title: JPA mapping issue with composite key
body: <p>I have a below mapping </p>
  
  <pre><code>@Entity
  @Table(name = "auctions")
  public class Auction{
  .
  .
      @OneToMany(cascade = CascadeType.ALL, mappedBy = "auction")
      private List&lt;AuctionParamValue&gt; auctionParamValueList;
  .
  .
  }
  
  
  @Entity
  @Table(name = "auction_param_values")
  public class AuctionParamValue {
  
      @EmbeddedId
      protected AuctionParamValuePK auctionParamValuePK;
  
      @JoinColumn(name = "auction_param_id", referencedColumnName = "auction_param_id",updatable=false,insertable=false)
      @ManyToOne 
          private AuctionParam auctionParam;
  
      @JoinColumn(name = "auction_id", referencedColumnName  = "auction_id",updatable=false,insertable=false)
      @ManyToOne @MapsId("auctionId") 
          private Auction auction;
  }
  
  @Embeddable
  public class AuctionParamValuePK {
      @Id 
      @Basic(optional = false)
      @Column(name = "auction_id")
      private long auctionId;
  
      @Id
      @Basic(optional = false)
      @Column(name = "auction_param_id")
      private int auctionParamId;
  }
  
  @Entity
  @Table(name = "auction_params")    
  public class AuctionParam {
      @OneToMany(cascade = CascadeType.ALL, mappedBy = "auctionParam")
      private List&lt;AuctionTypeParam&gt; auctionTypeParamList;
  
      @OneToMany(cascade = CascadeType.ALL, mappedBy = "auctionParam")
      private List&lt;AuctionParamValue&gt; auctionParamValueList;
   }
  </code></pre>
  
  <p>}</p>
  
  <p>When I try to persist auction I am getting below error</p>
  
  <pre><code> Internal Exception: com.mysql.jdbc.exceptions.MySQLIntegrityConstraintViolationException: Column 'auction_param_id' cannot be null
  Error Code: 1048
  Call: INSERT INTO auction_param_values (auction_param_val, create_ts, last_updt_ts, auction_param_id, auction_id) VALUES (?, ?, ?, ?, ?)
      bind =&gt; [500, 2011-01-25 20:11:01.22, 2011-01-25 20:11:01.22, null, null]
  Query: InsertObjectQuery(com.eaportal.domain.AuctionParamValue[auctionParamValuePK=null])
  Jan 25, 2011 8:11:01 PM org.apache.catalina.core.StandardWrapperValve invoke
  SEVERE: Servlet.service() for servlet dispatcher threw exception
  com.mysql.jdbc.exceptions.MySQLIntegrityConstraintViolationException: Column 'auction_param_id' cannot be null
  </code></pre>