Manipulating the synchronization of entity beans and datastores

We can indicating that a particular EJB type should not synchronize its state to persistent storage prior to each findBy invocation by using environment variables or a marker interface.

 

About this task

There are two options available for indicating that a particular EJB type should not synchronize its state to persistent storage prior to each findBy invocation:

• Set an EJB environment variable within the bean's deployment descriptor
• Have the bean implementation class implement a marker interface. This second technique is especially useful if you have a number of bean implementations that all extend a single root class; in this case we can have the root class implement the marker interface, causing all beans that extend this class to inherit the behavior as well.

 

Procedure

• To use the EJB environment variable technique, edit the EJB deployment descriptor using any standard Java 2, Enterprise Edition (J2EE) development tool. Use the following steps as a guide. (For information on your tool options, consult the Assembly tools article.)
  1. Start the tool.
  2. Select the EJB deployment descriptor of the bean you want to work with.
  3. Create an EJB environment variable with the name com/ibm/websphere/ejbcontainer/DisableFlushBeforeFind.
  4. Set the type of this variable to java.lang.Boolean.
  5. Set the value to True to prevent the pre-find synchronization, or False to enable the default behavior.
  6. Save your changes.
• To use a marker interface, code your bean implementation class to implement the com.ibm.websphere.ejbcontainer.DisableFlushBeforeFind interface. The bean implementation class need not directly implement the interface; any parent class can implement the interface. See the com.ibm.websphere.ejbcontainer package in the Reference > Developer > API documentation section of the information center.

  Ensuring data integrity for queries performed during a transaction

  If you choose to disable the automatic pre-find synchronization for certain bean types, it is very important that your application use other means to ensure that queries performed during the transaction are not performed on data that may no longer be valid. We can use the flushCache method on the com.ibm.websphere.ejbcontainer.EJBContextExtension class (an extension of javax.ejb.EJBContext) to perform a manual synchronization to persistent storage at application-defined times. For more information on EJBContextExtension and its related classes SessionContextExtension, EntityContextExtension and MessageDrivenContextExtension, see the com.ibm.websphere.ejbcontainer package in the Reference > Developer > API documentation section of the information center.

 

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