Spring JPA :: No converter found capable of converting from type

Question

I am using spring with JPA and trying to execute query using @query with SQL query.and trying to map the result to an object. I have different entity class and mapping to other

Answer 1

You can solve this issue and achieve the result by using projections by making your DTO an interface with getters for columns returned by the query. That's what I did when I faced the same issue.

For example in your case change StatsDTO to interface like shown below, make sure to give alias for your columns if you are using '.' operator:

public interface StatsDTO {
    Integer getUserCount();
    Byte getTypeId();
    Instant getModifiedAt();
}

Also in your query give alias for your columns like userCount, typeId, modifiedAt respectively so that it is mapped correctly.

Answer 2

replying to @Thanthu

the code should be like this

public interface StatsDTO {
    Integer getUserCount();
    Byte getTypeId();
    Instant getModifiedAt();
}

not this

public interface StatsDTO {
    Integer getUserCount;
    Byte getTypeId;
    Instant getModifiedAt;
}

Answer 3

Also you could try changing the UserRepository Interface declaration to below,

public interface UserRepository extends CrudRepository<StatsDTO, Long> {
    @Query(value = "select count(type_id) userCount, type_id, modified_at from "
                + "user_campaign_objective where camp_id = ?1 group by objective_type_id,modified_at", nativeQuery = true)

        List<StatsDTO> getStatsDTO(Long camp_id);
}

The change is : CrudRepository <StatsDTO, Long> from CrudRepository < UserEntity, Long>.

I faced the same issue while using a different data object inside a repository declared with another data object.

Answer 4

You can use the constructor expression JPQL query, your query looks like this:

select new StatsDTO(count(u),u.typeId,u.modifiedAt) from UserCampaignObjective u where campId = ? group by objectiveTypeId,modifiedAt

But you make sure the constructor StatsDTO existed already.

Answer 5

If you are still looking for an answer, here is how I did

@Data
@NoArgsConstructor
@AllArgsConstructor
public class StatsDTO {
    private Integer userCount;
    private Byte typeId;
    private Instant modifiedAt;
}

and your query should be like this

public interface UserRepository extends CrudRepository<UserEntity, Long> {
    @Query(value = "select new com.example.package.StatsDTO(count(type_id) userCount, typeId, modifiedAt from "
                + "UserCampaignObjective where campId = ?1 group by objectiveTypeId,modifiedAt")

        List<StatsDTO> getStatsDTO(Long camp_id);
}

make sure you have a constructor present in StatsDTO to map all fields.

Answer 6

You have a mismatch between the column names:

• userCount
• type_id
• modified_at

And your property names:

• userCount
• typeId
• modifiedAt

Since this is a native query the JPA naming strategy doesn't apply and the column names should match the property names. So if you change the query to the following, it should work:

select count(type_id) userCount, type_id as typeId, modified_at as modifiedAt from ...