Sorry to post it again, but it's really a emergency problem need to solve.
I map it with joined-subclass first and everything is ok. But when i try to map it with subclass tag i got the Exception.
Tks for any help.

3.1

<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">

<hibernate-mapping>
<class name="cn.test.dao.model.Metadata" table="metadata" catalog="test">
<id name="metaId" type="java.lang.String">
<column name="meta_id" length="48" />
<generator class="uuid" />
</id>
<discriminator column="meta_type" type="string"/>
<many-to-one name="member" class="cn.test.dao.model.Member" fetch="select" >
<column name="member_id" length="48" not-null="true" />
</many-to-one>
<many-to-one name="sort" class="cn.test.dao.model.Sort" fetch="select" lazy="false">
<column name="sort_id" length="48" not-null="true" />
</many-to-one>
<many-to-one name="city" class="cn.test.dao.model.City" fetch="select" lazy="false">
<column name="city_id" length="48" />
</many-to-one>
<property name="title" type="java.lang.String">
<column name="title" />
</property>
<property name="content" type="java.lang.String">
<column name="content" not-null="true" />
</property>
<property name="createtime" type="java.util.Date">
<column name="createtime" length="23" />
</property>
<property name="updatetime" type="java.util.Date">
<column name="updatetime" length="23" />
</property>
<property name="viewcounts" type="java.lang.Integer">
<column name="viewcounts" />
</property>
<property name="keywords" type="java.lang.String">
<column name="keywords" />
</property>
<property name="status" type="java.lang.Short">
<column name="status" />
</property>
<property name="price" type="java.math.BigDecimal">
<column name="price" />
</property>
<set name="videos" inverse="true" table="metadata_videos" catalog="test">
<key>
<column name="meta_id" length="48" not-null="true" />
</key>
<many-to-many entity-name="cn.test.dao.model.Video">
<column name="video_id" length="48" not-null="true" />
</many-to-many>
</set>
<set name="tags" inverse="true">
<key>
<column name="meta_id" length="48" />
</key>
<one-to-many class="cn.test.dao.model.Tag" />
</set>
<set name="attributeSets" inverse="true">
<key>
<column name="meta_id" length="48" not-null="true" />
</key>
<one-to-many class="cn.test.dao.model.AttributeSet" />
</set>
<set name="comments" inverse="true">
<key>
<column name="meta_id" length="48"/>
</key>
<one-to-many class="cn.test.dao.model.Comment" />
</set>
<set name="metadataHistories" inverse="true">
<key>
<column name="meta_id" length="48" not-null="true" />
</key>
<one-to-many class="cn.test.dao.model.MetadataHistory" />
</set>
<set name="photos" table="metadata_photos" inverse="true" cascade="all" catalog="test">
<key>
<column name="meta_id" length="48" not-null="true" />
</key>
<many-to-many entity-name="cn.test.dao.model.Photo">
<column name="photo_id" length="48" not-null="true" />
</many-to-many>
</set>
<set name="itineraries" table="itinerary_metadata" catalog="test" inverse="true">
<key>
<column name="meta_id" length="48" not-null="true" />
</key>
<many-to-many entity-name="cn.test.dao.model.Itinerary">
<column name="itinerary_id" length="48" not-null="true" />
</many-to-many>
</set>
<subclass name="cn.test.dao.model.Hotel" discriminator-value="hotel">
<join table="hotel">
<key column="meta_id"/>
<property name="ranking" type="java.lang.Integer">
<column name="ranking" />
</property>
<property name="address" type="java.lang.String">
<column name="address" />
</property>
<property name="phone" type="java.lang.String">
<column name="phone" />
</property>
<property name="zip" type="java.lang.String">
<column name="zip" />
</property>
<property name="location" type="java.lang.String">
<column name="location" />
</property>
<property name="rate" type="java.lang.String">
<column name="rate" />
</property>

<property name="facility" type="java.lang.String">
<column name="facility" />
</property>

<property name="roomAmenity" type="java.lang.String">
<column name="room_amenity" />
</property>
<property name="extraBedPrice" type="java.math.BigDecimal">
<column name="extra_bed_price" />
</property>
<property name="breakfastPrice" type="java.math.BigDecimal">
<column name="breakfast_price" />
</property>

<property name="rankings" type="java.math.BigDecimal">
<column name="rankings" />
</property>
<set name="rooms" inverse="true" cascade="all">
<key>
<column name="hotel_id" length="48"/>
</key>
<one-to-many class="cn.test.dao.model.Room" />
</set>
</join>
</subclass>
<subclass name="cn.test.dao.model.Room" discriminator-value="room">
<join table="room">
<key column="meta_id"/>
<property name="bed" type="java.lang.Integer">
<column name="bed" />
</property>
<many-to-one name="hotel" class="cn.test.dao.model.Hotel">
<column name="hotel_id" length="48" />
</many-to-one>
</join>
</subclass>
</class>
</hibernate-mapping>



Caused by: org.xml.sax.SAXParseException: The content of element type "join" must match "(subselect?,comment?,key,(property|many
to-one|component|dynamic-component|any)*,sql-insert?,sql-update?,sql-delete?)".
at org.apache.xerces.util.ErrorHandlerWrapper.createSAXParseException(Unknown Source)
at org.apache.xerces.util.ErrorHandlerWrapper.error(Unknown Source)
at org.apache.xerces.impl.XMLErrorReporter.reportError(Unknown Source)
at org.apache.xerces.impl.XMLErrorReporter.reportError(Unknown Source)
at org.apache.xerces.impl.dtd.XMLDTDValidator.handleEndElement(Unknown Source)
at org.apache.xerces.impl.dtd.XMLDTDValidator.endElement(Unknown Source)
at org.apache.xerces.impl.XMLNSDocumentScannerImpl.scanEndElement(Unknown Source)
at org.apache.xerces.impl.XMLDocumentFragmentScannerImpl$FragmentContentDispatcher.dispatch(Unknown Source)
at org.apache.xerces.impl.XMLDocumentFragmentScannerImpl.scanDocument(Unknown Source)
at org.apache.xerces.parsers.XML11Configuration.parse(Unknown Source)
at org.apache.xerces.parsers.XML11Configuration.parse(Unknown Source)
at org.apache.xerces.parsers.XMLParser.parse(Unknown Source)
at org.apache.xerces.parsers.AbstractSAXParser.parse(Unknown Source)
at org.dom4j.io.SAXReader.read(SAXReader.java:465)
at org.hibernate.cfg.Configuration.addInputStream(Configuration.java:505)
... 74 more

mysql5.5

Solved, Ha Ha
After a short study of hibernate dtd, i got the answer. Just move the set tag out of join.