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TransactionAwarePersistenceManagerFactoryProxy (Spring Framework API 2.0) - Spring Framework 2.0.5 API 文档英文版

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org.springframework.orm.jdo
Class TransactionAwarePersistenceManagerFactoryProxy

java.lang.Object
  org.springframework.orm.jdo.TransactionAwarePersistenceManagerFactoryProxy

All Implemented Interfaces:

FactoryBean

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public class TransactionAwarePersistenceManagerFactoryProxy
extends Object
implements FactoryBean

Proxy for a target JDO PersistenceManagerFactory, returning the current thread-bound PersistenceManager (the Spring-managed transactional PersistenceManager or a the single OpenPersistenceManagerInView PersistenceManager) on getPersistenceManager(), if any.

Essentially, getPersistenceManager() calls get seamlessly forwarded to PersistenceManagerFactoryUtils.getPersistenceManager(javax.jdo.PersistenceManagerFactory, boolean). Furthermore, PersistenceManager.close calls get forwarded to PersistenceManagerFactoryUtils.releasePersistenceManager(javax.jdo.PersistenceManager, javax.jdo.PersistenceManagerFactory).

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

Note that the behavior of this proxy matches the behavior that the JDO spec defines for a PersistenceManagerFactory as exposed by a JCA connector, when deployed in a J2EE server. Hence, DAOs could seamlessly switch between a JNDI PersistenceManagerFactory and this proxy for a local PersistenceManagerFactory, receiving the reference through Dependency Injection. This will work without any Spring API dependencies in the DAO code!

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

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

Since:

1.2

Author:

Juergen Hoeller

See Also:

PersistenceManagerFactory.getPersistenceManager(), PersistenceManager.close(), PersistenceManagerFactoryUtils.getPersistenceManager(javax.jdo.PersistenceManagerFactory, boolean), PersistenceManagerFactoryUtils.releasePersistenceManager(javax.jdo.PersistenceManager, javax.jdo.PersistenceManagerFactory)

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Constructor Summary
TransactionAwarePersistenceManagerFactoryProxy()

 

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.
javax.jdo.PersistenceManagerFactory	getTargetPersistenceManagerFactory()           Return the target JDO PersistenceManagerFactory that this proxy delegates to.
protected  boolean	isAllowCreate()           Return whether the PersistenceManagerFactory proxy is allowed to create a non-transactional PersistenceManager when no transactional PersistenceManager can be found for the current thread.
boolean	isSingleton()           Is the object managed by this factory a singleton?
void	setAllowCreate(boolean allowCreate)           Set whether the PersistenceManagerFactory proxy is allowed to create a non-transactional PersistenceManager when no transactional PersistenceManager can be found for the current thread.
void	setTargetPersistenceManagerFactory(javax.jdo.PersistenceManagerFactory target)           Set the target JDO PersistenceManagerFactory that this proxy should delegate to.

 

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

 

Constructor Detail

TransactionAwarePersistenceManagerFactoryProxy

public TransactionAwarePersistenceManagerFactoryProxy()

Method Detail

setTargetPersistenceManagerFactory

public void setTargetPersistenceManagerFactory(javax.jdo.PersistenceManagerFactory target)

Set the target JDO PersistenceManagerFactory that this proxy should delegate to. This should be the raw PersistenceManagerFactory, as accessed by JdoTransactionManager.

See Also:

JdoTransactionManager

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getTargetPersistenceManagerFactory

public javax.jdo.PersistenceManagerFactory getTargetPersistenceManagerFactory()

Return the target JDO PersistenceManagerFactory that this proxy delegates to.

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setAllowCreate

public void setAllowCreate(boolean allowCreate)

Set whether the PersistenceManagerFactory proxy is allowed to create a non-transactional PersistenceManager when no transactional PersistenceManager can be found for the current thread.

Default is "true". Can be turned off to enforce access to transactional PersistenceManagers, which safely allows for DAOs written to get a PersistenceManager without explicit closing (i.e. a PersistenceManagerFactory.getPersistenceManager() call without corresponding PersistenceManager.close() call).

See Also:

PersistenceManagerFactoryUtils.getPersistenceManager(javax.jdo.PersistenceManagerFactory, boolean)

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isAllowCreate

protected boolean isAllowCreate()

Return whether the PersistenceManagerFactory proxy is allowed to create a non-transactional PersistenceManager when no transactional PersistenceManager can be found for the current thread.

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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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