Make sure you use the latest MySQL driver. Are you sure that one of your columns is not NULL?
On Tue, Mar 27, 2012 at 6:42 AM, 344911009 <mudaom...@vip.qq.com> wrote: > windows XP 2G > runing MovieSite ,use mysql-connector-java-5.1.13-bin.jar, userID and > movieID are INTEGER ,but still has errors :java.lang.NullPointerException > anyone know how to solve it ? thanks! > 2012-3-26 16:31:11 org.apache.catalina.core.StandardWrapperValve invoke > 严重: Servlet.service() for servlet [movie-recommender] in context with path > [/MovieSite] threw exception > java.lang.NullPointerException > at com.mysql.jdbc.ResultSetImpl.getLong(ResultSetImpl.java:2843) > at com.mysql.jdbc.ResultSetImpl.getLong(ResultSetImpl.java:2830) > at > org.apache.tomcat.dbcp.dbcp.DelegatingResultSet.getLong(DelegatingResultSet.java:228) > at > org.apache.tomcat.dbcp.dbcp.DelegatingResultSet.getLong(DelegatingResultSet.java:228) > at > org.apache.mahout.cf.taste.impl.model.jdbc.AbstractJDBCDataModel.getLongColumn(AbstractJDBCDataModel.java:602) > at > org.apache.mahout.cf.taste.impl.model.jdbc.AbstractJDBCDataModel$ResultSetIDIterator.nextLong(AbstractJDBCDataModel.java:677) > at > org.apache.mahout.cf.taste.impl.model.jdbc.AbstractJDBCDataModel$ResultSetIDIterator.next(AbstractJDBCDataModel.java:666) > at > org.apache.mahout.cf.taste.impl.model.jdbc.AbstractJDBCDataModel$ResultSetIDIterator.next(AbstractJDBCDataModel.java:621) > at > org.apache.mahout.cf.taste.impl.recommender.TopItems.getTopUsers(TopItems.java:82) > at > org.apache.mahout.cf.taste.impl.neighborhood.NearestNUserNeighborhood.getUserNeighborhood(NearestNUserNeighborhood.java:100) > at > org.apache.mahout.cf.taste.impl.recommender.GenericUserBasedRecommender.recommend(GenericUserBasedRecommender.java:80) > at > org.apache.mahout.cf.taste.impl.recommender.AbstractRecommender.recommend(AbstractRecommender.java:52) > at > org.apache.mahout.cf.taste.impl.recommender.CachingRecommender$RecommendationRetriever.get(CachingRecommender.java:190) > at > org.apache.mahout.cf.taste.impl.recommender.CachingRecommender$RecommendationRetriever.get(CachingRecommender.java:177) > at > org.apache.mahout.cf.taste.impl.common.Cache.getAndCacheValue(Cache.java:101) > at org.apache.mahout.cf.taste.impl.common.Cache.get(Cache.java:77) > at > org.apache.mahout.cf.taste.impl.recommender.CachingRecommender.recommend(CachingRecommender.java:114) > at > org.apache.mahout.cf.taste.impl.recommender.CachingRecommender.recommend(CachingRecommender.java:96) > at > com.ibm.taste.example.movie.recommender.UserBasedRecommender.recommend(UserBasedRecommender.java:53) > at > com.ibm.taste.example.movie.servlet.MovieRecommenderServlet.doGet(MovieRecommenderServlet.java:81) > at javax.servlet.http.HttpServlet.service(HttpServlet.java:621) > at javax.servlet.http.HttpServlet.service(HttpServlet.java:722) > at > org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:304) > at > org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210) > at > org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:240) > at > org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:164) > at > org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:498) > at > org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:164) > at > org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:100) > at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:562) > at > org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118) > at > org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:394) > at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:243) > at > org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:188) > at > org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:166) > at > org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:302) > at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(Unknown Source) > at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source) > at java.lang.Thread.run(Unknown Source)