I have a generic CONTENT table in the Database that holds all the images and PDFs and other binary content. There is a CONTENTTYPE table to distinguish different types but ContentTypeID is not FK in CONTENT table. Instead, ContentTypeID is used as a PK of a table called PERSON_CONTENT to associate different types of content for a given person.

In Java implementation, ImageContent, PDFContent extends Content class. These children classes have additional identifiers of their own but all of the new properties in the children are totally Non-Persistent fields.

Given this DB schema, My approach was to go with a Table per class heirarchy and create a Content.hbm.xml with discriminator column as contentType ( this column is unfortunately not in Content table. So I tried using discriminator formula instead).

My content.hbm.xml looks like this:

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD 2.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd" >

<hibernate-mapping>

<class
name="com.xxx.Content"
table="CONTENT" discriminator-value="?(dont know what to put here)"
>
<id
name="contentId"
type="java.lang.Long"
column="CONTENT_ID"
>
<generator class="sequence">
<param name="sequence">TABLESEQ</param>
</generator>
</id>
<discriminator formula="SELECT content_type_id FROM content_type"/>
<property
name="title"
type="java.lang.String"
column="TITLE"
length="400"
/>
<subclass
name="ImageContentBean"
discriminator-value="11">
</subclass>

<subclass
name="PDFContentBean"
discriminator-value="12">
</subclass>
</class>
</hibernate-mapping>[/color]
With this, I am getting the exception that reads as follows:

Caused by: org.xml.sax.SAXParseException: The content of element type "class" must match "(meta*,subselect?,cache?,synchronize*,(id|composite-id),discriminator?,(version|timestamp)?,(property|many-to-one|one-to-one|component|dynamic-component|properties|any|map|set|list|bag|idbag|array|primitive-array|query-list)*,((join*,subclass*)|joined-subclass*|union-subclass*),loader?,sql-insert?,sql-update?,sql-delete?,filter*)".
at org.apache.xerces.util.ErrorHandlerWrapper.createSAXParseException(Unknown Source)
at org.apache.xerces.util.ErrorHandlerWrapper.error(Unknown Source)
...
Here are my questions:
1. Because the fields in the children class are not persistent, Do I still need to specify <subclass> in Content.hbm.xml?

2. What should be the discriminator value for the Content table? There is no unique type for the parent one. It can be any one from the children. ( Marked by Question_mark in the hbm.xml file above)

3. Do I require a separate mapping for each <subclass> item listed in Content.hbm.xml?

4.

Can anyone point me in the right direction?

Thanks in advance

what happens if you change



to

I was able to resolve the exception by putting the subclass tag after the association tags.
But I am still getting classcastException when I do

PDFContentBean pdfCb = (PDFContentBean)content.getContent();

Do I have to tweak anything else in my setting?