Help needed in mapping Mutiple one-to-one

mhatreakshay · **Joined:** Mon Feb 23, 2009 1:26 am **Posts:** 13

Hi All,
table A,B,C,d1,d2,d3,E,F
E-->A many:1
A --> B 1:1
B-->C 1:1
C-->d1 1:1
C-->d2 1:1
C-->d3 1:1
F-->C many:1

Please let me know how can I setup such a relation in .hbm.xml files to insert update delete & select.

Thank you in advance.

littypreethkr · **Posted:** Mon Feb 23, 2009 1:52 am

You can map these classes like any other class. There is no problem in one class having multiple relations. Plz give any specific doubts if you have any.

mhatreakshay · **Joined:** Mon Feb 23, 2009 1:26 am **Posts:** 13

can you please show me a sample mapping for table C?

littypreethkr · **Posted:** Mon Feb 23, 2009 2:59 am

I am assuming that ur 1-1 relations are using foreign keys with unique constraint.

Code:

    <class name="C" table="C">
       <id name="id" column="ID">
               <generator class="native"/>
       </id>
       
       <many-to-one name="d1" class="D1" column="D1_ID" unique="true"/>
       <many-to-one name="d2" class="D2" column="D2_ID" unique="true"/>
       <many-to-one name="d3" class="D3" column="D3_ID" unique="true"/>
       
       <one-to-one name="b" class="B" property-ref="c"/>
       
       <set name="fs" table="F">
           <key column="F_ID" />
           <one-to-many class="F"/>
         </set>
    </class>
    
In Mapping for B u ll have:

    <class name="B" table="B">
       ...........
       ...........
       <many-to-one name="c" class="C" column="C_ID" unique="true"/>
       ...........
       ...........
    </class>
    
In Mapping for D1, D2, D3 u ll have:
    <class name="D1" table="D1">
       ...........
       ...........
       <one-to-one name="c" class="C" property-ref="d1"/>
       ...........
       ...........
    </class>

mhatreakshay · **Joined:** Mon Feb 23, 2009 1:26 am **Posts:** 13

hi thx u for the reply ..but I dont want to create 3 seperate objects d1,d2,d3 in the C class.Can I not use another technique like subclass.
since One record in C wil always point to only one record of either of d1,d2,d3

littypreethkr · **Posted:** Mon Feb 23, 2009 3:13 am

Sure you can use, if in ur domain model d1, d2 d3 are subclasses of C then you should be using the sub-class construct than the one-to-one relation. So in that case instead of the unique foreign key, you should be using the primary key association technique.

So the subclass D1 will look like:

Code:

   <class name="C" table="C">
         ...........
         ...........
      <joined-subclass name="D1" table="D1">
         <key column="C_ID" />
         <property name="col1" column="COL1" />
         ...........
         ...........
      </joined-subclass>
   </class>

Now your table D1 will have primary key column C_ID referencing C.ID

mhatreakshay · **Joined:** Mon Feb 23, 2009 1:26 am **Posts:** 13

In Mapping for B u ll have:

<class name="B" table="B">
...........
...........
<many-to-one name="c" class="C" column="C_ID" unique="true"/>
...........
...........
</class>

why there should be a many-to-one mappig when the relationship is 1-to-1

littypreethkr · **Posted:** Mon Feb 23, 2009 3:59 am

This is how we map 1-1 with unique foreign key constraint. You can see that there is a unique=true attribute and this will distinguish the 1-1 from n-1.

So <many-to-one unique="true"/> is the original side of the relation (table has a unique foreign key column) and
<one-to-one property-ref="c"/> is the inverse of that relation.

mhatreakshay · **Joined:** Mon Feb 23, 2009 1:26 am **Posts:** 13

I tried doing below entry
in my class B
Underlying is my class C;
as per the Datamodel underlyingName (from Underling table) is a foreign key to my table B.
<many-to-one name="underlying" class="com.agdelta.trade.marketdata.model.Underlying" lazy="false"
column="underlyingName" unique="true"/>

throws below exception

org.hibernate.TransientObjectException: object references an unsaved transient instance - save the transient instance before flushing: com.agdelta.trade.marketdata.model.Underlying
at org.hibernate.engine.ForeignKeys.getEntityIdentifierIfNotUnsaved(ForeignKeys.java:219)
at org.hibernate.type.EntityType.getIdentifier(EntityType.java:397)
at org.hibernate.type.ManyToOneType.isDirty(ManyToOneType.java:242)
at org.hibernate.type.TypeFactory.findDirty(TypeFactory.java:597)
at org.hibernate.persister.entity.AbstractEntityPersister.findDirty(AbstractEntityPersister.java:3128)
at org.hibernate.event.def.DefaultFlushEntityEventListener.dirtyCheck(DefaultFlushEntityEventListener.java:479)
at org.hibernate.event.def.DefaultFlushEntityEventListener.isUpdateNecessary(DefaultFlushEntityEventListener.java:204)
at org.hibernate.event.def.DefaultFlushEntityEventListener.onFlushEntity(DefaultFlushEntityEventListener.java:127)
at org.hibernate.event.def.AbstractFlushingEventListener.flushEntities(AbstractFlushingEventListener.java:196)
at org.hibernate.event.def.AbstractFlushingEventListener.flushEverythingToExecutions(AbstractFlushingEventListener.java:76)
at org.hibernate.event.def.DefaultFlushEventListener.onFlush(DefaultFlushEventListener.java:26)
at org.hibernate.impl.SessionImpl.flush(SessionImpl.java:1000)
at org.hibernate.impl.SessionImpl.managedFlush(SessionImpl.java:338)
at org.hibernate.transaction.JDBCTransaction.commit(JDBCTransaction.java:106)
at com.agdelta.trade.marketdata.dao.QuoteDAO.addNewQuote(QuoteDAO.java:32)
at com.agdelta.trade.marketdata.QuoteTest.testQuote(QuoteTest.java:30)
at com.agdelta.trade.TradeStartupServlet.init(TradeStartupServlet.java:48)
at javax.servlet.GenericServlet.init(GenericServlet.java:212)
at org.apache.catalina.core.StandardWrapper.loadServlet(StandardWrapper.java:1139)
at org.apache.catalina.core.StandardWrapper.load(StandardWrapper.java:966)
at org.apache.catalina.core.StandardContext.loadOnStartup(StandardContext.java:3956)
at org.apache.catalina.core.StandardContext.start(StandardContext.java:4230)
at org.apache.catalina.core.StandardContext.reload(StandardContext.java:3025)
at org.apache.catalina.loader.WebappLoader.backgroundProcess(WebappLoader.java:432)
at org.apache.catalina.core.ContainerBase.backgroundProcess(ContainerBase.java:1278)
at org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.processChildren(ContainerBase.java:1570)
at org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.processChildren(ContainerBase.java:1579)
at org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.processChildren(ContainerBase.java:1579)
at org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.run(ContainerBase.java:1559)
at java.lang.Thread.run(Unknown Source)

