hibernate中sessionFactory问题

Question

一对多映射
感觉没错，求解啊！！！

 public class HibernateUtil {
    private static SessionFactory sessionFactory;
    private static Session session;
    static {
        //创建configuration对象，读取hibernate.cfg.xml文件，完成初始化
        Configuration config = new Configuration().configure();
        ServiceRegistry serviceRegistry = new ServiceRegistryBuilder().applySettings(config.getProperties()).buildServiceRegistry();
        sessionFactory = config.buildSessionFactory(serviceRegistry);            //16

    }

    //获取sessionFactory
    public static SessionFactory getSessionFactory() {
        return sessionFactory;
    }

    //获取session对象
    public static Session getSession() {
        session = sessionFactory.openSession();
        return session;
    }

    //关闭会话
    public static void closeSession(Session session) {
        if(session!=null) {
            session.close();
        }
    }

}
public class Test {

    public static void main(String[] args) {
        add();                                                                //14
    }

    //将学生添加到班级
    public static void add() 
    {
        Grade g = new Grade("java一班", "java软件开发一班");
        Student s1 = new Student("张三", "男");
        Student s2 = new Student("慕女神","女");

        g.getStudents().add(s1);
        g.getStudents().add(s2);

        //保存班级、学生信息
        Session session = HibernateUtil.getSession();                    //29
        Transaction transaction = session.beginTransaction();
        session.save(g);
        session.save(s1);
        session.save(s2);
        transaction.commit();
        HibernateUtil.closeSession(session);
    }
}
错误信息：
Exception in thread "main" java.lang.ExceptionInInitializerError
    at com.imooc.entity.Test.add(Test.java:29)
    at com.imooc.entity.Test.main(Test.java:14)
Caused by: org.hibernate.MappingException: Could not get constructor for org.hibernate.persister.entity.SingleTableEntityPersister
    at org.hibernate.persister.internal.PersisterFactoryImpl.create(PersisterFactoryImpl.java:185)
    at org.hibernate.persister.internal.PersisterFactoryImpl.createEntityPersister(PersisterFactoryImpl.java:135)
    at org.hibernate.internal.SessionFactoryImpl.<init>(SessionFactoryImpl.java:385)
    at org.hibernate.cfg.Configuration.buildSessionFactory(Configuration.java:1790)
    at com.imooc.util.HibernateUtil.<clinit>(HibernateUtil.java:16)
    ... 2 more
Caused by: org.hibernate.HibernateException: Unable to instantiate default tuplizer [org.hibernate.tuple.entity.PojoEntityTuplizer]
    at org.hibernate.tuple.entity.EntityTuplizerFactory.constructTuplizer(EntityTuplizerFactory.java:138)
    at org.hibernate.tuple.entity.EntityTuplizerFactory.constructDefaultTuplizer(EntityTuplizerFactory.java:188)
    at org.hibernate.tuple.entity.EntityMetamodel.<init>(EntityMetamodel.java:341)
    at org.hibernate.persister.entity.AbstractEntityPersister.<init>(AbstractEntityPersister.java:507)
    at org.hibernate.persister.entity.SingleTableEntityPersister.<init>(SingleTableEntityPersister.java:146)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source)
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source)
    at java.lang.reflect.Constructor.newInstance(Unknown Source)
    at org.hibernate.persister.internal.PersisterFactoryImpl.create(PersisterFactoryImpl.java:163)
    ... 6 more
Caused by: java.lang.reflect.InvocationTargetException
    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source)
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source)
    at java.lang.reflect.Constructor.newInstance(Unknown Source)
    at org.hibernate.tuple.entity.EntityTuplizerFactory.constructTuplizer(EntityTuplizerFactory.java:135)
    ... 15 more
Caused by: org.hibernate.PropertyNotFoundException: Could not find a getter for student in class com.imooc.entity.Grade
    at org.hibernate.property.BasicPropertyAccessor.createGetter(BasicPropertyAccessor.java:316)
    at org.hibernate.property.BasicPropertyAccessor.getGetter(BasicPropertyAccessor.java:310)
    at org.hibernate.mapping.Property.getGetter(Property.java:321)
    at org.hibernate.tuple.entity.PojoEntityTuplizer.buildPropertyGetter(PojoEntityTuplizer.java:444)
    at org.hibernate.tuple.entity.AbstractEntityTuplizer.<init>(AbstractEntityTuplizer.java:200)
    at org.hibernate.tuple.entity.PojoEntityTuplizer.<init>(PojoEntityTuplizer.java:82)
    ... 20 more

Answer 1

Caused by: org.hibernate.PropertyNotFoundException: Could not find a getter for student in class com.imooc.entity.Grade 这个字段缺少get方法