Tomcat启动报错java.net.AbstractPlainSocketImpl

Caused by: Unable to load configuration. - Class: java.net.AbstractPlainSocketImpl
    File: AbstractPlainSocketImpl.java
    Method: connect
    Line: 158 - java/net/AbstractPlainSocketImpl.java:158:-1
    at com.opensymphony.xwork2.config.ConfigurationManager.getConfiguration(ConfigurationManager.java:58)
    at org.apache.struts2.dispatcher.Dispatcher.init_PreloadConfiguration(Dispatcher.java:374)
    at org.apache.struts2.dispatcher.Dispatcher.init(Dispatcher.java:418)
    ... 20 more
    Caused by: Unable to load jar:file:/var/lib/tomcat6/webapps/webapps/cute/WEB-         INF/lib    /struts2-json-plugin-2.3.4.jar!/struts-plugin.xml - Class:    java.net.AbstractPlainSocketImpl
File: AbstractPlainSocketImpl.java
Method: connect
Line: 158 - java/net/AbstractPlainSocketImpl.java:158:-1
    at com.opensymphony.xwork2.config.providers.XmlConfigurationProvider.loadConfigurationFiles(XmlConfigurationProvider.java:898)
    at com.opensymphony.xwork2.config.providers.XmlConfigurationProvider.loadDocuments(XmlConfigurationProvider.java:143)
    at com.opensymphony.xwork2.config.providers.XmlConfigurationProvider.init(XmlConfigurationProvider.java:110)
    at com.opensymphony.xwork2.config.impl.DefaultConfiguration.reloadContainer(DefaultConfiguration.java:168)
    at com.opensymphony.xwork2.config.ConfigurationManager.getConfiguration(ConfigurationManager.java:55)
    ... 22 more
Caused by: struts.apache.org - Class: java.net.AbstractPlainSocketImpl
File: AbstractPlainSocketImpl.java
Method: connect
Line: 158 - java/net/AbstractPlainSocketImpl.java:158:-1
    at com.opensymphony.xwork2.util.DomHelper.parse(DomHelper.java:115)
    at com.opensymphony.xwork2.config.providers.XmlConfigurationProvider.loadConfigurationFiles(XmlConfigurationProvider.java:893)
    ... 26 more
Caused by: java.net.UnknownHostException: struts.apache.org
    at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:158)
    at java.net.Socket.connect(Socket.java:546)
    at java.net.Socket.connect(Socket.java:495)
    at sun.net.NetworkClient.doConnect(NetworkClient.java:174)
    at sun.net.www.http.HttpClient.openServer(HttpClient.java:409)
    at sun.net.www.http.HttpClient.openServer(HttpClient.java:530)
    at sun.net.www.http.HttpClient.<init>(HttpClient.java:240)
    at sun.net.www.http.HttpClient.New(HttpClient.java:321)
    at sun.net.www.http.HttpClient.New(HttpClient.java:338)
    at sun.net.www.protocol.http.HttpURLConnection.getNewHttpClient(HttpURLConnection.java:814)
    at sun.net.www.protocol.http.HttpURLConnection.plainConnect(HttpURLConnection.java:755)
    at sun.net.www.protocol.http.HttpURLConnection.connect(HttpURLConnection.java:680)
    at sun.net.www.protocol.http.HttpURLConnection.getInputStream(HttpURLConnection.java:1005)
    at com.sun.org.apache.xerces.internal.impl.XMLEntityManager.setupCurrentEntity(XMLEntityManager.java:653)
    at com.sun.org.apache.xerces.internal.impl.XMLEntityManager.startEntity(XMLEntityManager.java:1291)
    at com.sun.org.apache.xerces.internal.impl.XMLEntityManager.startDTDEntity(XMLEntityManager.java:1258)
    at com.sun.org.apache.xerces.internal.impl.XMLDTDScannerImpl.setInputSource(XMLDTDScannerImpl.java:259)
    at com.sun.org.apache.xerces.internal.impl.XMLDocumentScannerImpl$DTDDriver.dispatch(XMLDocumentScannerImpl.java:1167)
    at com.sun.org.apache.xerces.internal.impl.XMLDocumentScannerImpl$DTDDriver.next(XMLDocumentScannerImpl.java:1064)
    at com.sun.org.apache.xerces.internal.impl.XMLDocumentScannerImpl$PrologDriver.next(XMLDocumentScannerImpl.java:977)
    at com.sun.org.apache.xerces.internal.impl.XMLDocumentScannerImpl.next(XMLDocumentScannerImpl.java:624)
    at com.sun.org.apache.xerces.internal.impl.XMLNSDocumentScannerImpl.next(XMLNSDocumentScannerImpl.java:116)
    at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl.scanDocument(XMLDocumentFragmentScannerImpl.java:486)
    at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.java:810)
    at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.java:740)
    at com.sun.org.apache.xerces.internal.parsers.XMLParser.parse(XMLParser.java:110)
    at com.sun.org.apache.xerces.internal.parsers.AbstractSAXParser.parse(AbstractSAXParser.java:1208)
    at com.sun.org.apache.xerces.internal.jaxp.SAXParserImpl$JAXPSAXParser.parse(SAXParserImpl.java:525)
    at javax.xml.parsers.SAXParser.parse(SAXParser.java:392)
    at com.opensymphony.xwork2.util.DomHelper.parse(DomHelper.java:113)
    ... 27 more

解决方式：

<!DOCTYPE struts PUBLIC "-//Apache Software Foundation//DTD Struts Configuration 2.3//EN" "http://struts.apache.org/dtds/struts-2.3.dtd">

原因：把项目struts2的jar包升级到2.3 但是头部dtd没改