我在 catalina.out 的 tomcat 服务器中遇到错误
:ERROR Could not create an Appender. Reported error follows.
java.lang.ClassNotFoundException: org.apache.cloudstack.syslog.AlertsSyslogAppender
at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1484)
at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1329)
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Class.java:186)
at org.apache.log4j.helpers.Loader.loadClass(Loader.java:198)
at org.apache.log4j.xml.DOMConfigurator.parseAppender(DOMConfigurator.java:247)
at org.apache.log4j.xml.DOMConfigurator.findAppenderByName(DOMConfigurator.java:176)
at org.apache.log4j.xml.DOMConfigurator.findAppenderByReference(DOMConfigurator.java:191)
at org.apache.log4j.xml.DOMConfigurator.parseChildrenOfLoggerElement(DOMConfigurator.java:523)
at org.apache.log4j.xml.DOMConfigurator.parseCategory(DOMConfigurator.java:436)
at org.apache.log4j.xml.DOMConfigurator.parse(DOMConfigurator.java:999)
at org.apache.log4j.xml.DOMConfigurator.doConfigure(DOMConfigurator.java:867)
at org.apache.log4j.xml.DOMConfigurator.doConfigure(DOMConfigurator.java:755)
at org.apache.log4j.xml.XMLWatchdog.doOnChange(DOMConfigurator.java:1120)
at org.apache.log4j.helpers.FileWatchdog.checkAndConfigure(FileWatchdog.java:89)
at org.apache.log4j.helpers.FileWatchdog.<init>(FileWatchdog.java:58)
at org.apache.log4j.xml.XMLWatchdog.<init>(DOMConfigurator.java:1112)
at org.apache.log4j.xml.DOMConfigurator.configureAndWatch(DOMConfigurator.java:735)
at org.apache.log4j.xml.DOMConfigurator.configureAndWatch(DOMConfigurator.java:718)
at com.cloud.utils.LogUtils.initLog4j(LogUtils.java:32)
at com.cloud.bridge.service.EC2MainServlet.init(EC2MainServlet.java:66)
at org.apache.catalina.core.StandardWrapper.loadServlet(StandardWrapper.java:1173)
功能方面一切正常，即我的自定义附加程序被调用并执行该自定义附加程序中编写的任何内容。但是在 catalina.out 中，如果我在 log4j.xml 中进行一些修改，则会定期出现错误消息。可能是什么错误。