Problems with EJB relationship mapping (annotations)

Question

So, I'm part of a group working on a web-based project management system, and we're having some trouble with the relationship mapping between the entity beans.
I've been mainly working on a class called WorkPackage. So the mappings I've got:
Within the WorkPackage class
(A work package is one "module" of work within a project)
        @Entity
        @Table(name="WorkPackage")
        @IdClass(WorkPackagePK.class)
        public class WorkPackage implements java.io.Serializable
        @Id
        @Column(name="wpID")
        public String getWpID() { return wpID; }
     public void setWpID(String id) { this.wpID = id; }
     @Id
        @Column(name="projID")
        public String getProjId() { return projId; }
     public void setProjId(String projId) { this.projId = projId; }
        @ManyToOne // bidirectional - owner side
     @JoinColumn(name="projID")
     public Project getProject() { return project; }
     public void setProject(Project project) { this.project = project; }      And on the Project side
        @Entity
        @Table(name="Project")
        public class Project implements java.io.Serializable
        @Id
        @Column(name="projID")
        public String getId() { return id; }
     public void setId(String id) { this.id = id; }
       @OneToMany(mappedBy="project") // biderctional - target side
     public Set<WorkPackage> getWorkPackages() { return workPackages; }
     public void setWorkPackages(Set<WorkPackage> workPackages) { this.workPackages = workPackages; } The problem here is that its apparently seeing 'projID' as attempting to be mapped to 2 columns within the 'workpackage' table in the database instead of using the @Id one as the id, and the other as the foreign key to the 'project' table.
So, when I try to add a workpackage to the database via a JSF page, it gives me the error 'java.sql.BatchUpdateException: Column 'projID' specified twice'.
Maybe its something to do with variable in the project class being called 'id' even though its mapped to the database column 'projID'
Edited by: wormdundee on Mar 1, 2008 2:26 PM

Answer 1

I think the trouble is that you overrode the column names for the projID and project properties to the same value. Try
@Entity
        @Table(name="WorkPackage")
        @IdClass(WorkPackagePK.class)
        public class WorkPackage implements java.io.Serializable
        @Id
        @Column(name="WP_WP_ID")
        public String getWpID() { return wpID; }
     public void setWpID(String id) { this.wpID = id; }
     @Id
        @Column(name="WP_PROJ_ID")
        public String getProjId() { return projId; }
     public void setProjId(String projId) { this.projId = projId; }
        @ManyToOne // bidirectional - owner side
     @JoinColumn(name="WP_PROJECT_PROJ_ID")
     public Project getProject() { return project; }
     public void setProject(Project project) { this.project = project; }