Session.get拋出異常而不是null

我在程序下運行，並期望hibernate將撥打ObjectNotFoundException撥打load和null致電get。但我在輸出中看不到book : null。Session.get拋出異常而不是null

import org.hibernate.Session; 
import org.hibernate.SessionFactory; 
import org.hibernate.cfg.Configuration; 

public class LoadAndGetTest { 

public static void main(String[] args) { 
    Configuration configuration = new Configuration().configure(); 
    SessionFactory factory = configuration.buildSessionFactory(); 
    Session session = factory.openSession(); 

    try { 
     Book book = (Book) session.load(Book.class, "DOES_NOT_EXIST"); 
    } catch(Exception exception) { 
     exception.printStackTrace(); 
    } 
    Book book = (Book) session.get(Book.class, "DOES_NOT_EXIST"); 
    System.out.println("book : "+ book); 
} 
}

Book.java

import java.util.Date; 
import java.util.List; 

public class Book { 
    private String isbn; 
    private String name; 
    private Publisher publisher; 
    private Date publishDate; 
    private int price; 
    private List chapters; 
    // Getters and Setters 

    public Book() { 
    } 

    public Book(String isbn, String name, Publisher publisher, 
      Date publishDate, int price, List chapters) { 
     super(); 
     this.isbn = isbn; 
     this.name = name; 
     this.publisher = publisher; 
     this.publishDate = publishDate; 
     this.price = price; 
     this.chapters = chapters; 
    } 

    public String getIsbn() { 
     return isbn; 
    } 

    public String getName() { 
     return name; 
    } 
    public Publisher getPublisher() { 
     return publisher; 
    } 
    public Date getPublishDate() { 
     return publishDate; 
    } 
    public int getPrice() { 
     return price; 
    } 
    public List getChapters() { 
     return chapters; 
    } 

    public void setIsbn(String isbn) { 
     this.isbn = isbn; 
    } 

    public void setName(String name) { 
     this.name = name; 
    } 

    public void setPublisher(Publisher publisher) { 
     this.publisher = publisher; 
    } 

    public void setPublishDate(Date publishDate) { 
     this.publishDate = publishDate; 
    } 

    public void setPrice(int price) { 
     this.price = price; 
    } 

    public void setChapters(List chapters) { 
     this.chapters = chapters; 
    } 
}

和book.hbm.xml

<?xml version="1.0" encoding="UTF-8"?> 
<!DOCTYPE hibernate-mapping PUBLIC 
"-//Hibernate/Hibernate Mapping DTD 3.0//EN" 
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd"> 
<hibernate-mapping package="com.chatar.hibernate.receipes.example.domain"> 
    <class name="Book" table="BOOK"> 
     <id name="isbn" type="string" column="ISBN" /> 
     <property name="name" type="string" column="BOOK_NAME" /> 
     <property name="publishDate" type="date" column="PUBLISH_DATE" /> 
     <property name="price" type="int" column="PRICE" /> 
    </class> 
</hibernate-mapping>

而且

hibernate.cfg.xml 

<?xml version="1.0" encoding="UTF-8"?> 
<!DOCTYPE hibernate-configuration PUBLIC 
"-//Hibernate/Hibernate Configuration DTD 3.0//EN" 
"http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd"> 
<hibernate-configuration> 
    <session-factory> 
     <property name="connection.driver_class"> 
      org.apache.derby.jdbc.EmbeddedDriver 
     </property> 
     <property name="connection.url">jdbc:derby://localhost:1527/BookShopDB</property> 
     <property name="connection.username">book</property> 
     <property name="connection.password">book</property> 
     <property name="dialect">org.hibernate.dialect.DerbyDialect</property> 
     <mapping resource="com/chatar/hibernate/receipes/example/domain/book.hbm.xml" /> 
    </session-factory> 
</hibernate-configuration>

