班级可以查出来，执行Set<Student> s= g.getStudents();查不出内容，控制台提示

Hibernate: 

    select

        students0_.GID as GID4_0_1_,

        students0_.SID as SID1_1_1_,

        students0_.SID as SID1_1_0_,

        students0_.SNAME as SNAME2_1_0_,

        students0_.SEX as SEX3_1_0_ 

    from

        STUDENT students0_ 

    where

        students0_.GID=?

十月 23, 2016 12:21:15 上午 org.hibernate.engine.loading.internal.LoadContexts cleanup

WARN: HHH000100: Fail-safe cleanup (collections) : org.hibernate.engine.loading.internal.CollectionLoadContext@42e3c02a<rs=com.mysql.jdbc.JDBC4ResultSet@70ef6368>

十月 23, 2016 12:21:15 上午 org.hibernate.engine.loading.internal.CollectionLoadContext cleanup

WARN: HHH000160: On CollectionLoadContext#cleanup, localLoadingCollectionKeys contained [1] entries