Advanced Mapping

kennedyz · **Joined:** Mon Jun 20, 2005 7:09 pm **Posts:** 1

Hi,
I have searched the forums to a similar solution to this problem but have had no luck.
I have an existing schema that defines tables as follows:

Tables
Table 1: ledger_tx
----------------------
ledgerid int8 (primary key)

Table 2: invoice
----------------------
invoiceid (references ledger_tx.ledgerid)

Table 3: ledger_lines
-------------------
ledgerid (references ledger_tx.ledgerid)
seq_num
primary key (ledger_id, seq_num)

Table 4: invoice_lines
-------------------------
invoiceid (references invoice.invoice_id)
seq_num
unit_price
unit_qty
line_price
primary key (invoice_id,seq_num)

Classes

C1. BasicLedger
C2. BasicLedger.Line
C3. BasicInvoice (extends BasicLedger)
C4. BasicInvoice.Line (extends BasicLedger.Line )
C5. BasicPrice

Mappings:
This mapping describes what I am trying to acheive, but it doesn't work because BasicPrice is defined as a component of BasicInvoice.Line which is defined as a composite-element. I want to be able to save everything with a single call to
session.save(BasicInvoice).

Code:

<class name="BasicLedger" table="ledger">
    <id name="id" unsaved-value="null" />
    <property name="ledgerid" insert="false" update="false" />

   <list name="ledgerLines" table="ledger_lines">
       <key not-null="true">
          <column name="ledgerid"/>
       </key>
       <list-index column="seq_num" base="0" />
       <composite-element class="BasicLedger.Line">            
       </composite-element>
   </list>

   <!-- BasicInvoice extends BasicLedger -->
   <joined-subclass name="BasicInvoice" table="invoice">
        <key not-null="true">
            <column name="invoiceid" />
        </key>
        <list name="invoiceLines" table="invoice_lines">
            <key>
                <column name="invoiceid"/>
            </key>
            <list-index column="seq_num" base="0" />
            <!--BasicInvoice.Line extends BasicLedger.Line-->
            <composite-element class="BasicInvoice.Line">
                <component name="Price"
                           class="BasicPrice">
                    <property name="unitPrice" not=null="true" />
                    <property name="unitQty" not-null="true"/>
          <property name="linePrice" not-null="true" />
                </component>
             </composite-element>
         </list>
    </joined-subclass>
</class>

To work around the BasicPrice component problem, I went re-read the docs and I tried to use a nested-composite-element, but that caused another error saying that a nested-composite-element isn't allowed in a list.

The documentation suggested defining BasicInvoice.Line as an entity, and use a one-to-many relation. I don't like this idea for a few reasons:
1. I need to change my BasicInvoice.ItemLine class to support an ID class
2. I need to account for the list sequence number value in my business logic.
3. I need to manually assign the invoice id to the item.
...

Is there another way I can map the BasicInvoice.ItemList objects so that a call to session.save(BasicInvoice) will save everything in one shot?

LaLiLuna · **Posted:** Mon Jan 09, 2006 7:53 am

Hello kennedyz,

I have the following proposal.

I think that you could omit the table ledger_lines. It has no special purpose as the ledger_table, which keeps track of a unique id across all types of ledgers (like bill, invoice, ...).
In this case the following would work.
If you do not even need a concrete table ledger you could omit it and use the "table of concrete class" strategy with union-subclass

Best Regards
Sebastian
Please rate, if this a solution.

Code:

<class name="Ledger" table="tledger" >
    <id name="id" >
      <generator class="sequence">
        <param name="sequence" >tledger_id_seq</param>
      </generator>
    </id>

  <joined-subclass name="Bill" table="tbill">
    <key column="ledger_id"></key>
    <property name="date" type="timestamp"></property>
    <list name="lines" table="tbill_line">
    <key column="parent_id"></key>
    <list-index column="id"></list-index>
      <composite-element class="BillLine">
        <property name="quantity" type="integer"></property>
        <property name="price" type="float"></property>
      </composite-element>
    </list>
  </joined-subclass>
  </class>

Code:

CREATE TABLE examples.tledger
(
  id int4 NOT NULL DEFAULT nextval('tledger_id_seq'::regclass),
  CONSTRAINT ledger_pkey PRIMARY KEY (id)
) ;

CREATE TABLE examples.tbill
(
  ledger_id int4 NOT NULL,
  date timestamp,
  CONSTRAINT tbill_pkey PRIMARY KEY (ledger_id)
) ;
CREATE TABLE examples.tbill_line
(
  id int4 NOT NULL DEFAULT nextval('tbill_line_id_seq'::regclass),
  parent_id int4 NOT NULL,
  quantity int4,
  price float8,
  CONSTRAINT tbill_line_pkey PRIMARY KEY (id, parent_id)
) ;