Hibernate & primary keys

[Cornelius Reckinger]

Howdy, we are designing a new Spring based rewrite of an existing system and we wanted to use Hibernate to abstract out the persistence layer. One of the architects has stated that we cannot use Hibernate because it cannot handle tables that have been defined without primary keys and that iBatis is the best solution. Can anyone here validate that position?

[Mark Spritzler]

That is inaccurate as you can define your id as a composite of fields. You can map a legacy database to Hibernate.

Mark

[Cameron Wallace McKenzie]

Indeed, this shouldn't be a problem.

You can even map Hibernate based component to database views.

As far as doing compound keys, it's easy. Here's a simple table with two fields acting as keys together:



That scenario can be mapped as simply as using the following class:

  
package com.examscam.mappings;
import javax.persistence.Embeddable;
/* First Iteration of the CompoundKey Class */
@Embeddable
public class CompoundKey implements 
                             java.io.Serializable{
  private Long userId;
  private Long bankId;
  public CompoundKey() {}
  public CompoundKey(Long user, Long bank) {
    userId = user;
    bankId = bank;
  }
 
  public Long getBankId() {return bankId;}
  public void setBankId(Long bankId) {
    this.bankId = bankId;
  }
  public Long getUserId() {return userId;}
  public void setUserId(Long userId) {
    this.userId = userId;
  }
}
  

You can find the whole example here: Hibernate and Compound Primary Keys

-Cameron McKenzie
[ July 24, 2008: Message edited by: Cameron Wallace McKenzie ]