Add user as the apporver in workflow

Question

Hi,
    I have created workflow for Project. I would like to add a user as a approver by using the following code.
user = IapiAccountLocator.lookup(session,"noppong_test");
addApprover(user.getAccountObjectReference(), new CollaboratorApprovalRuleType(0));
When the document is moved to the phase the document is locked by workflow engine, but there is nothing happen.  i also found the error in the log.
P.S. If you have an example to add the user as the approver. I'm appreciated if you provide me .
Daemon-027: EVENT_WORKFLOW_ENGINE (-2147483548, 0)     event_workflow_engine     daemon     com.frictionless.api.common.exception.ApplicationException: This field is required and must have a value.     AssociatedAttribute=WORK_ITEMS - SourceBo=-2144361477:1907:Contract Approval - ValidatingParent=-2144361477:1907:Contract Approval - com.frictionless.api.common.exception.ApplicationException: At least one of the items above is invalid. Mouse over the highlighted area for more details.| at com.frictionless.api.common.exception.ChainedExceptionFactory.createApplicationException(ChainedExceptionFactory.java:90)
Thank you so much,
noppong

Answer 1

Hi Baski,
    Thank you so much for your response. It is so useful for me.
    The issue has been resolved by uising the XPDL template from SAP. I have some question about changing the phase. I have 3 phases as the following :
1. Draft
2. Approval -> Workflow is here . Prev phase is Draft and Next Phase is Approved.
3. Approved
I added script to change phase in post script on the block activity as following 
import com.sap.odp.api.common.*;
if(getApprovalStatus() != DENIED) {
     doc.getIBeanHomeIfc().upgradeToEdit(doc);
     doc.getIBeanHomeIfc().changePhase(doc,"Approved");
}else{
     doc.getIBeanHomeIfc().upgradeToEdit(doc);
     doc.getIBeanHomeIfc().changePhase(doc,"Draft");
When the approver approve the document i found the error in backgroud task status as following:
Stack Trace: Sourced file: inline evaluation of: ``import com.sap.odp.api.common.*; if(getApprovalStatus() != DENIED) { doc.get . . . '' : target exception : at Line: 5 : in file: inline evaluation of: ``import com.sap.odp.api.common.*; if(getApprovalStatus() != DENIED) { doc.get . . . '' : .changePhase ( doc , "Approved" )
Target exception: com.frictionless.api.common.exception.ApplicationException: You may not transition to the target phase Approved. It is neither a valid next nor previous phase.
at bsh.BSHPrimarySuffix.doSuffix(Unknown Source)
at bsh.BSHPrimaryExpression.eval(Unknown Source)
at bsh.BSHPrimaryExpression.eval(Unknown Source)
at bsh.BSHBlock.evalBlock(Unknown Source)
at bsh.BSHBlock.eval(Unknown Source)
at bsh.BSHBlock.eval(Unknown Source)
at bsh.BSHIfStatement.eval(Unknown Source)
at bsh.Interpreter.eval(Unknown Source)
at bsh.Interpreter.eval(Unknown Source)
at bsh.Interpreter.eval(Unknown Source)
at com.frictionless.comp.scripting.ScriptEnviro...
It seem like the document is automatically changed the phase  to 'Approved' and make the script error, and the document is locked on the Approved phase. I would like to ask you some more questions.
1. Why does the workflow change the phase automatically? On my understanding the phase should be handled in PostScript by the script
2. On my understanding the workflow engine will lock the document during the workflow. Why this workflow did not release the lock when the document was changed the phase to 'Approved'.
Thank you and appreciate your help
Noppong