Spring 4容器中的调度方法

Question

我正在使用Spring (4.2.5)和Security (4.0.3)开发一个web应用程序。我的问题是，我需要一个按设定时间间隔运行的方法，比如每30秒运行一次，但在执行之前，我必须确保用户已登录。

当用户提交登录表单时，HTTP请求将发送到外部服务器，如果凭据正确，则返回包含会话令牌的HTTP响应。

会话令牌对于所有其他请求都是基本的，包括我希望在赋时方法中转发的请求。

在我的控制器中，我可以从Security上下文中获取会话令牌，在每一刻：

String token = SecurityContextHolder.getContext().getAuthentication().getDetails().toString();

我尝试使用一个预定的任务，但不幸的是，这不起作用，因为这是在应用程序启动时启动的，此时没有会话，并且运行在与servlet容器分离的线程中。引发以下异常：

GRAVE: Unexpected error occurred in scheduled task.
java.lang.NullPointerException
    at service.RetrieveBettingOdds.retrieveMatchByNationality(RetrieveBettingOdds.java:54)
    at tasks.OddsTask.run(OddsTask.java:36)
    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:497)
    at org.springframework.scheduling.support.ScheduledMethodRunnable.run(ScheduledMethodRunnable.java:65)
    at org.springframework.scheduling.support.DelegatingErrorHandlingRunnable.run(DelegatingErrorHandlingRunnable.java:54)
    at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
    at java.util.concurrent.FutureTask.runAndReset(FutureTask.java:308)
    at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$301(ScheduledThreadPoolExecutor.java:180)
    at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:294)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
    at java.lang.Thread.run(Thread.java:745)

因为SecurityContextHolder.getContext()是空的。

OddsTask

@Component
public class OddsTask {
    @Autowired
    private BettingService bettingService;
    @Autowired
    private MatchDao matchDao;
    private List<Match> betfairMatches;
    private List<Match> databaseMatches;

    public void run() {
        betfairMatches = new ArrayList<>();
        databaseMatches = new ArrayList<>();
        databaseMatches = matchDao.retrieveAllMatches();

        for(Country country : Country.values()) {
            betfairMatches = bettingService.retrieveMatchByNationality(country.name(), getCompetitionId(country.name()));
        }
    //cut code
}

RetrieveBettingOdds

@Service
public class RetrieveBettingOdds implements BettingService {
    private static final String BETTING_END_POINT = "https://api.betfair.com/exchange/betting/json-rpc/v1";
    private static final String APP_KEY = "my_app_key";
    private String token;

    @Override
    public List<Match> retrieveMatchByNationality(String country, String competitionId) {
        token = SecurityContextHolder.getContext().getAuthentication().getDetails().toString();
    /**
    * Cut the following code, in which I create an HTTP request including the token
    **/
}

spring-mvc.xml

<bean id="oddsTask" class="tasks.OddsTask">
</bean>

<task:scheduler id="myScheduler" pool-size="10" />

<task:scheduled-tasks scheduler="myScheduler">
    <task:scheduled ref="oddsTask" method="run"
        fixed-delay="10000" initial-delay="60000" />
</task:scheduled-tasks>

我能用什么代替？我怎么才能修好它？

Answer 1

我有一个想法，不幸的是，我不能在这一点上测试，但我希望这在某种程度上有所帮助，或至少给你其他的想法，如何可以做到这一点。

如何定义使用活动会话更新数据结构的Http事件侦听器？

public class ActiveUsers implements HttpSessionListener {

    private ActiveUsersDao active = new ActiveUsersDao<>();

    @Override
    public void sessionCreated(HttpSessionEvent event) {
        active.add(event.getSession().getId());

    }

    @Override
    public void sessionDestroyed(HttpSessionEvent event) {
        active.remove(event.getSession().getId());
    }        
}

然后在web.xml中注册侦听器

<listener>
   <listener-class>com.stackoverflow.ActiveUsers</listener-class>
</listener>

最后，在您的计划bean中，您可以从DAO中获取数据。

@Service
public class TaskScheduler

   @Auotwired ActiveUsersDao activeUsers;

   @Scheduled
   public void run() {
      Set<String> snapshot = activeUsers.findAll();
      for(String user: snapshot) {
         //do what you've got to do
      }
   }