Error when return List in java google api testing locally -

Error when return List<Entity> in java google api testing locally -

public list<entity> getpersons() { query q = new query("person"); preparedquery pq = datastore.prepare(q); homecoming pq.aslist(fetchoptions.builder.withdefaults()); }

i can run mvn clean install , mvn appengine:devserver without problem, got error after add together getpersons() function homecoming list<entity> when run testing api locally

http error 500 problem accessing /_ah/api/explorer. reason: failed retrieve api configs status: 400

caused by:

java.io.ioexception: failed retrieve api configs status: 400 @ com.google.api.server.spi.tools.devserver.apiservlet.getapiconfigsources(apiservlet.java:104) @ com.google.api.server.spi.tools.devserver.apiservlet.initconfigsifnecessary(apiservlet.java:69) @ com.google.api.server.spi.tools.devserver.restapiservlet.service(restapiservlet.java:117) @ javax.servlet.http.httpservlet.service(httpservlet.java:717) @ org.mortbay.jetty.servlet.servletholder.handle(servletholder.java:511) @ org.mortbay.jetty.servlet.servlethandler$cachedchain.dofilter(servlethandler.java:1166) @ com.google.appengine.api.socket.dev.devsocketfilter.dofilter(devsocketfilter.java:74) @ org.mortbay.jetty.servlet.servlethandler$cachedchain.dofilter(servlethandler.java:1157) @ com.google.appengine.tools.development.responserewriterfilter.dofilter(responserewriterfilter.java:127) @ org.mortbay.jetty.servlet.servlethandler$cachedchain.dofilter(servlethandler.java:1157) @ com.google.appengine.tools.development.headerverificationfilter.dofilter(headerverificationfilter.java:34) @ org.mortbay.jetty.servlet.servlethandler$cachedchain.dofilter(servlethandler.java:1157) @ com.google.appengine.api.blobstore.dev.serveblobfilter.dofilter(serveblobfilter.java:63) @ org.mortbay.jetty.servlet.servlethandler$cachedchain.dofilter(servlethandler.java:1157) @ com.google.apphosting.utils.servlet.transactioncleanupfilter.dofilter(transactioncleanupfilter.java:43) @ org.mortbay.jetty.servlet.servlethandler$cachedchain.dofilter(servlethandler.java:1157) @ com.google.appengine.tools.development.staticfilefilter.dofilter(staticfilefilter.java:125) @ org.mortbay.jetty.servlet.servlethandler$cachedchain.dofilter(servlethandler.java:1157) @ com.google.appengine.tools.development.devappservermodulesfilter.dodirectrequest(devappservermodulesfilter.java:366) @ com.google.appengine.tools.development.devappservermodulesfilter.dodirectmodulerequest(devappservermodulesfilter.java:349) @ com.google.appengine.tools.development.devappservermodulesfilter.dofilter(devappservermodulesfilter.java:116) @ org.mortbay.jetty.servlet.servlethandler$cachedchain.dofilter(servlethandler.java:1157) @ org.mortbay.jetty.servlet.servlethandler.handle(servlethandler.java:388) @ org.mortbay.jetty.security.securityhandler.handle(securityhandler.java:216) @ org.mortbay.jetty.servlet.sessionhandler.handle(sessionhandler.java:182) @ org.mortbay.jetty.handler.contexthandler.handle(contexthandler.java:765) @ org.mortbay.jetty.webapp.webappcontext.handle(webappcontext.java:418) @ com.google.appengine.tools.development.devappenginewebappcontext.handle(devappenginewebappcontext.java:98) @ org.mortbay.jetty.handler.handlerwrapper.handle(handlerwrapper.java:152) @ com.google.appengine.tools.development.jettycontainerservice$apiproxyhandler.handle(jettycontainerservice.java:490) @ org.mortbay.jetty.handler.handlerwrapper.handle(handlerwrapper.java:152) @ org.mortbay.jetty.server.handle(server.java:326) @ org.mortbay.jetty.httpconnection.handlerequest(httpconnection.java:542) @ org.mortbay.jetty.httpconnection$requesthandler.headercomplete(httpconnection.java:923) @ org.mortbay.jetty.httpparser.parsenext(httpparser.java:547) @ org.mortbay.jetty.httpparser.parseavailable(httpparser.java:212) @ org.mortbay.jetty.httpconnection.handle(httpconnection.java:404) @ org.mortbay.io.nio.selectchannelendpoint.run(selectchannelendpoint.java:409) @ org.mortbay.thread.queuedthreadpool$poolthread.run(queuedthreadpool.java:582) powered jetty:// [1]: http://localhost:8080/_ah/api/explorer

java google-app-engine maven gae-datastore google-cloud-endpoints