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2.2.7. Mapping secondary tables

You can map a single entity bean to several tables using the @SecondaryTable or @SecondaryTables class level annotations. To express that a column is in a particular table, use the table parameter of @Column or @JoinColumn.
@SecondaryTables({ @SecondaryTable(name="Cat1", pkJoinColumns={ @PrimaryKeyJoinColumn(name="cat_id", referencedColumnName="id") ), @SecondaryTable(name="Cat2", uniqueConstraints={@UniqueConstraint(columnNames={"storyPart2"})}) })
public class Cat implements Serializable {

    private Integer id;
    private String name;
    private String storyPart1;
    private String storyPart2;

    @Id @GeneratedValue
    public Integer getId() {
        return id;

    public String getName() {
        return name;
    public String getStoryPart1() {
        return storyPart1;

    public String getStoryPart2() {
        return storyPart2;
In this example, name will be in MainCat. storyPart1 will be in Cat1 and storyPart2 will be in Cat2. Cat1 will be joined to MainCat using the cat_id as a foreign key, and Cat2 using id (ie the same column name, the MainCat id column has). Plus a unique constraint on storyPart2 has been set.
Check out the JBoss EJB 3 tutorial or the Hibernate Annotations unit test suite for more examples.