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TransactionAwareSessionAdapter (Spring Framework API 2.1) - Spring Framework 2.1.0 API 文档英文版

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org.springframework.orm.toplink.support
Class TransactionAwareSessionAdapter

java.lang.Object
  org.springframework.orm.toplink.support.TransactionAwareSessionAdapter

All Implemented Interfaces:

FactoryBean

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public class TransactionAwareSessionAdapter
extends Object
implements FactoryBean

This adapter FactoryBean takes a TopLink SessionFactory and exposes a corresponding transaction-aware TopLink Session as bean reference.

This adapter bean will usually be defined in front of a Spring LocalSessionFactoryBean, to allow for passing Session references to DAOs that expect to work on a raw TopLink Session. Your DAOs can then, for example, access the currently active Session and UnitOfWork via Session.getActiveSession() and Session.getActiveUnitOfWork(), respectively.

The main advantage of this proxy is that it allows DAOs to work with a plain TopLink Session reference, while still participating in Spring's (or a J2EE server's) resource and transaction management. DAOs will only rely on the TopLink API in such a scenario, without any Spring dependencies.

It is usually preferable to write your TopLink-based DAOs with Spring's TopLinkTemplate, offering benefits such as consistent data access exceptions instead of TopLinkExceptions at the DAO layer. However, Spring's resource and transaction management (and Dependency Injection) will work for DAOs written against the plain TopLink API too.

Of course, you can still access the target TopLink SessionFactory even when your DAOs go through this adapter, by defining a bean reference that points directly at your target SessionFactory bean.

Note that the actual creation of a transaction-aware TopLink Session is available on the TopLink SessionFactory itself. This adapter FactoryBean is just a convenient way to expose such a Session in a declarative fashion.

Since:

1.2

Author:

Juergen Hoeller

See Also:

LocalSessionFactoryBean, SessionFactory.createTransactionAwareSession(), Session.getActiveSession(), Session.getActiveUnitOfWork()

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Constructor Summary
TransactionAwareSessionAdapter()

 

Method Summary
Object	getObject()           Return an instance (possibly shared or independent) of the object managed by this factory.
Class	getObjectType()           Return the type of object that this FactoryBean creates, or null if not known in advance.
boolean	isSingleton()           Is the object managed by this factory a singleton?
void	setSessionFactory(SessionFactory sessionFactory)           Set the SessionFactory that this adapter is supposed to expose a transaction-aware TopLink Session for.

 

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

 

Constructor Detail

TransactionAwareSessionAdapter

public TransactionAwareSessionAdapter()

Method Detail

setSessionFactory

public void setSessionFactory(SessionFactory sessionFactory)

Set the SessionFactory that this adapter is supposed to expose a transaction-aware TopLink Session for. This should be the raw SessionFactory, as accessed by TopLinkTransactionManager.

See Also:

TopLinkTransactionManager

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getObject

public Object getObject()

Description copied from interface: FactoryBean

Return an instance (possibly shared or independent) of the object managed by this factory.

As with a BeanFactory, this allows support for both the Singleton and Prototype design pattern.

If this FactoryBean is not fully initialized yet at the time of the call (for example because it is involved in a circular reference), throw a corresponding FactoryBeanNotInitializedException.

As of Spring 2.0, FactoryBeans are allowed to return null objects. The factory will consider this as normal value to be used; it will not throw a FactoryBeanNotInitializedException in this case anymore. FactoryBean implementations are encouraged to throw FactoryBeanNotInitializedException themselves now, as appropriate.

Specified by:

getObject in interface FactoryBean

Returns:

an instance of the bean (can be null)

See Also:

FactoryBeanNotInitializedException

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getObjectType

public Class getObjectType()

Description copied from interface: FactoryBean

Return the type of object that this FactoryBean creates, or null if not known in advance.

This allows one to check for specific types of beans without instantiating objects, for example on autowiring.

In the case of implementations that are creating a singleton object, this method should try to avoid singleton creation as far as possible; it should rather estimate the type in advance. For prototypes, returning a meaningful type here is advisable too.

This method can be called before this FactoryBean has been fully initialized. It must not rely on state created during initialization; of course, it can still use such state if available.

NOTE: Autowiring will simply ignore FactoryBeans that return null here. Therefore it is highly recommended to implement this method properly, using the current state of the FactoryBean.

Specified by:

getObjectType in interface FactoryBean

Returns:

the type of object that this FactoryBean creates, or null if not known at the time of the call

See Also:

ListableBeanFactory.getBeansOfType(java.lang.Class)

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isSingleton

public boolean isSingleton()

Description copied from interface: FactoryBean

Is the object managed by this factory a singleton? That is, will FactoryBean.getObject() always return the same object (a reference that can be cached)?

NOTE: If a FactoryBean indicates to hold a singleton object, the object returned from getObject() might get cached by the owning BeanFactory. Hence, do not return true unless the FactoryBean always exposes the same reference.

The singleton status of the FactoryBean itself will generally be provided by the owning BeanFactory; usually, it has to be defined as singleton there.

NOTE: This method returning false does not necessarily indicate that returned objects are independent instances. An implementation of the extended SmartFactoryBean interface may explicitly indicate independent instances through its SmartFactoryBean.isPrototype() method. Plain FactoryBean implementations which do not implement this extended interface are simply assumed to always return independent instances if the isSingleton() implementation returns false.

Specified by:

isSingleton in interface FactoryBean

Returns:

if the exposed object is a singleton

See Also:

FactoryBean.getObject(), SmartFactoryBean.isPrototype()

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