MyBatis 基于注解的简单的CRUD

第一步：创建Maven项目

  junit
  junit
  4.12
  test


  log4j
  log4j
  1.2.17



  org.projectlombok
  lombok
  1.18.10



  org.mybatis
  mybatis
  3.5.4


  mysql
  mysql-connector-java
  8.0.18

第二步：创建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  

第三步：MySQL配置文件

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

第四步：MyBatis配置文件

注意：定义mapper时使用的class

第五步：实体类

@Data
@ToString
@AllArgsConstructor
@NoArgsConstructor
public class Emp implements Serializable {
	private Integer empno;
	private String ename;
	private String job;
	private Integer mgr;
	private Date hiredate;
	private double sal;
	private double comm;
	private int deptno;

}

第六步：EmpDao

 public interface EmpDao {
    @Insert("insert into tb_emp(empno,ename,job,mgr,hiredate,sal,comm,deptno) values(#{empno},#{ename},#{job},#{mgr},#{hiredate},#{sal},#{comm},#{deptno});")
    public void addEmp(Emp emp);

    @Delete("delete from tb_emp where empno=#{empno};")
    public void deleteEmpById(int empno);

    @Update("update tb_emp set ename=#{ename},job=#{job},mgr=#{mgr},hiredate=#{hiredate},sal=#{sal},comm=#{comm},deptno=#{deptno} where empno=#{empno};")
    public void updateEmp(Emp emp);

    @Select("Select * from tb_emp where empno=#{empno}")
    public Emp findEmpById(int empno);

    @Select("select * from tb_emp")
    public List findAllEmps();
}

第七步：工具类MyBatisUtil

 public class MyBatisUtil {
    private static String CONFIG_FILE_LOCATION = "mybatis-config.xml";
    private static final ThreadLocal threadLocal = new ThreadLocal();
    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);
        }
    }
}

第八步：测试代码

public class EmpDaoTest {

    @Test
    public void addEmp() {
        Emp emp = new Emp(123, "123", "123", 7788, new Date(), 123d, 123d, 20);
        SqlSession session = null;
        try {
            session = MyBatisUtil.getSession();
            EmpDao mapper = session.getMapper(EmpDao.class);
            mapper.addEmp(emp);
            session.commit();
        } catch (Exception e) {
            session.rollback();
            e.printStackTrace();
        } finally {
            MyBatisUtil.closeSession();
        }
    }

    @Test
    public void deleteEmpById() {
        int empno = 123;
        SqlSession session = null;
        try {
            session = MyBatisUtil.getSession();
            EmpDao mapper = session.getMapper(EmpDao.class);
            mapper.deleteEmpById(empno);
            session.commit();
        } catch (Exception e) {
            session.rollback();
            e.printStackTrace();
        } finally {
            MyBatisUtil.closeSession();
        }
    }

    @Test
    public void updateEmp() {
        Emp emp = new Emp(123, "aaa", "aaa", 7788, new Date(), 123d, 123d, 20);
        SqlSession session = null;
        try {
            session = MyBatisUtil.getSession();
            EmpDao mapper = session.getMapper(EmpDao.class);
            mapper.updateEmp(emp);
            session.commit();
        } catch (Exception e) {
            session.rollback();
            e.printStackTrace();
        } finally {
            MyBatisUtil.closeSession();
        }
    }

    @Test
    public void findEmpById() {
        int empno = 123;
        Emp emp = null;
        SqlSession session = null;
        try {
            session = MyBatisUtil.getSession();
            EmpDao mapper = session.getMapper(EmpDao.class);
            emp = mapper.findEmpById(empno);
            session.commit();
        } catch (Exception e) {
            session.rollback();
            e.printStackTrace();
        } finally {
            MyBatisUtil.closeSession();
        }
        System.out.println(emp);
    }

    @Test
    public void findAllEmps() {
        List res = null;
        SqlSession session = null;
        try {
            session = MyBatisUtil.getSession();
            EmpDao mapper = session.getMapper(EmpDao.class);
            res = mapper.findAllEmps();
            session.commit();
        } catch (Exception e) {
            session.rollback();
            e.printStackTrace();
        } finally {
            MyBatisUtil.closeSession();
        }
        for (Emp emp : res) {
            System.out.println(emp);
        }
    }
}