三、Mybatis注解开发

3.1 快速入门

3.1.1 常用注解说明

注解	功能
@Insert	新增
@Update	更新
@Delete	删除
@Select	查询
@Result	结果集封装
@Results	与@Result 一起使用，封装多个结果集
@One	一对一结果集封装
@Many	一对多结果集封装

3.1.2 注解实现开发

• SQL语句：

DROP TABLE IF EXISTS `user`;
CREATE TABLE `user`  (`id` int(11) NOT NULL AUTO_INCREMENT,`username` varchar(255) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL,`birthday` date NULL DEFAULT NULL,`sex` varchar(255) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL,`address` varchar(255) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL,PRIMARY KEY (`id`) USING BTREE
) ENGINE = InnoDB AUTO_INCREMENT = 3 CHARACTER SET = utf8 COLLATE = utf8_general_ci ROW_FORMAT = Dynamic;INSERT INTO `user` VALUES (1, '张三', '1999-02-04', '男', '佛山');
INSERT INTO `user` VALUES (2, '李四', '1998-01-15', '女', '湛江');

• 实体类：

package com.dfbz.entity;import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;import java.util.Date;
import java.util.List;/*** @author lscl* @version 1.0* @intro:*/
@Data
@AllArgsConstructor
@NoArgsConstructor
public class User {private int  id;private String username;private Date birthday;private String sex;private String address;
}

• dao接口：

package com.dfbz.dao;import com.dfbz.entity.User;
import org.apache.ibatis.annotations.Delete;
import org.apache.ibatis.annotations.Insert;
import org.apache.ibatis.annotations.Select;
import org.apache.ibatis.annotations.Update;import java.util.List;/*** @author lscl* @version 1.0* @intro:*/
public interface UserDao {@Select("select * from user where id=#{id}")User findById(int id);@Select("select * from user")List<User> findAll();@Insert("insert into user values(null,#{username},#{birthday},#{sex},#{address})")void save(User user);@Update("update user set username=#{username},birthday=#{birthday},sex=#{sex},address=#{address} where id=#{id}")void update(User user);@Delete("delete from user where id=#{id}")void delete(int id);
}

• 加载配置类：

• 测试类：

package com.dfbz.test;import com.dfbz.dao.UserDao;
import com.dfbz.entity.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 org.junit.After;
import org.junit.Before;
import org.junit.Test;import java.io.IOException;
import java.util.Date;
import java.util.List;public class Demo01 {private SqlSessionFactoryBuilder builder;private SqlSessionFactory factory;private SqlSession session;private UserDao userDao;@Beforepublic void before() throws IOException {builder=new SqlSessionFactoryBuilder();factory=builder.build(Resources.getResourceAsStream("SqlMapConfig.xml"));session= factory.openSession();userDao=session.getMapper(UserDao.class);}@Afterpublic void after(){session.commit();session.close();}@Testpublic void save(){         //增加User user=new User();user.setUsername("小龙");user.setBirthday(new Date());user.setSex("男");user.setAddress("广州");userDao.save(user);}@Testpublic void delete(){userDao.delete(1);}@Testpublic void update(){User user=new User();user.setId(2);user.setUsername("张三");user.setBirthday(new Date());user.setSex("男");user.setAddress("广州");userDao.update(user);}@Testpublic void findById(){User user = userDao.findById(2);System.out.println(user);}@Testpublic void findAll(){List<User> userList = userDao.findAll();for (User user : userList) {System.out.println(user);}}
}

3.2 注解实现一对一映射

3.2.1 接口

• Emp：

package com.dfbz.entity;import lombok.Data;/*** @author lscl* @version 1.0* @intro:*/
@Data
public class Emp {private Integer id;private String name;private Integer age;private String addr;private Double salary;// 一个员工属于一个部门private Dept dept;
}

• Dept：

package com.dfbz.entity;import lombok.Data;import java.util.List;/*** @author lscl* @version 1.0* @intro:*/
@Data
public class Dept {private Integer id;private String name;private String location;// 一个部门下有多个员工private List<Emp> empList;
}

• DeptDao：

package com.dfbz.dao;import com.dfbz.entity.Dept;
import org.apache.ibatis.annotations.Select;public interface DeptDao {@Select("select * from dept where id=#{id}")Dept findById(Integer id);
}

• EmpDao：

package com.dfbz.dao;import com.dfbz.entity.Dept;
import com.dfbz.entity.Emp;
import org.apache.ibatis.annotations.One;
import org.apache.ibatis.annotations.Result;
import org.apache.ibatis.annotations.Results;
import org.apache.ibatis.annotations.Select;
import org.apache.ibatis.mapping.FetchType;public interface EmpDao {@Select("select * from emp where id=#{id}")@Results({@Result(id = true, property = "id", column = "id"),@Result(property = "name", column = "name"),@Result(property = "age", column = "age"),@Result(property = "addr", column = "addr"),@Result(property = "salary", column = "salary"),@Result(property = "dept", column = "dept_id", javaType = Dept.class,one = @One(select = "com.dfbz.dao.DeptDao.findById",fetchType = FetchType.LAZY)),})Emp findById(Integer id);
}

3.2.2 测试类

@Test
public void test1() {Emp emp = empDao.findById(1);System.out.println(emp);
}

3.3 注解实现一对多映射

3.2.1 接口

• DeptDao：

@Select("select * from dept where id=#{id}")
@Results({@Result(id = true,property = "id",column = "id"),@Result(property = "name",column = "name"),@Result(property = "location",column = "location"),@Result(property = "empList",column = "id",javaType = List.class,many = @Many(select = "com.dfbz.dao.EmpDao.findByDeptId",fetchType = FetchType.LAZY))
})
Dept findDeptAllById(Integer id);

• EmpDao：

@Select("select * from emp where dept_id=#{deptId}")
List<Emp> findByDeptId(Integer deptId);

3.2.2 测试类

@Test
public void test2() {Dept dept = deptDao.findDeptAllById(1);System.out.println(dept);
}