【06-17】开发中遇到的异常

hibernate：

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bug:

　　Batch update returned unexpected row count from update [0]; actual row count: 0; expected: 1

solution:

　　hibernate在执行save(Object obj)时，如果obj的主键不为空，则会去update而不是save操作，此时如果obj的主键不为空，但是在数据库中查不到时则会抛出该异常，因此save时可以显示将主键字段设为Null。

　　也有可能是有级联关系的对象没有保存过，在save时

bug:

　　a different object with the same identifier value was already associated with the session

solution:

　　

bug:

　　identifier of an instance of ... is alterde from 150 to null

solution:

　　

bug:

　　org.hibernate.MappingException: Unknown entity

solution:

　　我用的是hibernate5，使用sessionFactory=new Configuration().configure().buildSessionFactory();能够获取到sessionFactory但是hibernate却找不到注解的实体类，抛出MappingException，使用以下方法才能够获取到注解类。

 1     public static SessionFactory sessionFactory;
 2     static{
 3 //        Configuration cfg= new Configuration();
 4 //        cfg.addClass(Person.class);
 5 //        cfg.addClass(Phone.class);
 6 //        cfg.addAnnotatedClass(entity.Person.class);
 7 //        cfg.addAnnotatedClass(entity.Phone.class);
 8 //        sessionFactory=new Configuration().configure().buildSessionFactory();
 9         final StandardServiceRegistry registry = new StandardServiceRegistryBuilder()
10                 .configure() // configures settings from hibernate.cfg.xml
11                 .build();
12         try {
13             sessionFactory = new MetadataSources( registry ).buildMetadata().buildSessionFactory();
14         }
15         catch (Exception e) {
16             // The registry would be destroyed by the SessionFactory, but we had trouble building the SessionFactory
17             // so destroy it manually.
18             StandardServiceRegistryBuilder.destroy( registry );
19         }
20         
21     }

 

 

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转载于:https://www.cnblogs.com/achievec/p/5595151.html