title: Spring Social Facebook: "The OAuth2 'state' parameter doesn't match"
body: <p>I am using Spring Social Facebook within a Spring MVC project to support Facebook login. This is working well in almost all cases, but occasionally I see the following exception in the logs.</p>
  
  <pre><code>ERROR org.springframework.social.connect.web.ProviderSignInController - Exception while completing OAuth 2 connection:
  java.lang.IllegalStateException: The OAuth2 'state' parameter doesn't match.
  at org.springframework.social.connect.web.ConnectSupport.verifyStateParameter(ConnectSupport.java:173)
  at org.springframework.social.connect.web.ConnectSupport.completeConnection(ConnectSupport.java:155)
  at org.springframework.social.connect.web.ProviderSignInController.oauth2Callback(ProviderSignInController.java:216)
  at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
  at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
  at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
  at java.lang.reflect.Method.invoke(Method.java:483)
  at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:221)
  at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:137) 
  at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:110) 
  at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandleMethod(RequestMappingHandlerAdapter.java:776) 
  at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:705) 
  at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:85) 
  at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:959) 
  at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:893) 
  at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:966) 
  at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:857) 
  at javax.servlet.http.HttpServlet.service(HttpServlet.java:618) 
  at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:842) 
  at javax.servlet.http.HttpServlet.service(HttpServlet.java:725) 
  at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:291) 
  at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) 
  at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52) 
  at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:239) 
  at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) 
  at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:316) 
  at org.springframework.security.web.access.intercept.FilterSecurityInterceptor.invoke(FilterSecurityInterceptor.java:126) 
  at org.springframework.security.web.access.intercept.FilterSecurityInterceptor.doFilter(FilterSecurityInterceptor.java:90) 
  at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:330) 
  at org.springframework.security.web.access.ExceptionTranslationFilter.doFilter(ExceptionTranslationFilter.java:114) 
  at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:330) 
  at org.springframework.security.web.session.SessionManagementFilter.doFilter(SessionManagementFilter.java:122) 
  at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:330) 
  at org.springframework.security.web.authentication.AnonymousAuthenticationFilter.doFilter(AnonymousAuthenticationFilter.java:111) 
  at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:330) 
  at org.springframework.security.web.servletapi.SecurityContextHolderAwareRequestFilter.doFilter(SecurityContextHolderAwareRequestFilter.java:168) 
  at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:330) 
  at org.springframework.security.web.savedrequest.RequestCacheAwareFilter.doFilter(RequestCacheAwareFilter.java:48) 
  at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:330) 
  at org.springframework.security.web.authentication.AbstractAuthenticationProcessingFilter.doFilter(AbstractAuthenticationProcessingFilter.java:205) 
  at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:330) 
  at org.springframework.security.web.authentication.logout.LogoutFilter.doFilter(LogoutFilter.java:120) 
  at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:330) 
  at org.springframework.security.web.header.HeaderWriterFilter.doFilterInternal(HeaderWriterFilter.java:64) 
  at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) 
  at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:330) 
  at org.springframework.security.web.context.SecurityContextPersistenceFilter.doFilter(SecurityContextPersistenceFilter.java:91) 
  at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:330) 
  at org.springframework.security.web.context.request.async.WebAsyncManagerIntegrationFilter.doFilterInternal(WebAsyncManagerIntegrationFilter.java:53) 
  at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) 
  at org.springframework.security.web.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:330) 
  at org.springframework.security.web.FilterChainProxy.doFilterInternal(FilterChainProxy.java:213) 
  at org.springframework.security.web.FilterChainProxy.doFilter(FilterChainProxy.java:176) 
  at org.springframework.web.filter.DelegatingFilterProxy.invokeDelegate(DelegatingFilterProxy.java:344) 
  at org.springframework.web.filter.DelegatingFilterProxy.doFilter(DelegatingFilterProxy.java:261) 
  at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:239) 
  at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) 
  at com.example.something.CorsFilter.doFilter(CorsFilter.java:49) 
  at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:239) 
  at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) 
  at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:85) 
  at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107) 
  at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:239) 
  at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) 
  at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:219) 
  at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:106) 
  at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:501) 
  at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:142) 
  at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79) 
  at org.apache.catalina.valves.RemoteIpValve.invoke(RemoteIpValve.java:673) 
  at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:610) 
  at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:88) 
  at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:516) 
  at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1086) 
  at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:659) 
  at org.apache.coyote.http11.Http11NioProtocol$Http11ConnectionHandler.process(Http11NioProtocol.java:223) 
  at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1558) 
  at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.run(NioEndpoint.java:1515) 
  at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142) 
  at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) 
  at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) 
  at java.lang.Thread.run(Thread.java:745)
  </code></pre>
  
  <p>I haven't been able to figure out when this occurs, and I haven't been able to reproduce it, but I have seen it happening for other users quite a few times. Below is my Spring Social Facebook configuration.</p>
  
  <pre><code>@Configuration
  public class SocialConfig {
      @Bean
      public ProviderSignInController providerSignInController() {
          ProviderSignInController controller = new ProviderSignInController(this.connectionFactoryLocator(), this.usersConnectionRepository(), new SpringSecuritySignInAdapter(this.accountRepository));
          controller.addSignInInterceptor(new RedirectToPreviousPageInterceptor(controller, this.analyticsService));
  
          return controller;
      }
  
      @Bean
      public ConnectionFactoryRegistry connectionFactoryLocator() {
          ConnectionFactoryRegistry connectionFactoryRegistry = new ConnectionFactoryRegistry();
          List&lt;ConnectionFactory&lt;?&gt;&gt; connectionFactories = new ArrayList&lt;ConnectionFactory&lt;?&gt;&gt;();
          connectionFactories.add(this.facebookConnectionFactory());
          connectionFactoryRegistry.setConnectionFactories(connectionFactories);
  
          return connectionFactoryRegistry;
      }
  
      @Bean
      public FacebookConnectionFactory facebookConnectionFactory() {
          FacebookConnectionFactory connectionFactory = new FacebookConnectionFactory(this.facebookAppId, this.facebookAppSecret);
          connectionFactory.setScope(this.scope);
  
          return connectionFactory;
      }
  
      @Bean
      @Scope(value = "request", proxyMode = ScopedProxyMode.INTERFACES)
      public Facebook facebook(ConnectionRepository repository) {
          Connection&lt;Facebook&gt; connection = repository.findPrimaryConnection(Facebook.class);
          return (connection != null ? connection.getApi() : null);
      }
  
      @Bean
      @Scope(value = "request", proxyMode = ScopedProxyMode.INTERFACES)
      public ConnectionRepository connectionRepository() {
          Authentication authentication = SecurityContextHolder.getContext().getAuthentication();
  
          if (authentication == null) {
              throw new IllegalStateException("Unable to get a ConnectionRepository: no user signed in");
          }
  
          Account account = (Account) authentication.getPrincipal();
          return this.usersConnectionRepository().createConnectionRepository(String.valueOf(account.getId()));
      }
  
      @Bean
      public JdbcUsersConnectionRepository usersConnectionRepository() {
          JdbcUsersConnectionRepository repository = new JdbcUsersConnectionRepository(this.dataSource, this.connectionFactoryLocator(), this.textEncryptor);
          repository.setConnectionSignUp(this.accountService);
  
          return repository;
      }
  }
  </code></pre>
  
  <p>Why does this occur, and what can I do to prevent this? Thanks.</p>