实体无法保存外键实体

Question

My Content has a Map of Footnote , and Footnote has a content_id column which is a foreign key back to Content . Unfortunately saving my Content with the footnoteMap containing a Footnote throws the following error:

ERROR: Cannot insert the value NULL into column 'content_id', table 'CMT_DEV.dbo.footnote'; column does not allow nulls. INSERT fails.
SEVERE: org.springframework.dao.DataIntegrityViolationException: Cannot insert the value NULL into column 'content_id', table 'CMT_DEV.dbo.footnote'; column does not allow nulls. INSERT fails.; SQL [n/a]; constraint [null]; nested exception is org.hibernate.exception.ConstraintViolationException: Cannot insert the value NULL into column 'content_id', table 'CMT_DEV.dbo.footnote'; column does not allow nulls. INSERT fails.

I must be missing something with the annotations required to make this work, but I can't figure out what it is.

Here is my JPA mapping:

public class Content implements EntityModel, Serializable {
    @OneToMany(mappedBy="contentId", cascade=CascadeType.ALL)
    @MapKey(name="number")
    @OrderBy("number ASC")
    private Map<Integer, Footnote> footnoteMap;

    ....
}

public class Footnote implements EntityModel, Serializable {
    @ManyToOne(cascade=CascadeType.ALL)
    @JoinColumn(name = "content_id", referencedColumnName= "id")
    private Content contentId;

    ....
}

* update *

Keep in mind that the point at which a Footnote is added, the content item has not been saved.

Answer 1

First of all, note that it's your responsibility to keep both sides of bidirectional relationships in consitent state, ie when you add a Footnote to Content you should also set its contentId appropriately.

If you did so but it still fails, then perhaps it's a mismatch between database schema and Hibernate mapping. Note that content_id column has a not null constraint, but nothing in the mapping tells Hibernate that such a constraint exists. Try @ManyToOne(cascade=CascadeType.ALL, optional = false) .

Answer 2

You need to have something like this...

public void addFootnote(Footnote footnote) {
    if (footnote == null) {
        throw new IllegalArgumentException("Null argument not allowed");
    }
    footnote.setContent(this);
    footNoteMap.put(<KEY_OF_MAP>, footnote);
}

which will make sure that content is populated for Footnote instance.