Java 8 Singleton,无法进入可运行任务
我正在尝试自动运行任务(所有30秒) 为此,我构建了一个singleton:Java 8 Singleton,无法进入可运行任务,java-8,runnable,scheduledexecutorservice,vaadin8,Java 8,Runnable,Scheduledexecutorservice,Vaadin8,我正在尝试自动运行任务(所有30秒) 为此,我构建了一个singleton: public class PortalSingleton { private static final Logger LOG = LoggerFactory.getLogger(PortalSingleton.class); private static final int INITIAL_DELAY = 0; private static final int DELAY = 30;
public class PortalSingleton {
private static final Logger LOG = LoggerFactory.getLogger(PortalSingleton.class);
private static final int INITIAL_DELAY = 0;
private static final int DELAY = 30;
private static volatile ScheduledExecutorService instance;
private static HomepageView homeView = new HomepageView();
private PortalSingleton() {}
public static final void refreshGridHomePageAutomatically() {
Runnable task = () -> UI.getCurrent().access(() -> {
homeView.refreshGrid();
LOG.info("The grid has been refreshed Automatically");
});
getInstance().scheduleWithFixedDelay(task, INITIAL_DELAY, DELAY, TimeUnit.SECONDS);
}
public final static ScheduledExecutorService getInstance() {
if (instance == null) {
synchronized (ScheduledExecutorService.class) {
if (instance == null) {
instance = Executors.newScheduledThreadPool(1);
}
}
}
return instance;
}
}
但是,我没有任何问题/错误,我没有日志消息,我的网格也没有刷新
预期的行为是:
homeView.refreshGrid()代码>,我没有日志消息
我做错了什么
谢谢
编辑:我通过执行以下操作来调用它:PortalSingleton.refreshGridHomePageAutomatically()代码>
EDIT2,谢谢@Holger:
public class PortalSingleton {
private static final Logger LOG = LoggerFactory.getLogger(PortalSingleton.class);
private static final int INITIAL_DELAY = 0;
private static final int DELAY = 30;
private static final ScheduledExecutorService instance = Executors.newScheduledThreadPool(1);
private static HomepageView homeView = new HomepageView();
private PortalSingleton() {
}
public static final void refreshGridHomePageAutomatically() {
Runnable task = () -> UI.getCurrent().access(() -> {
homeView.refreshGrid();
LOG.info("The grid has been refreshed Automatically");
});
try {
getInstance().scheduleWithFixedDelay(task, INITIAL_DELAY, DELAY, TimeUnit.SECONDS);
} catch (Exception e) {
LOG.error("error" + e);
}
}
public final static ScheduledExecutorService getInstance() {
return instance;
}
}
当您计划一个操作时,当异常发生时,您不会得到反馈。相反,它将停止执行它:
:
…如果任务的任何执行遇到异常,则会抑制后续执行
因此,您必须在操作本身中使用try…catch
块来报告它,例如在定义Runnable
的lambda表达式中:
Runnable task = () -> {
try { UI.getCurrent().access(…); }
catch (Exception e) { LOG.error("error" + e); }
};
在我看来,您正在从非UI线程调用UI.getCurrent()
,我怀疑该线程返回null
,在尝试对其调用方法时导致NullPointerException
。没有抱怨。。我希望看到消息“网格已自动刷新”和我的网格刷新,但我没有预期的行为。所以我不明白我做错了什么,因为,我没有任何错误消息…@Holger,我编辑了我的帖子,更清楚了吗?谢谢你的帮助!我尝试对ScheduledExecutorService使用try/catch(请参阅我文章中的EDIT2)。我认为这不好,因为我没有任何错误,仍然没有预期的行为。你是对的!!NPE!谢谢你的帮助!!!你想把它作为答案吗?我可以结束这篇文章。是的,你完全正确:我不应该调用UI.getCurrent(),我删除了它。我不在UI中。当我调试时,UI.getCurrent()上没有NPE,但NPE显示为Try/Catch再次感谢您的帮助!