为什么onSuceeded（...）在JavaFX的方法不是所谓的第一次？

问题描述 投票：0回答：1

我试图从服务器加载数据。然后，加载的数据经由JavaFX的视图中显示。我使用的是服务执行网络操作，我使用Apache HttpClients这一点。起初，我认为错误是与网络相关联。我做了一些穴居式的调试和认识到的错误与该服务相关联。古怪，服务调用，当它运行第二（不同的实例，我没有重新启动服务）的onSucceeded（）方法。我无法弄清楚，为什么服务调用onSucceeded（）方法只是第二次。

这里的服务类我为执行网络操作来实现。

public class HttpClientService extends Service<String> {

    private static final String TAG = HttpClientService.class.getName();
    private static final Logger logger = Logger.getLogger(TAG);

    private ObjectProperty<URL> url = new SimpleObjectProperty<>();
    private ObservableList<NameValuePair> parameters = FXCollections.observableArrayList();

    public HttpClientService(String url, Map<String, String> map) throws MalformedURLException {
        setUrl(new URL(url));
        for (String name : map.keySet()) {
            String value = map.get(name);
            parameters.add(new BasicNameValuePair(name, value));
        }
    }

    public HttpClientService(String url, NameValuePair ... parameters) throws MalformedURLException {
        setUrl(new URL(url));
        getParameters().addAll(parameters);
    }

    public HttpClientService(URL url, NameValuePair ... parameters) {
        setUrl(url);
        getParameters().addAll(parameters);
    }

    protected Task<String> createTask() {
        return new HttpClientTask(getUrl(), getParameters());
    }

    public URL getUrl() {
        return url.get();
    }

    public ObjectProperty<URL> urlProperty() {
        return url;
    }

    public void setUrl(URL url) {
        this.url.set(url);
    }

    public ObservableList<NameValuePair> getParameters() {
        return parameters;
    }

    public void setParameters(ObservableList<NameValuePair> parameters) {
        this.parameters = parameters;
    }

    @Override
    protected void succeeded() {
        System.out.println("## Successful...");
    }

    @Override
    protected void failed() {
        Throwable exception = getException();

        System.out.println("Error: Failed to download guest profiles.");
        exception.printStackTrace();
    }

    @Override
    protected void cancelled() {
        System.out.println("HttpClientService was stopped.");
    }

    @Override
    protected void running() {
        logger.log(Level.INFO, "Running service...");
    }
}

下面是该调用服务和数据注入到一个视图的方法。

private void loadBlocks() {
    try {
        // TODO: Get the property identifier and set!
        Integer propertyIdentifier = 1;

        Map<String, String> parameters = new HashMap<>();
        parameters.put("property", propertyIdentifier.toString());

        HttpClientService service = new HttpClientService(UrlPath.ADMINISTRATION_PROPERTY_BLOCK_LIST_ALL, parameters);
        service.setOnSucceeded(workerStateEvent -> {
            logger.log(Level.INFO, "Successfully loaded blocks");

            try {
                String result = (String)workerStateEvent.getSource().getValue();
                logger.log(Level.INFO, result);

                List<Block> blocks = mapper.readValue(result, new TypeReference<ArrayList<Block>>(){});

                ObservableList<Block> items = blocksTableView.getItems();
                items.clear();
                items.addAll(blocks);

                NotificationHelper.postNotification(eventBus, "Successfully loaded blocks", 500);
            }
            catch (IOException exception) {
                exception.printStackTrace();
            }
        });
        service.stateProperty().addListener((observableValue, state, t1) -> System.out.println(t1));
        service.start();
    }
    catch (MalformedURLException exception) {
        exception.printStackTrace();
    }
}

