hibernate延迟加载org.hibernate.LazyInitializationException: failed to lazily initialize a collection of role: com.javakc.hibernate.onetomany.entity.DeptEntity.emp, could not initialize proxy

public static void main(String[] args) {
 
　　DeptEntity dept = getDept("402882e762ae888d0162ae888e420000");

　　//dept.getEmp()得到子表的记录集合
　　System.out.println(dept.getEmp());

}

private static DeptEntity getDept(String did){
　　Session session = sessionFactory.openSession();
　　DeptEntity dept = (DeptEntity)session.get(DeptEntity.class, did);
　　session.close();
　　return dept;
}

运行结果：

Exception in thread "main" org.hibernate.LazyInitializationException: failed to lazily initialize a collection of role: com.javakc.hibernate.onetomany.entity.DeptEntity.emp, could not initialize proxy - no Session
at org.hibernate.collection.internal.AbstractPersistentCollection.throwLazyInitializationException(AbstractPersistentCollection.java:566)
at org.hibernate.collection.internal.AbstractPersistentCollection.withTemporarySessionIfNeeded(AbstractPersistentCollection.java:186)
at org.hibernate.collection.internal.AbstractPersistentCollection.initialize(AbstractPersistentCollection.java:545)
at org.hibernate.collection.internal.AbstractPersistentCollection.read(AbstractPersistentCollection.java:124)
at org.hibernate.collection.internal.PersistentSet.toString(PersistentSet.java:326)
at java.lang.String.valueOf(String.java:2827)
at java.io.PrintStream.println(PrintStream.java:771)
at com.javakc.hibernate.onetomany.action.TestAction.main(TestAction.java:74)

集合延迟加载初始化失败，不能初始化一个代理。就是集合在非一对一对象关系中，为了节省资源是默认延迟加载，而get方法又是非延迟加载，所以在执行完一次数据库查询后就执行session.close();关闭了session，而集合是延迟加载，在使用集合时再加载，此时session已经关闭，所以得不到代理。解决方法：可以在主表的hbm配置文件中，在<set>标签里设置lazy="false"，集合就不延迟加载了，因此在执行get方法时，集合也获取到了，就不会出现延迟加载问题了。