异常描述：运行项目期间不定时出现此异常
具体异常信息：
严重: Unexpected death of background thread ContainerBackgroundProcessor[StandardEngine[Catalina]]
java.lang.OutOfMemoryError: PermGen space
at java.lang.ClassLoader.defineClass1(Native Method)
at java.lang.ClassLoader.defineClass(ClassLoader.java:800)
at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142)
at org.apache.catalina.loader.WebappClassLoader.findClassInternal(WebappClassLoader.java:2957)
at org.apache.catalina.loader.WebappClassLoader.findClass(WebappClassLoader.java:1210)
at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1690)
at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1571)
at freemarker.template.Template.<init>(Template.java:166)
at freemarker.cache.TemplateCache.loadTemplate(TemplateCache.java:447)
at freemarker.cache.TemplateCache.getTemplate(TemplateCache.java:360)
at freemarker.cache.TemplateCache.getTemplate(TemplateCache.java:235)
at freemarker.template.Configuration.getTemplate(Configuration.java:578)
at freemarker.template.Configuration.getTemplate(Configuration.java:543)
at org.apache.struts2.dispatcher.DefaultDispatcherErrorHandler.init(DefaultDispatcherErrorHandler.java:48)
at org.apache.struts2.dispatcher.Dispatcher.init(Dispatcher.java:488)
at org.apache.struts2.dispatcher.ng.InitOperations.initDispatcher(InitOperations.java:74)
at org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter.init(StrutsPrepareAndExecuteFilter.java:57)
at org.apache.catalina.core.ApplicationFilterConfig.initFilter(ApplicationFilterConfig.java:279)
at org.apache.catalina.core.ApplicationFilterConfig.getFilter(ApplicationFilterConfig.java:260)
at org.apache.catalina.core.ApplicationFilterConfig.<init>(ApplicationFilterConfig.java:105)
at org.apache.catalina.core.StandardContext.filterStart(StandardContext.java:4854)
at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5542)
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
at org.apache.catalina.core.StandardContext.reload(StandardContext.java:4033)
at org.apache.catalina.loader.WebappLoader.backgroundProcess(WebappLoader.java:425)
at org.apache.catalina.core.ContainerBase.backgroundProcess(ContainerBase.java:1345)
at org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.processChildren(ContainerBase.java:1546)
at org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.processChildren(ContainerBase.java:1556)
at org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.processChildren(ContainerBase.java:1556)
at org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.run(ContainerBase.java:1524)
at java.lang.Thread.run(Thread.java:745)
Exception in thread "ContainerBackgroundProcessor[StandardEngine[Catalina]]" java.lang.OutOfMemoryError: PermGen space
at java.lang.ClassLoader.defineClass1(Native Method)
at java.lang.ClassLoader.defineClass(ClassLoader.java:800)
at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142)
at org.apache.catalina.loader.WebappClassLoader.findClassInternal(WebappClassLoader.java:2957)
at org.apache.catalina.loader.WebappClassLoader.findClass(WebappClassLoader.java:1210)
at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1690)
at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1571)
at freemarker.template.Template.<init>(Template.java:166)
at freemarker.cache.TemplateCache.loadTemplate(TemplateCache.java:447)
at freemarker.cache.TemplateCache.getTemplate(TemplateCache.java:360)
at freemarker.cache.TemplateCache.getTemplate(TemplateCache.java:235)
at freemarker.template.Configuration.getTemplate(Configuration.java:578)
at freemarker.template.Configuration.getTemplate(Configuration.java:543)
at org.apache.struts2.dispatcher.DefaultDispatcherErrorHandler.init(DefaultDispatcherErrorHandler.java:48)
at org.apache.struts2.dispatcher.Dispatcher.init(Dispatcher.java:488)
at org.apache.struts2.dispatcher.ng.InitOperations.initDispatcher(InitOperations.java:74)
at org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter.init(StrutsPrepareAndExecuteFilter.java:57)
at org.apache.catalina.core.ApplicationFilterConfig.initFilter(ApplicationFilterConfig.java:279)
at org.apache.catalina.core.ApplicationFilterConfig.getFilter(ApplicationFilterConfig.java:260)
at org.apache.catalina.core.ApplicationFilterConfig.<init>(ApplicationFilterConfig.java:105)
at org.apache.catalina.core.StandardContext.filterStart(StandardContext.java:4854)
at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5542)
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
at org.apache.catalina.core.StandardContext.reload(StandardContext.java:4033)
at org.apache.catalina.loader.WebappLoader.backgroundProcess(WebappLoader.java:425)
at org.apache.catalina.core.ContainerBase.backgroundProcess(ContainerBase.java:1345)
at org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.processChildren(ContainerBase.java:1546)
at org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.processChildren(ContainerBase.java:1556)
at org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.processChildren(ContainerBase.java:1556)
at org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.run(ContainerBase.java:1524)
at java.lang.Thread.run(Thread.java:745)
解决方法：
参考网址：http://www.cnblogs.com/hongten/archive/2012/11/16/java_PermGen_space.html
1.按照参考网址中的方法1，结果：失败；
2.按照参考网址的方法2，结果：成功
java.lang.OutOfMemoryError: PermGen space
原文：http://www.cnblogs.com/wql025/p/4865673.html