Network Deployment (Distributed operating systems), v8.0 > Administer applications and their environment > Administer Work area > Manage local work with a work area

Manage local work with a work area

Be sure that your client has a reference to the UserWorkArea interface, as described in the Accessing the UserWorkArea partition topic, or a reference to a user defined partition, as defined in the Accessing a user defined work area partition topic. The following steps use the UserWorkArea partition as an illustration. However a user defined partition can be used in the exact same way.

In a business application that uses work areas, server objects typically retrieve the work area properties and use them to guide local work.

Procedure

1. Retrieve the name of the active work area to determine whether the calling thread is associated with a work area.

   Applications use the getName method on the UserWorkArea interface to retrieve the name of the current work area. If the thread is not associated with a work area, the getName method returns null. In the following code example, the name of the work area corresponds to the name of the class in which the work area was begun.

   public class SimpleSampleBeanImpl implements SessionBean {
   
       ...
   
       public String [] test() {
          // Get the work-area reference from JNDI.
          ...
   
          // Retrieve the name of the work area. In this example,
   
         // the name is used to identify the class in which the
          // work area was begun.
          String invoker = userWorkArea.getName();
          ...
   
   }
   

2. Ovveride work area properties. Server objects can override client work area properties by creating their own, nested work area. Refer to the Overriding work area properties article for more information.
3. Retrieve properties from a work area by using the get method.

   The get method is intentionally lightweight; there are no declared exceptions to handle. If there is no active work area, or if there is no such property set in the current work area, the get method returns null.

   The get method can raise a NotSerializableError in the relatively rare scenario in which CORBA clients set composed data types and invoke enterprise-bean interfaces.

   The following example shows the retrieval of the site-identifier and priority properties by the SimpleSampleBean. Notice that one property was set into an outer work area by the client and the other property was set into the nested work area by the server-side bean; the nesting is transparent to the retrieval of the properties.

   public class SimpleSampleBeanImpl implements SessionBean {
   
       public String [] test() {
         ...
   
         // Begin a nested work area.
         userWorkArea.begin("SimpleSampleBean");
         try {
           userWorkArea.set("company",
                            SimpleSampleCompany.London_Development);
         }
         catch (NotOriginator e) {
         }
   
         SimpleSampleCompany company =
            (SimpleSampleCompany) userWorkArea.get("company");
         SimpleSamplePriority priority =
            (SimpleSamplePriority) userWorkArea.get("priority");
          ...
   
   }
   
   
   

4. Optional: Retrieve a list of all the keys visible from a work area.

   The UserWorkArea interface provides the retrieveAllKeys method for retrieving a list of all the keys visible from a work area. This method takes no arguments and returns an array of strings. The retrieveAllKeys method returns null if there is no work area associated with the thread. If there is an associated work area that does not contain any properties, the method returns an array of size 0.

5. Query the mode of a work area property using the getMode method.

   The UserWorkArea interface provides the getMode method determine the mode of a specific property. This method takes the property's key as an argument and returns the mode as a PropertyModeType object. If the specified key does not exist in the work area, the method returns PropertyModeType.normal, indicating that the property can be set and removed without error.

6. Optional: Delete a work area property.

   The UserWorkArea interface provides the remove method to delete a property from the current scope of a work area. If the property was initially set in the current scope, removing it deletes the property. If the property was initially set in an enclosing work area, removing it deletes the property until the current scope is completed. When the current work area is completed, the deleted property is restored.

   The remove method takes the property's key as an argument. Only properties with the modes normal and read-only can be removed. Attempting to remove a fixed property creates the PropertyFixed exception. Attempting to remove properties in work areas that originated in other processes creates the NotOriginator exception.

Example

The server side of the SimpleSample application example, which is included in the Developing applications that use work areas topic, accepts remote invocations from clients. With each remote call, the server also gets a work area from the client if the client has created one. The work area is propagated transparently. None of the remote methods includes the work area on its argument list.

In the example application, the server objects use the work area interface for demonstration purposes only. For example, the SimpleSampleBean intentionally attempts to write directly to an imported work area, which creates the NotOriginator exception. Likewise, the bean intentionally attempts to mask the read only SimpleSampleCompany, which triggers the PropertyReadOnly exception. The SimpleSampleBean also nests a work area and successfully overrides the priority property before invoking the SimpleSampleBackendBean. A true business application would extract the work area properties and use them to guide the local work. The SimpleSampleBean mimics this by writing a message that function is denied when a request emanates from a sales environment.

Related

Work area service settings
Ovveride work area properties
retrieveAllKeys method
Nested work areas
Overview of work area service
twa_develop.html
twa_partition.html
twa_manage.html
Access the UserWorkArea partition
Access a user defined work area partition

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