Java hibernate save objects in different schemas which are in one database

Question

I am using DB2 database and hibernate framework. There are two tables such as Word and Litter and their relationship is one to many.

Schema A:

Table Word: ID,
IDLIT -> references to ID of Litter table
Name

Schema B:

Table Litter ID,
Short_Name,
Long_Name.

Both tables are located in two different schemas but in one database. I have an POJO and XML mapping files to map the tables. Now how can I save the objects into database while handling the many to one relationship(Litter - Word)? Is the any suggestion? If yes please provide me with detailed instructions, thanks in advance!

Updated question

Also I have changed because my mapping xml files different for each POJO class. Here is the code for running:

 Session session = HibernateUtility.getSessionFactory().openSession();
   session.beginTransaction();

   Word word = new Word();
   Word word1 =new Word();

   Litter litter = new Litter();
   litter.setFullname("bla bla");
   word.setLitter(litter);    
   word1.setLitter(litter); //Here I have to handle one to many relationship

   Set Words =new  HashSet();
   Words.add(word);
   Words.add(word1);
   litter.setWords(words);
   session.save(litter);
   session.save(word);
   session.save(word1);
  session.getTransaction().commit();
  session.close();

But this code giving an exception: JDBCExceptionReporter logExceptions Is the approach which I am using is correct?

Stack trace------------------
INFO: schema update complete
Hibernate: select max(ID) from LITTER
сен 25, 2012 7:33:42 PM org.hibernate.util.JDBCExceptionReporter logExceptions
WARNING: SQL Error: -204, SQLState: 42704
сен 25, 2012 7:33:42 PM org.hibernate.util.JDBCExceptionReporter logExceptions
SEVERE: DB2 SQL Error: SQLCODE=-204, SQLSTATE=42704, SQLERRMC=BIMASH.LITTER, DRIVER=3.64.104
сен 25, 2012 7:33:42 PM org.hibernate.util.JDBCExceptionReporter logExceptions
WARNING: SQL Error: -204, SQLState: 42704
сен 25, 2012 7:33:42 PM org.hibernate.util.JDBCExceptionReporter logExceptions
SEVERE: DB2 SQL Error: SQLCODE=-204, SQLSTATE=42704, SQLERRMC=BIMASH.LITTER, DRIVER=3.64.104
сен 25, 2012 7:33:42 PM org.hibernate.util.JDBCExceptionReporter logExceptions
WARNING: SQL Error: -727, SQLState: 56098
сен 25, 2012 7:33:42 PM org.hibernate.util.JDBCExceptionReporter logExceptions
SEVERE: DB2 SQL Error: SQLCODE=-727, SQLSTATE=56098, SQLERRMC=2;-204;42704;BIMASH.LITTER, DRIVER=3.64.104
Exception in thread "main" org.hibernate.exception.SQLGrammarException: could not fetch initial value for increment generator
    at org.hibernate.exception.SQLStateConverter.convert(SQLStateConverter.java:67)
    at org.hibernate.exception.JDBCExceptionHelper.convert(JDBCExceptionHelper.java:43)
    at org.hibernate.id.IncrementGenerator.getNext(IncrementGenerator.java:107)
    at org.hibernate.id.IncrementGenerator.generate(IncrementGenerator.java:44)
    at org.hibernate.event.def.AbstractSaveEventListener.saveWithGeneratedId(AbstractSaveEventListener.java:99)
    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)
    at Main.main(Main.java:73)

Can you please post the relevant part of the stack trace and the mapping of the association? — Xavi López
– Xavi López, Commented Sep 25, 2012 at 12:56
<hibernate-mapping > <class name="pojopackage.Word" table="Word" schema ="A" > </class></hibernate-mapping> <hibernate-mapping > <class name="pojopackage.Litter" table="Litter" schema ="B" ></class> </hibernate-mapping> how can i display <> tags in the question area? — Olzhas
– Olzhas, Commented Sep 25, 2012 at 13:27
just use the tags in code snippets. Surround them with ` or just select and click code sample. See Markdown help. — Xavi López
– Xavi López, Commented Sep 25, 2012 at 14:04

Community · Accepted Answer · 2017-05-23 11:43:12Z

0

You can define the schema a mapped class belongs to with the schema attribute of the <class> element in the mapping file. Notice this will override the setting in the general <hibernate-mapping>'s schema attribute.

<!-- A is set to be the default schema -->
<hibernate-mapping schema="A">
    <class name="mypackage.Word" table="WORD" >
    ....
    </class>

    <!-- Overriding the schema definition for this class -->
    <class name="mypackage.Litter" table="LITTER" schema="B">
    ....
    </class>
</hibernate-mapping>

The following Hibernate reference chapter might be worth a read: Chapter 5. Basic O/R Mapping, specially the sections about the <hibernate-mapping> and <class> elements.

UPDATE

Seeing the stack trace, it seems that a <generator class="increment"> is being used in the class. If it's the case (it seems so by the select max(ID) from LITTER query), you'll also have to specify the schema in the <generator> so that the issued query transforms into select max(ID) from B.LITTER. You can achieve that with a <param> named schema in the <generator>:

<generator class="increment">
    <param name="schema">B</param>
</generator>

For more details see this almost duplicate question: Hibernate: ID generator using increment and Oracle Schema

edited May 23, 2017 at 11:43

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answered Sep 25, 2012 at 9:58

Xavi López

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8 Comments

Olzhas Over a year ago

I am new to hibernate, therefore should I create two hibernate.cfg.xml? I have created classes through reverse engineering which I have two file Word.java and Word.hbm.xml and Iam using Netbeans. What else files should I change?

Xavi López Over a year ago

If you've used Hibernate Tools to do the reverse engineering, you can specify which schemas to reverse engineer with the <schema-selection> option in the hibernate.reveng.xml file. Alternatively, just use the schema attribute in the <hibernate-mapping> or <class> tag of the Entity that is not in the default schema.

Olzhas Over a year ago

i am grateful for your effort, I have changed schema for hibernate-mapping tag of Word, but its giving an exception, i have updated the question. Can you have a look?

Xavi López Over a year ago

Have you tried adding the schema attribute in the <class> element instead?

Olzhas Over a year ago

yeap, I have putted 'schema' attribute in the '<class>' element. Here the another exception: SQLGrammarException: could not fetch initial value for increment generator

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