About ManyToMany

javax.persistence.ManyToMany

Defines a many-valued association with many-to-many multiplicity.(Annotation of JPA)

Explains how to define and use primary keys in JPA, including composite and embedded primary keys.... See JavaDoc Reference Page... , ManyToMany javax.persistence.ManyToMany JPA annotation Defines a many-valued association with ...

JPA Annotations for Relationships

Reference (JavaDoc) of JPA 2 relationship annotations, including @ManyToMany, @ManyToOne, @OneToMany, @OneToOne, @OrderBy and @MapKey.... the following annotations: javax.persistence.ManyToMany javax.persistence.ManyToOne ...

Removing objects where ManyToMany relationships exist

Consider you have an entity Entity with the following unidirectional relationship: @ManyToMany private Set<OtherEntity> setOfOtherEntities; public Set<OtherEntity> getOtherEntities() { if (setOfOtherEntities == null) { setOfOtherEntities = new TreeSet<OtherEntity>(); } return setOfOtherEntities; } ... with the following unidirectional relationship: @ManyToMany private Set<OtherEntity> setOfOtherEntities; ...

javax.persistence.OrderBy

Specifies the ordering of the elements of a collection valued association or element collection at the point when the association or collection is retrieved.(Annotation of JPA)

Mysterious "Attempt to persist a reference to a non managed instance" error

I've been working with ObjectDB for the past several months, and it's behaved pretty much as expected. I made a few modifications to a working set of classes today, and it's started throwing exceptions at commit time. I've stripped it down to a set of files that seem to be of trivial complexity, but it's still failing. It involves two entities, Index and Ostrich. The thing to note is that the Index structure is recursive through maps; but that's never caused any problem for me in the past. ... . Id ; import javax. persistence . ManyToMany ; import javax. persistence . OneToOne ; ... ) public Ostrich ostrich ; @ ManyToMany ( cascade = ALL ) public ...

javax.persistence.AssociationOverride

Used to override a mapping for an entity relationship.(Annotation of JPA)

javax.persistence.MapKeyEnumerated

Specifies the enum type for a map key whose basic type is an enumerated type.(Annotation of JPA)

javax.persistence.MapKeyJoinColumn

Specifies a mapping to an entity that is a map key.(Annotation of JPA)

Speeding up reporting queries with size() on list

Hi, I'm working on some reporting stuff in our application. One of few different reports should include activity on last modified objects. The query for now looks like this: select date(insp.lastModificationDate), insp.modifiedBy, insp.description.length(), insp.products.size(), insp.picture from Inspiration insp order by date(insp.lastModificationDate) desc insp.description is normal String field in Inspiration entity. insp.products is a list with 0 to 600 objects. Definition: ... a list with 0 to 600 objects. Definition: @ ManyToMany ( targetEntity = Product. class , fetch = ...