mhatreakshay · **Joined:** Mon Feb 23, 2009 1:26 am **Posts:** 13

I got the answer for the same.Actually I was trying to set the value in d1 from Class B ,where as I should set the value in C.
Thanks a lot.You have really helped me to get the things clear.
cheers.

mhatreakshay · **Joined:** Mon Feb 23, 2009 1:26 am **Posts:** 13

Hi,
I am getting one more exception.Class Cast Exception.
Following are the details
table C mapped to d1,d2,d3 using subclass
E --> C many : many
but the E to C is via a mapping table between them which contains only the primary keys of table E & C.
While I try to persist to database I set the object of "C" into the object of "E" and then save the Object E.
But this throws me a classcast exception.

Mapping in class E

<class name="E" table="ee" >
<id name="eId" type="int">
<column name="eId" />
<generator class="assigned" />
</id>
.
.
.
<set name="cData" table="cematrix" lazy="false" cascade="all">
<key column="e"/>
<many-to-many column="cName" class="C"/>
</set>

</class>
</hibernate-mapping>

Mapping in class C

<hibernate-mapping>
<class name="C" table="c" >
<id name="cName" type="string">
<column name="cName" />
<generator class="assigned" />
</id>
.
.
.
<joined-subclass name="D1" table="dd1">
<key column="d1" update="true"></key>

.
.
.
</joined-subclass>

<joined-subclass name="D2" table="dd2">
<key column="d2" update="true"></key>

.
.
.
</joined-subclass>

<joined-subclass name="D3" table="dd3">
<key column="d3" update="true"></key>

.
.
.
</joined-subclass>

</class>
</hibernate-mapping>

Code for persist the object

E spc = new E(1);
spc.set..("AC1");
spc.set..("BDC1");
spc.set..("C1");
spc.setEID(1);
spc.set..("COT");
spc.set..("I1");

C u = new C("U1");
spc.setC(u);
eDAO dao = new eDAO();
dao.addNewE(spc);

This throws Class Cast Exception

java.lang.ClassCastException: com..trade.md.model.C
at org.hibernate.type.SetType.wrap(SetType.java:39)
at org.hibernate.event.def.WrapVisitor.processArrayOrNewCollection(WrapVisitor.java:84)
at org.hibernate.event.def.WrapVisitor.processCollection(WrapVisitor.java:51)
at org.hibernate.event.def.AbstractVisitor.processValue(AbstractVisitor.java:101)
at org.hibernate.event.def.WrapVisitor.processValue(WrapVisitor.java:98)
at org.hibernate.event.def.AbstractVisitor.processEntityPropertyValues(AbstractVisitor.java:55)
at org.hibernate.event.def.AbstractSaveEventListener.visitCollectionsBeforeSave(AbstractSaveEventListener.java:371)
at org.hibernate.event.def.AbstractSaveEventListener.performSaveOrReplicate(AbstractSaveEventListener.java:273)
at org.hibernate.event.def.AbstractSaveEventListener.performSave(AbstractSaveEventListener.java:181)
at org.hibernate.event.def.AbstractSaveEventListener.saveWithGeneratedId(AbstractSaveEventListener.java:121)
at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.saveWithGeneratedOrRequestedId(DefaultSaveOrUpdateEventListener.java:187)
at org.hibernate.event.def.DefaultSaveEventListener.saveWithGeneratedOrRequestedId(DefaultSaveEventListener.java:33)
at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.entityIsTransient(DefaultSaveOrUpdateEventListener.java:172)
at org.hibernate.event.def.DefaultSaveEventListener.performSaveOrUpdate(DefaultSaveEventListener.java:27)
at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.onSaveOrUpdate(DefaultSaveOrUpdateEventListener.java:70)
at org.hibernate.impl.SessionImpl.fireSave(SessionImpl.java:535)
at org.hibernate.impl.SessionImpl.save(SessionImpl.java:523)
at org.hibernate.impl.SessionImpl.save(SessionImpl.java:519)

littypreethkr · **Posted:** Tue Feb 24, 2009 2:00 am

Why are you doing this?

Code:

C u = new C("U1");
spc.setC(u); 

Your E->C is MTM then you should be setting a collection of C to E not an object of C. So you should do something like:

Code:

C u = new C("U1");
Set<C> cs=new HashSet<C>();
cs.add(u);
spc.setC(cs);

mhatreakshay · **Joined:** Mon Feb 23, 2009 1:26 am **Posts:** 13

yes u are right.Its working now.
thank you.