String index out of range: -1

java.lang.StringIndexOutOfBoundsException: String index out of range: -1
	at java.lang.String.substring(String.java:1937)
	at java.lang.String.substring(String.java:1904)
	at de.mms.avp.cae.uri.GenericExportController.resolveExportHookKey(GenericExportController.java:226)
	at de.mms.avp.cae.uri.GenericExportController.handleRequestInternal(GenericExportController.java:109)
	at de.mms.avp.cae.uri.CachedGenericExportController.handleRequestInternal(CachedGenericExportController.java:52)
	at org.springframework.web.servlet.mvc.AbstractController.handleRequest(AbstractController.java:153)
	at org.springframework.web.servlet.mvc.SimpleControllerHandlerAdapter.handle(SimpleControllerHandlerAdapter.java:48)
	at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:875)
	at com.coremedia.objectserver.web.DispatcherServlet.doDispatch(DispatcherServlet.java:56)
	at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:807)
	at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:571)
	at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:501)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:690)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
	at de.mms.avp.cae.filter.CharacterEncodingFilter.doFilter(CharacterEncodingFilter.java:53)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
	at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)
	at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:175)
	at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:128)
	at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
	at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
	at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:286)
	at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:844)
	at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:583)
	at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:447)
	at java.lang.Thread.run(Thread.java:662)