Question

I have a domain object annotated like this for hibernate support.

@Entity
@Table(name = "INPUT")
public class AppInput {

  /**
   * Unique id for this request
   */
  @Id
  @GeneratedValue
  @Column(name = "INPUT_ID")
  private long requestId;
  /**
   * 
   */
  @Column(name = "EMAIL_ID")
  private String emailId;
  /**
   * 
   */
  @Column(name = "REQUEST_DATE")
      private Date requestDate;
  /**
    * 
   */
  @Column(name = "INPUT_STATUS")
   private char status;
  /**
   * 
   */
   @Column(name = "EXPECTED_ORDER_DATE")
  private Date expectedOrdDt;

//Getter and setters
   }

The property emailId is a foreign key referring to say emailId column in User table. Lets say i add a property like this to AppInput.java
private User userDetails;
How do i annotate this so that, whenever i fetch AppInput from db, the corresponding user details also get populated?

Answer 1

The property emailId is a foreign key referring to say emailId column in User table.

Then don’t add the emailId property, add a User.

(…) How do i annotate this so that, whenever i fetch AppInput from db, the corresponding user details also get populated?

Not sure since it could be a ManyToOne or OneToOne but I’ll assume it’s a ManyToOne:

@ManyToOne(fetch=FetchType.EAGER)
@JoinColumn(name="USERDETAILS_EMAIL_ID", referencedColumnName="EMAIL_ID")
private User userDetails;

The fetch annotation element is for demonstration purpose, EAGER being actually the default value. The name and referencedColumn annotation elements in JoinColumn are also optional. Below a short summary from the JPA specification:

11.1.21 JoinColumn Annotation

The JoinColumn annotation is used to
specify a column for joining an entity
association or element collection.

Table 20 lists the annotation elements
that may be specified for the
JoinColumn annotation and their
default values.

If the JoinColumn annotation itself
is defaulted, a single join column is
assumed and the default values
described in Table 20 apply.

The name annotation element defines
the name of the foreign key column.
The remaining annotation elements
(other than referencedColumnName)
refer to this column and have the same
semantics as for the Column
annotation.

If the
referencedColumnName element is
missing, the foreign key is assumed to
refer to the primary key of the
referenced table.

See the Table 20 in the spec for complete and exhaustive details.