Spring Data Projection and Error: "No aliases found in result tuple! Make sure your query defines aliases!"

Question

The below approach to get a Spring Data Projection from a JPA Query doesn't work for me:

https://stackoverflow.com/a/45443776/1005607

My table:

LOOKUP_T

id   description    display_order_num
------------------------------------
1    Category #1    1
2    Category #2    2

ACTIVITIES_T (activity_category_id maps to LOOKUP_T.id)

id  activity_category_id  activity_title
---------------------------------------
1      2                  Sleeping
2      2                  Eating
3      2                  Travel

Spring Data DAO Interface to get certain fields from this join:

@Repository
public interface ActivitiesDAO extends JpaRepository<ActivitiesT, Integer> {

    @Query("select a.activityTitle, l.description as category, " + 
           "l.displayOrderNum as categoryDisplayOrderNum " + 
           "from ActivitiesT a, LookupT l " + 
           "where a.lookupT.id = l.id order by l.displayOrderNum asc ")
    public List<MySpringDataProjection> findCustom();

}

Spring Data Projection Model Interface:

public interface MySpringDataProjection {

    public String getActivityTitle();

    public String getCategory();

    public Integer getCategoryDisplayOrderNum();

}

Everything is the same as in that accepted answer. But getting this error:

org.springframework.dao.InvalidDataAccessApiUsageException: No aliases found in result tuple! Make sure your query defines aliases!; nested exception is java.lang.IllegalStateException: No aliases found in result tuple! Make sure your query defines aliases!
    org.springframework.orm.jpa.EntityManagerFactoryUtils.convertJpaAccessExceptionIfPossible(EntityManagerFactoryUtils.java:381)
    org.springframework.orm.jpa.AbstractEntityManagerFactoryBean.translateExceptionIfPossible(AbstractEntityManagerFactoryBean.java:489)
    org.springframework.dao.support.ChainedPersistenceExceptionTranslator.translateExceptionIfPossible(ChainedPersistenceExceptionTranslator.java:59)
    org.springframework.dao.support.DataAccessUtils.translateIfNecessary(DataAccessUtils.java:213)

I don't want to use select new Obj(..) in the Query, it's dirty and relies on Hibernate which we're abstracting out to JPA.

I want to get this Projection approach to work.

Related question which had the (non-working) answer I referenced, Spring data JPA: getting No aliases found in result tuple! error when executing custom query

Answer 1

I encounter the same problem. After try several changes, I found we just need to add "as" for each column(even the column name is not changed) in NativeQuery. For you here, change your sql like :

    @Query("select a.activityTitle **as activityTitle**, l.description as category, " + 
       "l.displayOrderNum as categoryDisplayOrderNum " + 
       "from ActivitiesT a, LookupT l " + 
       "where a.lookupT.id = l.id order by l.displayOrderNum asc ")

Answer 2

I had the same problem and i think i solve it. What i did is to use alias in all field, even if they have the same name. Use alias in activityTitle too. Like this:

@Repository
public interface ActivitiesDAO extends JpaRepository<ActivitiesT, Integer> {

    @Query("select a.activityTitle as activityTitle, l.description as category, " + 
           "l.displayOrderNum as categoryDisplayOrderNum " + 
           "from ActivitiesT a, LookupT l " + 
           "where a.lookupT.id = l.id order by l.displayOrderNum asc ")
    public List<MySpringDataProjection> findCustom();

}