Tomcat   App   Reload之后出现log4j错误

log4j:ERROR Error occured while converting date. java.lang.NullPointerException at java.lang.System.arraycopy(Native Method) at java.lang.AbstractStringBuilder.getChars(AbstractStringBuilder.java:340) at java.lang.StringBuffer.getChars(StringBuffer.java:224) at org.apache.log4j.helpers.ISO8601DateFormat.format(ISO8601DateFormat.java:128) at java.text.DateFormat.format(DateFormat.java:314) at org.apache.log4j.helpers.PatternParser$DatePatternConverter.convert(PatternParser.java:444) at org.apache.log4j.helpers.PatternConverter.format(PatternConverter.java:64) at org.apache.log4j.PatternLayout.format(PatternLayout.java:503) at org.apache.log4j.WriterAppender.subAppend(WriterAppender.java:301) at org.apache.log4j.RollingFileAppender.subAppend(RollingFileAppender.java:236) at org.apache.log4j.WriterAppender.append(WriterAppender.java:159) at org.apache.log4j.AppenderSkeleton.doAppend(AppenderSkeleton.java:230) at org.apache.log4j.helpers.AppenderAttachableImpl.appendLoopOnAppenders(AppenderAttachableImpl.java:65) at org.apache.log4j.Category.callAppenders(Category.java:203) at org.apache.log4j.Category.forcedLog(Category.java:388) at org.apache.log4j.Category.log(Category.java:853) at org.apache.commons.logging.impl.Log4JLogger.debug(Log4JLogger.java:110) at org.apache.catalina.session.ManagerBase.processExpires(ManagerBase.java:685) at org.apache.catalina.session.ManagerBase.backgroundProcess(ManagerBase.java:663) at org.apache.catalina.core.ContainerBase.backgroundProcess(ContainerBase.java:1284) at org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.processChildren(ContainerBase.java:1569) at org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.processChildren(ContainerBase.java:1578) at org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.processChildren(ContainerBase.java:1578) at org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.run(ContainerBase.java:1558) at java.lang.Thread.run(Thread.java:595)