Customizing entity associations

The EntityModule attempts to automatically detect related entities and creates associations mainly to facilitate UI generation. Currently @OneToMany, @ManyToMany and @ManyToOne annotations from javax.persistence API are all scanned and used to build EntityAssociation entries.

In the administrative UI the management of related entities can often be done either through the property or the association. This is especially the case for @ManyToMany and @OneToMany associations that are mapped through a property with collection type. By default related entity management will be done through the property and the association will be generated but hidden.

If you want to enable management through the association interface, you should manipulate the hidden property of both the association and the property using an EntityConfigurer. 
@Override
public void configure( EntitiesConfigurationBuilder entities ) {
    // Groups should be managed through the association instead of the property
    entities.withType( MachinePrincipal.class )
                 .properties( props -> props.property( "groups" ).hidden( true ) )
                 .association( ab -> ab.name( "machinePrincipal.groups" ).show() );
}

Association type

Every EntityAssociation is of a specific type, configured through the associationType property. The association type determines how the associated values can be managed through the user interface.

The following association types are possible:

Association type Behaviour

LINKED

The related entities are only linked to. The tab of the parent entity shows the list of related entities, but any modify action will navigate away from the parent entity.

This is the appropriate type if your related entities can in turn have other related entities. Usually this also means the related entity type has a main menu item.

EMBEDDED

The related entities will be managed through the tab of their parent entity. Modifying a related entity will be displayed as modifying the parent entity, no action will leave the context of the parent entity.

Use this type if the related entities only exist if their parent exists. Usually the related entity type does not have any menu item, nor sub tabs (the latter would not be displayed).

By default an association is of type LINKED.

ParentDeleteMode

An EntityAssociation has a parentDeleteMode property that determines how associated items will influence the ability to delete in the user interface. The default value is SUPPRESS but can be set through the EntitiesConfigurationBuilder.

For more information see the delete view chapter.

Association naming and location

Associations are added to the EntityConfiguration for which it makes most sense to manage them from a UI perspective. The association naming however is done according to the entity class and property names.

Example:

  • entity Group

  • entity User has a one to many with Group on property groups

  • association user.groups will be created on the entity configuration of Group

Customize associated entity creation

You can customize the creation of an associated entity in the form views, by setting a custom EntityFactory. This is especially useful for manually creating associations.

An EntityAssociation can have an EntityFactory.class attribute set that contains the EntityFactory that should be used for creating associated items. If no factory is set as attribute on the association, the default EntityFactory of the target configuration will be used.

If there is an EntityFactory attribute set on the association, that factory will be used:

  • when creating a DTO of an entity instance: the createDto() factory method

  • when creating a new associated entity instance: the createNew() factory method will get called with the parent entity (for whom an associated item is being created) as single method argument.

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