDBC"/>
<dataSource type="POOLED"> <!-- 數據源的配置,連接到數據庫 -->
<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 class="com.hc.many2one.dao.DeptDao"/>
<mapper class="com.hc.many2one.dao.EmpDao"/>
</mappers>
</configuration>
第二步:創建Dao接口
- DeptDao
public interface DeptDao {
@Select("select * from tb_dept where deptno= #{deptno}")
Dept selectDeptByDeptno(Integer deptno);
}
- EmpDao
public interface EmpDao {
@Select("select * from tb_emp where empno = #{empno}")
@Results({
@Result(
property = "dept",column = "deptno",
one = @One(select = "com.hc.many2one.dao.DeptDao.selectDeptByDeptno")
)
})
Emp selectEmpByEmpno(Integer empno);
}
測試代碼
public class EmpDaoTest {
//多對一
@Test
public void selectEmpByEmpno(){
SqlSession session = MyBatisUtil.getSession();
EmpDao empDao = session.getMapper(EmpDao.class);
Emp emp = empDao.selectEmpByEmpno(7788);
System.out.println(emp);
}
}