SQL Error: 0, SQLState: 42703 with message "The column name str_id was not found in this ResultSet" - jpa

Question

this is my first question ever in StackOverflow and as suggested, I have looked at other similar questions and attempted to use their responses for my problem. So far, no luck.
The situation is as follows:
I have a custom query in JPA.
#Query(value="SELECT u.str_id,u.str_exercise_name, u.str_target_body_part,u.char_effect FROM training_schema.exercise_entity u WHERE u.str_exercise_name = ?1 and u.str_target_body_part= ?2", nativeQuery=true)
ExerciseEntity findExerciseEntityByNameAndTargetBodyPart(String str_exercise_name,String str_target_body_part);
If I remove the name of the columns (u.str_id, u.str_exercise_name, u.str_target_body_part, u.char_effect) and replace the query with:
#Query(value="SELECT u FROM training_schema.exercise_entity u WHERE u.str_exercise_name = ?1 and u.str_target_body_part= ?2", nativeQuery=true)
ExerciseEntity findExerciseEntityByNameAndTargetBodyPart(String str_exercise_name,String str_target_body_part);
I get the following error:
"The column name str_id was not found in this ResultSet"
The fact that the error doesn't come when I mention all the columns and is generated when I use alias 'u' doesn't make sense because this would mean that if I ever had to work with a larger table with, say, 10 columns, I would have to write them all out.
One more piece of information that hopefully helps: With the version of the query where I am using 'u' instead of the column names, the error is ONLY generated when a matching record is found. For a null return from the database, there is no problem.
Using Java Spring and PostgresSQL.

Answer 1

I was able to figure out the problem.
In the query where I am using the alias 'u' ALONE, I had to make a slight change. Instead of just saying 'u', I changed it to:
#Query(value="SELECT u.* FROM training_schema.exercise_entity u WHERE u.str_exercise_name = ?1 and u.str_target_body_part= ?2", nativeQuery=true)
ExerciseEntity findExerciseEntityByNameAndTargetBodyPart(String str_exercise_name,String str_target_body_part);
Using only 'u', was returning a record set WITHOUT any headers. Adding the '*' caused the query to return a resultset with column names which made the error go away.