Java 程序在 cronjob 调用后没有关闭

Question

我编写了一个 Java 程序来从我的邮件帐户中检索邮件。

此 jar 由 Ubuntu 服务器上的 cronjob 每 15 分钟调用一次。

定时任务:

/bin/sh /root/scripte/cron_bugtracker.sh

cron_bugtracker.sh:

java -jar /path/to/file.jar

jar 工作正常，但程序没有退出。

当我执行 ps ax | grep java 它总是以 java -jar/path/to/file.jar 作为命令显示很多 java 进程:

32208 ? Sl 0:59 java -jar /path/to/file.jar

我的 Java 程序是这样工作的:

1. 主要是调用构造函数
2. 在构造函数中，我调用了使用 javax.mail.* 获取邮件的方法
3. 那么程序就完成了……至少应该是

有谁知道为什么程序不退出？请帮忙。

编辑:

在日志文件中我发现了这个:

“Control”是我的主类的名称。

Full thread dump Java HotSpot(TM) Client VM (23.1-b03 mixed mode):

"Service Thread" daemon prio=10 tid=0xb76bd000 nid=0x292 runnable [0x00000000]
   java.lang.Thread.State: RUNNABLE

"C1 CompilerThread0" daemon prio=10 tid=0xb76bb400 nid=0x291 waiting on condition [0x00000000]
   java.lang.Thread.State: RUNNABLE

"Signal Dispatcher" daemon prio=10 tid=0xb76b9800 nid=0x290 waiting on condition [0x00000000]
   java.lang.Thread.State: RUNNABLE

"Finalizer" daemon prio=10 tid=0xb7681c00 nid=0x28f in Object.wait() [0xa10ad000]
   java.lang.Thread.State: WAITING (on object monitor)
        at java.lang.Object.wait(Native Method)
        - waiting on <0xa1585650> (a java.lang.ref.ReferenceQueue$Lock)
        at java.lang.ref.ReferenceQueue.remove(Unknown Source)
        - locked <0xa1585650> (a java.lang.ref.ReferenceQueue$Lock)
        at java.lang.ref.ReferenceQueue.remove(Unknown Source)
        at java.lang.ref.Finalizer$FinalizerThread.run(Unknown Source)

"Reference Handler" daemon prio=10 tid=0xb7680000 nid=0x28e in Object.wait() [0xa10fe000]
   java.lang.Thread.State: WAITING (on object monitor)
        at java.lang.Object.wait(Native Method)
        - waiting on <0xa1585228> (a java.lang.ref.Reference$Lock)
        at java.lang.Object.wait(Object.java:503)
        at java.lang.ref.Reference$ReferenceHandler.run(Unknown Source)
        - locked <0xa1585228> (a java.lang.ref.Reference$Lock)

"main" prio=10 tid=0xb7606000 nid=0x28c runnable [0xb77ae000]
   java.lang.Thread.State: RUNNABLE

        at java.lang.ClassLoader.findBootstrapClass(Native Method)
        at java.lang.ClassLoader.findBootstrapClassOrNull(Unknown Source)
        at java.lang.ClassLoader.loadClass(Unknown Source)
        - locked <0xa1855398> (a java.lang.Object)
        at java.lang.ClassLoader.loadClass(Unknown Source)
        at com.sun.mail.pop3.POP3Folder.createMessage(POP3Folder.java:362)
        at com.sun.mail.pop3.POP3Folder.getMessage(POP3Folder.java:343)
        - locked <0xa18261a0> (a com.sun.mail.pop3.POP3Folder)
        at javax.mail.Folder.getMessages(Folder.java:947)
        - locked <0xa18261a0> (a com.sun.mail.pop3.POP3Folder)
        at javax.mail.Folder.search(Folder.java:1231)
        at Control.receive(Control.java:53)
        at Control.<init>(Control.java:29)
        at Control.main(Control.java:24)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
        at java.lang.reflect.Method.invoke(Unknown Source)
        at org.eclipse.jdt.internal.jarinjarloader.JarRsrcLoader.main(JarRsrcLoader.java:58)

"VM Thread" prio=10 tid=0xb767a800 nid=0x28d runnable

"VM Periodic Task Thread" prio=10 tid=0xb76bf800 nid=0x293 waiting on condition

JNI global references: 163

Heap
 def new generation   total 4928K, used 2907K [0xa1580000, 0xa1ad0000, 0xa6ad0000)
  eden space 4416K,  65% used [0xa1580000, 0xa1856e20, 0xa19d0000)
  from space 512K,   0% used [0xa19d0000, 0xa19d0000, 0xa1a50000)
  to   space 512K,   0% used [0xa1a50000, 0xa1a50000, 0xa1ad0000)
 tenured generation   total 10944K, used 0K [0xa6ad0000, 0xa7580000, 0xb1580000)
   the space 10944K,   0% used [0xa6ad0000, 0xa6ad0000, 0xa6ad0200, 0xa7580000)
 compacting perm gen  total 12288K, used 2688K [0xb1580000, 0xb2180000, 0xb5580000)
   the space 12288K,  21% used [0xb1580000, 0xb1820230, 0xb1820400, 0xb2180000)
No shared spaces configured.

Answer 1

执行线程转储以找出仍在运行的内容:如果您使用的是 Oracle JVM，则可以使用 jstack PID。