Hello ,
i'm using hibernate annotation and my database contain around 800 tables , i have created annotation for all table's using Hibernate reverse engineering .

now i'm trying to fetch data from any table . but i'm getting following error in each case .

%%%% Error Creating SessionFactory %%%%

org.hibernate.AnnotationException: Mixing nullable and non nullable columns in a property is not allowed: org.hibernate.annotation.FixedAssetMeterfixedAssetMaint
at org.hibernate.cfg.Ejb3Column.checkPropertyConsistency(Ejb3Column.java:414)
at org.hibernate.cfg.AnnotationBinder.bindManyToOne(AnnotationBinder.java:1875)
at org.hibernate.cfg.AnnotationBinder.processElementAnnotations(AnnotationBinder.java:1311)
at org.hibernate.cfg.AnnotationBinder.bindClass(AnnotationBinder.java:733)
at org.hibernate.cfg.AnnotationConfiguration.processArtifactsOfType(AnnotationConfiguration.java:498)
at org.hibernate.cfg.AnnotationConfiguration.secondPassCompile(AnnotationConfiguration.java:277)
at org.hibernate.cfg.Configuration.buildSessionFactory(Configuration.java:1286)
at org.hibernate.cfg.AnnotationConfiguration.buildSessionFactory(AnnotationConfiguration.java:915)
at org.hibernate.cfg.HibernateSessionFactory.<clinit>(HibernateSessionFactory.java:32)
at org.hibernate.cfg.First.main(First.java:23)
%%%% Error Creating SessionFactory %%%%

org.hibernate.DuplicateMappingException: Duplicate class/entity mapping org.hibernate.annotation.BudgetRole
at org.hibernate.cfg.Mappings.addClass(Mappings.java:118)
at org.hibernate.cfg.AnnotationBinder.bindClass(AnnotationBinder.java:769)
at org.hibernate.cfg.AnnotationConfiguration.processArtifactsOfType(AnnotationConfiguration.java:498)
at org.hibernate.cfg.AnnotationConfiguration.secondPassCompile(AnnotationConfiguration.java:277)
at org.hibernate.cfg.Configuration.buildSessionFactory(Configuration.java:1286)
at org.hibernate.cfg.AnnotationConfiguration.buildSessionFactory(AnnotationConfiguration.java:915)
at org.hibernate.cfg.HibernateSessionFactory.rebuildSessionFactory(HibernateSessionFactory.java:71)
at org.hibernate.cfg.HibernateSessionFactory.getSession(HibernateSessionFactory.java:54)
at org.hibernate.cfg.First.main(First.java:23)
Exception in thread "main" java.lang.NullPointerException
at org.hibernate.cfg.First.main(First.java:44)


may some one help me to resolve this error.
Thanks in advance.