SpringBoot JPA实践之EntityManage查询返回自定义DTO

JPA

admin 发布于：2020-05-01 22:13:33

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在很多时候我更喜欢随意组合查询出来返回一个DTO对象的实现，JPA提供的多数查询均以返回Entity居多，它提供的EntityManager对象可以实现将SQL语句查询的结果转换为自定义DTO对象（这与@Query注解查询返回接口结果集相似），本篇文章围绕不使用任何Entity与对象级联配置的情况，将原生SQL查询的结果集转换为自定义DTO对象。

参考代码

package cn.chendd.example.jpa.user.dao;

/**
* @author chendd
* @date 2020/5/5 22:26
*/
@Repository
@Transactional(readOnly = true)
public class UserQueryCustomResultDao {

    @PersistenceContext
    private EntityManager entityManager;

    public List<Map<String , Object>> nativeSqlQuery2Map() {
        String sql = "select 7 age , 3.1415 pi , name userName , createTime createTime " +
                " from user a where a.name = ?";
        NativeQueryImpl query = entityManager.createNativeQuery(sql).unwrap(NativeQueryImpl.class);
        query.setParameter(1, "chendd");
        query.setResultTransformer(Transformers.ALIAS_TO_ENTITY_MAP);
        List<Map<String, Object>> resultList = query.getResultList();
        return resultList;
    }

    public List<UserResultDto> nativeSqlQuery2Bean() {
        String sql = "select id, name userName , createTime , 3.1415 pi , 100.00 amount , 1 status" +
                " from user a where a.name = ?";
        NativeQueryImpl query = entityManager.createNativeQuery(sql).unwrap(NativeQueryImpl.class);
        query.setResultTransformer(Transformers.aliasToBean(UserResultDto.class));
        query.setParameter(1, "chendd");
        query.addScalar("id", StandardBasicTypes.STRING);
        query.addScalar("userName", StandardBasicTypes.STRING);
        query.addScalar("createTime", StandardBasicTypes.TIMESTAMP);
        query.addScalar("pi", StandardBasicTypes.DOUBLE);
        query.addScalar("amount", StandardBasicTypes.BIG_DECIMAL);
        /*query.addScalar("status", StandardBasicTypes.NUMERIC_BOOLEAN);*/
        query.addScalar("status" , StandardBasicTypes.BOOLEAN);
        List<UserResultDto> resultList = query.getResultList();
        return resultList;
    }

}