Example: processing a page flow that is started by a to-do task using the Business Process Choreographer EJB API

IBM BPM, V8.0.1, All platforms > Programming IBM BPM > Developing client applications for BPEL processes and tasks > Developing EJB client applications > Developing applications for BPEL processes and human tasks
Processing a page flow that is started by a to-do task

Some workflows are performed by only one person, for example, ordering books from an online bookstore. This example shows how to use both the Business Flow Manager and the Human Task Manager APIs are to process this type of workflow.

Ensure that the process model that contains the page flow meets the following criteria:

Because the next activity in the page flow is made available in the transaction of the activity that completed, the transactional behavior of all the human task activities must be set to participates.
To ensure that the next human task in the page flow can be found at run time, transaction boundaries are not introduced between tasks. To do this, for example, make sure that any invoke activities between two human task activities also have the transactional behavior set to participates, and that they do not use services, such as wait activities, that require a transaction boundary.
If the page flow is to be used in Business Space, each of the human tasks in the page flow must have the htm.hasNext custom property set to true, except the last human task in the sequence. This task must have the htm.hasNext custom property set to false.

A page flow is also referred to as a single person workflow or a screen flow. There are two kinds of page flows:

Client-side page flows, where the navigation between the different pages is realized using client-side technology, such as a multi-page Lotus Forms form.
Server-side page flows are realized using a BPEL process and a set of human tasks that are modeled so that subsequent tasks are assigned to the same person.
Server-side page flows are more powerful than client-side page flows, but they consume more server resources to process them. Therefore, consider using this type of workflow primarily in the following situations:

You need to invoke services between steps carried out in a user interface, for example, to retrieve or update data.
You have auditing requirements that require CEI events to be written after a user interface interaction completes.
In many situations, using a mix of server-side and client-side page flows is appropriate. This example shows a server-side page flow.
In an online bookstore, the purchaser completes a sequence of actions to order a book. This sequence of actions can be implemented as a series of human task activities (to-do tasks). If the purchaser decides to order several books, this is equivalent to claiming the next human task activity. Information about the sequence of tasks is maintained by Business Flow Manager, while the tasks themselves are maintained by Human Task Manager.
Compare this example with the example of a page flow that starts with the BPEL process.

Procedure
Use the Business Flow Manager API to get the process instance that you want to work on.
In this example, an instance of the CustomerOrder process.
ProcessInstanceData processInstance = 
   process.getProcessInstance("CustomerOrder");
String piid = processInstance.getID().toString();
Use the Human Task Manager API to query the ready to-do tasks (kind participating) that are part of the specified process instance.
Use the containment context ID of the task to specify the containing process instance. For a page flow, the query returns the to-do task that is associated with the first human task activity in the sequence of human task activities.
//
 // Query the list of to-do tasks that can be claimed by the logged-on user 
 // for the specified process instance //
FilterOptions fo = new FilterOptions();
fo.setSelectedAttributes("TKIID");
fo.setQueryCondition("CONTAINMENT_CTX_ID = ID('" + piid + "') AND STATE = STATE_READY AND KIND = KIND_PARTICIPATING AND WI.REASON = REASON_POTENTIAL_OWNER");
EntityResultSet result = task.queryEntities("TASK", fo, null, null);
Claim the to-do task that is returned.
if (result.getEntities().size() > 0)
{
  Entity entity = (Entity) result.getEntities().get(0);
  TKIID tkiid = (TKIID) entity.getAttributeValue("TKIID");
  ClientObjectWrapper input = task.claim(tkiid);
  DataObject activityInput = null ;
  if ( input.getObject()!= null && input.getObject() instanceof DataObject )
  {
    taskInput = (DataObject)input.getObject();
    // read the values     ...
  }  }
When the task is claimed, the input message of the task is returned.
Determine the human task activity that is associated with the to-do task.
You can use one of the following methods to correlate activities to their tasks.
The task.getActivityID method:
AIID aiid = task.getActivityID(tkiid);
The parent context ID that is part of the task object:
AIID aiid = null;
Task taskInstance = task.getTask(tkiid);

OID oid = taskInstance.getParentContextID();
if ( oid != null and oid instanceof AIID )
{
  aiid = (AIID)oid;}
When work on the task is finished, use the Business Flow Manager API to complete the task and its associated human task activity, and claim the next human task activity in the process instance.
To complete the human task activity, an output message is passed. When you create the output message, you must specify the message type name so that the message definition is contained.
ActivityInstanceData activity = process.getActivityInstance(aiid);
ClientObjectWrapper output = 
      process.createMessage(aiid, activity.getOutputMessageTypeName());
DataObject myMessage = null ;
if ( output.getObject()!= null && output.getObject() instanceof DataObject )
{
  myMessage = (DataObject)output.getObject();
  //set the parts in your message, for example, an order number   myMessage.setInt("OrderNo", 4711);} 
//complete the human task activity and its associated to-do task, // and claim the next human task activity CompleteAndClaimSuccessorResult successor = 
   process.completeAndClaimSuccessor(aiid, output);
This action sets an output message that contains the order number and claims the next human task activity in the sequence. If AutoClaim is set for successor activities and if there are multiple paths that can be followed, all of the successor activities are claimed and a random activity is returned as the next activity. If there are no more successor activities that can be assigned to this user, Null is returned.
If the process contains parallel paths that can be followed and these paths contain human task activities for which the logged-on user is a potential owner of more than one of these activities, a random activity is claimed automatically and returned as the next activity.
Work on the next human task activity.
ClientObjectWrapper nextInput = successor.getInputMessage();
if ( nextInput.getObject()!= 
               null && nextInput.getObject() instanceof DataObject )
{
  activityInput = (DataObject)input.getObject();
  // read the values   ...}  

aiid = successor.getAIID();
Continue with step 5 to complete the human task activity and to retrieve the next human task activity.
Developing applications for BPEL processes and human tasks

Related concepts:
Transactional behavior of long-running BPEL processes

Related tasks:
Processing a page flow that starts with the BPEL process

Related reference:
BPEL process editor: Server tab