Question
Pegasystems Inc.
JP
Last activity: 4 Oct 2018 13:54 EDT
7.1.9 How to remove page group or page list element within a single loop
I got "java.lang.UnsupportedOperationException: use ClipboardPage.remove(Object) " run-time exception, if I was trying to remove element of a page group property, (i.e. Work-.pyWorkParty) within a single loop using Engine API.
Is this a known issue or am I missing something here? Below is my java step.
//get iterator for pyWorkParty page group
java.util.Iterator pyWorkPartyIterator = tools.getPrimaryPage().getProperty("pyWorkParty").iterator();
// loop the pyWorkParty
while(pyWorkPartyIterator.hasNext()){
// get workParty
ClipboardPage currentWorkParty = ((ClipboardProperty)pyWorkPartyIterator.next()).getPageValue();
// if the workParty is Assignee, remove it.
if("Assignee".equalsIgnoreCase(currentWorkParty.getString("pxPartyRole"))){
pyWorkPartyIterator.remove(); // this step throws run-time exception
}
}
Below is the Engine API Java doc.
com.pega.pegarules.pub.clipboard
Interface ClipboardProperty
iterator
java.util.Iterator iterator()
Returns an iterator allowing access to values contained in this list, page, or group property. Note that this iterator reflects the contents of this property at the time of its creation. Further changes to this property will not be reflected in this iterator.
I got "java.lang.UnsupportedOperationException: use ClipboardPage.remove(Object) " run-time exception, if I was trying to remove element of a page group property, (i.e. Work-.pyWorkParty) within a single loop using Engine API.
Is this a known issue or am I missing something here? Below is my java step.
//get iterator for pyWorkParty page group
java.util.Iterator pyWorkPartyIterator = tools.getPrimaryPage().getProperty("pyWorkParty").iterator();
// loop the pyWorkParty
while(pyWorkPartyIterator.hasNext()){
// get workParty
ClipboardPage currentWorkParty = ((ClipboardProperty)pyWorkPartyIterator.next()).getPageValue();
// if the workParty is Assignee, remove it.
if("Assignee".equalsIgnoreCase(currentWorkParty.getString("pxPartyRole"))){
pyWorkPartyIterator.remove(); // this step throws run-time exception
}
}
Below is the Engine API Java doc.
com.pega.pegarules.pub.clipboard
Interface ClipboardProperty
iterator
java.util.Iterator iterator()
Returns an iterator allowing access to values contained in this list, page, or group property. Note that this iterator reflects the contents of this property at the time of its creation. Further changes to this property will not be reflected in this iterator.
- Returns:
- the iterator. For most properties, the objects returned by Iterator.next() are ClipboardProperty instances. Lightweight page lists are the exception; in this case the objects are String arrays (String[]).
- Throws:
-
WrongModeException- this property does not contain a list, page, or group
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Accepted Solution
Cognizant
IN
Solution: While iterating through pagelist, for the page which needs to be deleted, mark this as pyDeletedObject to true.
After the loop is iterated, use function RemoveDeletedObjects(<PageList>). Then all the pages marked with pyDeletedObject set to true will be deleted from the page list.
Pegasystems
US
In some languages, you can't remove an element while looping over them, since the looping relies on the elements staying linked together. I don't know whether this language is one of those or not, but to be safe, how about moving all the elements you want to keep onto a new list, something like this:
PSEUDO CODE:
new list = empty list;
for (each element of old list) {
if (we want to keep it)
new list (<append>) = old list (<current>);
}
Pegasystems Inc.
JP
Perhaps Engine API didn't implement remove method of java.util.Iterator interface defined in the Java doc Iterator (Java Platform SE 7 )
Curious for the reason behind it.
java.util
Interface Iterator<E>
remove
void remove()
Removes from the underlying collection the last element returned by this iterator (optional operation). This method can be called only once per call to next(). The behavior of an iterator is unspecified if the underlying collection is modified while the iteration is in progress in any way other than by calling this method.
Perhaps Engine API didn't implement remove method of java.util.Iterator interface defined in the Java doc Iterator (Java Platform SE 7 )
Curious for the reason behind it.
java.util
Interface Iterator<E>
remove
void remove()
Removes from the underlying collection the last element returned by this iterator (optional operation). This method can be called only once per call to next(). The behavior of an iterator is unspecified if the underlying collection is modified while the iteration is in progress in any way other than by calling this method.
- Throws:
-
UnsupportedOperationException- if theremoveoperation is not supported by this iterator -
IllegalStateException- if thenextmethod has not yet been called, or theremovemethod has already been called after the last call to thenextmethod
Pegasystems Inc.
US
Exactly and this is clearly by design and intentional and it has been so since the very beginning for the PageIterator class. But that is an entirely different question.
Pegasystems Inc.
US
The error shows what you need to use that is:
| /** |
* Remove a property from the clipboard.
* @param aReference A String containing the reference to the
* property to be removed.
| * @return <code>null</code> | |
| * @throws InvalidReferenceException <code>aReference</code> is not a syntactically correct reference | |
| * @throws ReadOnlyException This page is read-only and cannot be modified. | |
| * @throws UnmodifiablePropertyException target property is unmodifiable | |
| * */ | |
| public Object remove(Object aReference); |
Pegasystems Inc.
AU
Hey Chunzhi,
Is there an expanded use case for this?
I'm not seeing the need for this to be a java step, Page-Remove on an activity loop for each embedded page should work on the described scenario.
Updated: 2 Feb 2016 1:29 EST
Pegasystems Inc.
JP
Hi Joel,
I've experienced IndexOutOfBoundsException many times when using "Page-Remove" step in a loop.
so I just wanted to explorer Engine API to see if it can be easier to deal with page list or page group.
Chunzhi
Pegasystems Inc.
AU
Hey Chunzhi,
I've never experienced that with a page group using the above method; the only time I've seen it is using a child step in a page list iteration using .PageList(Param.pyForEachCount) as the step page which is somewhat expected.
The above is how I've managed to steer clear of that issue.
UnitedHealth Group
IN
We have faced this issue and dealt it by using temporary Page and PageList.
Instead of doing a Page-Remove on a loop which is bound to fail, we used Page-Copy or Property-Set.
Steps:
1. Loop on Page.PL --- For Each Embedded Page (PageList abbreviated as PL)
When Condition
Copy Page.PL(<CURRENT>) to TempPage.PL(<APPEND>)
2. Property-Remove --- Page.PL
3. Property-Set - Page.PL = TempPage.PL
This will solve your problem and you will be able to accomplish it with efficiency of order n.
EvonSys Inc
US
Do you how to use this logic in to a Data Transform? (Instead of using Activity rule)
In DT, we cannot create/ initilate tempory lists. Do u know any solution?
Accepted Solution
Cognizant
IN
Solution: While iterating through pagelist, for the page which needs to be deleted, mark this as pyDeletedObject to true.
After the loop is iterated, use function RemoveDeletedObjects(<PageList>). Then all the pages marked with pyDeletedObject set to true will be deleted from the page list.