Exception "argument type mismatch" with projection bean and oneToMany association

I have an association manyToMany between User and Role entities (User >—< Role)

I wanted to perform this query:

    createQuery()
            .from(qUser)
            .leftJoin(qUser.roles, qRole)
            .where(qUser.login.eq(login))
            .singleResult(
                    Projections.bean(User.class,
                            qUser.id,
                            qUser.login,
                            qUser.password,
                            GroupBy.set(Projections.bean(Role.class,
                                    qRole.id,
                                    qRole.code
                            )).as(qUser.roles)
                    )
            );

The generated query looks like this, for me it’s perfect:

    SELECT user0_.ID AS col_0_0_,
           user0_.LOGIN AS col_1_0_,
           user0_.PASSWORD AS col_2_0_,
           role2_.ID AS col_4_0_,
           role2_.CODE AS col_5_0_
    FROM public.USER user0_
    LEFT OUTER JOIN public.USER_ROLE roles1_ ON user0_.ID=roles1_.USER_ID
    LEFT OUTER JOIN public.ROLE role2_ ON roles1_.ROLE_ID=role2_.ID
    WHERE user0_.LOGIN=? LIMIT ?

But I have a java.lang.IllegalArgumentException: argument type mismatch.

I debugged and I found out that data from database id loaded without problem. This is when QueryDsl/Hibernate did some introspection to create and initialise my entities that the exception is throwed.

The problem is that the User.setRoles(Set<Role>) method has called with a long parameter: The ID of the first Role entity list of the User. Instead of create a Set of Role an then associate these roles to the User.

Is there a problem with the query? Or is it not supported by QueryDsl?

I am using the QueryDsl 3.6.6 (I tested with 3.7.4: same result)

[thibaudsowa]

@ilumer unfortunately we didn’t know how to solve this issue. So as an ugly workaround we do that with two requests: the first one without the sub-list and in the second one we request only the list. Finally we rebuild the object manually…

User user = createQuery()
        .from(qUser)
        .where(qUser.login.eq(login))
        .singleResult(
                Projections.bean(User.class,
                        qUser.id,
                        qUser.login,
                        qUser.password
                )
        );


List<Role> roles = createQuery()
        .from(qUser)
        .innerJoin(qUser.roles, qRole)
        .where(qUser.id.eq(user.getId()))
        .list(
                Projections.bean(Role.class,
                        qRole.id,
                        qRole.code
                )
        );

user.setRoles(roles);

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