springboot+jpa多表查询

背景

关联起来查询三个表的数据

步骤

1. 定义接收结果的中间类
2. 在 @Query 中编写 HSQL
3. 从数据库查询

代码

定义接收结果的中间类

IterationVo.java

/**
 * IterationVo
 * @description 封装查询到的迭代详细信息
 * @author daleyzou
 * @date 2019年11月20日 20:09
 * @version 3.0.0
 */
public class IterationVo implements Serializable {
    private String businessUnitName;

    private String businessLineName;

    private int id;

    private int businessUnitId;

    private int businessLineId;

    private String iterationName;

    private String item;

    private String itemCode;

    private String version;

    private String note;

    private String baseBranchInfo;

    private Date createTime;

    public IterationVo(IterationPo iterationPo, String businessUnitName, String businessLineName) {
        this.id = iterationPo.getId();
        this.businessLineId = iterationPo.getBusinessLineId();
        this.businessUnitId = iterationPo.getBusinessUnitId();
        this.version = iterationPo.getVersion();
        this.item = iterationPo.getItem();
        this.itemCode = iterationPo.getItemCode();
        this.baseBranchInfo = iterationPo.getBaseBranchInfo();
        this.note = iterationPo.getNote();
        this.iterationName = iterationPo.getIterationName();
        this.createTime = iterationPo.getCreateTime();

        this.businessUnitName = businessUnitName;
        this.businessLineName = businessLineName;
    }

    set方法  ...
    get方法 ...
}

IterationPo.java

@Entity
@Table(name = "iteration")
@EntityListeners(AuditingEntityListener.class)
@DynamicInsert
@DynamicUpdate
public class IterationPo {
    private int id;

    private int businessUnitId;

    private int businessLineId;

    private String iterationName;

    private String item;

    private String itemCode;

    private String createUserName;

    private String updateUserName;

    private String version;

    private String note;

    private Date createTime;

    private Date updateTime;

    private String baseBranchInfo;

    private int publishing;

    private boolean published;

    private boolean canFullRelease;
}

在 @Query 中编写 HSQL

IterationDao.java

/**
 * IterationDao
 * @description 迭代数据库操作
 * @author daleyzou
 * @date 2019年11月08日 10:53
 * @version 3.0.0
 */
@Repository
public interface IterationDao extends JpaRepository<IterationPo, Integer> {
    // 分页查询
    @Query(value = "SELECT new com.daleyzou.middleware.mwgrayscaledubbo.base.vo.IterationVo(iteration, unit.name, line.name) FROM IterationPo iteration, BusinessUnitPo unit, BusinessLinePo line WHERE iteration.businessUnitId=unit.id and iteration.businessLineId=line.id ")
    Page<IterationVo> findIterationInfo(Pageable pageable);

    // 根据主键查询
    @Query(value = "SELECT new com.daleyzou.middleware.mwgrayscaledubbo.base.vo.IterationVo(iteration, unit.name, line.name) FROM IterationPo iteration, BusinessUnitPo unit, BusinessLinePo line WHERE iteration.businessUnitId=unit.id and iteration.businessLineId=line.id and iteration.id=:id")
    IterationVo findIterationInfoById(@Param("id") Integer id);
}

从数据库查询

使用 @Autowried 依赖注入后调用即可

分页在 service 层这样调用

public Page<IterationVo> getIterationList(Integer page, Integer size) {
        Pageable pageable = new PageRequest(page, size, Sort.Direction.DESC, "createTime");
        return iterationDao.findIterationInfo(pageable);
    }