Java hibernate将对象保存在一个数据库中的不同模式中

Question

我正在使用DB2数据库和hibernate框架。有两个表，如Word和Litter，它们的关系是一对多。

>

架构A：

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

Table Litter ID,
Short_Name,
Long_Name.

 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();

但是这段代码给出了一个异常：JDBCExceptionReporter logExceptions是我正在使用的方法吗？

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)

Answer 1

可以使用映射文件中 元素的schema属性定义映射类所属的架构。注意，这将覆盖常规 的schema属性中的设置。

<!-- 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>

下面的Hibernate参考章节可能值得一读：第5章。基本的O/R映射，特别是关于 和 元素的部分。

看到堆栈跟踪，类中似乎正在使用 。如果是这样（select max(ID)from litter查询似乎是这样），您还必须在 中指定模式，以便发出的查询转换为select max(ID)from b.litter。您可以在 中使用名为架构的来实现此目的：

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

有关更多详细信息，请参阅这个几乎重复的问题：使用增量和Oracle模式的hibernate：ID生成器