springboot 之mybatis 多表关联查询
数据库表
一对多查询
自定义实体类：
package com.example.entity;
import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;
import java.io.Serializable;
import java.util.List;
/**
* (Dept)实体类
*
* @author makejava
* @since 2020-09-02 08:40:43
*/
@Data
@AllArgsConstructor
@NoArgsConstructor
public class Dept implements Serializable {
private static final long serialVersionUID = 735011413198873745L;
private Integer deptno;
private String dname;
private String loc;
private List<Emp> emps;
}
dao层：
package com.example.dao;
import com.example.entity.Dept;
import org.apache.ibatis.annotations.Param;
import java.util.List;
/**
* (Dept)表数据库访问层
*
* @author makejava
* @since 2020-09-02 08:40:46
*/
public interface DeptDao {
/**
* 通过ID查询单条数据
*
* @param deptno 主键
* @return 实例对象
*/
Dept queryById(Integer deptno);
/**
* 查询指定行数据
*
* @param offset 查询起始位置
* @param limit 查询条数
* @return 对象列表
*/
List<Dept> queryAllByLimit(@Param("offset") int offset, @Param("limit") int limit);
/**
* 无条件查询
*
* @return 对象列表
*/
List<Dept> getAll();
/**
* 通过实体作为筛选条件查询
*
* @param dept 实例对象
* @return 对象列表
*/
List<Dept> queryAll(Dept dept);
/**
* 新增数据
*
* @param dept 实例对象
* @return 影响行数
*/
int insert(Dept dept);
/**
* 修改数据
*
* @param dept 实例对象
* @return 影响行数
*/
int update(Dept dept);
/**
* 通过主键删除数据
*
* @param deptno 主键
* @return 影响行数
*/
int deleteById(Integer deptno);
}
直接三层调用即可 ：dao层—> Service 层---->Controller 层：
mapper文件
<mapper namespace="com.example.dao.DeptDao">
<resultMap type="com.example.entity.Dept" id="DeptMap">
<result property="deptno" column="deptno" jdbcType="INTEGER"/>
<result property="dname" column="dname" jdbcType="VARCHAR"/>
<result property="loc" column="loc" jdbcType="VARCHAR"/>
<collection property="emps" javaType="list" ofType="com.example.entity.Emp">
<id property="empno" column="id">id>
<result property="ename" column="ename">result>
<result property="hiredate" column="hiredate">result>
<result property="job" column="job">result>
collection>
resultMap>
<select id="queryById" resultMap="DeptMap">
select
d.deptno, d.dname, d.loc,e.empno id, e.ename,e.hiredate,e.job
from db_rabc.dept d, db_rabc.emp e
where d.deptno=e.deptno and d.deptno = #{deptno}
select>
<select id="queryAllByLimit" resultMap="DeptMap">
select
deptno, dname, loc
from db_rabc.dept
limit #{offset}, #{limit}
select>
<select id="queryAll" resultMap="DeptMap">
select
deptno, dname, loc
from db_rabc.dept
<where>
<if test="deptno != null">
and deptno = #{deptno}
if>
<if test="dname != null and dname != ''">
and dname = #{dname}
if>
<if test="loc != null and loc != ''">
and loc = #{loc}
if>
where>
select>
<insert id="insert" keyProperty="deptno" useGeneratedKeys="true">
insert into db_rabc.dept(dname, loc)
values (#{dname}, #{loc})
insert>
<update id="update">
update db_rabc.dept
<set>
<if test="dname != null and dname != ''">
dname = #{dname},
if>
<if test="loc != null and loc != ''">
loc = #{loc},
if>
set>
where deptno = #{deptno}
update>
<delete id="deleteById">
delete from db_rabc.dept where deptno = #{deptno}
delete>
<select id="getAll" resultMap="DeptMap">
select
d.deptno, d.dname, d.loc,e.empno id, e.ename,e.hiredate,e.job
from db_rabc.dept d, db_rabc.emp e
where d.deptno=e.deptno
select>
mapper>
效果图：
无条件查询：
多对一查询
自定义实体类：
package com.example.entity;
import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;
import java.io.Serializable;
import java.util.Date;
/**
* (Emp)实体类
*
* @author makejava
* @since 2020-09-02 08:40:50
*/
@Data
@AllArgsConstructor
@NoArgsConstructor
public class Emp implements Serializable {
private static final long serialVersionUID = -10111395061902311L;
private Integer empno;
private String ename;
private String job;
