RedirectingEntityResolver.java

package org.deegree.commons.xml.schema;

import java.io.IOException;
import java.io.InputStream;
import java.net.URL;

import nl.ipo.cds.utils.UrlUtils;

import org.apache.http.HttpResponse;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.DefaultHttpClient;
import org.apache.xerces.xni.XMLResourceIdentifier;
import org.apache.xerces.xni.XNIException;
import org.apache.xerces.xni.parser.XMLEntityResolver;
import org.apache.xerces.xni.parser.XMLInputSource;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * Overrides the standard deegree-provided class to work around SNI-related problems when fetching GML application schemas:
 * 
 * http://stackoverflow.com/questions/7615645/ssl-handshake-alert-unrecognized-name-error-since-upgrade-to-java-1-7-0 
 */
public class RedirectingEntityResolver implements XMLEntityResolver {

    private static final Logger LOG = LoggerFactory.getLogger( RedirectingEntityResolver.class );

    private static final String SCHEMAS_OPENGIS_NET_URL = "http://schemas.opengis.net/";

    private static final String ROOT = "/META-INF/SCHEMAS_OPENGIS_NET/";

    private static final URL baseURL;

    static {
        baseURL = RedirectingEntityResolver.class.getResource( ROOT );
        if ( baseURL == null ) {
            LOG.warn( "'"
                                    + ROOT
                                    + "' could not be found on the classpath. Schema references to 'http://schemas.opengis.net' will not be redirected, but fetched from their original location.  " );
        }
    }

    /**
     * Redirects the given entity URL, returning a local URL if available.
     * 
     * @param systemId
     *            entity URL, must not be <code>null</code>
     * @return redirected URL, identical to input if it cannot be redirected, never <code>null</code>
     */
    public String redirect( String systemId ) {
        if ( systemId.startsWith( SCHEMAS_OPENGIS_NET_URL ) ) {
            String localPart = systemId.substring( SCHEMAS_OPENGIS_NET_URL.length() );
            URL u = RedirectingEntityResolver.class.getResource( ROOT + localPart );
            if ( u != null ) {
                LOG.debug( "Local hit: " + systemId );
                return u.toString();
            }
        } else if ( systemId.equals( "http://www.w3.org/2001/xml.xsd" ) ) {
            // workaround for schemas that include the xml base schema...
            return RedirectingEntityResolver.class.getResource( "/w3c/xml.xsd" ).toString();
        } else if ( systemId.equals( "http://www.w3.org/1999/xlink.xsd" ) ) {
            // workaround for schemas that include the xlink schema...
            return RedirectingEntityResolver.class.getResource( "/w3c/xlink.xsd" ).toString();
        }
        return systemId;
    }

    @Override
    public XMLInputSource resolveEntity( XMLResourceIdentifier identifier )
                            throws XNIException, IOException {

        String systemId = identifier.getExpandedSystemId();
        String redirectedSystemId = systemId != null ? redirect( systemId ) : null;
        LOG.debug( "'" + systemId + "' -> '" + redirectedSystemId + "'" );
        if (redirectedSystemId != null && redirectedSystemId.startsWith ("https:")) {
			InputStream is = UrlUtils.open(new URL(redirectedSystemId));
            return new XMLInputSource( null, systemId, redirectedSystemId, is, null );
        }
        return new XMLInputSource( null, systemId, redirectedSystemId );
    }

}