下面是应用程序的日志。

SCHEDULED
RUNNING
Nov 10, 2018 2:28:26 PM com.onecube.pms.client.service.HttpClientService running
INFO: Running service...
Nov 10, 2018 2:28:26 PM com.onecube.pms.client.task.HttpClientTask call
INFO: [Content-Type: application/x-www-form-urlencoded,Content-Length: 10,Chunked: false]
14:28:26.778 [Thread-3] DEBUG org.apache.http.client.protocol.RequestAddCookies - CookieSpec selected: default
14:28:26.794 [Thread-3] DEBUG org.apache.http.client.protocol.RequestAuthCache - Auth cache not set in the context
14:28:26.796 [Thread-3] DEBUG org.apache.http.impl.conn.PoolingHttpClientConnectionManager - Connection request: [route: {}->http://localhost:8080][total kept alive: 0; route allocated: 0 of 100; total allocated: 0 of 200]
14:28:26.809 [Thread-3] DEBUG org.apache.http.impl.conn.PoolingHttpClientConnectionManager - Connection leased: [id: 0][route: {}->http://localhost:8080][total kept alive: 0; route allocated: 1 of 100; total allocated: 1 of 200]
14:28:26.810 [Thread-3] DEBUG org.apache.http.impl.execchain.MainClientExec - Opening connection {}->http://localhost:8080
14:28:26.829 [Thread-3] DEBUG org.apache.http.impl.conn.DefaultHttpClientConnectionOperator - Connecting to localhost/127.0.0.1:8080
14:28:26.830 [Thread-3] DEBUG org.apache.http.impl.conn.DefaultHttpClientConnectionOperator - Connection established 127.0.0.1:63671<->127.0.0.1:8080
14:28:26.831 [Thread-3] DEBUG org.apache.http.impl.execchain.MainClientExec - Executing request POST /administration/property/block/listAll HTTP/1.1
14:28:26.831 [Thread-3] DEBUG org.apache.http.impl.execchain.MainClientExec - Target auth state: UNCHALLENGED
14:28:26.834 [Thread-3] DEBUG org.apache.http.impl.execchain.MainClientExec - Proxy auth state: UNCHALLENGED
14:28:26.836 [Thread-3] DEBUG org.apache.http.headers - http-outgoing-0 >> POST /administration/property/block/listAll HTTP/1.1
14:28:26.836 [Thread-3] DEBUG org.apache.http.headers - http-outgoing-0 >> Content-Length: 10
14:28:26.836 [Thread-3] DEBUG org.apache.http.headers - http-outgoing-0 >> Content-Type: application/x-www-form-urlencoded
14:28:26.836 [Thread-3] DEBUG org.apache.http.headers - http-outgoing-0 >> Host: localhost:8080
14:28:26.836 [Thread-3] DEBUG org.apache.http.headers - http-outgoing-0 >> Connection: Keep-Alive
14:28:26.836 [Thread-3] DEBUG org.apache.http.headers - http-outgoing-0 >> User-Agent: Apache-HttpClient/4.5.6 (Java/11.0.1)
14:28:26.836 [Thread-3] DEBUG org.apache.http.headers - http-outgoing-0 >> Accept-Encoding: gzip,deflate
14:28:26.837 [Thread-3] DEBUG org.apache.http.wire - http-outgoing-0 >> "POST /administration/property/block/listAll HTTP/1.1[\r][\n]"
14:28:26.837 [Thread-3] DEBUG org.apache.http.wire - http-outgoing-0 >> "Content-Length: 10[\r][\n]"
14:28:26.837 [Thread-3] DEBUG org.apache.http.wire - http-outgoing-0 >> "Content-Type: application/x-www-form-urlencoded[\r][\n]"
14:28:26.837 [Thread-3] DEBUG org.apache.http.wire - http-outgoing-0 >> "Host: localhost:8080[\r][\n]"
14:28:26.837 [Thread-3] DEBUG org.apache.http.wire - http-outgoing-0 >> "Connection: Keep-Alive[\r][\n]"
14:28:26.837 [Thread-3] DEBUG org.apache.http.wire - http-outgoing-0 >> "User-Agent: Apache-HttpClient/4.5.6 (Java/11.0.1)[\r][\n]"
14:28:26.837 [Thread-3] DEBUG org.apache.http.wire - http-outgoing-0 >> "Accept-Encoding: gzip,deflate[\r][\n]"