private Integer mgr;
private Date hiredate;
private Integer sal;
private Integer comm;
private Integer deptno;
private Dept dept;
}
mapper文件：
<mapper namespace="com.example.dao.EmpDao">
<resultMap type="com.example.entity.Emp" id="EmpMap">
<result property="empno" column="empno" jdbcType="INTEGER"/>
<result property="ename" column="ename" jdbcType="VARCHAR"/>
<result property="job" column="job" jdbcType="VARCHAR"/>
<result property="mgr" column="mgr" jdbcType="INTEGER"/>
<result property="hiredate" column="hiredate" jdbcType="TIMESTAMP"/>
<result property="sal" column="sal" jdbcType="INTEGER"/>
<result property="comm" column="comm" jdbcType="INTEGER"/>
<result property="deptno" column="deptno" jdbcType="INTEGER"/>
<association property="dept" column="dname" javaType="com.example.entity.Dept">
<result property="dname" column="dname">result>
association>
resultMap>
<select id="queryById" resultMap="EmpMap">
select
e.empno, e.ename, e.job, e.mgr, e.hiredate, e.sal, e.comm, d.dname
from db_rabc.emp e,db_rabc.dept d
where empno = #{empno}
select>
<select id="queryAllByLimit" resultMap="EmpMap">
select
empno, ename, job, mgr, hiredate, sal, comm, deptno
from db_rabc.emp
limit #{offset}, #{limit}
select>
<select id="queryAll" resultMap="EmpMap">
select
empno, ename, job, mgr, hiredate, sal, comm, deptno
from db_rabc.emp
<where>
<if test="empno != null">
and empno = #{empno}
if>
<if test="ename != null and ename != ''">
and ename = #{ename}
if>
<if test="job != null and job != ''">
and job = #{job}
if>
<if test="mgr != null">
and mgr = #{mgr}
if>
<if test="hiredate != null">
and hiredate = #{hiredate}
if>
<if test="sal != null">
and sal = #{sal}
if>
<if test="comm != null">
and comm = #{comm}
if>
<if test="deptno != null">
and deptno = #{deptno}
if>
where>
select>
<insert id="insert" keyProperty="empno" useGeneratedKeys="true">
insert into db_rabc.emp(ename, job, mgr, hiredate, sal, comm, deptno)
values (#{ename}, #{job}, #{mgr}, #{hiredate}, #{sal}, #{comm}, #{deptno})
insert>
<update id="update">
update db_rabc.emp
<set>
<if test="ename != null and ename != ''">
ename = #{ename},
if>
<if test="job != null and job != ''">
job = #{job},
if>
<if test="mgr != null">
mgr = #{mgr},
if>
<if test="hiredate != null">
hiredate = #{hiredate},
if>
<if test="sal != null">
sal = #{sal},
if>
<if test="comm != null">
comm = #{comm},
if>
<if test="deptno != null">
deptno = #{deptno},
if>
set>
where empno = #{empno}
update>
<delete id="deleteById">
delete from db_rabc.emp where empno = #{empno}
delete>
<select id="getAll" resultMap="EmpMap">
select
e.empno, e.ename, e.job, e.mgr, e.hiredate, e.sal, e.comm, d.dname
from db_rabc.emp e,db_rabc.dept d
select>
mapper>
Dao 层
package com.example.dao;
import com.example.entity.Emp;
import org.apache.ibatis.annotations.Param;
import org.springframework.stereotype.Component;
import java.util.List;
/**
* (Emp)表数据库访问层
*
* @author makejava
* @since 2020-09-02 08:40:50
*/
@Component
public interface EmpDao {
/**
* 通过ID查询单条数据
*
* @param empno 主键
* @return 实例对象
*/
Emp queryById(Integer empno);
/**
* 查询指定行数据
*
* @param offset 查询起始位置
* @param limit 查询条数
* @return 对象列表
*/
List<Emp> queryAllByLimit(@Param("offset") int offset, @Param("limit") int limit);
/**
* 无条件查询
*
* @return 对象列表
*/
List<Emp> getAll();
/**
* 通过实体作为筛选条件查询
*
* @param emp 实例对象
* @return 对象列表
*/
List<Emp> queryAll(Emp emp);
/**
* 新增数据
*
* @param emp 实例对象
* @return 影响行数
*/
int insert(Emp emp);
/**
* 修改数据
*
* @param emp 实例对象
* @return 影响行数
*/
int update(Emp emp);
/**
* 通过主键删除数据
*
* @param empno 主键
* @return 影响行数
*/
int deleteById(Integer empno);
Emp getEmpAndDept();
}
直接三层调用即可 ：dao层—> Service 层---->Controller 层
测试效果图：
其他同理做法即可