Шаблон Spring Neo4j выбрасывает исключение нулевого указателя

Question

Я работаю с Spring social, чтобы найти друзей пользователей и добавить их в базу данных, но каждый раз, когда я компилирую и запускаю приложение, выдает эту ошибку. Мой класс находится ниже ошибки.

SEVERE: Servlet.service() for servlet [appServlet] in context with path [/see-my-style] threw exception [Request processing failed; nested exception is java.lang.NullPointerException] with root cause
java.lang.NullPointerException
    at org.springframework.data.neo4j.support.Neo4jTemplate.getMappingPolicy(Neo4jTemplate.java:486)
    at org.springframework.data.neo4j.support.Neo4jTemplate.getMappingPolicy(Neo4jTemplate.java:656)
    at org.springframework.data.neo4j.support.Neo4jTemplate.save(Neo4jTemplate.java:293)
    at org.springframework.data.neo4j.support.Neo4jTemplate.save(Neo4jTemplate.java:287)
    at org.springframework.social.quickstart.HomeController.home(HomeController.java:64)
    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:601)
    at org.springframework.web.method.support.InvocableHandlerMethod.invoke(InvocableHandlerMethod.java:219)
    at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:132)
    at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:104)
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandleMethod(RequestMappingHandlerAdapter.java:745)
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:686)
    at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:80)
    at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:925)
    at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:856)
    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:936)
    at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:827)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:621)
    at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:812)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:728)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
    at org.springframework.web.filter.HiddenHttpMethodFilter.doFilterInternal(HiddenHttpMethodFilter.java:77)
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:243)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
    at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:88)
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:243)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:222)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:123)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:502)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:171)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:99)
    at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:953)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:408)
    at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1023)
    at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:589)
    at org.apache.tomcat.util.net.AprEndpoint$SocketProcessor.run(AprEndpoint.java:1852)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603)
    at java.lang.Thread.run(Thread.java:722)

Вот класс, с которым я работаю

package org.springframework.social.quickstart;

import java.util.List;

import javax.inject.Inject;
import org.neo4j.graphdb.GraphDatabaseService;
import org.neo4j.graphdb.factory.GraphDatabaseFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.ImportResource;
import org.springframework.data.neo4j.support.Neo4jTemplate;
import org.springframework.data.neo4j.template.Neo4jOperations;

import org.springframework.social.facebook.api.Facebook;
import org.springframework.social.facebook.api.FacebookProfile;
import org.springframework.social.facebook.api.PagedList;
import org.springframework.social.facebook.api.Reference;
import org.springframework.social.quickstart.repository.PersonRepository;
import org.springframework.stereotype.Controller;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;

/**
 * Simple little @Controller that invokes Facebook and renders the result.
 * The injected {@link Facebook} reference is configured with the required authorization credentials for the current user behind the scenes.
 * @author Keith Donald
 */
@Controller
public class HomeController {

    private final Facebook facebook;
        private static final String DB_PATH = "target/neo4j-hello-db";
        GraphDatabaseService graphDb = new GraphDatabaseFactory().newEmbeddedDatabase(DB_PATH);

        Neo4jOperations neo = new Neo4jTemplate(graphDb);


    @Inject
    public HomeController(Facebook facebook) {
        this.facebook = facebook;    
    }

    @RequestMapping(value = "/", method = RequestMethod.GET)
    public String home(Model model) {
        List<Reference> friends = facebook.friendOperations().getFriends();

                for(Reference friend: friends)
                {
                    neo.save(friend.getName());
                }
        return "home";
    }

Answer 1

1. Убедитесь, что Друг помечен @NodeEntity,
2. Скажите Spring местоположение (пакет (ы)) всех объектов вашего узла, чтобы он знал отображение.
3. Вместо того, чтобы создавать граф db самостоятельно, позвольте Spring управлять им за вас (используйте пространство имен neo4j)

4. Я думаю, что вы должны сохранить Friend сущность вместо имени. то есть изменить ниже

   neo.save (friend.getName());

в

neo.save(friend);