Question

我正在使用spring social来获取用户朋友并将它们添加到数据库中，但每次我编译并且应用程序启动它都会抛出此错误我的类低于错误。

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)

以下是使用

的课程

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

确保使用@NodeEntity注释好友。
告诉spring所有节点实体的位置（包），以便它知道映射。
不要自己创建图表数据库，而是让spring为您管理（使用neo4j命名空间）
我认为您应该保存Friend实体而不是名称。即改变以下

neo.save（friend.getName（））;

到

neo.save(friend);

Spring Neo4j模板抛出空指针异常

1 个答案: