错误：
java.lang.AbstractMethodError: org.apache.xerces.dom.DocumentImpl.setXmlVersion(Ljava/lang/String;)V
at com.sun.org.apache.xalan.internal.xsltc.trax.SAX2DOM.setDocumentInfo(Unknown Source)
at com.sun.org.apache.xalan.internal.xsltc.trax.SAX2DOM.startElement(Unknown Source)
at com.sun.org.apache.xml.internal.serializer.ToXMLSAXHandler.closeStartTag(Unknown Source)
at com.sun.org.apache.xml.internal.serializer.ToSAXHandler.flushPending(Unknown Source)
at com.sun.org.apache.xml.internal.serializer.ToXMLSAXHandler.startElement(Unknown Source)
at com.sun.org.apache.xalan.internal.xsltc.trax.TransformerHandlerImpl.startElement(Unknown Source)
at com.opensymphony.xwork2.util.DomHelper$DOMBuilder.startElement(DomHelper.java:245)
at com.opensymphony.xwork2.util.location.LocationAttributes$Pipe.startElement(LocationAttributes.java:317)
at com.opensymphony.xwork2.util.DomHelper$StartHandler.startElement(DomHelper.java:308)
at com.sun.org.apache.xerces.internal.parsers.AbstractSAXParser.startElement(Unknown Source)
at com.sun.org.apache.xerces.internal.parsers.AbstractXMLDocumentParser.emptyElement(Unknown Source)
at com.sun.org.apache.xerces.internal.impl.dtd.XMLDTDValidator.emptyElement(Unknown Source)
at com.sun.org.apache.xerces.internal.impl.XMLNSDocumentScannerImpl.scanStartElement(Unknown Source)
at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl$FragmentContentDriver.next(Unknown Source)
at com.sun.org.apache.xerces.internal.impl.XMLDocumentScannerImpl.next(Unknown Source)
at com.sun.org.apache.xerces.internal.impl.XMLNSDocumentScannerImpl.next(Unknown Source)
at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl.scanDocument(Unknown Source)
at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(Unknown Source)
at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(Unknown Source)
at com.sun.org.apache.xerces.internal.parsers.XMLParser.parse(Unknown Source)
at com.sun.org.apache.xerces.internal.parsers.AbstractSAXParser.parse(Unknown Source)
at com.sun.org.apache.xerces.internal.jaxp.SAXParserImpl$JAXPSAXParser.parse(Unknown Source)
at javax.xml.parsers.SAXParser.parse(Unknown Source)
at com.opensymphony.xwork2.util.DomHelper.parse(DomHelper.java:117)
at com.opensymphony.xwork2.config.providers.XmlConfigurationProvider.loadConfigurationFiles(XmlConfigurationProvider.java:1009)
at com.opensymphony.xwork2.config.providers.XmlConfigurationProvider.loadDocuments(XmlConfigurationProvider.java:165)
at com.opensymphony.xwork2.config.providers.XmlConfigurationProvider.init(XmlConfigurationProvider.java:132)
at com.opensymphony.xwork2.config.impl.DefaultConfiguration.reloadContainer(DefaultConfiguration.java:225)
at com.opensymphony.xwork2.config.ConfigurationManager.getConfiguration(ConfigurationManager.java:67)
at org.apache.struts2.dispatcher.Dispatcher.init_PreloadConfiguration(Dispatcher.java:429)
at org.apache.struts2.dispatcher.Dispatcher.init(Dispatcher.java:473)
at org.apache.struts2.dispatcher.ng.InitOperations.initDispatcher(InitOperations.java:74)
at org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter.init(StrutsPrepareAndExecuteFilter.java:51)
at org.apache.catalina.core.ApplicationFilterConfig.initFilter(ApplicationFilterConfig.java:273)
at org.apache.catalina.core.ApplicationFilterConfig.getFilter(ApplicationFilterConfig.java:254)
at org.apache.catalina.core.ApplicationFilterConfig.setFilterDef(ApplicationFilterConfig.java:372)
at org.apache.catalina.core.ApplicationFilterConfig.<init>(ApplicationFilterConfig.java:98)
at org.apache.catalina.core.StandardContext.filterStart(StandardContext.java:4562)
at org.apache.catalina.core.StandardContext$2.call(StandardContext.java:5240)
at org.apache.catalina.core.StandardContext$2.call(StandardContext.java:5235)
at java.util.concurrent.FutureTask$Sync.innerRun(Unknown Source)
at java.util.concurrent.FutureTask.run(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)
解决：
干掉xercesImpl.jar包，或者换一种合适的版本。
有原因：
Xerces是一个开放源代码的XML语法分析器，我也不知道具体什么，应该是jar冲突引起的，解决方法是版本换掉或者去除。
来源：https://www.cnblogs.com/sl-shilong/p/3275186.html