Struts, XML and DTD linking

I have the problem about standard xml files for struts application. The only thing I want is to launch standard application "struts-blank". All xml files have links to dtd files on the struts and java servers that is why Tomcat gives me an error that he can't establish connection (I use proxy and tomcat or xerses tries to establish direct connection). I wrote doctype in this way:
<!DOCTYPE struts-config SYSTEM "struts-config_1_2.dtd">

Now I got an error for Tomcat 4.1.29:
2004-10-19 10:36:56 ContextConfig[/struts-blank] Parse error in application web.xml
java.lang.NullPointerException
at java.util.Hashtable.get(Hashtable.java:333)
at org.apache.catalina.util.xml.XmlMapper.resolveEntity(XmlMapper.java:441)
at org.apache.xerces.readers.DefaultEntityHandler.startReadingFromExternalEntity(DefaultEntityHandler.java:755)
at org.apache.xerces.readers.DefaultEntityHandler.startReadingFromExternalSubset(DefaultEntityHandler.java:571)
at org.apache.xerces.framework.XMLDTDScanner.scanDoctypeDecl(XMLDTDScanner.java:1139)
at org.apache.xerces.framework.XMLDocumentScanner.scanDoctypeDecl(XMLDocumentScanner.java:2145)
at org.apache.xerces.framework.XMLDocumentScanner.access$0(XMLDocumentScanner.java:2100)
at org.apache.xerces.framework.XMLDocumentScanner$PrologDispatcher.dispatch(XMLDocumentScanner.java:831)
at org.apache.xerces.framework.XMLDocumentScanner.parseSome(XMLDocumentScanner.java:381)
at org.apache.xerces.framework.XMLParser.parse(XMLParser.java:1098)
at org.xml.sax.helpers.XMLReaderAdapter.parse(XMLReaderAdapter.java:223)
at javax.xml.parsers.SAXParser.parse(SAXParser.java:314)
at javax.xml.parsers.SAXParser.parse(SAXParser.java:89)
at org.apache.catalina.util.xml.XmlMapper.readXml(XmlMapper.java:275)

This error happens if I write so:
<!DOCTYPE struts-config SYSTEM "/WEB-INF/struts-config_1_2.dtd">

I have tried all possible variants but system tries to get dtd file from external resource. Please, help me with this problem or give me a link where I can read about xerses. Thanks a lot.