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;

    @Before
    public void before() throws IOException {
        builder=new SqlSessionFactoryBuilder();
        factory=builder.build(Resources.getResourceAsStream("SqlMapConfig.xml"));
        session= factory.openSession();
        userDao=session.getMapper(UserDao.class);
    }
    @After
    public void after(){
        session.commit();
        session.close();
    }

    @Test
    public 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);

    }
    @Test
    public void delete(){
        userDao.delete(1);
    }
    @Test
    public 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);

    }
    @Test
    public void findById(){
        User user = userDao.findById(2);
        System.out.println(user);
    }

    @Test
    public 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);
}