I'm just getting started with GAE and cloud endpoints. I created a sample persistent class, and I created the enpoint class using the google menu in Eclipse. Now I'm just after some tutorial on how to use curl and return a nice json string, and it seems that when I try to list all the values by throwing a nullpointerexception , surprisingly, when I provide the url string id, then it magically works. Now, these two methods bother me: listContinent and getContinent
This is what creates the error.
curl http://localhost:8888/_ah/api/app/v1/continent
the calling method of listContinent , which causes an error.
and this one only works
curl http://localhost:8888/_ah/api/app/v1/continent/1
which calls the getContinent method, and when the correct Id is passed to the URL, it works as expected.
This is my final class -
@Api(name = "app") public class ContinentEndpoint { @SuppressWarnings({ "cast", "unchecked" }) public List<Continent> listContinent() { PersistenceManager mgr = getPersistenceManager(); List<Continent> result = new ArrayList<Continent>(); try { Query query = mgr.newQuery(Continent.class); for (Object obj : (List<Object>) query.execute()) { result.add(((Continent) obj)); } } finally { mgr.close(); } return result; } public Continent getContinent(@Named("id") Long id) { PersistenceManager mgr = getPersistenceManager(); Continent continent = null; try { continent = mgr.getObjectById(Continent.class, id); } finally { mgr.close(); } return continent; } private static PersistenceManager getPersistenceManager() { return PMF.get().getPersistenceManager(); } }
and this is my permanent class -
@PersistenceCapable(identityType = IdentityType.APPLICATION) @Version(strategy = VersionStrategy.VERSION_NUMBER) public class Continent { public long getContinentId() { return continentId; } public void setContinentId(long continentId) { this.continentId = continentId; } public String getContinentName() { return continentName; } public void setContinentName(String continentName) { this.continentName = continentName; } public Date getCreatedOn() { return createdOn; } @PrimaryKey @Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY) private long continentId; private String continentName; private Date createdOn = new Date(); }
This is my stack.
Nov 12, 2012 3:07:10 PM com.google.apphosting.utils.jetty.JettyLogger info INFO: Logging to JettyLogger(null) via com.google.apphosting.utils.jetty.JettyLogger Nov 12, 2012 3:07:10 PM com.google.apphosting.utils.config.AppEngineWebXmlReader readAppEngineWebXml INFO: Successfully processed /home/soham/Workspace/cloudcv/war/WEB-INF/appengine-web.xml Nov 12, 2012 3:07:10 PM com.google.apphosting.utils.config.AbstractConfigXmlReader readConfigXml INFO: Successfully processed /home/soham/Workspace/cloudcv/war/WEB-INF/web.xml Nov 12, 2012 8:37:11 PM com.google.appengine.tools.development.DevAppServerImpl start INFO: The server is running at http://localhost:8888/ Nov 12, 2012 8:37:11 PM com.google.appengine.tools.development.DevAppServerImpl start INFO: The admin console is running at http://localhost:8888/_ah/admin Nov 12, 2012 8:37:53 PM com.google.api.server.spi.SystemService invokeServiceMethod SEVERE: null java.lang.NullPointerException at com.google.appengine.datanucleus.query.QueryEntityPKFetchFieldManager.fetchLongField(QueryEntityPKFetchFieldManager.java:74) at org.datanucleus.identity.IdentityUtils.getApplicationIdentityForResultSetRow(IdentityUtils.java:101) at com.google.appengine.datanucleus.EntityUtils.entityToPojo(EntityUtils.java:1009) at com.google.appengine.datanucleus.query.DatastoreQuery$2.apply(DatastoreQuery.java:228) at com.google.appengine.datanucleus.query.DatastoreQuery$2.apply(DatastoreQuery.java:225) at com.google.appengine.datanucleus.query.LazyResult.resolveNext(LazyResult.java:96) at com.google.appengine.datanucleus.query.LazyResult$LazyAbstractListIterator.computeNext(LazyResult.java:229) at com.google.appengine.datanucleus.query.AbstractIterator.tryToComputeNext(AbstractIterator.java:131) at com.google.appengine.datanucleus.query.AbstractIterator.hasNext(AbstractIterator.java:126) at com.google.appengine.datanucleus.query.LazyResult$AbstractListIterator.hasNext(LazyResult.java:183) at com.cloudcv.ContinentEndpoint.listContinent(ContinentEndpoint.java:23) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:616) at com.google.appengine.tools.development.agent.runtime.Runtime.invoke(Runtime.java:115) at com.google.api.server.spi.SystemService.invokeServiceMethod(SystemService.java:254) at com.google.api.server.spi.SystemServiceServlet.execute(SystemServiceServlet.java:135) at com.google.api.server.spi.SystemServiceServlet.doPost(SystemServiceServlet.java:106) at javax.servlet.http.HttpServlet.service(HttpServlet.java:637) at javax.servlet.http.HttpServlet.service(HttpServlet.java:717) at org.mortbay.jetty.servlet.ServletHolder.handle(ServletHolder.java:511) at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1166) at com.google.appengine.api.socket.dev.DevSocketFilter.doFilter(DevSocketFilter.java:74) at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157) at com.google.appengine.tools.development.ResponseRewriterFilter.doFilter(ResponseRewriterFilter.java:123) at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157) at com.google.appengine.tools.development.HeaderVerificationFilter.doFilter(HeaderVerificationFilter.java:34) at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157) at com.google.appengine.api.blobstore.dev.ServeBlobFilter.doFilter(ServeBlobFilter.java:61) at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157) at com.google.apphosting.utils.servlet.TransactionCleanupFilter.doFilter(TransactionCleanupFilter.java:43) at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157) at com.google.appengine.tools.development.StaticFileFilter.doFilter(StaticFileFilter.java:125) at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157) at com.google.appengine.tools.development.BackendServersFilter.doFilter(BackendServersFilter.java:97) at org.mortbay.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1157) at org.mortbay.jetty.servlet.ServletHandler.handle(ServletHandler.java:388) at org.mortbay.jetty.security.SecurityHandler.handle(SecurityHandler.java:216) at org.mortbay.jetty.servlet.SessionHandler.handle(SessionHandler.java:182) at org.mortbay.jetty.handler.ContextHandler.handle(ContextHandler.java:765) at org.mortbay.jetty.webapp.WebAppContext.handle(WebAppContext.java:418) at com.google.appengine.tools.development.DevAppEngineWebAppContext.handle(DevAppEngineWebAppContext.java:94) at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152) at com.google.appengine.tools.development.JettyContainerService$ApiProxyHandler.handle(JettyContainerService.java:383) at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152) at org.mortbay.jetty.Server.handle(Server.java:326) at org.mortbay.jetty.HttpConnection.handleRequest(HttpConnection.java:542) at org.mortbay.jetty.HttpConnection$RequestHandler.content(HttpConnection.java:938) at org.mortbay.jetty.HttpParser.parseNext(HttpParser.java:755) at org.mortbay.jetty.HttpParser.parseAvailable(HttpParser.java:218) at org.mortbay.jetty.HttpConnection.handle(HttpConnection.java:404) at org.mortbay.io.nio.SelectChannelEndPoint.run(SelectChannelEndPoint.java:409) at org.mortbay.thread.QueuedThreadPool$PoolThread.run(QueuedThreadPool.java:582)
I did some debugging, and I found out that the query in Query query = mgr.newQuery(Continent.class); returns nothing, and the for each loop does not populate the ArrayList .