Fix npe in delete sensor

[EHJ-52n]

Fixes:

2017-06-05 16:29:26,290 ERROR [http-nio-127.0.0.1-8080-exec-20] [SosEventBus.java:261] Error handling event SensorDeletion[request=org.n52.sos.request.DeleteSensorRequest[service=SOS, version=2.0.0, operation=DeleteSensor], response=org.n52.sos.response.DeleteSensorResponse[service=SOS, version=2.0.0]] by handler org.n52.sos.cache.ctrl.DefaultContentModificationListener@24a5d753
java.lang.NullPointerException: null
	at org.n52.sos.cache.InMemoryCacheImpl.removeFeaturesOfInterestForOffering(InMemoryCacheImpl.java:1363) ~[InMemoryCacheImpl.class:na]
	at org.n52.sos.cache.ctrl.action.SensorDeletionUpdate.execute(SensorDeletionUpdate.java:101) ~[SensorDeletionUpdate.class:na]
	at org.n52.sos.cache.ctrl.ContentCacheControllerImpl$PartialUpdate.execute(ContentCacheControllerImpl.java:254) ~[ContentCacheControllerImpl$PartialUpdate.class:na]
	at org.n52.sos.cache.ctrl.ContentCacheControllerImpl.executePartial(ContentCacheControllerImpl.java:146) ~[ContentCacheControllerImpl.class:na]
	at org.n52.sos.cache.ctrl.ContentCacheControllerImpl.update(ContentCacheControllerImpl.java:122) ~[ContentCacheControllerImpl.class:na]
	at org.n52.sos.cache.ctrl.DefaultContentModificationListener.handle(DefaultContentModificationListener.java:112) ~[DefaultContentModificationListener.class:na]
	at org.n52.sos.cache.ctrl.DefaultContentModificationListener.handle(DefaultContentModificationListener.java:94) ~[DefaultContentModificationListener.class:na]
	at org.n52.sos.event.SosEventBus$HandlerExecution.run(SosEventBus.java:259) ~[SosEventBus$HandlerExecution.class:na]
	at org.n52.sos.event.SosEventBus.submit(SosEventBus.java:162) [SosEventBus.class:na]
	at org.n52.sos.event.SosEventBus.fire(SosEventBus.java:70) [SosEventBus.class:na]
	at org.n52.sos.request.operator.SosDeleteSensorOperatorV20.receive(SosDeleteSensorOperatorV20.java:70) [SosDeleteSensorOperatorV20.class:na]
	at org.n52.sos.request.operator.SosDeleteSensorOperatorV20.receive(SosDeleteSensorOperatorV20.java:53) [SosDeleteSensorOperatorV20.class:na]
	at org.n52.sos.request.operator.AbstractRequestOperator.receiveRequest(AbstractRequestOperator.java:173) [AbstractRequestOperator.class:na]
	at org.n52.sos.request.operator.AbstractTransactionalRequestOperator.receiveRequest(AbstractTransactionalRequestOperator.java:68) [AbstractTransactionalRequestOperator.class:na]
	at org.n52.sos.service.operator.AbstractServiceOperator.receiveRequest(AbstractServiceOperator.java:61) [AbstractServiceOperator.class:na]
	at org.n52.sos.binding.PoxBinding.doPostOperation(PoxBinding.java:73) [PoxBinding.class:na]
	at org.n52.sos.service.SosService.doPost(SosService.java:140) [SosService.class:na]

[autermann]

I think this may be a bigger issue... A NPE at this point would mean that featuresOfInterestForOfferings and offeringsForFeaturesOfInterest got out sync somehow... Both model one part of an n x n relation and when we remove a feature for an offering it should be guaranteed that there is matching offering for the feature...

[autermann]

See my previous comment.

[EHJ-52n]

So, your recommendation is to check the delete sensor workflow at all for race conditions or similar!?

[himanshusharma27]

I want to work on this issue . Please assign me this issue .