[英]Scheduled Executor Service isn't working
I want a specific task to run everyday (every 24 hours).我希望每天(每 24 小时)运行一个特定任务。 I used a scheduled executor service but after I tested it with 20 seconds to see if the task would run, it didn't.我使用了计划的执行程序服务,但在我用 20 秒测试它以查看任务是否会运行后,它没有。 Am I doing something wrong?难道我做错了什么? Any help would be greatly appreciated.任何帮助将不胜感激。
ScheduledExecutorService scheduler = Executors
.newScheduledThreadPool(1);
scheduler.scheduleWithFixedDelay(new TimerTask() {
public void run() {
ArrayList<Integer> people = new ArrayList<Integer>();
try {
shelf.g.setOverdue();
for (int i = 1; i < 1000; i++) {
if (shelf.book[i] != null
&& shelf.book[i].checkedOut != null) {
if (shelf.book[i].overdue == true) {
for (int i2 = 0; i < 600; i++) {
if (account.person[i] == null) {
account.person[i] = new account();
}
if (account.person[i2].name
.equalsIgnoreCase(shelf.book[i].personName)) {
people.add(i2);
}
}
}
}
}
Set<Integer> s = new LinkedHashSet<Integer>(people);
people = new ArrayList<Integer>(s);
ArrayList<String> books = new ArrayList<String>();
Properties props = new Properties();
Session session = Session.getInstance(props);
MimeMessage msg = new MimeMessage(session);
Transport t = null;
Address from = new InternetAddress(
"LGCCLibrary42@gmail.com", "LGCC Library");
for (int i = 0; i < people.size(); i++) {
for (int i2 = 1; i2 < 1000; i2++) {
if (shelf.book[i2] != null
&& shelf.book[i2].checkedOut != null) {
if (shelf.book[i2].overdue == true) {
if (account.person[people.get(i)].name
.equalsIgnoreCase(shelf.book[i2].personName)) {
books.add("Book " + i2 + " - " + shelf.book[i2].bookName
+ "\n");
}
}
}
}
String thePerson = account.person[people.get(i)].name;
Address to = new InternetAddress(account.person[people
.get(i)].eMail);
msg.setText(thePerson
+ " , you have the following books overdue"
+ "\n" + books.toString().replace("[", "").replace("]", ""));
msg.setFrom(from);
msg.setRecipient(Message.RecipientType.TO, to);
msg.setSubject("LGCC library overdue books");
t = session.getTransport("smtps");
t.connect("smtp.gmail.com", "LGCCLibrary42", "4JesusChrist");
t.sendMessage(msg, msg.getAllRecipients());
books.clear();
}
t.close();
} catch (UnsupportedEncodingException ex) {
// TODO Auto-generated catch block
JOptionPane.showMessageDialog(null, "Something went wrong",
"Alert", JOptionPane.ERROR_MESSAGE);
} catch (AddressException ex) {
// TODO Auto-generated catch block
JOptionPane.showMessageDialog(null, "Something went wrong",
"Alert", JOptionPane.ERROR_MESSAGE);
} catch (MessagingException ex) {
// TODO Auto-generated catch block
JOptionPane.showMessageDialog(null, "Something went wrong",
"Alert", JOptionPane.ERROR_MESSAGE);
}
}
}, 0, 24, TimeUnit.HOURS);
As @JeremeyFarrell said, use a Runnable
instead of a TimerTask
; 正如@JeremeyFarrell所说,使用Runnable
而不是TimerTask
; there is no functionality or benefit to be gained from using a TimerTask
. 使用TimerTask
没有任何功能或好处。
I've simplified your code and it just works without problems: 我已经简化了你的代码,它只是没有问题的工作:
ScheduledExecutorService scheduler = Executors
.newScheduledThreadPool(1);
scheduler.scheduleWithFixedDelay(new Runnable() {
public void run() {
System.out.println("Do something useful");
}
}, 0, 1, TimeUnit.SECONDS);
The most likely cause of your problem can be found in the Javadoc of scheduleWithFixedDelay
: 您可能在scheduleWithFixedDelay
的Javadoc中找到问题的最可能原因:
If any execution of the task encounters an exception , subsequent executions are suppressed. 如果任务的任何执行遇到异常 ,则后续执行被禁止。
You probably had an exception, possibly a RuntimeException
(such as a NullPointerException
), which stopped further invocations. 您可能有一个异常,可能是RuntimeException
(例如NullPointerException
),它停止了进一步的调用。
One way to solve that is to catch all exceptions and log them. 解决这个问题的一种方法是捕获所有异常并记录它们。
scheduler.scheduleWithFixedDelay(new Runnable() {
public void run() {
try {
doTheRealWork(); // Such as "sendEmail()"
} catch (Exception e) {
e.printStackTrace(); // Or better, use next line if you have configured a logger:
logger.error("Exception in scheduled e-mail task", e);
}
}
}, 0, 1, TimeUnit.SECONDS);
(Note: of course, replace 1, TimeUnit.SECONDS
with 24, TimeUnit.HOURS
once you are satisfied that things work as expected) (注意:当然,一旦你对事情按预期工作,请将1, TimeUnit.SECONDS
替换为24, TimeUnit.HOURS
)
A few things to point out: 有几点需要指出:
JOptionPane.showMessageDialog
from a Thread that is not the UI thread. 您正在从不是UI线程的Thread调用JOptionPane.showMessageDialog
。 Swing doesn't support doing UI work from any thread except the main UI thread; Swing不支持从主UI线程以外的任何线程执行UI工作; if you still do, you can get all kinds of race conditions. 如果你仍然这样做,你可以获得各种竞争条件。 It is possible an exception occurs within the Task or also Runnable. Task 或 Runnable 中可能发生异常。 You will not recognize it.你不会认出它。 Try to implement something very simple first.首先尝试实现一些非常简单的东西。 Like a System.out.println("hello world").就像 System.out.println("hello world")。 Once this runs, work your way up to a more complex implementation.一旦运行,就可以逐步实现更复杂的实现。
声明:本站的技术帖子网页,遵循CC BY-SA 4.0协议,如果您需要转载,请注明本站网址或者原文地址。任何问题请咨询:yoyou2525@163.com.