resolver.java

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// Resolver.java - Represents an extension of OASIS Open Catalog files.

/*
 * Copyright 2001-2004 The Apache Software Foundation or its licensors,
 * as applicable.
 * 
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * 
 *      http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.sun.org.apache.xml.internal.resolver;

import java.io.IOException;
import java.io.InputStream;
import java.io.FileNotFoundException;
import java.util.Enumeration;
import java.util.Vector;
import java.net.URL;
import java.net.URLConnection;
import java.net.MalformedURLException;
import com.sun.org.apache.xml.internal.resolver.readers.SAXCatalogReader;
import com.sun.org.apache.xml.internal.resolver.readers.OASISXMLCatalogReader;
import com.sun.org.apache.xml.internal.resolver.readers.TR9401CatalogReader;
import javax.xml.parsers.SAXParserFactory;

/**
 * An extension to OASIS Open Catalog files, this class supports
 * suffix-based matching and an external RFC2483 resolver.
 *
 * @see Catalog
 *
 * @author Norman Walsh
 * <a href="mailto:[e-mail]">[e-mail]</a>
 *
 * @version 1.0
 */
public class Resolver extends Catalog {
  /**
   * The URISUFFIX Catalog Entry type.
   *
   * <p>URI suffix entries match URIs that end in a specified suffix.</p>
   */
  public static final int URISUFFIX = CatalogEntry.addEntryType("URISUFFIX", 2);

  /**
   * The SYSTEMSUFFIX Catalog Entry type.
   *
   * <p>System suffix entries match system identifiers that end in a
   * specified suffix.</p>
   */
  public static final int SYSTEMSUFFIX = CatalogEntry.addEntryType("SYSTEMSUFFIX", 2);

  /**
   * The RESOLVER Catalog Entry type.
   *
   * <p>A hook for providing support for web-based backup resolvers.</p>
   */
  public static final int RESOLVER = CatalogEntry.addEntryType("RESOLVER", 1);

  /**
   * The SYSTEMREVERSE Catalog Entry type.
   *
   * <p>This is a bit of a hack. There's no actual SYSTEMREVERSE entry,
   * but this entry type is used to indicate that a reverse lookup is
   * being performed. (This allows the Resolver to implement
   * RFC2483 I2N and I2NS.)
   */
  public static final int SYSTEMREVERSE
    = CatalogEntry.addEntryType("SYSTEMREVERSE", 1);

  /**
   * Setup readers.
   */
  public void setupReaders() {
    SAXParserFactory spf = SAXParserFactory.newInstance();
    spf.setNamespaceAware(true);
    spf.setValidating(false);

    SAXCatalogReader saxReader = new SAXCatalogReader(spf);

    saxReader.setCatalogParser(null, "XMLCatalog",
			       "com.sun.org.apache.xml.internal.resolver.readers.XCatalogReader");

    saxReader.setCatalogParser(OASISXMLCatalogReader.namespaceName,
			       "catalog",
			       "com.sun.org.apache.xml.internal.resolver.readers.ExtendedXMLCatalogReader");

    addReader("application/xml", saxReader);

    TR9401CatalogReader textReader = new TR9401CatalogReader();
    addReader("text/plain", textReader);
  }

  /**
   * Cleanup and process a Catalog entry.
   *
   * <p>This method processes each Catalog entry, changing mapped
   * relative system identifiers into absolute ones (based on the current
   * base URI), and maintaining other information about the current
   * catalog.</p>
   *
   * @param entry The CatalogEntry to process.
   */
  public void addEntry(CatalogEntry entry) {
    int type = entry.getEntryType();

    if (type == URISUFFIX) {
      String suffix = normalizeURI(entry.getEntryArg(0));
      String fsi = makeAbsolute(normalizeURI(entry.getEntryArg(1)));

      entry.setEntryArg(1, fsi);

      catalogManager.debug.message(4, "URISUFFIX", suffix, fsi);
    } else if (type == SYSTEMSUFFIX) {
      String suffix = normalizeURI(entry.getEntryArg(0));
      String fsi = makeAbsolute(normalizeURI(entry.getEntryArg(1)));

      entry.setEntryArg(1, fsi);

      catalogManager.debug.message(4, "SYSTEMSUFFIX", suffix, fsi);
    }

    super.addEntry(entry);
  }

  /**
   * Return the applicable URI.
   *
   * <p>If a URI entry exists in the Catalog
   * for the URI specified, return the mapped value.</p>
   *
   * <p>In the Resolver (as opposed to the Catalog) class, if the
   * URI isn't found by the usual algorithm, URISUFFIX entries are
   * considered.</p>
   *
   * <p>URI comparison is case sensitive.</p>
   *
   * @param uri The URI to locate in the catalog.
   *
   * @return The resolved URI.
   *
   * @throws MalformedURLException The system identifier of a
   * subordinate catalog cannot be turned into a valid URL.
   * @throws IOException Error reading subordinate catalog file.
   */
  public String resolveURI(String uri)
    throws MalformedURLException, IOException {

    String resolved = super.resolveURI(uri);
    if (resolved != null) {
      return resolved;
    }

    Enumeration en = catalogEntries.elements();
    while (en.hasMoreElements()) {
      CatalogEntry e = (CatalogEntry) en.nextElement();
      if (e.getEntryType() == RESOLVER) {
	resolved = resolveExternalSystem(uri, e.getEntryArg(0));
	if (resolved != null) {
	  return resolved;
	}
      } else if (e.getEntryType() == URISUFFIX) {
	String suffix = e.getEntryArg(0);
	String result = e.getEntryArg(1);

	if (suffix.length() <= uri.length()
	    && uri.substring(uri.length()-suffix.length()).equals(suffix)) {
	  return result;
	}
      }
    }

