場景：測試伺服器上，在未停止tomcat的情況下直接修改了配置檔案(properties檔案)，稍後再有請求進來時(該請求會使用到properties檔案中的屬性)，引發了OOM

tomcat7.0.50配置檔案：
	conf/server.xml中：
		<Context docBase="advertise-war" path="/advertise-war" reloadable="true" />
		path：		訪問該Web應用的URL入口
		reloadable：tomcat在執行時會監控 WEB-INF/classes 和 WEB-INF/lib目錄下的class檔案，如果監測到有class檔案被更新的，tomcat會自動重新載入(先解除安裝，再部署)Web應用。

分析：
	1)在解除安裝的過程中，(大概是由於檔案被修改後)程式可能出錯，導致原來的web應用解除安裝失敗，從而導致原來的web應用仍然存在於Tomcat的快取之中。
	2)雖然解除安裝失敗，但是tomcat仍然會部署修改後的web應用。
	3)從而導致：tomcat在重新部署web應用時，由於無法刪除已有的快取，故可能會出現記憶體溢位的異常。
	
建議：
	1)將reloadable屬性設為false。
	2)將需要經常修改的配置檔案(properties檔案等)的配置資訊持久化到資料庫中。
		即：獲取配置資訊的策略由 配置檔案的形式 改為 從資料庫中獲取(如果頻繁使用,則放到快取中)。
		
		
		
 

之後進行本地測試時，部分日誌的擷取：


注：雖然沒有報OOM，但是從日誌可以推斷出：如果重啟前，正在執行的執行緒比較多的話，則在重啟的過程中很可能報OOM。


 7:39:42 下午 org.apache.catalina.core.StandardContext reload
資訊: Reloading Context with name [/landpage-***-war] has started
 7:39:42 下午 org.apache.catalina.core.StandardWrapper unload
資訊: Waiting for 1 instance(s) to be deallocated for Servlet [advertise-landpage]
 7:39:43 下午 org.apache.catalina.core.ApplicationContext log
資訊: Destroying Spring FrameworkServlet 'advertise-landpage'
 7:39:43 下午 org.apache.catalina.core.ApplicationContext log
資訊: Closing Spring root WebApplicationContext
 7:39:43 下午 org.apache.catalina.loader.WebappClassLoaderBase clearReferencesJdbc
警告: The web application [landpage-***-war] registered the JDBC driver [com.mysql.jdbc.Driver] but failed to unregister it when the web application was stopped. To prevent a memory leak, the JDBC Driver has been forcibly unregistered.
 7:39:43 下午 org.apache.catalina.loader.WebappClassLoaderBase clearReferencesThreads
警告: The web application [landpage-***-war] appears to have started a thread named [Abandoned connection cleanup thread] but has failed to stop it. This is very likely to create a memory leak. Stack trace of thread:
java.lang.Object.wait(Native Method)
java.lang.ref.ReferenceQueue.remove(Unknown Source)
com.mysql.jdbc.AbandonedConnectionCleanupThread.run(AbandonedConnectionCleanupThread.java:40)
 7:39:43 下午 org.apache.catalina.loader.WebappClassLoaderBase clearReferencesThreads
警告: The web application [landpage-***-war] appears to have started a thread named [Timer-0] but has failed to stop it. This is very likely to create a memory leak.

Stack trace of thread:
java.lang.Object.wait(Native Method)
java.util.TimerThread.mainLoop(Unknown Source)
java.util.TimerThread.run(Unknown Source)
 7:39:43 下午 org.apache.catalina.loader.WebappClassLoaderBase clearReferencesThreads
警告: The web application [landpage-***-war] appears to have started a thread named [MySQL Statement Cancellation Timer] but has failed to stop it. This is very likely to create a memory leak. Stack trace of thread:
java.lang.Object.wait(Native Method)
java.lang.Object.wait(Unknown Source)
java.util.TimerThread.mainLoop(Unknown Source)
java.util.TimerThread.run(Unknown Source)
 7:39:43 下午 org.apache.catalina.loader.WebappClassLoaderBase checkThreadLocalMapForLeaks
嚴重: The web application [landpage-***-war] created a ThreadLocal with key of type [org.springframework.core.NamedThreadLocal] (value [Locale context]) and a value of type [org.springframework.context.i18n.SimpleLocaleContext] (value [zh_CN]) but failed to remove it when the web application was stopped. Threads are going to be renewed over time to try and avoid a probable memory leak.
 7:39:43 下午 org.apache.catalina.loader.WebappClassLoaderBase checkThreadLocalMapForLeaks
嚴重: The web application [landpage-***-war] created a ThreadLocal with key of type [org.springframework.core.NamedThreadLocal] (value [Request attributes]) and a value of type [org.springframework.web.context.request.ServletRequestAttributes] (value [o[email protected]]) but failed to remove it when the web application was stopped. Threads are going to be renewed over time to try and avoid a probable memory leak.
 7:39:46 下午 org.apache.jasper.servlet.TldScanner scanJars
資訊: At least one JAR was scanned for TLDs yet contained no TLDs. Enable debug logging for this logger for a complete list of JARs that were scanned but no TLDs were found in them. Skipping unneeded JARs during scanning can improve startup time and JSP compilation time.
 7:39:46 下午 org.apache.catalina.core.ApplicationContext log
資訊: No Spring WebApplicationInitializer types detected on classpath

 7:39:46 下午 org.apache.catalina.core.ApplicationContext log
資訊: Initializing Spring root WebApplicationContext

 7:39:49 下午 org.apache.catalina.core.ApplicationContext log
資訊: Initializing Spring FrameworkServlet 'advertise-landpage'

 7:39:50 下午 org.apache.catalina.core.StandardContext reload
資訊: Reloading Context with name [/landpage-***-war] is completed