Struts2.0构建中遇到的错误1

在Struts2构建在遇到如下错误：

引用

严重: Error reading tld listeners java.lang.NullPointerException
java.lang.NullPointerException
at org.apache.log4j.Category.isEnabledFor(Category.java:737)
at org.apache.commons.logging.impl.Log4JLogger.isTraceEnabled(Log4JLogger.java:333)
at org.apache.catalina.startup.TldConfig.tldScanResourcePaths(TldConfig.java:573)
at org.apache.catalina.startup.TldConfig.execute(TldConfig.java:281)
at org.apache.catalina.core.StandardContext.processTlds(StandardContext.java:4251)
at org.apache.catalina.core.StandardContext.start(StandardContext.java:4107)
at org.apache.catalina.core.ContainerBase.addChildInternal(ContainerBase.java:759)
at org.apache.catalina.core.ContainerBase.addChild(ContainerBase.java:739)
at org.apache.catalina.core.StandardHost.addChild(StandardHost.java:524)
at org.apache.catalina.startup.HostConfig.deployDirectory(HostConfig.java:910)
at org.apache.catalina.startup.HostConfig.deployDirectories(HostConfig.java:873)
at org.apache.catalina.startup.HostConfig.deployApps(HostConfig.java:474)
at org.apache.catalina.startup.HostConfig.start(HostConfig.java:1118)
at org.apache.catalina.startup.HostConfig.lifecycleEvent(HostConfig.java:310)
at org.apache.catalina.util.LifecycleSupport.fireLifecycleEvent(LifecycleSupport.java:119)
at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1020)
at org.apache.catalina.core.StandardHost.start(StandardHost.java:718)
at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1012)
at org.apache.catalina.core.StandardEngine.start(StandardEngine.java:442)
at org.apache.catalina.core.StandardService.start(StandardService.java:450)
at org.apache.catalina.core.StandardServer.start(StandardServer.java:700)
at org.apache.catalina.startup.Catalina.start(Catalina.java:551)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at org.apache.catalina.startup.Bootstrap.start(Bootstrap.java:275)
at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:413)
2011-8-9 10:58:36 org.apache.catalina.startup.ContextConfig processDefaultWebConfig
严重: Parse error in default web.xml
java.lang.NullPointerException
at org.apache.tomcat.util.digester.Digester.createSAXException(Digester.java:2719)
at org.apache.tomcat.util.digester.Digester.createSAXException(Digester.java:2745)
at org.apache.tomcat.util.digester.Digester.startElement(Digester.java:1278)
at com.sun.org.apache.xerces.internal.parsers.AbstractSAXParser.startElement(AbstractSAXParser.java:501)
at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl.scanStartElement(XMLDocumentFragmentScannerImpl.java:1357)
at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl$FragmentContentDriver.next(XMLDocumentFragmentScannerImpl.java:2740)
at com.sun.org.apache.xerces.internal.impl.XMLDocumentScannerImpl.next(XMLDocumentScannerImpl.java:645)
at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl.scanDocument(XMLDocumentFragmentScannerImpl.java:508)
at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.java:807)
at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.java:737)
at com.sun.org.apache.xerces.internal.parsers.XMLParser.parse(XMLParser.java:107)
at com.sun.org.apache.xerces.internal.parsers.AbstractSAXParser.parse(AbstractSAXParser.java:1205)
at com.sun.org.apache.xerces.internal.jaxp.SAXParserImpl$JAXPSAXParser.parse(SAXParserImpl.java:522)
at org.apache.tomcat.util.digester.Digester.parse(Digester.java:1561)
at org.apache.catalina.startup.ContextConfig.processDefaultWebConfig(ContextConfig.java:697)
at org.apache.catalina.startup.ContextConfig.defaultWebConfig(ContextConfig.java:634)
at org.apache.catalina.startup.ContextConfig.start(ContextConfig.java:1054)
at org.apache.catalina.startup.ContextConfig.lifecycleEvent(ContextConfig.java:261)
at org.apache.catalina.util.LifecycleSupport.fireLifecycleEvent(LifecycleSupport.java:119)
at org.apache.catalina.core.StandardContext.start(StandardContext.java:4111)
at org.apache.catalina.core.ContainerBase.addChildInternal(ContainerBase.java:759)
at org.apache.catalina.core.ContainerBase.addChild(ContainerBase.java:739)
at org.apache.catalina.core.StandardHost.addChild(StandardHost.java:524)
at org.apache.catalina.startup.HostConfig.deployDirectory(HostConfig.java:910)
at org.apache.catalina.startup.HostConfig.deployDirectories(HostConfig.java:873)
at org.apache.catalina.startup.HostConfig.deployApps(HostConfig.java:474)
at org.apache.catalina.startup.HostConfig.start(HostConfig.java:1118)
at org.apache.catalina.startup.HostConfig.lifecycleEvent(HostConfig.java:310)
at org.apache.catalina.util.LifecycleSupport.fireLifecycleEvent(LifecycleSupport.java:119)
at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1020)
at org.apache.catalina.core.StandardHost.start(StandardHost.java:718)
at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1012)
at org.apache.catalina.core.StandardEngine.start(StandardEngine.java:442)
at org.apache.catalina.core.StandardService.start(StandardService.java:450)
at org.apache.catalina.core.StandardServer.start(StandardServer.java:700)
at org.apache.catalina.startup.Catalina.start(Catalina.java:551)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at org.apache.catalina.startup.Bootstrap.start(Bootstrap.java:275)
at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:413)
2011-8-9 10:58:36 org.apache.catalina.startup.ContextConfig processDefaultWebConfig

在网上查找了一下，说是包冲突，可我搭建的Struts2.0例程没有问题，所以断定是什么东西没有配置，比对启动日志发现是log4j没有配置。
解决方法是：
在src文件夹下新建log4j.properties文件内容如下：

引用

#
# Log4J Settings for log4j 1.2.x (via jakarta-commons-logging)
#
# The five logging levels used by Log are (in order):
#
#   1. DEBUG (the least serious)
#   2. INFO
#   3. WARN
#   4. ERROR
#   5. FATAL (the most serious)


# Set root logger level to WARN and append to stdout
log4j.rootLogger=WARN, stdout

log4j.appender.stdout=org.apache.log4j.ConsoleAppender
log4j.appender.stdout.layout=org.apache.log4j.PatternLayout

# Pattern to output the caller's file name and line number.
log4j.appender.stdout.layout.ConversionPattern=%d %5p (%c:%L) - %m%n

# Print only messages of level ERROR or above in the package noModule.
log4j.logger.noModule=FATAL

# OpenSymphony Stuff
log4j.logger.com.opensymphony=INFO
log4j.logger.org.apache.struts2=DEBUG

# Spring Stuff
log4j.logger.org.springframework=INFO