Grails：如何在异步网络请求后将对象保存到数据库？

Question

我很难对并行服务进行编程。目标是使用异步 API 调用从 Facebook 检索数据，然后迭代同步执行 GORM 操作的检索数据。

异步获取数据的第一步似乎适用于：

List<Activity> activityList = Activity.findAllByFacebookPageIsNotNullAndFetchEvents(true, [max: 100])
PromiseList promiseList = new PromiseList()
activityList.each { Activity activity->
    promiseList << { fetchEventData(activity.facebookPage, null) }
}

现在我正在尝试迭代结果，例如：

promiseList.onComplete { List results ->
    results.each { ArrayList eventSet ->
        eventSet.each { LazyMap eventData ->
            createEvent(eventData)
        }
    }
}

createEvent() 方法尝试保存新的 Event。此操作失败并显示：

2017-04-11 10:56:47.018 ERROR --- [ctor Thread 129] o.h.engine.jdbc.spi.SqlExceptionHelper : No operations allowed after statement closed. 2017-04-11 10:56:47.024 ERROR --- [ctor Thread 124] o.h.engine.jdbc.spi.SqlExceptionHelper : No operations allowed after statement closed. 2017-04-11 10:56:47.024 ERROR --- [ctor Thread 125] o.h.engine.jdbc.spi.SqlExceptionHelper : Cannot convert value '2017-01-11 23:31:39' from column 3 to TIMESTAMP. 2017-04-11 10:56:47.025 ERROR --- [ctor Thread 105] o.h.engine.jdbc.spi.SqlExceptionHelper : No operations allowed after statement closed. 2017-04-11 10:56:47.026 ERROR --- [ctor Thread 103] o.h.engine.jdbc.spi.SqlExceptionHelper : No operations allowed after statement closed. 2017-04-11 10:56:47.026 ERROR --- [ctor Thread 107] o.h.engine.jdbc.spi.SqlExceptionHelper : No operations allowed after statement closed.

所以我猜 createEvent() 是从各种线程而不是 "main" 线程调用的。

有人可以告诉我如何以正确的方式做到这一点吗？

编辑：

我也试过：

List<ArrayList> promiseResult = promiseList.get()
promiseResult.each { ArrayList<LazyMap> eventList ->
    eventList.each {
        Event.findByFacebookId((String) it['id'])
        //createEvent(it)
    }
}

失败 java.lang.NullPointerException

Answer 1

试试这个

Event.withNewSession {
    Event.withNewTransaction {
        // Event update code here
    }
}

Answer 2

感谢您的回答。我认为他们让我走上了正确的道路。也许我不清楚我想要达到的目标。 GORM 调用不一定是异步的。虽然这似乎仍然是个好主意！我的方法是放慢速度：D

但是我使用 waitAll() 实现了所需的行为，然后进行了数据库处理。

一个工作示例是：

List<Activity> activityList = Activity.findAllByFacebookPageIsNotNullAndFetchEvents(true, [max: 100])
List promises = []
activityList.each { Activity activity->
    promises << task { fetchEventData(activity.facebookPage, null) } // query website asynchronously; this is really fast!
}

def promisesResults = waitAll(promises)

promisesResults.each { ArrayList<LazyMap> eventList ->
    eventList.each { LazyMap eventData ->
        try {
           createEvent(eventData) // DB actions; this is pretty slow
        } catch (e) {
            log.error(e.toString())
        }
    }
}

Grails：如何在异步网络请求后将对象保存到数据库？

Grails: How to save objects to DB after async web requests?

grails

multithreading

jdbc

grails-orm