???????????
??????Java????????????User Thread(??????)??Daemon Thread(??????)
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????Daemon?????????????????????????????????????????????? GC (??????????)?????????????????????
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????User??Daemon??????????????????????????????????????? User Thread????????????????????Daemon Thread??????????????????? ???????????????Daemon???й?????????????м??????г?????????
?????????????????????飬?????????????????????????????Daemon??????????????????????
????????????????????????????????????е???????????????????
??????JVM?????е?????????????????JVM????????????????????????????????????JVM?????????
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????????ó??????comet?????????????У?????????????????????????????ChatServlet??servlet?????????servlet??init??????????servlet???????????????????????servlet??????????????????Servlet???????????????????????????????????????????Servlet??????????
?????????????????
????????????????????ClassLoader?????????Web??ó?????????Щ???????????JVM??????????????????JVM?????????????Web ????????????????????????????????????Web??ó?????????????????????????Web????????????????????????????????????? ?????????????о????????????????Web???????????????
?????????????????JDK Timer??Quartz??Scheduler??????Web???????????Timer????Web?????????????????????????Timer??????Timer?е?????????????У?
????Spring? JDK Timer ?? Quartz Scheduler ??????TimerFactoryBean ?? SchedulerFactoryBean?????Spring????????????????????? Spring???????????????????????Spring??????????????????????????Spring???????????FactoryBean?????????????? Spring IoC ?л???????????y??????????????????????Web??????????????????е?????????????????????????Timer??Scheduler???粻???ж??????????????????????