我在Netbeans中设置了一个项目,创建了一个脚本,用javadb建立了一个新的数据库.我可以通过gui连接到它 – 显示表内容等,但当我运行一个应用程序时：

EntityManager em = Persistence.createEntityManagerFactory("lab5PU").createEntityManager();

我得到这个很长的例外：

[EL Info]: 2013-04-05 21:40:45.554--ServerSession(1198260109)--EclipseLink, version: Eclipse Persistence Services - 2.3.0.v20110604-r9504

[EL Severe]: 2013-04-05 21:40:45.574--ServerSession(1198260109)--Local Exception Stack:

Exception [EclipseLink-4003] (Eclipse Persistence Services - 2.3.0.v20110604-r9504): org.eclipse.persistence.exceptions.DatabaseException

Exception in thread "AWT-EventQueue-0" javax.persistence.PersistenceException: Exception [EclipseLink-4003] (Eclipse Persistence Services - 2.3.0.v20110604-r9504): org.eclipse.persistence.exceptions.DatabaseException

Exception Description: Configuration error. Class [org.apache.derby.jdbc.ClientDriver] not found.

Exception Description: Configuration error. Class [org.apache.derby.jdbc.ClientDriver] not found.

at org.eclipse.persistence.exceptions.DatabaseException.configurationErrorClassNotFound(DatabaseException.java:82)

我可以在服务的驱动程序部分看到javadb驱动程序,所以我不知道错误是什么.

编辑：persistance.xml按要求：

org.eclipse.persistence.jpa.PersistenceProvider

lab5.Colleagues