而這裏的例外

950 [main] INFO org.hibernate.event.def.DefaultLoadEventListener - Error performing load command 
org.hibernate.ObjectNotFoundException: No row with the given identifier exists: [com.chatar.hibernate.receipes.example.domain.Book#DOES_NOT_EXIST] 
    at org.hibernate.impl.SessionFactoryImpl$2.handleEntityNotFound(SessionFactoryImpl.java:449) 
    at org.hibernate.event.def.DefaultLoadEventListener.returnNarrowedProxy(DefaultLoadEventListener.java:320) 
    at org.hibernate.event.def.DefaultLoadEventListener.proxyOrLoad(DefaultLoadEventListener.java:277) 
    at org.hibernate.event.def.DefaultLoadEventListener.onLoad(DefaultLoadEventListener.java:152) 
    at org.hibernate.impl.SessionImpl.fireLoad(SessionImpl.java:1080) 
    at org.hibernate.impl.SessionImpl.get(SessionImpl.java:997) 
    at org.hibernate.impl.SessionImpl.get(SessionImpl.java:990) 
    at com.chatar.hibernate.receipes.example.LoadAndGetTest.main(LoadAndGetTest.java:21) 
Exception in thread "main" org.hibernate.ObjectNotFoundException: No row with the given identifier exists: [com.chatar.hibernate.receipes.example.domain.Book#DOES_NOT_EXIST] 
    at org.hibernate.impl.SessionFactoryImpl$2.handleEntityNotFound(SessionFactoryImpl.java:449) 
    at org.hibernate.event.def.DefaultLoadEventListener.returnNarrowedProxy(DefaultLoadEventListener.java:320) 
    at org.hibernate.event.def.DefaultLoadEventListener.proxyOrLoad(DefaultLoadEventListener.java:277) 
    at org.hibernate.event.def.DefaultLoadEventListener.onLoad(DefaultLoadEventListener.java:152) 
    at org.hibernate.impl.SessionImpl.fireLoad(SessionImpl.java:1080) 
    at org.hibernate.impl.SessionImpl.get(SessionImpl.java:997) 
    at org.hibernate.impl.SessionImpl.get(SessionImpl.java:990) 
    at com.chatar.hibernate.receipes.example.LoadAndGetTest.main(LoadAndGetTest.java:21)

但是如果我刪除調用它來加載，然後我可以在輸出中看到book : null。

LoadAndGetTest.java無需調用load

public class LoadAndGetTest { 

    public static void main(String[] args) { 
     Configuration configuration = new Configuration().configure(); 
     SessionFactory factory = configuration.buildSessionFactory(); 
     Session session = factory.openSession(); 

     Book book = (Book) session.get(Book.class, "DOES_NOT_EXIST"); 
     System.out.println("book : "+ book); 
    } 
}

輸出

書：空

此外，當我叫get前兩次和load後，可看到一贈印之前，但而不是後一個。

這裏的LoadAndGetTest再次

public class LoadAndGetTest { 

    public static void main(String[] args) { 
     Configuration configuration = new Configuration().configure(); 
     SessionFactory factory = configuration.buildSessionFactory(); 
     Session session = factory.openSession(); 

     Book book1 = (Book) session.get(Book.class, "DOES_NOT_EXIST"); 
     System.out.println("book : "+ book1); 

     try { 
      Book book = (Book) session.load(Book.class, "DOES_NOT_EXIST"); 
     } catch(Exception exception) { 
      exception.printStackTrace(); 
     } 
     Book book = (Book) session.get(Book.class, "DOES_NOT_EXIST"); 
     System.out.println("book : "+ book); 
    } 
}

