Yes, looks like your GeneralRecommender is passing null to refreshData() for items. What examples do you mean?
The fix would be to not do that! On Sat, Sep 24, 2011 at 4:56 AM, Octavian Covalschi < [email protected]> wrote: > Hey guys, > > Has anyone succeeded to use MongoDBDataModel at all? > > Basically I'm getting a NPE: > > java.lang.NullPointerException > at > com.google.common.base.Preconditions.checkNotNull(Preconditions.java:186) > at > me.demo.taste.core.MongoDBDataModel.checkData(MongoDBDataModel.java:738) > at > me.demo.taste.core.MongoDBDataModel.refreshData(MongoDBDataModel.java:356) > at > > me.demo.taste.core.GeneralRecommender.recommend(GeneralRecommender.java:151) > at > me.demo.taste.web.RecommenderServlet.doGet(RecommenderServlet.java:80) > at javax.servlet.http.HttpServlet.service(HttpServlet.java:617) > at javax.servlet.http.HttpServlet.service(HttpServlet.java:717) > at > > org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290) > 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:191) > at > > org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127) > at > > org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102) > at > > org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109) > at > > com.springsource.insight.collection.tcserver.request.HttpRequestOperationCollectionValve.invoke(HttpRequestOperationCollectionValve.java:64) > at > org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:298) > at > org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:857) > at > > org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:588) > at > > org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:409) > at > > java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886) > at > > java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908) > at java.lang.Thread.run(Thread.java:662) > > > This is the code I'm using: > > GeneralRecommender recommender = new GeneralRecommender(); > try { > recommender.start(new MongoDBDataModel()); > } catch (UnknownHostException e) { > // TODO Auto-generated catch block > e.printStackTrace(); > } catch (MongoException e) { > // TODO Auto-generated catch block > e.printStackTrace(); > } > > try { > ArrayList<ArrayList<String>> items = > recommender.recommend(userIDString, null, true); > items.size(); > } catch (NullPointerException e) { > // TODO Auto-generated catch block > e.printStackTrace(); > } catch (NoSuchUserException e) { > // TODO Auto-generated catch block > e.printStackTrace(); > } catch (NoSuchItemException e) { > // TODO Auto-generated catch block > e.printStackTrace(); > } catch (IllegalArgumentException e) { > // TODO Auto-generated catch block > e.printStackTrace(); > } > > > From what I can tell the error seems to be correct, since it does check for > the passed items, however examples of it's usage all have items = null, so > I'm confused a bit, should I or should not pass null for items ? > > Thank you in advance. >
