稳定运行的系统中，突然报logback不能用的错误，如下：
Reported exception:
ch.qos.logback.core.joran.spi.JoranException: I/O error occurred while parsing xml file
at ch.qos.logback.core.joran.event.SaxEventRecorder.recordEvents(SaxEventRecorder.java:75)
at ch.qos.logback.core.joran.GenericConfigurator.doConfigure(GenericConfigurator.java:122)
at ch.qos.logback.core.joran.GenericConfigurator.doConfigure(GenericConfigurator.java:93)
at ch.qos.logback.core.joran.GenericConfigurator.doConfigure(GenericConfigurator.java:52)
at ch.qos.logback.classic.util.ContextInitializer.configureByResource(ContextInitializer.java:77)
at ch.qos.logback.classic.util.ContextInitializer.autoConfig(ContextInitializer.java:150)
at org.slf4j.impl.StaticLoggerBinder.init(StaticLoggerBinder.java:85)
at org.slf4j.impl.StaticLoggerBinder.<clinit>(StaticLoggerBinder.java:55)
at org.slf4j.LoggerFactory.bind(LoggerFactory.java:121)
at org.slf4j.LoggerFactory.performInitialization(LoggerFactory.java:111)
at org.slf4j.LoggerFactory.getILoggerFactory(LoggerFactory.java:268)
at org.slf4j.LoggerFactory.getLogger(LoggerFactory.java:241)
at org.slf4j.LoggerFactory.getLogger(LoggerFactory.java:254)
at com.ebiz.mmt.web.listener.ResourceListener.<init>(ResourceListener.java:25)
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)
at java.lang.reflect.Constructor.newInstance(Constructor.java:513)
at java.lang.Class.newInstance0(Class.java:355)
at java.lang.Class.newInstance(Class.java:308)
at org.apache.catalina.core.StandardContext.listenerStart(StandardContext.java:3774)
at org.apache.catalina.core.StandardContext.start(StandardContext.java:4337)
at org.apache.catalina.core.StandardContext.reload(StandardContext.java:3086)
at org.apache.catalina.loader.WebappLoader.backgroundProcess(WebappLoader.java:404)
at org.apache.catalina.core.ContainerBase.backgroundProcess(ContainerBase.java:1309)
at org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.processChildren(ContainerBase.java:1601)
at org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.processChildren(ContainerBase.java:1610)
at org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.processChildren(ContainerBase.java:1610)
at org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.run(ContainerBase.java:1590)
at java.lang.Thread.run(Thread.java:619)
Caused by: java.net.ConnectException: Connection timed out: connect根据错误日志，看相应jar包的代码，发现在程序执行dtd验证时出错。 <!DOCTYPE html PUBLIC"-//W3C//DTD XHTML 1.0 Strict//EN"" http://www.w3.org/2002/xmlspec/dtd/2.10/xmlspec.dtd">
两种方式解决：
1、注释掉DOCTYPE
2、把xmlspec.dtd下载到本地，然后应用 相对路径指定方式 <!DOCTYPE html PUBLIC"-//W3C//DTD XHTML 1.0 Strict//EN""xmlspec.dtd"> xmlspec.dtd和logback-test.xml放在同一目录
