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one-to-one mapping with formula

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barbalib

Post subject: one-to-one mapping with formula

Posted: Tue Aug 26, 2008 9:15 am

Newbie

Joined: Tue Aug 26, 2008 8:57 am
Posts: 3

Newbie in trouble, hope you can help.

At the moment I have two tables account and arrears_notice; there can be 0 or 1 rows on the arrears notice table.

Code:

<class
    name="com.xxx.Account"
    table="ACCOUNT"
>
    <id
        name="accountId"
        type="java.lang.Long"
        column="ACCOUNT_ID"
        unsaved-value="0"
    >
    .......
    <one-to-one name="arrearsNotice"
       class="com.xxx.ArrearsNotice"
       fetch="join"
       lazy="no-proxy"
       property-ref="account" />
    ......
</class>

   <class name="com.xxx.ArrearsNotice" table="ARREARS_NOTICE" lazy="true" >
        <id name="arrearsNoticeId" column="ARREARS_NOTICE_ID" unsaved-value="0">
            <generator class="sequence">
                <param name="sequence">seq_arrears_notice</param>
            </generator>
        </id>
        <many-to-one name="account"
          class="com.xxx.Account"
          column="ACCOUNT_ID"
          not-null="true"
          lazy="no-proxy" />
        ......
    </class>

I've now added an activeNotice column to the arrears notice table. There will only ever be one active notice row (active_notice = 1).

I want to change the mapping in the account table so that it only joins to the active row (or no row). As is, it falls over when there are multiple rows on the notice table. I don't want to change the mapping to a set, I'd like to leave it as a one-to-one.

I've tried several ways of doing this using 'formula' but am really struggling and would appreciate any help.

I'm using hibernate 3 and an Oracle database.

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nordborg

Post subject:

Posted: Tue Aug 26, 2008 5:10 pm

Expert

Joined: Wed Mar 03, 2004 6:35 am
Posts: 1240
Location: Lund, Sweden

I have done something that is very similar. Though it was a long time ago and now that I look at it I can't really explain why it is working. In any case, I think it translates to something like this for your mappings.

In mapping for ArrearsNotice:

Code:

<properties
   name="activeArrearsNotice"
   >
   <property
      name="activeNotice"
      type="int"
      column="ACTIVE_NOTICE"
      not-null="true"
   />
   <many-to-one 
      name="account"
      class="com.xxx.Account"
      column="ACCOUNT_ID"
      not-null="true"
      lazy="no-proxy" 
   /> 
</properties>

And in the mapping for Account:

Code:

<one-to-one 
   name="arrearsNotice"
   class="com.xxx.ArrearsNotice"
   fetch="join"
   lazy="no-proxy"
   property-ref="activeArrearsNotice"> 
  <formula>1</formula>
  <formula>ACCOUNT_ID</formula>
</one-to-one>

I think that the two formulas in the one-to-one mapping is mapped to the property and many-to-one mapping in the order they appear in the mapping documents thus creating a condition like the one below:

Code:

ARREARS_NOTICE.ACTIVE_NOTICE = 1 and ARREARS_NOTICE.ACCOUNT_ID = ACCOUNT.ACCOUNT_ID

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barbalib

Post subject:

Posted: Wed Aug 27, 2008 5:47 am

Newbie

Joined: Tue Aug 26, 2008 8:57 am
Posts: 3

Thank you so much, that works now. I'd tried something like that, but I thought I had to reference active_notice in the formula. I can kind of see how it works now and why it's account_id instead.

You've saved me a lot of re-writing.

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