Get process instance data values

hello everybody I tried to get process instance data variables through REST API http://localhost:8080/bonita/API/bpm/caseVariable?p=0&c=10&f=case_id%3d1...

its through this exception any suggestion ? THANX IN ADVANCE

{"exception":"class org.bonitasoft.web.toolkit.client.common.exception.api.APIException","message":"Error when getting case variables","stacktrace":"[org.bonitasoft.web.rest.server.datastore.bpm.cases.CaseVariableDatastore.findByCaseId(CaseVariableDatastore.java:93), org.bonitasoft.web.rest.server.api.bpm.cases.APICaseVariable.runSearch(APICaseVariable.java:49), org.bonitasoft.web.rest.server.framework.APIServletCall.doGet(APIServletCall.java:165), org.bonitasoft.web.toolkit.server.servlet.ToolkitHttpServlet.doGet(ToolkitHttpServlet.java:183), javax.servlet.http.HttpServlet.service(HttpServlet.java:617), org.bonitasoft.web.toolkit.server.servlet.ToolkitHttpServlet.service(ToolkitHttpServlet.java:75), javax.servlet.http.HttpServlet.service(HttpServlet.java:723), org.bonitasoft.web.toolkit.server.servlet.ToolkitHttpServlet.service(ToolkitHttpServlet.java:226), org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290), org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206), org.bonitasoft.console.common.server.login.filter.AbstractAuthorizationFilter.doFilter(AbstractAuthorizationFilter.java:60), org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235), org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206), org.bonitasoft.console.common.server.login.filter.AbstractAuthorizationFilter.doFilter(AbstractAuthorizationFilter.java:60), org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235), org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206), org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233), org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191), org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127), org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:103), org.bonitasoft.console.security.SessionFixationValve.invoke(SessionFixationValve.java:77), org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109), org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:293), org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:861), org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:606), org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:489), java.lang.Thread.run(Unknown Source)]","api":"bpm","resource":"caseVariable"}