HSQ休眠更新问题

Question

我正在尝试更新一个对象，但 hibernate 正在尝试在数据库中新插入该对象，结果我收到了一个违规错误，因为该对象已存在于数据库中。

例如

    Category X= getCategory();//returns me a category which i then update  
    Transaction tx = null;
    try
    {
        tx=session.beginTransaction();
        tx.begin();
        session.Update(X);
        tx.commit();
        return true;
    }
    catch (Exception e)
    {
        tx.rollback();
        e.printStackTrace();
        return false;
    }

我收到此错误，因为该类别已存在于数据库中

org.hibernate.exception.ConstraintViolationException: Could not execute JDBC batch update

我通过使用session.update，hibernate自动更新对象。有谁知道不写sql怎么更新？？

完全错误：

Hibernate: select nextval ('hibernate_sequence')
Hibernate: select nextval ('hibernate_sequence')
Hibernate: select nextval ('hibernate_sequence')
Hibernate: select nextval ('hibernate_sequence')
Hibernate: insert into CATEGORY (CATEGORYNAME, PARENT_CATEGORY_ID, CATEGORYID) values (?, ?, ?)
org.hibernate.exception.ConstraintViolationException: Could not execute JDBC batch update
    at org.hibernate.exception.SQLStateConverter.convert(SQLStateConverter.java:96)
    at org.hibernate.exception.JDBCExceptionHelper.convert(JDBCExceptionHelper.java:66)
    at org.hibernate.jdbc.AbstractBatcher.executeBatch(AbstractBatcher.java:275)
    at org.hibernate.jdbc.AbstractBatcher.prepareStatement(AbstractBatcher.java:114)
    at org.hibernate.jdbc.AbstractBatcher.prepareStatement(AbstractBatcher.java:109)
    at org.hibernate.jdbc.AbstractBatcher.prepareBatchStatement(AbstractBatcher.java:244)
    at org.hibernate.persister.entity.AbstractEntityPersister.insert(AbstractEntityPersister.java:2395)
    at org.hibernate.persister.entity.AbstractEntityPersister.insert(AbstractEntityPersister.java:2858)
    at org.hibernate.action.EntityInsertAction.execute(EntityInsertAction.java:79)
    at org.hibernate.engine.ActionQueue.execute(ActionQueue.java:268)
    at org.hibernate.engine.ActionQueue.executeActions(ActionQueue.java:260)
    at org.hibernate.engine.ActionQueue.executeActions(ActionQueue.java:179)
    at org.hibernate.event.def.AbstractFlushingEventListener.performExecutions(AbstractFlushingEventListener.java:321)
    at org.hibernate.event.def.DefaultFlushEventListener.onFlush(DefaultFlushEventListener.java:51)
    at org.hibernate.impl.SessionImpl.flush(SessionImpl.java:1206)
    at org.hibernate.impl.SessionImpl.managedFlush(SessionImpl.java:375)
    at org.hibernate.transaction.JDBCTransaction.commit(JDBCTransaction.java:137)
    at com.BiddingSystem.server.ServiceImpl.TestSaveCategory(ServiceImpl.java:280)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
    at java.lang.reflect.Method.invoke(Method.java:597)
    at net.sf.gilead.gwt.PersistentRemoteService.processCall(PersistentRemoteService.java:174)
    at com.google.gwt.user.server.rpc.RemoteServiceServlet.processPost(RemoteServiceServlet.java:243)
    at com.google.gwt.user.server.rpc.AbstractRemoteServiceServlet.doPost(AbstractRemoteServiceServlet.java:62)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:637)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
    at org.mortbay.jetty.servlet.ServletHolder.handle(ServletHolder.java:487)
    at org.mortbay.jetty.servlet.ServletHandler.handle(ServletHandler.java:362)
    at org.mortbay.jetty.security.SecurityHandler.handle(SecurityHandler.java:216)
    at org.mortbay.jetty.servlet.SessionHandler.handle(SessionHandler.java:181)
    at org.mortbay.jetty.handler.ContextHandler.handle(ContextHandler.java:729)
    at org.mortbay.jetty.webapp.WebAppContext.handle(WebAppContext.java:405)
    at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152)
    at org.mortbay.jetty.handler.RequestLogHandler.handle(RequestLogHandler.java:49)
    at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152)
    at org.mortbay.jetty.Server.handle(Server.java:324)
    at org.mortbay.jetty.HttpConnection.handleRequest(HttpConnection.java:505)
    at org.mortbay.jetty.HttpConnection$RequestHandler.content(HttpConnection.java:843)
    at org.mortbay.jetty.HttpParser.parseNext(HttpParser.java:647)
    at org.mortbay.jetty.HttpParser.parseAvailable(HttpParser.java:211)
    at org.mortbay.jetty.HttpConnection.handle(HttpConnection.java:380)
    at org.mortbay.io.nio.SelectChannelEndPoint.run(SelectChannelEndPoint.java:395)
    at org.mortbay.thread.QueuedThreadPool$PoolThread.run(QueuedThreadPool.java:488)
Caused by: java.sql.BatchUpdateException: Batch entry 0 insert into CATEGORY (CATEGORYNAME, PARENT_CATEGORY_ID, CATEGORYID) values ('Laptop', '0', '397') was aborted.  Call getNextException to see the cause.
    at org.postgresql.jdbc2.AbstractJdbc2Statement$BatchResultHandler.handleError(AbstractJdbc2Statement.java:2598)
    at org.postgresql.core.v3.QueryExecutorImpl.processResults(QueryExecutorImpl.java:1836)
    at org.postgresql.core.v3.QueryExecutorImpl.execute(QueryExecutorImpl.java:407)
    at org.postgresql.jdbc2.AbstractJdbc2Statement.executeBatch(AbstractJdbc2Statement.java:2737)
    at org.hibernate.jdbc.BatchingBatcher.doExecuteBatch(BatchingBatcher.java:70)
    at org.hibernate.jdbc.AbstractBatcher.executeBatch(AbstractBatcher.java:268)
    ... 41 more

Answer 1

没有看到getCategory() 做什么，很难回答你的问题。根据休眠文档， Session.update 期望被传递一个 detached 实体，这是一个由 Session.load() 或 Session.get() 从之前的会话返回的实体关闭。

事实证明，在正常的休眠使用中，很少需要更新。这是因为 hibernate 可以自动检测对象的变化。这是一个更常见的模式：

Transaction tx = null; try { tx=session.beginTransaction(); tx.begin(); Category X = session.load(Category.class,[categoryId]) X.setXXX(...) // update the category tx.commit(); return true; } catch (Exception e) { tx.rollback(); e.printStackTrace(); return false; }

提交后，hibernate 会知道从 Load 返回的类别已被修改，并会自动向数据库发出更新。

更正式地说，hibernate 将自动检测对持久实体所做的更改，并在事务提交时自动发出 UPDATE。持久实体是从 Session.get、Session.load 或任何会话查询函数返回的任何实体。

可以在此处找到有关持久、分离和瞬态对象的更多信息

http://docs.jboss.org/hibernate/core/3.3/reference/en/html/objectstate.html#objectstate-overview