need good example of hibernate with composit key

[Rauhl Roy]

may i know a good example of hibernet with composit key and the code.

[Cameron Wallace McKenzie]

Here's a little tutorial I put together on the topic of Hibernate JPA and Compound Primary Keys:

Hibernate Composite Key Mapping Example



The tutorial shows several ways to do it.

  
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;
  }
}  

  package com.examscam.mappings;import javax.persistence.Embeddable;
/* Final 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;
  }

  public boolean equals(Object key) {
   boolean result = true;
   if (!(key instanceof CompoundKey)) {return false;}
    Long otherUserId = ((CompoundKey)key).getUserId();
    Long otherBankId = ((CompoundKey)key).getBankId();
    if (bankId == null || otherBankId == null) {
      result = false;
    }else {
      result = bankId.equals(otherBankId);
    }
    if (userId == null || otherUserId == null) {
      result = false;
    }else {
      result = userId.equals(otherUserId);
    }
   return result;
  }

  public int hashCode() {
    int code = 0;
    if (userId!=null) {code +=userId;}
    if (bankId!=null) {code +=bankId;}
    return code;
  }
}  

  package com.examscam.mappings;
import javax.persistence.*; import org.hibernate.Session;
import com.examscam.HibernateUtil;
@Entity
public class Interest {

  private CompoundKey id;
  private double rate;

  @Id
  public CompoundKey getId() {return id;}
  public void setId(CompoundKey id) {this.id=id;}
  public double getRate() {return rate;}
  public void setRate(double rate) {this.rate=rate;}

  public static void main(String args[]) {
    Interest rate = new Interest();
    rate.setRate(18.5);

    Long wayne=new Long(99); Long mario=new Long(88);
    CompoundKey key = new CompoundKey(wayne, mario);
    rate.setId(key);

    HibernateUtil.recreateDatabase();
    Session session = HibernateUtil.beginTransaction();
    session.save(rate);
    HibernateUtil.commitTransaction();
  }
}  

-Cameron McKenzie

[Rauhl Roy]

does Hibernate fully supports composite key? or we should look of some other technology? or simply use JDBC?

[Rauhl Roy]

Good to see your post, is using JPA is a must to implement Composite key or else we can also do it with simple Hibernate?

[Cameron Wallace McKenzie]

I like JPA annotations. There is an equivalent entry in a Hibernate mapping file, if you please.

[Rauhl Roy]

Cameron Wallace McKenzie wrote:I like JPA annotations. There is an equivalent entry in a Hibernate mapping file, if you please.

but no where it is mentioned in your tutorial as to how to create .hbm.xml file for all java class may i know where can i find it?

thanks in advance,
ra.

[Rauhl Roy]

Cameron Wallace McKenzie wrote:I like JPA annotations. There is an equivalent entry in a Hibernate mapping file, if you please.

you used @@Embeddable @Id @Entity, but i do not want to use and implement the annotations and EJB. can you please let me know how to proced with plaing old hibernate(composit-key)?

many thanks in advance,
rahul.

[Kumar Raja]

Hello All,

I'm relatively new to Hibernate and ORM world and having absolutely zero knowledge in JPA and annotations. I did some programming in Hibernate for my learning purpose but have not really used composite keys. I'm not sure, if this thread is the right thread for that, but would like to utilize the conversation already started.

1) Is there any alternative way to declare the composite keys using mapping xmls? If so, a small example is appreciated.

2) When we say session.save(object), it returns a serializable object identity. How would this behave, when I have composite keys in the database?


THanks
Kumar