SOS Troubleshooting

This page is dedicated to people who have problems with getting, installing or using the SOS. If your problem is not mentioned here or in the forum at, please use the 52°North Sensor Web mailing list at org or post in the forum (the list and the forum are synched, so don't post in both).

Installation problems

A <nop>NullPointerException is thrown in the class <nop>CapabilitiesCacheController

  • Check whether the database properties are set correct in your config files, see SOS_tutorial.

Eclipse could not find classes in package javax.xml.soap in rt.jar of JDK

  • Check whether the JRE is set to compliance level 1.6 (and not <1.6).

Deploying the web application as described in fails.

Make sure that the following items are true.
  • You have set the correct path of your Apache Tomcat Installation in the SOS\pom.xml file.
  • Tomcat is running.
  • You've copied the .jar files of your Postgresql installation folder to the SOS\lib folder

Where do I find the administrator username and password of my Tomcat?

Known Issues

Incorrect shutdown of threads

Since Apache Tomcat 6.0.24 messages for detected Threads that were not shut down correctly and which may cause memory leaks are logged ( These problems are caused by external jar files, e.g. XmlBeans, PostGIS-JDBC. The problems appear when the web apllication is stopped, reloaded or undeployed. In a running system this has no effect. To prevent these problems, TimerThread and ThreadLocal can be killed by Apache Tomcat if two parameters are set to true in the context.xml file.
  • Open the context.xml file (/[Tomcat folder]/conf/context.xml)
  • Add clearReferencesThreadLocals="true" and clearReferencesStopTimerThreads="true" to the -Tag
  • Then the -Tag looks like this:
  • Save the changes and restart the Tomcat

XmlBeans – memory leaks

  • org.apache.xmlbeans.XmlBeans$1 (ThreadLocal)
  • org.apache.xmlbeans.impl.schema.SchemaTypeLoaderImpl$1 (ThreadLocal)
  •$1 (ThreadLocal)
  •$1 (ThreadLocal)

PostGIS driver

  • org.postgresql.Driver (failed to unregister, forcibly unregistered)

Maximal size of response document

The Sensor Observation Service was tested at a Server with the following configuration:
  • Intel Pentium 4 2.66 Ghz
  • 1.5 GB RAM
The O&M response size is limited up to 6.04 MB, if the standard configuration of initial and maximum java memory pool is not changed (tomcat default configuration). This size accords to a number of about 6000 observations in the O&M document. You may have to adjust the tomcat configuration in order to enable larger responses.

Version of schema files

The SOS is an adopted OGC specification. There may occure minor changes in the SOS schemas in future. As those potential changes are not yet known, they could not be addressed in this release. The xml beans libraries are generated from the schema files of version 1.0.0 (state of 2008-02-11).

OM reponse document

The 52N-SOS-3.x always returns an ObservationCollection as response for SOS 1.0.0 requests. If the procedure represents a procedure package, in the specification is stated that the response should be a ComplexObservation.

Problems using the SOS

Setting the logging level to DEBUG

  • Open the file <SOS webapp directory>/WEB-INF/classes/logback.xml and set the property level="DEBUG". For details of Logback configuration see
Topic revision: r7 - 20 Nov 2012, CarstenHollmann
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