composite-key

Following this link I would like to use OneToMany instead ManyToMany annotation, having middle class with composite key in it using Ebean. I have this error: java.lang.RuntimeException: Error reading annotations for models.SoftwareTagPk This is my SoftwareTagPk class: @Embeddable public class SoftwareTagPk implements Serializable { @ManyToOne private Tag tag; @ManyToOne private Software software; ... } And SoftwareTag class: @Entity public class SoftwareTag extends Model { @EmbeddedId private SoftwareTagPk pk = new SoftwareTagPk(); @Transient public Tag getTag() { return pk.getTag(); } public

I have the following existing DB schema, which I'd like to recreate with Java and plain JPA annotations (using hibernate as provider, so hibernate specific annotations would work as a last resort): CREATE TABLE users ( user_id NUMBER NOT NULL -- pk ); CREATE TABLE userdata_keys ( userdata_key_id NUMBER NOT NULL, -- pk key VARCHAR2(128) NOT NULL ); CREATE TABLE users_userdata ( user_id NUMBER NOT NULL, -- fk users.user_id userdata_key_id NUMBER NOT NULL, -- fk userdata_keys.userdata_key_id value VARCHAR2(256) ); I've thus created the following classes and annotations: class User { @Id Long id;

I am designing a database using Entity Framework's "model-first" approach. Based on excellent feedback I recieved here, I am adopting a super-type/sub-type pattern for part of the DB. This pattern requires composite keys based on 2 columns in at least 2 tables (see schema below). I've searched the forum for "entity framework" and "composite keys", but none of the questions I found were on this more basic level: Can I set up an entity model so that it will generate one table (using "Generate Database from Model...") with a composite primary key on 2 columns, such that one is a foreign key on a

Given a simple parent -> child (CK,CK) setup like this .. I am having trouble with adding a new child object and it getting the parent reference. So I would add the object in such a way .. var parent = new Parent{ Children = new List<Child>{ new Child{ Other = otherReference } } }; Or even adding it using the Add() method... parent.Children.Add(new Child { Other = other }); The reference to the Parent does not get pushed through. It just ends up as a null property. I get the following exception. {"Cannot insert the value NULL into column 'ParentId', table 'mssql_test.Children'; column does not