title: Dspace OAI - Estado HTTP 500 - Request processing failed; nested exception is java.lang.NullPointerException
body: <p>When we can access to:
  <a href="http://dspace/oai/request?verb=ListRecords&amp;metadataPrefix=oai_dc" rel="nofollow noreferrer">http://dspace/oai/request?verb=ListRecords&amp;metadataPrefix=oai_dc</a>
  we have the following error:</p>
  
  <pre><code>ene 16, 2018 12:54:02 PM org.apache.catalina.core.StandardWrapperValve invoke
  GRAVE: El Servlet.service() para el servlet [oai] en el contexto con ruta [/oai] lanzó la excepción [Request processing failed; nested exception is java.lang.NullPointerException] con causa raíz
  java.lang.NullPointerException
          at org.apache.xalan.transformer.TransformerImpl.setOutputProperty(TransformerImpl.java:966)
          at com.lyncode.xoai.util.XSLPipeline.apply(XSLPipeline.java:24)
          at com.lyncode.xoai.dataprovider.handlers.ListRecordsHandler.createRecord(ListRecordsHandler.java:159)
          at com.lyncode.xoai.dataprovider.handlers.ListRecordsHandler.handle(ListRecordsHandler.java:124)
          at com.lyncode.xoai.dataprovider.OAIDataProvider.handle(OAIDataProvider.java:213)
          at org.dspace.xoai.controller.DSpaceOAIDataProvider.contextAction(DSpaceOAIDataProvider.java:104)
          at sun.reflect.GeneratedMethodAccessor127.invoke(Unknown Source)
          at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
          at java.lang.reflect.Method.invoke(Method.java:498)
          at org.springframework.web.method.support.InvocableHandlerMethod.invoke(InvocableHandlerMethod.java:213)
          at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:126)
          at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:96)
          at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:617)
          at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:578)
          at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:80)
          at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:923)
          at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:852)
          at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:882)
          at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:778)
          at javax.servlet.http.HttpServlet.service(HttpServlet.java:624)
          at javax.servlet.http.HttpServlet.service(HttpServlet.java:731)
          at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:303)
          at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
          at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
          at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
          at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
          at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:220)
          at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:122)
          at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:505)
          at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:169)
          at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:103)
          at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:956)
          at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:116)
          at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:436)
          at org.apache.coyote.ajp.AjpProcessor.process(AjpProcessor.java:190)
          at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:625)
          at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:316)
          at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
          at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
          at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
          at java.lang.Thread.run(Thread.java:748)
  </code></pre>
  
  <p>We try import and clear cache of oai using:</p>
  
  <h1>./dspace oai import -c</h1>
  
  <h1>./dsapce oai clear-cache</h1>
  
  <p>but the error persist
  Thanks for your help.</p>