Storing a Map<String,String> using JPA

JPA 2.0 supports collections of primitives through the @ElementCollection annotation that you can use in conjunction with the support of java.util.Map collections. Something like this should work:

@Entitypublic class Example {    @Id long id;    // ....    @ElementCollection    @MapKeyColumn(name="name")    @Column(name="value")    @CollectionTable(name="example_attributes", joinColumns=@JoinColumn(name="example_id"))    Map<String, String> attributes = new HashMap<String, String>(); // maps from attribute name to value}

See also (in the JPA 2.0 specification)

• 2.6 - Collections of Embeddable Classes and Basic Types
• 2.7 Map Collections
• 10.1.11 - ElementCollection Annotation
• 11.1.29 MapKeyColumn Annotation

  @ElementCollection(fetch = FetchType.LAZY)  @CollectionTable(name = "raw_events_custom", joinColumns = @JoinColumn(name =     "raw_event_id"))  @MapKeyColumn(name = "field_key", length = 50)  @Column(name = "field_val", length = 100)  @BatchSize(size = 20)  private Map<String, String> customValues = new HashMap<String, String>();

This is an example on how to set up a map with control over column and table names and field length.