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+3 A:

Well, let's see

You have a @AssociationOverride annotation which its API says:

This annotation is used to override a many-to-one or one-to-one mapping of property or field for an entity relationship.

And

It may be applied to an entity that extends a mapped superclass to override a many-to-one or one-to-one mapping defined by the mapped superclass

I have not seen neither @ManyToOne nor @OnoToOne in your question. So, There is something wrong with your question.

But i have seen the following log in your StackTrace

A Foreign key refering Reporting from Reporting has the wrong number of column. should be 2

You have a Compound primary key defined by a @EmbeddedId annotation which has two properties (fileName and xmlContent)

Now, let's see your @CollectionOfElements

@CollectionOfElements(fetch=FetchType.EAGER)
@JoinTable(name="t_reports", 
    // Your mistake goes here
    joinColumns=@JoinColumn(name="log_report"))
@Fetch(FetchMode.SELECT)
private List<ReportingFile> reports;

Its Foreign key just contains one property whereas your Compound primary key contains two properties. Both must match. It explains why you see this nice message

A Foreign key refering Reporting from Reporting has the wrong number of column. should be 2

Your right mapping should looks like this

@CollectionOfElements(fetch=FetchType.EAGER)
@JoinTable(name="t_reports", 
    joinColumns={
        // The number of columns defined by our Compound primary key (2)
        // must match the number of columns defined by its Foreign key (2)
        @JoinColumn(name="file_name", referencedColumnName="file_name"),
        @JoinColumn(name="xml_content", referencedColumnName="xml_content")})
@Fetch(FetchMode.SELECT)
private List<ReportingFile> reports;

And more: i do not know whether your target database supports a Clob as primary key. So keep it in mind.

Added to original answer according to your reply

1º First scenario (without @CollectionOfElements)

@Entity
public class Reporting {

    // You said you just want a single fileName as primary key
    @Id
    @Column(name="file_name", nullable=false)
    private String fileName;

    // You said you still want to have the whole ReportingFile object
    @Embedded
    private ReportingFile reportingFile;

    @Embeddable
    public static class ReportingFile implements Serializable {

        // You must set up insertable=false, updatable=false
        @Column(name="file_name", insertable=false, updatable=false)
        private String fileName;

        @Column(name="xml_content")
        private Clob xmlContent;

   }

}

Keep in mind the following: Hibernate does not allow you define two properties where both share the same column. Because of that, i have to define insertable=false, updatable=false in fileName property.

And when i do the following

Reporting reporting = new Reporting();
reporting.setFileName("home.pdf");

ReportingFile reportingFile = new ReportingFile();
// It will not persisted because of insertable=false, updatable=false
reportingFile.setFileName("home.pdf");
reportingFile.setXmlContent(someClobObject);

session.save(reporting); // It works

2º First scenario (with @CollectionOfElements)

@Entity
public class Reporting {

    // You said you just want a single fileName as primary key
    @Id
    @Column(name="file_name", nullable=false)
    private String fileName;

    // You said you still want to have the whole ReportingFile object
    @Embedded
    private ReportingFile reportingFile;

    @CollectionOfElements(fetch=FetchType.EAGER)
    @JoinTable(
        name="t_reports",
        joinColumns=@JoinColumn(name="file_name", referencedColumnName="file_name", insertable=false, updatable=false))
    private List<ReportingFile> reports;

    @Embeddable
    public static class ReportingFile implements Serializable {

        // You must set up insertable=false, updatable=false
        @Column(name="file_name", insertable=false, updatable=false)
        private String fileName;

        @Column(name="xml_content")
        private Clob xmlContent;

   }

}

And when i do the following

Reporting reporting = new Reporting();
reporting.setFileName("home.pdf");

ReportingFile reportingFile = new ReportingFile();
// It will not persisted because of insertable=false, updatable=false
reportingFile.setFileName("home.pdf");
reportingFile.setXmlContent(someClobObject);

reporting.getReports().add(reportingFile);

session.save(reporting); // It does not work

Hibernate will complain

repeated column in mapping for collection: reports column: file_name

So, when you have a @CollectionOfElements which shares a foreign key, it will not work as expected. But you can do a workaround

@Entity
public class Reporting {

    // You said you just want a single fileName as primary key
    @Id
    @Column(name="file_name", nullable=false)
    private String fileName;

    // You said you still want to have the whole ReportingFile object
    @Embedded
    private ReportingFile reportingFile;

    // Your workaround goes here
    @CollectionOfElements(fetch=FetchType.EAGER)
    @JoinTable(
        name="t_reports",
        joinColumns=@JoinColumn(name="file_name", referencedColumnName="file_name"))
    private List<Clob> xmlContents;

    @Transient
    public List<ReportingFile> getReports() {
        List<ReportingFile> reports = new ArrayList<ReportingFile>();

        for(Clob xmlContent: getXmlContents())
            reports.add(new ReportingFile(getFileName(), xmlContent));

        return reports;
    }

    @Embeddable
    public static class ReportingFile implements Serializable {

        // required no-arg  constructor
        public ReportingFile() {}

        public ReportingFile(String fileName, Clob xmlContent) {
            this.fileName = fileName;
            this.xmlContent = xmlContent;
        }

        // You must set up insertable=false, updatable=false
        @Column(name="file_name", insertable=false, updatable=false)
        private String fileName;

        @Column(name="xml_content")
        private Clob xmlContent;

   }

}

Notice you can define a @Embeddable class as static when using inside your owning class.

Arthur Ronald F D Garcia 2010-03-16 04:01:28

Ok thank you !The fact is, i wanted to have only fileName as primary key, like you said, to avoid using a Clob as primary key.But i don't know how to specify to the EmbeddedId (and if it's possible) that it should take only the fileName attribute of the ReportingFile.That's what i tried to do with the @AssociationOverride. (with the mistake you highlighted) That's also why in my @CollectionOfElements, i wanted to have only one param.

RoD 2010-03-16 10:01:05

So, I changed that ( adding @OneToOne): @OneToOne @Column(name="file_name",length=255) private String fileName;in order to respect the API.I have the following error:Caused by: org.hibernate.AnnotationException: Illegal attempt to define a @JoinColumn with a mappedBy association: logRequest.fileNameIt seems that it's not the way to chose only one param for the PK.

RoD 2010-03-16 10:02:18

Sorry, maybe i was not really clear ;)I only want the fileName (logRequest.fileName) as PK of the Reporting, but i still want to have the whole ReportingFile object ( more the private List<ReportingFile> reports; ).In what you suggest me, i'll lose the "content" of my file.If i added @Column(name="xml_content") private Clob xmlContent;to the Reporting class you gave, it would be ok, but i would not use the "ReportingFile" object for this (which is exactly a fileName + content ).

RoD 2010-03-16 16:19:07

@Arthur Ronald F D Garcia - Thanks a lot ! It was more complicated than expected :D

RoD 2010-03-17 09:40:46

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