JPA: Mapping ManyToMany relationship refers to inc

Question

This question is related to previous question that I asked yesterday. I have many-to-many relationship between Employee and SkillSet table, with additional column numberOfYears for each relation

employeeId  skillSetId  numberOfYears 
10          101         2

Since I do not have ID column in EmployeeSkillSet table, I am using @IdClass to define the composite key

@Entity
class Employee {
    private @Id Long id;
    @OneToMany(mappedBy="employeeId")
    private List<EmployeeSkillSet> skillSets;
}
class SkillSet {
    private @Id Long id;
}

@IdClass(EmpSkillKey.class)
@Entity
class EmployeeSkillSet {
    @Id 
    @Column("employee_id")
    private Long employeeId;
    @Id
    @Column("skill_id")
    private @Id Long skillId;

    @ManyToOne  
    private Employee employee;
    private int numberOfYears;
}

class EmpSkillKey{
   private int employeeId;
   private int skillId;
}


interface EmployeeRepository extends JPARepository{
   List<Employee> getEmployeesBySkillSetSkillId(long id);
}

The above JPA repository method works fine and gives me list of Employees as per the skillSet ID. But when I try to iterate over the list and get the EmployeeSkillSet object then it throws error, as it tries to map to incorrect column employee instead of employeeId.

List<Employee> emps = employeeRepository.getEmployeesBySkillSetSkillId(101);
for(Employee e: emps){  // this line throws error
  EmployeeSkillSet  ess = e.getEmployeeSkillSet();
  int n = ess.getNumberOfYears();
}

Query generated is something like this. (I have converted it to Employee use case, cannot share actual query)

select ud.employee_id , ud.employee_id , ud.employee , ud.employee_value , rd.employee_id 
 from employee_skill_set ud left outer join employee rd 
 on ud.employee=rd.employee_id 
 where ud.employee_id=?

Exception

WARN  - SqlExceptionHelper         - SQL Error: 207, SQLState: ZZZZZ
ERROR - SqlExceptionHelper         - Invalid column name 'employee'.
org.hibernate.exception.GenericJDBCException: could not extract ResultSet
    at org.hibernate.exception.internal.StandardSQLExceptionConverter.convert(StandardSQLExceptionConverter.java:54)
    at org.hibernate.engine.jdbc.spi.SqlExceptionHelper.convert(SqlExceptionHelper.java:126)
    at org.hibernate.engine.jdbc.spi.SqlExceptionHelper.convert(SqlExceptionHelper.java:112)
    at org.hibernate.engine.jdbc.internal.ResultSetReturnImpl.extract(ResultSetReturnImpl.java:91)
    at org.hibernate.loader.plan.exec.internal.AbstractLoadPlanBasedLoader.getResultSet(AbstractLoadPlanBasedLoader.java:449)
    at org.hibernate.loader.plan.exec.internal.AbstractLoadPlanBasedLoader.executeQueryStatement(AbstractLoadPlanBasedLoader.java:202)
    at org.hibernate.loader.plan.exec.internal.AbstractLoadPlanBasedLoader.executeLoad(AbstractLoadPlanBasedLoader.java:137)
    at org.hibernate.loader.plan.exec.internal.AbstractLoadPlanBasedLoader.executeLoad(AbstractLoadPlanBasedLoader.java:102)
    at org.hibernate.loader.collection.plan.AbstractLoadPlanBasedCollectionInitializer.initialize(AbstractLoadPlanBasedCollectionInitializer.java:100)
    at org.hibernate.persister.collection.AbstractCollectionPersister.initialize(AbstractCollectionPersister.java:693)
    at org.hibernate.event.internal.DefaultInitializeCollectionEventListener.onInitializeCollection(DefaultInitializeCollectionEventListener.java:92)
    at org.hibernate.internal.SessionImpl.initializeCollection(SessionImpl.java:1933)
    at org.hibernate.collection.internal.AbstractPersistentCollection$4.doWork(AbstractPersistentCollection.java:559)
    at org.hibernate.collection.internal.AbstractPersistentCollection.withTemporarySessionIfNeeded(AbstractPersistentCollection.java:261)
    at org.hibernate.collection.internal.AbstractPersistentCollection.initialize(AbstractPersistentCollection.java:555)
    at org.hibernate.collection.internal.AbstractPersistentCollection.read(AbstractPersistentCollection.java:143)
    at org.hibernate.collection.internal.PersistentBag.iterator(PersistentBag.java:294)

May be I cannot define @Id employeeId and @ManyToOne employee in same class. But then how to resolve this?

Answer 1

Nevermind, I found out the solution. Annotated the @ManyToOne relation with @JoinColumn and with actual column name. Not sure why it asked for making updatable and insertable as false. Have to get my basics clear :)

@IdClass(EmpSkillKey.class)
@Entity
class EmployeeSkillSet {
    @Id 
    @Column("employee_id")
    private Long employeeId;
    @Id
    @Column("skill_id")
    private @Id Long skillId;

    @JoinColumn(name="employee_id", insertable=false, updatable=false)
    @ManyToOne  
    private Employee employee;
    private int numberOfYears;
}