I wrote a simple application to parse an rss feed and store it into database. I am using Hibernate mapping to store the rss data objects into into mysql DB.

The application worked fine until I changed the application to use Threads. After implementing threads I have started getting the following errors:

[java] Exception in thread "ReaderThread Number4" java.lang.NullPointerException
[java] 1119438564
[java] at org.hibernate.cache.impl.bridge.RegionFactoryCacheProviderBridge.nextTimestamp(RegionFactoryCacheProviderBridge.java:85)
[java] 1119438564
[java] at org.hibernate.impl.SessionFactoryImpl.openSession(SessionFactoryImpl.java:557)
[java] Title=Coffee Table (Trussville) $50
[java] at org.hibernate.context.ThreadLocalSessionContext.buildOrObtainSession(ThreadLocalSessionContext.java:142)
[java] 1119487285
[java] at org.hibernate.context.ThreadLocalSessionContext.currentSession(ThreadLocalSessionContext.java:103)
[java] 1119487285
[java] at org.hibernate.impl.SessionFactoryImpl.getCurrentSession(SessionFactoryImpl.java:574)
[java] at com.closebyme.feeds.reader.CraigslistFeed.createPosting(Unknown Source)
[java] at com.closebyme.feeds.reader.CraigslistFeed.processFeed(Unknown Source)
[java] at com.closebyme.craigslist.manager.CraigslistManager$ReaderThread.run(Unknown Source)
[java] at java.lang.Thread.run(Thread.java:595)
[java] Exception in thread "ReaderThread Number1" java.lang.NullPointerException
[java] at org.hibernate.cache.impl.bridge.RegionFactoryCacheProviderBridge.nextTimestamp(RegionFactoryCacheProviderBridge.java:85)
[java] at org.hibernate.impl.SessionFactoryImpl.openSession(SessionFactoryImpl.java:557)
[java] at org.hibernate.context.ThreadLocalSessionContext.buildOrObtainSession(ThreadLocalSessionContext.java:142)
[java] at org.hibernate.context.ThreadLocalSessionContext.currentSession(ThreadLocalSessionContext.java:103)
[java] at org.hibernate.impl.SessionFactoryImpl.getCurrentSession(SessionFactoryImpl.java:574)


I have been trying to find good examples on implementing multi-threaded application using hibernate but I haven't been able to find good examples. I am not sure if there are specific caveats or guidelines for implementing multithreaded apps with hibernate.



Need help with Hibernate? Read this first:
http://www.hibernate.org/ForumMailingli ... AskForHelp

Hibernate version:

Mapping documents:

Code between sessionFactory.openSession() and session.close():

Full stack trace of any exception that occurs:

Name and version of the database you are using:

The generated SQL (show_sql=true):

Debug level Hibernate log excerpt:


Problems with Session and transaction handling?

Read this: http://hibernate.org/42.html

How you have implemented multithreaded. Send me your code then i will be able to help you.

getCurrentSession gets the Session for the current thread; when using multiple threads you should make sure that each thread is opening it's own Session, don't share them. Also it's not a good idea to transfer attached objects to another thread, make sure you detach your object graph before handing it over to another thread.

If you need to "preload" some information for other threads make sure to configure proper second level cache, if the preloading thread is making the same queries that the other thread is going to do you won't hit the database a second time.