Spring启动社交脸书抛出NPE

Question

我遵循“访问Facebook数据”的入门指南，并将其中的代码集成到使用web界面创建的现有spring boot应用程序中。当我访问/connectURL以访问facebook数据时，我在HelloController中注入的facebook对象中得到null。虽然相同的appId和appSecret可以在spring从github克隆的代码中工作，以访问facebook数据，因此我的测试facebook应用程序似乎根本没有问题。

堆栈跟踪：

2016-11-01 13:31:23.727 ERROR 7956 --- [nio-8080-exec-4] o.a.c.c.C.[.[.[/].[dispatcherServlet]    : Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed; nested exception is java.lang.NullPointerException] with root cause

java.lang.NullPointerException: null
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_71]
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_71]
    at sun.reflect.DelegatingMethodAccessorImpl.__invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_71]
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java) ~[na:1.8.0_71]
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java) ~[na:1.8.0_71]
    at java.lang.reflect.Method.invoke(Method.java:497) ~[na:1.8.0_71]
    at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:333) ~[spring-aop-4.3.3.RELEASE.jar:4.3.3.RELEASE]
    at org.springframework.aop.framework.ReflectiveMethodInvocation.invokeJoinpoint(ReflectiveMethodInvocation.java:190) ~[spring-aop-4.3.3.RELEASE.jar:4.3.3.RELEASE]
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:157) ~[spring-aop-4.3.3.RELEASE.jar:4.3.3.RELEASE]
    at org.springframework.aop.support.DelegatingIntroductionInterceptor.doProceed(DelegatingIntroductionInterceptor.java:133) ~[spring-aop-4.3.3.RELEASE.jar:4.3.3.RELEASE]
    at org.springframework.aop.support.DelegatingIntroductionInterceptor.invoke(DelegatingIntroductionInterceptor.java:121) ~[spring-aop-4.3.3.RELEASE.jar:4.3.3.RELEASE]
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179) ~[spring-aop-4.3.3.RELEASE.jar:4.3.3.RELEASE]
    at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:213) ~[spring-aop-4.3.3.RELEASE.jar:4.3.3.RELEASE]
    at com.sun.proxy.$Proxy97.toString(Unknown Source) ~[na:na]
    at java.lang.String.valueOf(String.java:2994) ~[na:1.8.0_71]
    at java.lang.StringBuilder.append(StringBuilder.java:131) ~[na:1.8.0_71]
    at com.example.controller.web.FacebookSocialController.helloFacebook(FacebookSocialController.java:35) ~[classes/:na]
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_71]
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_71]
    at sun.reflect.DelegatingMethodAccessorImpl.__invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_71]
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java) ~[na:1.8.0_71]
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java) ~[na:1.8.0_71]
    at java.lang.reflect.Method.invoke(Method.java:497) ~[na:1.8.0_71]
    at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:221) ~[spring-web-4.3.3.RELEASE.jar:4.3.3.RELEASE]
    at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:136) ~[spring-web-4.3.3.RELEASE.jar:4.3.3.RELEASE]
    at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:114) ~[spring-webmvc-4.3.3.RELEASE.jar:4.3.3.RELEASE]
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:827) ~[spring-webmvc-4.3.3.RELEASE.jar:4.3.3.RELEASE]
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:738) ~[spring-webmvc-4.3.3.RELEASE.jar:4.3.3.RELEASE]
    at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:85) ~[spring-webmvc-4.3.3.RELEASE.jar:4.3.3.RELEASE]
    at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:963) ~[spring-webmvc-4.3.3.RELEASE.jar:4.3.3.RELEASE]
    at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:897) ~[spring-webmvc-4.3.3.RELEASE.jar:4.3.3.RELEASE]
    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:970) ~[spring-webmvc-4.3.3.RELEASE.jar:4.3.3.RELEASE]
    at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:861) ~[spring-webmvc-4.3.3.RELEASE.jar:4.3.3.RELEASE]
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:622) ~[tomcat-embed-core-8.5.5.jar:8.5.5]
    at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:846) ~[spring-webmvc-4.3.3.RELEASE.jar:4.3.3.RELEASE]
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:729) ~[tomcat-embed-core-8.5.5.jar:8.5.5]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:230) ~[tomcat-embed-core-8.5.5.jar:8.5.5]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165) ~[tomcat-embed-core-8.5.5.jar:8.5.5]
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52) ~[tomcat-embed-websocket-8.5.5.jar:8.5.5]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:192) ~[tomcat-embed-core-8.5.5.jar:8.5.5]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165) ~[tomcat-embed-core-8.5.5.jar:8.5.5]
