Application profiling tasks
Tasks are named units of work. They are the mechanism by which the runtime environment determines which access intent policies to apply when an entity bean's data is loaded from the back end system.
Application profiles enable developers to configure an entity bean with multiple access intent policies; if there are n instances of profiles in a given application, each bean can be configured with as many as n access intent policies.
A task is associated with a transaction or an ActivitySession at the initiation of the unit of work. The task, which cannot change for the lifetime of the unit of work, is always available anywhere within the scope of that unit of work to apply the access intent policy configured for that particular unit of work.
If an enterprise application is configured to use application profiling in any part of the application, then application profiling is active and method-level access intent configurations are ignored when units of works are associated with known-to-application tasks.
If an entity bean is loaded in a unit of work that is not associated with a task, or is associated with a task that is unassociated with an application profile, the default bean-level access intent or the method-level access intent configuration is applied. If a unit of work is associated with a task that is configured with an application profile, the bean-level access intent configuration within the appropriate application profile is applied.
The application profile configuration is application scope configuration data. If any enterprise Javabean (EJB) module contains an application profile configuration, all other EJB modules are implicitly regulated by the Application Profiling service even if they do not contain application profile configuration data.
For example, an application has two EJB modules: EJBModule1 and EJBModule2.
The EJBModule1 has an application profile named AppProfile1. This AppProfile1 is registered by a task named task1. This task1 becomes a known-to-application task and is honored when associated with a unit of work within this application. With the presence of any known-to-application task, method level access intent configurations are ignored and only bean level access intent configurations are applied.
The EJBModule2 contains no application profile configuration data. All entity beans are not configured with bean level access intent explicitly, but some methods have method level access intent configurations. If an entity bean in the EJBModule2 is loaded in a unit of work that is associated with task1, the bean-level access intent configuration is applied and method level access intent configuration is ignored. Because the bean level access intent is not set explicitly, the default bean level access intent, which is wsPessimisticUpdate-WeakestLockAtLoad, is applied.
The active task depends upon the current unit of work mechanism. If the current unit of work is a global transaction, then the task is the name associated with that transaction. If the global transaction was not named when it was initiated, then there is no active task anywhere in the scope of that transaction.
If the current unit of work is a local transaction associated with an ActivitySession, then the task is the name associated with that ActivitySession. If the ActivitySession was not named when it was initiated, then there is no active task for any local transaction bound to that ActivitySession. If the current unit of work is a local transaction that is not associated with an ActivitySession, then the task is the name associated with that local transaction. If the local transaction was not associated with a task when the local transaction was initiated, then there is no active task for the duration of that local transaction. In other words, the active task is the task associated with the unit of work on the thread that is coordinating database resources. If the controlling unit of work was not associated with a task when that unit of work was initiated, then there is no active task in the scope of that unit of work.
For example, consider a school district application that calls through a session bean in order to interact with student records. One method on the session bean allows administrators to modify the students' records; another method supports student requests to view their own records. Without application profiling, the two tasks would operate anonymously and the runtime environment would be unable to distinguish work operating on behalf of one task or the other. To optimize the application, a developer can configure one of the methods on the session bean with the task "updateRecords" and the other method on the session bean with the task "readRecords". When registered with an application profile that has the student bean configured with the appropriate locking access intent, the "updateRecords" task is assured that it is not unnecessarily blocking transactions that need to only read the records. For more information about the relationships between tasks and units of work, see Tasks and units of work considerations.
Tasks can be configured to be managed by the container or to be programmatically established by the application. Container managed tasks can be configured on servlets, JavaServer Pages files, application clients, and the methods of EJB. Configured container-managed tasks are only associated with units of work that the container initiates after the task name is set. Application managed tasks can be configured on all J2EE components. In the case of enterprise beans they must be bean managed transactions."
Best practice: If you select the 5.x Compatibility
Mode attribute on the Application Profile Service's console page, then tasks
configured on J2EE 1.3 applications are not necessarily associated with units
of work and can arbitrarily be applied and overridden. This is not a recommended
mode of operation and can lead to unexpected deadlocks during database access.
Tasks are not communicated on requests between applications that are running
under the Application Profiling 5.x Compatibility Mode and applications that
are not running under the compatibility mode.
For a Version
6.x client to interact with applications run under the Application Profiling
5.x Compatibility Mode, set the appprofileCompatibility system
property to true in the client process. You can do this by specifying
the -CCDappprofileCompatibility=true option when invoking the launchClient command.
bprac
Related concepts
Application profiles
Tasks and units of work considerations
Related tasks
Automatically configuring application profiles and tasks
Use the TaskNameManager interface
Configure container-managed tasks for application clients
Configure container-managed tasks for Web components
Configure container-managed tasks for Enterprise JavaBeans
Configure application-managed tasks for application clients
Configure application-managed tasks for Web components
Configure application-managed tasks for Enterprise JavaBeans