Jira: How to obtain the previous value for a custom field in a custom IssueEventListener - event-handling

Question

So how does one obtain the previous value of a custom field in a Jira IssueEventListener? I am writing a custom handler for the issueUpdated(IssueEvent) event and I would like to alter the handler's behavior if a certain custom field has changed. To detect the type of change I would like to compare the previous and current values.
(I'm am not asking about how to obtain its current value - I know how to get that from the related Issue)
I am developing against Jira 4.0.2 on Windows.
Is the best way to scan the change history for the last known value?
List changes = changeHistoryManager.getChangeHistoriesForUser(issue, user);

Answer 1

I'm assuming the original poster is writing a JIRA plugin with Java. I cannot be certain of how to accomplish this task in JIRA v4.0.2, but here is how I managed to do so with JIRA v5.0.2 (the solutions may very well be the same):
public void workflowEvent( IssueEvent event )
{
Long eventTypeId = event.getEventTypeId();
if( eventTypeId.equals( EventType.ISSUE_UPDATED_ID ) )
{
List<GenericValue> changeItemList = null;
try
{
changeItemList = event.getChangeLog().getRelated( "ChildChangeItem" );
}
catch( GenericEntityException e )
{
// Error or do what you need to do here.
e.printStackTrace();
}
if( changeItemList == null )
{
// Same deal here.
return;
}
Iterator<GenericValue> changeItemListIterator = changeItemList.iterator();
while( changeItemListIterator.hasNext() )
{
GenericValue changeItem = ( GenericValue )changeItemListIterator.next();
String fieldName = changeItem.get( "field" ).toString();
if( fieldName.equals( customFieldName ) ) // Name of custom field.
{
Object oldValue = changeItem.get( "oldvalue" );
Object newValue = changeItem.get( "newvalue" );
}
}
}
}
Some possible key values for changeItem are:
newvalue
oldstring
field
id
fieldtype
newstring
oldvalue
group
For many of the custom field types Object oldValue is probably just a String. But I don't think that's true for every case.

Answer 2

Try this example :
String codeProjetOldValue= "";
List<GenericValue> changeItemList = issueEvent.getChangeLog().getRelated("ChildChangeItem");
for (GenericValue genericValue : changeItemList) {
if(champCodeProjet.equals(genericValue.get("field"))){
codeProjetOldValue=genericValue.getString("oldstring");
break;
}
}
Note that : champCodeProjet is the name of customfield.