Hi all, I am new to Hibernate. I am entangled with Collection-Mappping.I need some good tutorial having complete example program on Collection Mapping.
Also, i tried the following to test Collection mapping.
I wrote the following POJO class:
I wrote the following class to persist an object of type Book into the MYSQL database running on local host:
The following is the content of my mapping file:
When run the second program, i am getting the following output: log4j:WARN No appenders could be found for logger (org.hibernate.cfg.Environment). log4j:WARN Please initialize the log4j system properly. null Exception in thread "main" java.lang.NullPointerException at roseindia.tutorial.hibernatecollection.BookInsert.main(BookInsert.java:52)
So you are trying to flush a session that is null. So I would assume that something has gone wrong in these two lines:
What other exception messages do you have in your log? Has the SessionFactory been properly configured? Is the DataSource valid and can you connect to the database. [ September 11, 2008: Message edited by: Paul Sturrock ]