Am 16.01.2013 um 09:14 schrieb Jörn Kottmann <[email protected]>: > Hi all, > > I am getting a NullPointerException while calling ArrayFS.get(). > > Here is the exception: > java.lang.NullPointerException > at org.apache.uima.cas.impl.CASImpl.ll_getFSForRef(CASImpl.java:3117) > at org.apache.uima.cas.impl.CASImpl.createFS(CASImpl.java:1773) > at org.apache.uima.cas.impl.ArrayFSImpl.get(ArrayFSImpl.java:50) > > > The code causing this exception looks like this: > ArrayFS mentionArray = (ArrayFS) > entityAnnotation.getFeatureValue(mentionsFeature); > > for (int i = 0; i < mentionArray.size(); i++) { > AnnotationFS mentionAnn = (AnnotationFS) mentionArray.get(i); > ... > } > > The actual bug here is in the AE which is creating the array and filling > it with Feature Structures a few nodes before in the pipeline. > In that AE the scope of a variable was wrong (instance instead of local) > and it accidentally wrote FSes from another CAS passed previously to the > process method into the ArrayFS. > > I am wondering if it would be worth making mistakes like this fail fast, > with other words it should throw an exception while putting the dangling FS > into the array. > > Any opinions?
Throwing an exception when inserting dangling FSes sounds like a good idea. To check if a CAS address is still resolving, a lookup can be made via the CAS address directly, thus, the time effort shouldn't be too high. Maybe do the same check when settings a feature to an FS value? However, even a resolving CAS address doesn't mean that the FS is still valid. The CAS might meanwhile have been reset and the address might just again have been assigned. Maintaining a serial number in the CAS and in every FS sounds like overkill. So given a check for an resolving CAS address doesn't catch 100% of the problem cases and costs extra time, is it worth to this check at all? Any better ideas to check for dangling references? -- Richard -- ------------------------------------------------------------------- Richard Eckart de Castilho Technical Lead Ubiquitous Knowledge Processing Lab (UKP-TUD) FB 20 Computer Science Department Technische Universität Darmstadt Hochschulstr. 10, D-64289 Darmstadt, Germany phone [+49] (0)6151 16-7477, fax -5455, room S2/02/B117 [email protected] www.ukp.tu-darmstadt.de Web Research at TU Darmstadt (WeRC) www.werc.tu-darmstadt.de -------------------------------------------------------------------
