[udig-devel] Filter is not thread safe (GT 2.2.x branch) and it causes j

["Vitali Diatchkov" <vitali@xxxxxxxxxxxx>]

Hello!

I have faced with a problem of concurrent modification of Filter that leads
to exception throwing:

java.util.ConcurrentModificationException
	at
java.util.AbstractList$Itr.checkForComodification(AbstractList.java:449)
	at java.util.AbstractList$Itr.next(AbstractList.java:420)
	at
org.geotools.filter.LogicFilterImpl.contains(LogicFilterImpl.java:165)
	at
org.geotools.data.FilteringFeatureReader.hasNext(FilteringFeatureReader.java
:121)
	at
org.geotools.data.ReTypeFeatureReader.hasNext(ReTypeFeatureReader.java:149)
	at
org.geotools.data.DefaultFeatureResults.getCount(DefaultFeatureResults.java:
242)
	at
org.geotools.data.store.DataFeatureCollection.size(DataFeatureCollection.jav
a:257)
	at
org.geotools.data.store.DataFeatureCollection.accepts(DataFeatureCollection.
java:582)


The thread where the exception is thrown is processing FeatureVisitor passed
to  FeatureCollection while another thread tries to call Filter.and(Filter
filter) that modifies the LogicFilterImpl.

This use case is coming from UDIG. 

Shouldn't all the Filter objects be immutable? (Just a quick mind). Or what
does the Filter design say about Filter modifications and multi-threading
issues?


For UDIG team: for the time being I suggest to revisit the Filter
construction in  methods MapImpl.select(*) to make them thread-safe by
creating a new instance each time .

Vitali.