Parsing an XML doc with unavailable entity (DTD)

Question

Hi all,
I am trying to parse an XML file (web.xml) that has the following DOCTYPE in the head of the document:
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE web-app PUBLIC "-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN" "http://java.sun.com/dtd/web-app_2_3.dtd">
<web-app id="WebApp">When the parser starts, it will look for the DTD on the Sun site, however my work firewall blocks access to this so I get an exception when parsing.
To resolve this, I have tried to force the parser to look for a local copy of the DTD instead of the Sun site but to no avail. I still get the same error but don't know why it wont look at the local DTD.
Here is my code:
* InterceptingXml.java
* Created on 04 April 2006, 15:58
* To change this template, choose Tools | Template Manager
* and open the template in the editor.
package org.xmldemos;
import java.io.File;
import java.io.FileReader;
import java.io.IOException;
import java.net.URI;
import java.net.URISyntaxException;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;
import org.w3c.dom.Document;
import org.xml.sax.EntityResolver;
import org.xml.sax.InputSource;
import org.xml.sax.SAXException;
* @author CS781RJ
public class InterceptingXml
    /** Creates a new instance of InterceptingXml */
    public InterceptingXml() { }
    public void parse(String filename)
        try
            // Create an XML parser
            DocumentBuilder builder = DocumentBuilderFactory.newInstance().newDocumentBuilder();
            // Install the entity resolver
            builder.setEntityResolver(new MyResolver());
            // Parse the XML file
            Document doc = builder.parse(new File(filename));
        catch (SAXException e) { e.printStackTrace(); }
        catch (ParserConfigurationException e) { e.printStackTrace(); }
        catch (IOException e) { e.printStackTrace(); }
        catch (Exception e) { e.printStackTrace(); }
    public class MyResolver implements EntityResolver
        // This method is called whenever an external entity is accessed
        // for the first time.
        public InputSource resolveEntity(String publicId, String systemId)
            try
                System.out.println("publicId: " + publicId + " systemId: " + systemId);
                // Wrap the systemId in a URI object to make it convenient
                // to extract the components of the systemId
                URI uri = new URI(systemId);
                System.out.println("URI scheme: " + uri.getScheme());
                System.out.println("URI scheme specific: " + uri.getSchemeSpecificPart());
                // Check if external source is a file
                if ("http".equals(uri.getScheme()))
                    String filename = uri.getSchemeSpecificPart();
                    filename = "file:/C:/web-app_2_3.dtd";
                    InputSource isrc = new InputSource(new FileReader(filename));
                    return isrc;
            catch (URISyntaxException e) { }
            catch (IOException e) { }
            // Returning null causes the caller to try accessing the systemid
            return null;
    public static void main(String[] args)
        InterceptingXml ixml = new InterceptingXml();
        ixml.parse("c:\\web.xml");
}And here is the exception:
init:
deps-jar:
compile-single:
run-single:
publicId: -//Sun Microsystems, Inc.//DTD Web Application 2.3//EN systemId: http://java.sun.com/dtd/web-app_2_3.dtd
URI scheme: http
URI scheme specific: //java.sun.com/dtd/web-app_2_3.dtd
java.net.UnknownHostException: java.sun.com
        at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:177)
        at java.net.Socket.connect(Socket.java:507)
        at java.net.Socket.connect(Socket.java:457)
        at sun.net.NetworkClient.doConnect(NetworkClient.java:157)
        at sun.net.www.http.HttpClient.openServer(HttpClient.java:365)
        at sun.net.www.http.HttpClient.openServer(HttpClient.java:477)
        at sun.net.www.http.HttpClient.<init>(HttpClient.java:214)
        at sun.net.www.http.HttpClient.New(HttpClient.java:287)
        at sun.net.www.http.HttpClient.New(HttpClient.java:299)
        at sun.net.www.protocol.http.HttpURLConnection.getNewHttpClient(HttpURLConnection.java:792)
        at sun.net.www.protocol.http.HttpURLConnection.plainConnect(HttpURLConnection.java:744)
        at sun.net.www.protocol.http.HttpURLConnection.connect(HttpURLConnection.java:669)
        at sun.net.www.protocol.http.HttpURLConnection.getInputStream(HttpURLConnection.java:913)
        at com.sun.org.apache.xerces.internal.impl.XMLEntityManager.setupCurrentEntity(XMLEntityManager.java:973)
        at com.sun.org.apache.xerces.internal.impl.XMLEntityManager.startEntity(XMLEntityManager.java:905)
        at com.sun.org.apache.xerces.internal.impl.XMLEntityManager.startDTDEntity(XMLEntityManager.java:872)
        at com.sun.org.apache.xerces.internal.impl.XMLDTDScannerImpl.setInputSource(XMLDTDScannerImpl.java:282)
        at com.sun.org.apache.xerces.internal.impl.XMLDocumentScannerImpl$DTDDispatcher.dispatch(XMLDocumentScannerImpl.java:1021)
        at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl.scanDocument(XMLDocumentFragmentScannerImpl.java:368)
        at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.java:834)
        at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.java:764)
        at com.sun.org.apache.xerces.internal.parsers.XMLParser.parse(XMLParser.java:148)
        at com.sun.org.apache.xerces.internal.parsers.DOMParser.parse(DOMParser.java:250)
        at com.sun.org.apache.xerces.internal.jaxp.DocumentBuilderImpl.parse(DocumentBuilderImpl.java:292)
        at javax.xml.parsers.DocumentBuilder.parse(DocumentBuilder.java:172)
        at org.xmldemos.InterceptingXml.parse(InterceptingXml.java:45)
        at org.xmldemos.InterceptingXml.main(InterceptingXml.java:88)
BUILD SUCCESSFUL (total time: 18 seconds)I have noticed that return isrc; does not get executed even though the debugger steps to the line above it.
Thanks in advance.
Riz

Answer 1

What's the point of all that code in your EntityResolver? Would the code work just as well if the DTD didn't even exist? Then do this:public InputSource resolveEntity(String publicId, String systemId)
            return new InputSource(new StringReader(""));
        }However if you really do need to redirect to a local copy of the DTD then consider this:catch (IOException e) { }can be a real barrier to understanding in the case that an IOException is thrown. At least print a stacktrace. And: the FileReader class wants a file name in its constructor, not a URI. And in this code:String filename = uri.getSchemeSpecificPart();
filename = "file:/C:/web-app_2_3.dtd";you could write this instead:String filename = "file:/C:/web-app_2_3.dtd";which would be both shorter and easier to understand.