使用JPA自定义VO接收返回结果集(unwrap)

目录

• JPA自定义VO接收返回结果集(unwrap)
• JPA返回自定义VO

JPA自定义VO接收返回结果集(unwrap)

JPA跟mybitis比较，简单的业务搜索是方便的，但是设计到复杂的SQL搜索时，我们需要自定义SQL。

1.@Query直接写SQL,缺点是无法动态的组装条件

2.JPA的Specification对象动态组装where搜索条件

3.entityManager执行CriteriaBuilder

4.entityManger直接使用createNativeQuery，执行原生SQL。这里设计到返回结果集的承载体必须是数据库对应的实体。

这里说一个自定义的VO承接返回结果集的方法

ProjectAttendanceEntity
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    @Column(name = "f_id")
    private Long fId;

    @Column(name = "user_id")
    private Integer userId;

    @Column(name = "zh_name")
    private String zhName;

    @Column(name = "po_code")
    private String poCode;

    @Column(name = "po_name")
    private String poName;

    @Column(name = "punch_date")
    private String punchDate;

    @Column(name = "is_original")
    private String isOriginal;

    @Column(name = "attendance_hours")
    private String attendanceHours;

    @Column(name = "work_hours")
    private String workHours;

    @Column(name = "punch_area")
    private String punchArea;

结果集承接VO (AttendancePoSzVO)

    private String poId;
    private String poName;
    private String zhName;

执行接口：

/**
     * 批量修改项目名称
     * @return
     */
    @PostMapping("/po/sz/batch/{project}/{pn}/{ps}")
    public PageResultVO findBatchPoInfoByUserIdAndDate(@RequestBody List<Long> ids,@PathVariable String project,@PathVariable Integer pn,@PathVariable Integer ps){
        log.info("url:/po/sz/batch/"+"|param:"+ids);
        //通过id查询数据
        List<ProjectAttendanceEntity> projects = projectAttendanceEntityRepository.findByIdIn(ids);
        //获取SQL
        String sql = getSQL(projects,pn,ps);
        Query query = entityManager.createNativeQuery(sql);
        List<AttendancePoSzVO> list = query.unwrap(NativeQuery.class).setResultTransformer(Transformers.aliasToBean(AttendancePoSzVO.class)).getResultList();
        //初始化结果集
        List<DropDownVO> result = new ArrayList<>();
        for(AttendancePoSzVO poSz : list){
            result.add(new DropDownVO(poSz.getPoName(),poSz.getPoId()));
        }
        return new PageResultVO(GlobalReturnCode.SUCCESS_CODE,"SUCCESS",ps,pn,result);
    } 

    /**
     * 组装查询SQL
     * @return
     */
    public String getSQL(List<ProjectAttendanceEntity> poStatus, Integer pn, Integer ps){
        StringBuilder sql = new StringBuilder("SELECT DISTINCT res.po_id as poId,res.po_name as poName, GROUP_CONCAT(DISTINCT res.user_id) AS zhName ");
            sql.append(" FROM (");
            sql.append(" SELECT tt.po_name,tt.po_id,tt.user_id");
            sql.append(" FROM sie_sz_po_attendance_v tt ");
            sql.append(" WHERE");
            for(ProjectAttendanceEntity po : poStatus){
                sql.append("(tt.user_id = ").append(po.getUserId()).append(" and tt.rt_begin_date <= '").append(po.getPunchDate())
                    .append("' and tt.rt_end_date >= '").append(po.getPunchDate()).append("') OR ");
            }
            //截掉最后一个OR
            sql = new StringBuilder(sql.substring(0,sql.length()-3));
            sql.append(" ) res");
            sql.append(" GROUP BY res.po_name,res.po_id");
            sql.append(" HAVING ");
            for(ProjectAttendanceEntity po : poStatus){
                sql.append(" INSTR(zhName,").append(po.getUserId()).append(") >0").append(" AND ");
            }
            //截取最后一个AND
            sql = new StringBuilder(sql.substring(0,sql.length()-4));
            sql.append(" LIMIT ").append(pn).append(",").append((pn+1)*ps);
        return sql.toString();
    }

核心代码：

List<AttendancePoSzVO> list = query.unwrap(NativeQuery.class).setResultTransformer(Transformers.aliasToBean(AttendancePoSzVO.class)).getResultList();

但是这里的 setResultTransformer 已经过时了。

所以接下来寻找 setResultTransformer的替代API。

JPA返回自定义VO

最近做项目用到了JPA，很多地方需要返回自定义vo，最开始用@Query注解返回自定义List<Objec[]>，在用forEach遍历存入List实在是不方便，找了一些资料做下笔记。

一般需要返回自定VO都是做连表动态查询，下面直接贴测试代码

User（Entity）

@Data
@Entity
@Table(name = "jpa_user")
@AllArgsConstructor
@NoArgsConstructor
@Accessors(chain = true)
public class User {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Integer id;
    @Column(name ="name")
    private String name;
    @Column(name ="age")
    private Integer age;
    @Column(name ="sex")
    private String sex;
    @Column(name ="card")
    private String card;
    @Column(name ="children")
    private Boolean children;
}

UserRespDto(自定义VO)

@Data
public class UserRespDto implements Serializable {
    private String myname;
    private String mycard;
}

JPA接口不说了，继承JpaRepository和JpaSpecificationExecutor就行

测试

    /**
     * 返回Entity对象，要求是数据库中字段全部查询 即findAll或者理解为select *
     */
    @Test
    public void t2() {
        StringBuilder sb = new StringBuilder();
        sb.append("select * from jpa_user where 1=1 ");
        //自行根据条件动态拼接，仅做演示
        sb.append("  and name like '%李%' ");
        Query nativeQueryPo = entityManager.createNativeQuery(sb.toString(), User.class);
        List resultList = nativeQueryPo.getResultList();
        System.out.println(resultList);
    }
    /**
     * 返回自定义VO对象，要求是查询别名必须和VO中属性名一致
     */
    @Test
    //注意，很重要，事务必须开启，不开启会报错提示无法转化，具体原因和动态代理有关系
    @Transactional(readOnly = true)
    public void t3() {
        StringBuilder sb = new StringBuilder();
        sb.append("select name myname,card mycard from jpa_user where 1=1 ");
        //自行根据条件动态拼接，仅做演示
        sb.append("  and name like '%李%' ");
        Query nativeQuery = entityManager.createNativeQuery(sb.toString());
        List list = nativeQuery.unwrap(NativeQueryImpl.class).setResultTransformer(Transformers.aliasToBean(UserRespDto.class)).list();
        System.out.println(list);
    }

以上为个人经验，希望能给大家一个参考，也希望大家多多支持我们。