14:28:26.837 [Thread-3] DEBUG org.apache.http.wire - http-outgoing-0 >> "[\r][\n]"
14:28:26.838 [Thread-3] DEBUG org.apache.http.wire - http-outgoing-0 >> "property=1"
14:28:26.845 [Thread-3] DEBUG org.apache.http.wire - http-outgoing-0 << "HTTP/1.1 200 [\r][\n]"
14:28:26.846 [Thread-3] DEBUG org.apache.http.wire - http-outgoing-0 << "Content-Type: application/json;charset=UTF-8[\r][\n]"
14:28:26.846 [Thread-3] DEBUG org.apache.http.wire - http-outgoing-0 << "Transfer-Encoding: chunked[\r][\n]"
14:28:26.846 [Thread-3] DEBUG org.apache.http.wire - http-outgoing-0 << "Date: Sat, 10 Nov 2018 08:58:26 GMT[\r][\n]"
14:28:26.846 [Thread-3] DEBUG org.apache.http.wire - http-outgoing-0 << "[\r][\n]"
14:28:26.846 [Thread-3] DEBUG org.apache.http.wire - http-outgoing-0 << "2[\r][\n]"
14:28:26.846 [Thread-3] DEBUG org.apache.http.wire - http-outgoing-0 << "[][\r][\n]"
14:28:26.846 [Thread-3] DEBUG org.apache.http.wire - http-outgoing-0 << "0[\r][\n]"
14:28:26.846 [Thread-3] DEBUG org.apache.http.wire - http-outgoing-0 << "[\r][\n]"
14:28:26.850 [Thread-3] DEBUG org.apache.http.headers - http-outgoing-0 << HTTP/1.1 200 
14:28:26.850 [Thread-3] DEBUG org.apache.http.headers - http-outgoing-0 << Content-Type: application/json;charset=UTF-8
java.lang.Throwable
    at com.onecube.pms.client.task.HttpClientTask.call(HttpClientTask.java:81)
    at com.onecube.pms.client.task.HttpClientTask.call(HttpClientTask.java:32)
    at javafx.concurrent.Task$TaskCallable.call(Task.java:1425)
    at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:264)
    at javafx.concurrent.Service.lambda$executeTask$6(Service.java:725)
    at java.base/java.security.AccessController.doPrivileged(Native Method)
    at javafx.concurrent.Service.lambda$executeTask$7(Service.java:724)
    at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128)
    at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628)
    at java.base/java.lang.Thread.run(Thread.java:834)
14:28:26.850 [Thread-3] DEBUG org.apache.http.headers - http-outgoing-0 << Transfer-Encoding: chunked
14:28:26.850 [Thread-3] DEBUG org.apache.http.headers - http-outgoing-0 << Date: Sat, 10 Nov 2018 08:58:26 GMT
14:28:26.856 [Thread-3] DEBUG org.apache.http.impl.execchain.MainClientExec - Connection can be kept alive indefinitely
14:28:26.860 [Thread-3] DEBUG org.apache.http.impl.conn.PoolingHttpClientConnectionManager - Connection [id: 0][route: {}->http://localhost:8080] can be kept alive indefinitely
14:28:26.861 [Thread-3] DEBUG org.apache.http.impl.conn.DefaultManagedHttpClientConnection - http-outgoing-0: set socket timeout to 0
14:28:26.861 [Thread-3] DEBUG org.apache.http.impl.conn.PoolingHttpClientConnectionManager - Connection released: [id: 0][route: {}->http://localhost:8080][total kept alive: 1; route allocated: 1 of 100; total allocated: 1 of 200]
SCHEDULED
RUNNING
Nov 10, 2018 2:28:43 PM com.onecube.pms.client.service.HttpClientService running
INFO: Running service...
Nov 10, 2018 2:28:43 PM com.onecube.pms.client.task.HttpClientTask call
INFO: [Content-Type: application/x-www-form-urlencoded,Content-Length: 10,Chunked: false]
14:28:43.429 [Thread-4] DEBUG org.apache.http.client.protocol.RequestAddCookies - CookieSpec selected: default
14:28:43.430 [Thread-4] DEBUG org.apache.http.client.protocol.RequestAuthCache - Auth cache not set in the context
