Error in JPA mapping - Fetch Comments
eclipselink, java, jpa
Solution
A `Ticket` object obviously cannot be equal to 751. Its ID can. So `WHERE c.ticket.id = 751`
(For the future: I doubt you will be hardcoding the ID, so use a named parameter)
Problem
I'm trying to fetch comments using the ticket field as a foreign key but I'm getting the following errors: ``` Caused by: Exception [EclipseLink-6078] (Eclipse Persistence Services - 2.0.1.v20100213-r6600): org.eclipse.persistence.exceptions.QueryException Exception Description: The class of the argument for the object comparison is incorrect. Expression: [ Base com.test.forum.model.Comment] Mapping: [org.eclipse.persistence.mappings.OneToOneMapping[ticket]] Argument: [751] ``` This is the code i'm using in my javabean: - Hide quoted text - ``` @JoinColumn(name = "ticket", referencedColumnName = "id") @ManyToOne(optional = false) private Ticket ticket; public List<Comment> findComment(int id) { Query q = em.createQuery("SELECT c FROM Comment c WHERE c.ticket = 751"); return q.getResultList(); } ``` Thanks