one-to-many mapping help please

erik.jogi · **Posted:** Mon Jun 28, 2004 1:09 pm

Hello,

I have the following table structure:

Code:

ACCOUNTS
  ID : VARCHAR(32) PK
  TYPE : CHAR(1)

BALANCES
  ACCOUNT_ID : VARCHAR(32) PK
  CURRENCY : CHAR(3) PK
  BALANCE : NUMERIC(16,2)

In other words there are accounts which can have balances in several currencies. The BALANCES table's primary key consists of two fields.

I have an Account class:

Code:

/**
 * @hibernate.class table="ACCOUNTS"
 */
public class Account {

  private String id;
  private char type;
  private Set balances;

  /**
   * @hibernate.id generator-class="assigned"
   */
  public String getId() { return id; }
  public void setId(String id) { this.id = id; }

  /**
   * @hibernate.property
   */
  public char getType() { return type; }
  public void setType(char type) { this.type = type; }

  /**
   * @hibernate.set
   * @hibernate.collection-key column="ACCOUNT_ID"
   * @hibernate.collection-???????
   */
  public Set getBalances() { return balances; }
  public void setBalances(Set balances) { this.balances = balances; }
}

And a Balance class:

Code:

public class Balance {

  private String currency;
  private BigDecimal amount;

  public String getCurrency() { return currency; }
  public void setCurrency(String currency) { this.currency = currency; }

  public BigDecimal getAmount() { return amount; }
  public void setAmount(BigDecimal amount) { this.amount = amount; }
}

And the question is what do I write in place of the question marks in the Account.getBalances() javadoc?

Initially I thought that one-to-many would be great but as the PK for BALANCES table is in two fields then I would probably have to add the accounId field to Balance class?

Another option I thought of was using the Balance as a component. This means I should implement equals() and hashCode() in Balance. In the equals method - would it be ok to compare the values of the currency fields?

Are there any other possibilities?

Any advice would be greatly appreciated,

disfunction · **Posted:** Mon Jun 28, 2004 3:13 pm

I think you should add the account to the balance classe since a balance has an account, and than go ahead with
/**
* @hibernate.set
* @hibernate.collection-key column="ACCOUNT_ID"
* @hibernate.collection-one-to-many class="Balance"
*/
public Set getBalances() { return balances; }

This is just a guess but I think it should work out for you. Of course, you have to map Balance as well.