14:28:43.431 [Thread-4] DEBUG org.apache.http.impl.conn.PoolingHttpClientConnectionManager - Connection request: [route: {}->http://localhost:8080][total kept alive: 0; route allocated: 0 of 100; total allocated: 0 of 200]
14:28:43.431 [Thread-4] DEBUG org.apache.http.impl.conn.PoolingHttpClientConnectionManager - Connection leased: [id: 1][route: {}->http://localhost:8080][total kept alive: 0; route allocated: 1 of 100; total allocated: 1 of 200]
14:28:43.431 [Thread-4] DEBUG org.apache.http.impl.execchain.MainClientExec - Opening connection {}->http://localhost:8080
14:28:43.431 [Thread-4] DEBUG org.apache.http.impl.conn.DefaultHttpClientConnectionOperator - Connecting to localhost/127.0.0.1:8080
14:28:43.432 [Thread-4] DEBUG org.apache.http.impl.conn.DefaultHttpClientConnectionOperator - Connection established 127.0.0.1:63675<->127.0.0.1:8080
14:28:43.432 [Thread-4] DEBUG org.apache.http.impl.execchain.MainClientExec - Executing request POST /administration/property/block/listAll HTTP/1.1
14:28:43.432 [Thread-4] DEBUG org.apache.http.impl.execchain.MainClientExec - Target auth state: UNCHALLENGED
14:28:43.433 [Thread-4] DEBUG org.apache.http.impl.execchain.MainClientExec - Proxy auth state: UNCHALLENGED
14:28:43.433 [Thread-4] DEBUG org.apache.http.headers - http-outgoing-1 >> POST /administration/property/block/listAll HTTP/1.1
14:28:43.434 [Thread-4] DEBUG org.apache.http.headers - http-outgoing-1 >> Content-Length: 10
14:28:43.434 [Thread-4] DEBUG org.apache.http.headers - http-outgoing-1 >> Content-Type: application/x-www-form-urlencoded
14:28:43.434 [Thread-4] DEBUG org.apache.http.headers - http-outgoing-1 >> Host: localhost:8080
14:28:43.434 [Thread-4] DEBUG org.apache.http.headers - http-outgoing-1 >> Connection: Keep-Alive
14:28:43.434 [Thread-4] DEBUG org.apache.http.headers - http-outgoing-1 >> User-Agent: Apache-HttpClient/4.5.6 (Java/11.0.1)
14:28:43.434 [Thread-4] DEBUG org.apache.http.headers - http-outgoing-1 >> Accept-Encoding: gzip,deflate
14:28:43.434 [Thread-4] DEBUG org.apache.http.wire - http-outgoing-1 >> "POST /administration/property/block/listAll HTTP/1.1[\r][\n]"
14:28:43.434 [Thread-4] DEBUG org.apache.http.wire - http-outgoing-1 >> "Content-Length: 10[\r][\n]"
14:28:43.434 [Thread-4] DEBUG org.apache.http.wire - http-outgoing-1 >> "Content-Type: application/x-www-form-urlencoded[\r][\n]"
14:28:43.434 [Thread-4] DEBUG org.apache.http.wire - http-outgoing-1 >> "Host: localhost:8080[\r][\n]"
14:28:43.434 [Thread-4] DEBUG org.apache.http.wire - http-outgoing-1 >> "Connection: Keep-Alive[\r][\n]"
14:28:43.434 [Thread-4] DEBUG org.apache.http.wire - http-outgoing-1 >> "User-Agent: Apache-HttpClient/4.5.6 (Java/11.0.1)[\r][\n]"
14:28:43.434 [Thread-4] DEBUG org.apache.http.wire - http-outgoing-1 >> "Accept-Encoding: gzip,deflate[\r][\n]"
14:28:43.435 [Thread-4] DEBUG org.apache.http.wire - http-outgoing-1 >> "[\r][\n]"
14:28:43.435 [Thread-4] DEBUG org.apache.http.wire - http-outgoing-1 >> "property=1"
java.lang.Throwable
    at com.onecube.pms.client.task.HttpClientTask.call(HttpClientTask.java:81)
    at com.onecube.pms.client.task.HttpClientTask.call(HttpClientTask.java:32)
    at javafx.concurrent.Task$TaskCallable.call(Task.java:1425)
    at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:264)
    at javafx.concurrent.Service.lambda$executeTask$6(Service.java:725)
