Difference between @OneToMany and @ElementCollection?

Question

What is the difference between using a @OneToMany and @ElementCollection annotation since both work on the one-to-many relationship?

Answer 1

@ElementCollection allows you to simplify code when you want to implement one-to-many relationship with simple or embedded type. For instance in JPA 1.0 when you wanted to have a one-to-many relationship to a list of Strings, you had to create a simple entity POJO (StringWrapper) containing only primary key and the String in question:

@OneToMany
private Collection strings;

//...

public class StringWrapper {
  @Id
  private int id;

  private String string;
}

With JPA 2.0 you can simply write:

@ElementCollection
private Collection strings;

Simpler, isn't it? Note that you can still control the table and column names using @CollectionTable annotation.

See also:

• Java Persistence/ElementCollection