Question

I m 试图用票场作为外国钥匙提出评论,但Im 却发现以下错误:

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();
    }

增编

Answer 1

www.un.org/Depts/DGACM/index_spanish.htm 物体显然不能等于751。其身份证可以。 So WHERE c.ticket.id = 751

(今后:我怀疑你会硬化身份证,因此使用一个标明的参数)

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