    at java.base/java.security.AccessController.doPrivileged(Native Method)
    at javafx.concurrent.Service.lambda$executeTask$7(Service.java:724)
    at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128)
    at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628)
    at java.base/java.lang.Thread.run(Thread.java:834)
Nov 10, 2018 2:28:43 PM com.onecube.pms.client.controller.administration.room.ManageBlocksController lambda$loadBlocks$2
INFO: Successfully loaded blocks
Nov 10, 2018 2:28:43 PM com.onecube.pms.client.controller.administration.room.ManageBlocksController lambda$loadBlocks$2
INFO: []
14:28:43.444 [Thread-4] DEBUG org.apache.http.wire - http-outgoing-1 << "HTTP/1.1 200 [\r][\n]"
14:28:43.449 [Thread-4] DEBUG org.apache.http.wire - http-outgoing-1 << "Content-Type: application/json;charset=UTF-8[\r][\n]"
14:28:43.449 [Thread-4] DEBUG org.apache.http.wire - http-outgoing-1 << "Transfer-Encoding: chunked[\r][\n]"
14:28:43.449 [Thread-4] DEBUG org.apache.http.wire - http-outgoing-1 << "Date: Sat, 10 Nov 2018 08:58:43 GMT[\r][\n]"
14:28:43.449 [Thread-4] DEBUG org.apache.http.wire - http-outgoing-1 << "[\r][\n]"
14:28:43.449 [Thread-4] DEBUG org.apache.http.wire - http-outgoing-1 << "2[\r][\n]"
14:28:43.449 [Thread-4] DEBUG org.apache.http.wire - http-outgoing-1 << "[][\r][\n]"
14:28:43.449 [Thread-4] DEBUG org.apache.http.wire - http-outgoing-1 << "0[\r][\n]"
14:28:43.449 [Thread-4] DEBUG org.apache.http.wire - http-outgoing-1 << "[\r][\n]"
14:28:43.450 [Thread-4] DEBUG org.apache.http.headers - http-outgoing-1 << HTTP/1.1 200 
14:28:43.450 [Thread-4] DEBUG org.apache.http.headers - http-outgoing-1 << Content-Type: application/json;charset=UTF-8
14:28:43.450 [Thread-4] DEBUG org.apache.http.headers - http-outgoing-1 << Transfer-Encoding: chunked
14:28:43.451 [Thread-4] DEBUG org.apache.http.headers - http-outgoing-1 << Date: Sat, 10 Nov 2018 08:58:43 GMT
14:28:43.452 [Thread-4] DEBUG org.apache.http.impl.execchain.MainClientExec - Connection can be kept alive indefinitely
14:28:43.453 [Thread-4] DEBUG org.apache.http.impl.conn.PoolingHttpClientConnectionManager - Connection [id: 1][route: {}->http://localhost:8080] can be kept alive indefinitely
14:28:43.453 [Thread-4] DEBUG org.apache.http.impl.conn.DefaultManagedHttpClientConnection - http-outgoing-1: set socket timeout to 0
14:28:43.453 [Thread-4] DEBUG org.apache.http.impl.conn.PoolingHttpClientConnectionManager - Connection released: [id: 1][route: {}->http://localhost:8080][total kept alive: 1; route allocated: 1 of 100; total allocated: 1 of 200]
## Successful...
SUCCEEDED
javafx concurrency apache-httpclient-4.x javafx-11
1个回答
1
投票

从你告诉我们，你的代码没有任何地方抱持着强烈的参考HttpClientService。这使我相信，HttpClientService正在garbage collected其HttpClientTask完成之前。一些快速测试证实这是可能的。而事实上documentation特别警告一下：

一旦服务启动时，它会安排其工作，并听取了更改任务的状态。任务不成立，以启动它，这意味着正在运行的任务将无法防止服务被垃圾收集服务的参考。

为了解决这个问题，你需要保持一个强大的参考HttpClientService实例。这可以通过地方存放在loadBlocks()属于类完成（假定说类的实例也被强烈引用）。然后，当服务终止您可以删除引用（因为你目前没有重用服务）。另一种解决方案是直接用HttpClientTask只有使用HttpClientService当你准备好实施。

需要注意的是HttpClientTask没有垃圾收集。这是因为它是从执行它的Thread强可到达。因此，你的后台任务正常完成，但不再有一个HttpClientService通知您。

此外，还有就是你运行该代码的第一时间和任何后续时间之间没有差别。它适用于第二次调用的事实仅仅是运气。该HttpClientService受每次调用此方法时，垃圾收集;然而，谁也不能保证垃圾收集周期将运行，这意味着你会得到幸运不时。

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