    // Otherwise, look in the subordinate catalogs
    return resolveSubordinateCatalogs(Catalog.URI,
				      null,
				      null,
				      uri);
  }

  /**
   * Return the applicable SYSTEM system identifier, resorting
   * to external RESOLVERs if necessary.
   *
   * <p>If a SYSTEM entry exists in the Catalog
   * for the system ID specified, return the mapped value.</p>
   *
   * <p>In the Resolver (as opposed to the Catalog) class, if the
   * URI isn't found by the usual algorithm, SYSTEMSUFFIX entries are
   * considered.</p>
   *
   * <p>On Windows-based operating systems, the comparison between
   * the system identifier provided and the SYSTEM entries in the
   * Catalog is case-insensitive.</p>
   *
   * @param systemId The system ID to locate in the catalog.
   *
   * @return The system identifier to use for systemId.
   *
   * @throws MalformedURLException The formal system identifier of a
   * subordinate catalog cannot be turned into a valid URL.
   * @throws IOException Error reading subordinate catalog file.
   */
  public String resolveSystem(String systemId)
    throws MalformedURLException, IOException {

    String resolved = super.resolveSystem(systemId);
    if (resolved != null) {
      return resolved;
    }

    Enumeration en = catalogEntries.elements();
    while (en.hasMoreElements()) {
      CatalogEntry e = (CatalogEntry) en.nextElement();
      if (e.getEntryType() == RESOLVER) {
	resolved = resolveExternalSystem(systemId, e.getEntryArg(0));
	if (resolved != null) {
	  return resolved;
	}
      } else if (e.getEntryType() == SYSTEMSUFFIX) {
	String suffix = e.getEntryArg(0);
	String result = e.getEntryArg(1);

	if (suffix.length() <= systemId.length()
	    && systemId.substring(systemId.length()-suffix.length()).equals(suffix)) {
	  return result;
	}
      }
    }

    return resolveSubordinateCatalogs(Catalog.SYSTEM,
				      null,
				      null,
				      systemId);
  }

  /**
   * Return the applicable PUBLIC or SYSTEM identifier, resorting
   * to external resolvers if necessary.
   *
   * <p>This method searches the Catalog and returns the system
   * identifier specified for the given system or
   * public identifiers. If
   * no appropriate PUBLIC or SYSTEM entry is found in the Catalog,
   * null is returned.</p>
   *
   * <p>Note that a system or public identifier in the current catalog
   * (or subordinate catalogs) will be used in preference to an
   * external resolver. Further, if a systemId is present, the external
   * resolver(s) will be queried for that before the publicId.</p>
   *
   * @param publicId The public identifier to locate in the catalog.
   * Public identifiers are normalized before comparison.
   * @param systemId The nominal system identifier for the entity
   * in question (as provided in the source document).
   *
   * @throws MalformedURLException The formal system identifier of a
   * subordinate catalog cannot be turned into a valid URL.
   * @throws IOException Error reading subordinate catalog file.
   *
   * @return The system identifier to use.
   * Note that the nominal system identifier is not returned if a
   * match is not found in the catalog, instead null is returned
   * to indicate that no match was found.
   */
  public String resolvePublic(String publicId, String systemId) 
    throws MalformedURLException, IOException {

    String resolved = super.resolvePublic(publicId, systemId);
    if (resolved != null) {
      return resolved;
    }

    Enumeration en = catalogEntries.elements();
    while (en.hasMoreElements()) {
      CatalogEntry e = (CatalogEntry) en.nextElement();
      if (e.getEntryType() == RESOLVER) {
	if (systemId != null) {
	  resolved = resolveExternalSystem(systemId,
					   e.getEntryArg(0));
	  if (resolved != null) {
	    return resolved;
	  }
	}
	resolved = resolveExternalPublic(publicId, e.getEntryArg(0));
	if (resolved != null) {
	  return resolved;
	}
      }
    }

    return resolveSubordinateCatalogs(Catalog.PUBLIC,
				      null,
				      publicId,
				      systemId);
  }

    /**
     * Query an external RFC2483 resolver for a system identifier.
     *
     * @param systemId The system ID to locate.
     * @param resolver The name of the resolver to use.
     *
     * @return The system identifier to use for the systemId.
     */
    protected String resolveExternalSystem(String systemId, String resolver)
	throws MalformedURLException, IOException {
	Resolver r = queryResolver(resolver, "i2l", systemId, null);
	if (r != null) {
	    return r.resolveSystem(systemId);
	} else {
	    return null;
	}
    }

    /**
     * Query an external RFC2483 resolver for a public identifier.
     *
     * @param publicId The system ID to locate.
     * @param resolver The name of the resolver to use.
     *
     * @return The system identifier to use for the systemId.
     */
    protected String resolveExternalPublic(String publicId, String resolver)
	throws MalformedURLException, IOException {
	Resolver r = queryResolver(resolver, "fpi2l", publicId, null);
	if (r != null) {
	    return r.resolvePublic(publicId, null);
	} else {
	    return null;
	}
    }

    /**
     * Query an external RFC2483 resolver.
     *
     * @param resolver The URL of the RFC2483 resolver.
     * @param command The command to send the resolver.