    at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:99) ~[spring-web-4.3.3.RELEASE.jar:4.3.3.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) ~[spring-web-4.3.3.RELEASE.jar:4.3.3.RELEASE]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:192) ~[tomcat-embed-core-8.5.5.jar:8.5.5]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165) ~[tomcat-embed-core-8.5.5.jar:8.5.5]
    at org.springframework.web.filter.HttpPutFormContentFilter.doFilterInternal(HttpPutFormContentFilter.java:89) ~[spring-web-4.3.3.RELEASE.jar:4.3.3.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) ~[spring-web-4.3.3.RELEASE.jar:4.3.3.RELEASE]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:192) ~[tomcat-embed-core-8.5.5.jar:8.5.5]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165) ~[tomcat-embed-core-8.5.5.jar:8.5.5]
    at org.springframework.web.filter.HiddenHttpMethodFilter.doFilterInternal(HiddenHttpMethodFilter.java:77) ~[spring-web-4.3.3.RELEASE.jar:4.3.3.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) ~[spring-web-4.3.3.RELEASE.jar:4.3.3.RELEASE]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:192) ~[tomcat-embed-core-8.5.5.jar:8.5.5]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165) ~[tomcat-embed-core-8.5.5.jar:8.5.5]
    at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:197) ~[spring-web-4.3.3.RELEASE.jar:4.3.3.RELEASE]
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) ~[spring-web-4.3.3.RELEASE.jar:4.3.3.RELEASE]
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:192) ~[tomcat-embed-core-8.5.5.jar:8.5.5]
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165) ~[tomcat-embed-core-8.5.5.jar:8.5.5]
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:198) ~[tomcat-embed-core-8.5.5.jar:8.5.5]
    at org.apache.catalina.core.StandardContextValve.__invoke(StandardContextValve.java:108) [tomcat-embed-core-8.5.5.jar:8.5.5]
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java) [tomcat-embed-core-8.5.5.jar:8.5.5]
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:472) [tomcat-embed-core-8.5.5.jar:8.5.5]
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:140) [tomcat-embed-core-8.5.5.jar:8.5.5]
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79) [tomcat-embed-core-8.5.5.jar:8.5.5]
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:87) [tomcat-embed-core-8.5.5.jar:8.5.5]
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:349) [tomcat-embed-core-8.5.5.jar:8.5.5]
    at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:784) [tomcat-embed-core-8.5.5.jar:8.5.5]
    at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66) [tomcat-embed-core-8.5.5.jar:8.5.5]
    at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:802) [tomcat-embed-core-8.5.5.jar:8.5.5]
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1410) [tomcat-embed-core-8.5.5.jar:8.5.5]
    at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) [tomcat-embed-core-8.5.5.jar:8.5.5]
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142) [na:1.8.0_71]
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) [na:1.8.0_71]
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) [tomcat-embed-core-8.5.5.jar:8.5.5]
    at java.lang.Thread.run(Thread.java:745) [na:1.8.0_71]

控制器（同https://github.com/spring-guides/gs-accessing-facebook/blob/master/complete/src/main/java/hello/HelloController.java):

@GetMapping
public String helloFacebook(Model model){
    System.out.println("FacebookSocialController.helloFacebook : connecting to facebook");
    if(connectionRepository.findPrimaryConnection(Facebook.class)!=null){
        System.out.println("Redirecting to provider");
        return "redirect:/connect/facebook";
    }

    System.out.println("facebook = " + facebook); // NPE thrown
    model.addAttribute("facebookProfile", 
         facebook.userOperations().getUserProfile()); // facebook object is null
    PagedList<Post> feed = facebook.feedOperations().getFeed();

    model.addAttribute("feed", feed);
    return "facebookFeed";
}

在github有一个错误，但它的旧版本。我使用的新代码有这个固定。有人能告诉我我错过了什么吗？

项目可以在github上访问。

Answer 1

在控制器中更改返回“facebookFeed”；返回“connect/facebookFeed”，并将您的facebookFeed模板保留在connect文件夹中。

Answer 2

我想，在加载依赖项时出现了一些问题。我刚刚重新导入了项目的maven依赖项（Intellij idea）。

Right click your project > Maven > Reimport

我还改变了工作目录，然后问题得到了解决。