Use local DTD for XML parsing, http://blog.bensmann.com/http-503-when-parsing-xml

CachedDTD.groovy

package com.bensmann.xml
class CachedDTD {
    /**
     * Return DTD 'systemId' as InputSource.
     * @param publicId
     * @param systemId
     * @return InputSource for locally cached DTD.
     */
    def static entityResolver = [
        resolveEntity: { publicId, systemId ->
            try {
                new org.xml.sax.InputSource(CachedDTD.class.getResourceAsStream("dtd/" + systemId.split("/").last()))
            } catch (e) {
                e.printStackTrace()
                null
            }
        }
    ] as org.xml.sax.EntityResolver
}

CachedDTD.java

package com.bensmann.xml;
import java.io.IOException;
import org.xml.sax.EntityResolver;
import org.xml.sax.InputSource;
import org.xml.sax.SAXException;

public class CachedDTD implements EntityResolver {
    /**
     * Return DTD 'systemId' as InputSource.
     * @param publicId
     * @param systemId
     * @return InputSource for locally cached DTD.
     */
    public InputSource resolveEntity(String publicId, String systemId) throws SAXException, IOException {
        String[] resource = systemId.split("/");
        try {
            InputStream uri = CachedDTD.class.getResourceAsStream("dtd/" + resource[resource.length - 1]);
            return new InputSource(uri);
        } catch (Exception e) {
            e.printStackTrace();
            return null;
        }
    }
}

UseCachedDTD.groovy

// Create instance of XmlSlurper and set EntityResolver
def slurper = new XmlSlurper()
slurper.setEntityResolver(com.bensmann.xml.CachedDTD.entityResolver)
// Parse UTF-8 XML file
slurper.parseText(new File("/Users/rbe/example.xml").getText("UTF-8"))