Mapping java.util.Map with JPA

Question

I have Java EE application with Hibernate mapped classes (I use *.hbm.xml mappings). Now I need to remake mappings with JPA annotations. All is fine but I can't create correct mapping with my Map property.

@Entity
@Table(name = DataBaseConstants.EMPLOYEE_TABLE)
public class Employee implements Serializable {
private static final long serialVersionUID = 1L;
@Id
@SequenceGenerator(name = DataBaseConstants.EMPLOYEE_ID, sequenceName = DataBaseConstants.EMPLOYEE_SEQ)
@GeneratedValue(generator = DataBaseConstants.EMPLOYEE_ID)
@Column(name = DataBaseConstants.EMPLOYEE_ID)
private long id = 0;
@Column(name = DataBaseConstants.EMPLOYEE_NAME)
private String name = null;
@ManyToOne(cascade = CascadeType.ALL)
@JoinColumn(name = DataBaseConstants.ADDRESS_ID_FK)
private Address address = null; 

private Map<Office, Position> officePositions = null;

Here is part of data model in data base. DB MODEL IMAGE (Sorry I can't post images) Help me please to mapping officeEmployee MAP

In Hibernate i used this way and everything was OK.

<map name="officePositions" table="EMPLOYEE_POSITION_OFFICE" lazy="false"
                fetch="join" batch-size="100">
            <key>
            <column name="EMPLOYEE_ID"></column>
        </key>
        <map-key-many-to-many class="com.example.jpajdbctask.entities.Office">
            <column name="OFFICE_ID">
            </column>
        </map-key-many-to-many>
        <many-to-many column="POSITION_ID"
            class="com.example.jpajdbctask.entities.Position" />
        </map>

Tomer · Accepted Answer · 2012-07-24 13:06:05Z

1

I never used it myself so i can't help you with the exact implementation, but you need to use the @CollectionOfElements annotation, an example would be:

@CollectionOfElements(fetch=FetchType.EAGER)
@JoinTable(
    name = "MappingTable", 
    joinColumns = @JoinColumn(name = "mapOwner"))
@Column(
   name = "mapValueItem", 
   nullable = false
)  
@org.hibernate.annotations.MapKey(
    columns={
        @Column(
             name="mapKeyItem"
        )
   }
)
protected Map<String, String> getMapping() {
    return mapping_;
}

this forum might be helpful.

answered Jul 24, 2012 at 13:06

Tomer

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CroWell Over a year ago

thx, i have tried, but my db model does not suitable for it, Hibernate tries to access "officePositions_ID" column and etc. I add hibernate mapping of this class in persistence.xml

Art Licis · Accepted Answer · 2012-07-24 13:10:30Z

0

For a basic case (where key is some primitive), here's a JavaDoc for MapKey annotation with an example.

It seems that in your case @MapKeyColumn should be used; here's an example very similar to yours.

You'll have to change your Map within Employee class to Map<Office, EmployeePositionOffice>.

edited Jul 24, 2012 at 13:10

answered Jul 24, 2012 at 13:04

Art Licis

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