Hibernate 带有 POJO 构造函数的 JoinColumn（没有实体）

Question

I have a POJO that looks something like this

@AllArgsConstructor
public class POJO {
  @Getter
  @Setter
  private String name;

  @Getter
  @Setter
  private int age;
}

I use this POJO to set values from a hql query as in

session.createQuery("Select new fullyQualifiedName.POJO(emp.name, emp.age) From Employee emp where emp.id = 1");

Recently, I've been asked to make a request to add a List property to the POJO. As in,

@AllArgsConstructor
public class POJO {
  @Getter
  @Setter
  private String name;

  @Getter
  @Setter
  private int age;

  @Getter
  @Setter
  private List<Hobby> hobbies;
}

However, at this point, I do not know how to join Hobby table, get values as a list and pass to the constructor.

What are the possible ways to accomplish this?

Answer 1

I don't think you can achieve what you want with the new keyword anymore. Maybe others might be more helpful on this construct but I have not seen any example providing a collection with the new keyword, yet. I think this construct has some limitations.

As for the solution I propose:

1. Change your query to Select emp, h From Employee emp left join Hobby h where emp.id = 1 . You can also use inner join depending on your use case.

2. Set a custom ResultTransformer to your query object. Something like:

    query.setResultTransformer(
        new ResultTransformer() {
            @Override
            public Object transformTuple(Object[] tuple, String[] aliases) {            
                return tuple;
            }
            @Override
            public List transformList(List collection) {
               //Each member of collection is a Object[], we are working at row level 
               //You should process the collection, eliminate duplicates etc and return a 
               //List containing a single POJO object
            }
        }
    );