輸出

book : null 
1292 [main] INFO org.hibernate.event.def.DefaultLoadEventListener - Error performing load command 
org.hibernate.ObjectNotFoundException: No row with the given identifier exists: [com.chatar.hibernate.receipes.example.domain.Book#DOES_NOT_EXIST] 
    at org.hibernate.impl.SessionFactoryImpl$2.handleEntityNotFound(SessionFactoryImpl.java:449) 
    at org.hibernate.event.def.DefaultLoadEventListener.returnNarrowedProxy(DefaultLoadEventListener.java:320) 
    at org.hibernate.event.def.DefaultLoadEventListener.proxyOrLoad(DefaultLoadEventListener.java:277) 
    at org.hibernate.event.def.DefaultLoadEventListener.onLoad(DefaultLoadEventListener.java:152) 
    at org.hibernate.impl.SessionImpl.fireLoad(SessionImpl.java:1080) 
    at org.hibernate.impl.SessionImpl.get(SessionImpl.java:997) 
    at org.hibernate.impl.SessionImpl.get(SessionImpl.java:990) 
    at com.chatar.hibernate.receipes.example.LoadAndGetTest.main(LoadAndGetTest.java:24) 
Exception in thread "main" org.hibernate.ObjectNotFoundException: No row with the given identifier exists: [com.chatar.hibernate.receipes.example.domain.Book#DOES_NOT_EXIST] 
    at org.hibernate.impl.SessionFactoryImpl$2.handleEntityNotFound(SessionFactoryImpl.java:449) 
    at org.hibernate.event.def.DefaultLoadEventListener.returnNarrowedProxy(DefaultLoadEventListener.java:320) 
    at org.hibernate.event.def.DefaultLoadEventListener.proxyOrLoad(DefaultLoadEventListener.java:277) 
    at org.hibernate.event.def.DefaultLoadEventListener.onLoad(DefaultLoadEventListener.java:152) 
    at org.hibernate.impl.SessionImpl.fireLoad(SessionImpl.java:1080) 
    at org.hibernate.impl.SessionImpl.get(SessionImpl.java:997) 
    at org.hibernate.impl.SessionImpl.get(SessionImpl.java:990) 
    at com.chatar.hibernate.receipes.example.LoadAndGetTest.main(LoadAndGetTest.java:24)

來源

2015-07-02 TheCodingFrog

好吧，得問：你肯定**'書：null'是不是在第一種情況下？請記住，異常堆棧跟蹤去'System.err'和要打印'書：對'System.out' null'。這是可能的，由於緩衝等，那'書：null'可能出現* *前的異常堆棧跟蹤，因爲這兩個流不一定同步。 – dcsohl

是的 - 我確定它不在那裏。我知道兩個流可能不同步，但我期望'book：null'被打印出來 – TheCodingFrog

確定。我是能夠檢查源代碼和以下堆棧跟蹤後，要弄清楚：

如果你打電話呼叫負載後得到看來，Hibernate使用代理對象。這裏的電話序列，

1. Book book = (Book) session.get(Book.class, "DOES_NOT_EXIST"); 
2. SessionImpl.get 
    public Object get(Class entityClass, Serializable id) throws HibernateException { 
     return get(entityClass.getName(), id); 
    } 
3. fireLoad(event, LoadEventListener.GET); 
4. DefaultLoadEventListener.onLoad 
//return a proxy if appropriate 
      if (event.getLockMode() == LockMode.NONE) { 
       event.setResult(proxyOrLoad(event, persister, keyToLoad, loadType)); 
      } 
5. DefaultLoadEventListener.proxyOrLoad 
if (proxy != null) { 
      return returnNarrowedProxy(event, persister, keyToLoad, options, persistenceContext, proxy); 
     } 
6. DefaultLoadEventListener.returnNarrowedProxy 
if (!options.isAllowProxyCreation()) { 
      impl = load(event, persister, keyToLoad, options); 
      if (impl == null) { 
       event.getSession().getFactory().getEntityNotFoundDelegate().handleEntityNotFound(persister.getEntityName(), keyToLoad.getIdentifier()); 
      } 
     } 
7. SessionFactoryImpl.handleEntityNotFound 
// EntityNotFoundDelegate 
     EntityNotFoundDelegate entityNotFoundDelegate = cfg.getEntityNotFoundDelegate(); 
     if (entityNotFoundDelegate == null) { 
      entityNotFoundDelegate = new EntityNotFoundDelegate() { 
       public void handleEntityNotFound(String entityName, Serializable id) { 
        throw new ObjectNotFoundException(id, entityName); 
       } 
       public boolean isEntityNotFoundException(RuntimeException exception) { 
        return ObjectNotFoundException.class.isInstance(exception); 
       } 
      }; 
     }

來源

2015-07-02 15:11:23 TheCodingFrog

Session.get拋出異常而不是null

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