Problème en EJB

Bonsoir,
après avoir développé mon ejb session avec état et le déployer et puis créer la classe client qui utilise une servlet, celle ci fait appel au composant EJB.
Quand j essai de lancer l'application un message d 'erreur s'affiche comme suit:
19:36:10,235 INFO [STDOUT] ENTRE DANS POST
19:36:10,235 INFO [STDOUT] Erreur java.lang.NullPointerException
19:36:10,235 ERROR [STDERR] java.lang.NullPointerException
19:36:10,235 ERROR [STDERR] at ConfigurationServlet.getConfigRef(ConfigurationServlet.java:45)
19:36:10,235 ERROR [STDERR] at ConfigurationServlet.doPost(ConfigurationServlet.java:87)
19:36:10,235 ERROR [STDERR] at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
19:36:10,235 ERROR [STDERR] at javax.servlet.http.HttpServlet.service(HttpServlet.java:810)
19:36:10,235 ERROR [STDERR] at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:252)
19:36:10,235 ERROR [STDERR] at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173)
19:36:10,235 ERROR [STDERR] at org.jboss.web.tomcat.filters.ReplyHeaderFilter.doFilter(ReplyHeaderFilter.java:96)
19:36:10,235 ERROR [STDERR] at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:202)
19:36:10,235 ERROR [STDERR] at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173)
19:36:10,235 ERROR [STDERR] at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:213)
19:36:10,266 ERROR [STDERR] at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:178)
19:36:10,266 ERROR [STDERR] at org.jboss.web.tomcat.security.SecurityAssociationValve.invoke(SecurityAssociationValve.java:175)
19:36:10,266 ERROR [STDERR] at org.jboss.web.tomcat.security.JaccContextValve.invoke(JaccContextValve.java:74)
19:36:10,266 ERROR [STDERR] at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:126)
19:36:10,266 ERROR [STDERR] at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:105)
19:36:10,266 ERROR [STDERR] at org.jboss.web.tomcat.tc5.jca.CachedConnectionValve.invoke(CachedConnectionValve.java:156)
19:36:10,266 ERROR [STDERR] at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:107)
19:36:10,266 ERROR [STDERR] at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:148)
19:36:10,266 ERROR [STDERR] at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:869)
19:36:10,266 ERROR [STDERR] at org.apache.coyote.http11.Http11BaseProtocol$Http11ConnectionHandler.processConnection(Http11BaseProtocol.java:664)
19:36:10,266 ERROR [STDERR] at org.apache.tomcat.util.net.PoolTcpEndpoint.processSocket(PoolTcpEndpoint.java:527)
19:36:10,266 ERROR [STDERR] at org.apache.tomcat.util.net.MasterSlaveWorkerThread.run(MasterSlaveWorkerThread.java:112)
19:36:10,266 ERROR [STDERR] at java.lang.Thread.run(Unknown Source)
19:36:10,266 ERROR [[ConfigurationServlet]] Servlet.service() for servlet ConfigurationServlet threw exception
java.lang.NullPointerException
at ConfigurationServlet.doPost(ConfigurationServlet.java:88)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:810)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:252)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173)
at org.jboss.web.tomcat.filters.ReplyHeaderFilter.doFilter(ReplyHeaderFilter.java:96)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:202)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:213)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:178)
at org.jboss.web.tomcat.security.SecurityAssociationValve.invoke(SecurityAssociationValve.java:175)
at org.jboss.web.tomcat.security.JaccContextValve.invoke(JaccContextValve.java:74)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:126)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:105)
at org.jboss.web.tomcat.tc5.jca.CachedConnectionValve.invoke(CachedConnectionValve.java:156)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:107)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:148)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:869)
at org.apache.coyote.http11.Http11BaseProtocol$Http11ConnectionHandler.processConnection(Http11BaseProtocol.java:664)
at org.apache.tomcat.util.net.PoolTcpEndpoint.processSocket(PoolTcpEndpoint.java:527)
at org.apache.tomcat.util.net.MasterSlaveWorkerThread.run(MasterSlaveWorkerThread.java:112)
at java.lang.Thread.run(Unknown Source)
merci pour votre aide si vous me dites de quoi il s'agit vraiment.