此篇接上篇：SpringBoot-15-之整合MyBatis-注解篇+分页

0.项目结构

java
    dao
    |---SwordDao
    entity
    |---Sword
resources
    mapper
    |---Sword.xml
    application.yml

---

1.application.yml

#坑点0 配置mybatis的xml位置
mybatis:
  mapper-locations: classpath:mapper/*.xml

2.新建dao文件夹，新建dao接口：SwordDao.java

public interface SwordDao {

    List<Sword> findALL();

    Sword findByName(@Param("name") String name);
    //坑点1 java没有保存形参的记录，所以多参数用户@Param("name")起名字，不然无法识别
    int insert(@Param("name") String name,
                @Param("atk") Integer atk,
                @Param("hit") Integer hit,
                @Param("crit") Integer crit,
                @Param("attr_id") Integer attr_id,
                @Param("type_id") Integer type_id
    );
}

3.在resources下新建mapper文件夹，再建Sword.xml文件，为dao层提供SQL语句

<?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">
<!--坑点2：命名空间指向对应dao类名-->
<mapper namespace="com.toly1994.toly_mybatis.dao.SwordDao">
    <!--坑点3：id为dao中相应方法名-->
    <insert id="insert">
      insert into sword(name,atk,hit,crit,attr_id,type_id)
      values (#{name},#{atk},#{hit},#{crit},#{attr_id},#{type_id})
    </insert>
    <!--坑点4：返回实体或实体集合时 resultType 指向对应实体类名-->
    <select id="findByName" resultType="com.toly1994.toly_mybatis.entity.Sword">
        SELECT*FROM sword WHERE NAME=#{name}
    </select>

    <select id="findALL" resultType="com.toly1994.toly_mybatis.entity.Sword">
        SELECT*FROM sword
    </select>
</mapper>

4.将dao添加扫包范围：com.toly1994.toly_mybatis.TolyMybatisApplication

//坑点5:将dao添加扫包范围
@MapperScan(basePackages = {"com.toly1994.toly_mybatis.mapper","com.toly1994.toly_mybatis.dao"})

---

5.单元测试：test文件夹下

com.toly1994.toly_mybatis.dao.SwordDaoTest

@RunWith(SpringRunner.class)
@SpringBootTest
public class SwordDaoTest {
    @Autowired
    private SwordDao mSwordDao;

    @Test
    public void findALL() {
        List<Sword> all = mSwordDao.findALL();
        System.out.println(all.get(5));
//Sword(id=6, name=风跃, atk=9020, hit=10, crit=10, attr_id=2, type_id=2)
    }

    @Test
    public void findByName() {
        Sword 赤凰 = mSwordDao.findByName("赤凰");
        System.out.println(赤凰);
//Sword(id=13, name=赤凰, atk=0, hit=100, crit=5, attr_id=1, type_id=2)
    }

    @Test
    public void insert() {
        int insert = mSwordDao.insert("尤恨", 4000, 100, 100, 1, 1);
        System.out.println(insert);//1
    }
}

---

6.联合查询：可能会疑惑attr_id和type_id是干嘛的，其实是两张关联表

修改实体类两个字段：

@Data//=@Getter +@Setter
public class Sword {
    private Integer id;
    private String name;
    private Integer atk;
    private Integer hit;
    private Integer crit;
    private String type_name;//改为String
    private String attr;//改为String
}

修改查询所有的SQL语句

    <select id="findALL" resultType="com.toly1994.toly_mybatis.entity.Sword">
       SELECT id,name,atk,hit,crit,type_name,attr FROM sword AS s
      INNER JOIN sword_type AS t ON s.type_id = t.type_id
      INNER JOIN sword_attr AS a ON s.attr_id = a.attr_id;
    </select>

测试：可见两张表和主表连在一起了

    @Test
    public void findALL() {
        List<Sword> all = mSwordDao.findALL();
        System.out.println(all.get(5));
        //Sword(id=6, name=风跃, atk=9020, hit=10, crit=10, type_name=仙界, attr=木)
    }