Mapping java.util.Map with JPA
===

I have JEE 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](http://imgur.com/S1ZWu.jpg)
 (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> 
