Java example source code file (ResolvingXMLFilter.java)

This example Java source code file (ResolvingXMLFilter.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

attributes, catalogmanager, catalogresolver, failed, inputsource, internalerror, ioexception, malformedurlexception, net, network, resolvingxmlfilter, sax, saxexception, string, url, xmlfilterimpl

The ResolvingXMLFilter.java Java example source code

/*
 * reserved comment block
 * DO NOT REMOVE OR ALTER!
 */
// ResolvingXMLFilter.java - An XMLFilter that performs catalog resolution

/*
 * 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.tools;

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

import org.xml.sax.InputSource;
import org.xml.sax.SAXException;
import org.xml.sax.XMLReader;
import org.xml.sax.Attributes;
import org.xml.sax.helpers.XMLFilterImpl;

import com.sun.org.apache.xml.internal.resolver.Catalog;
import com.sun.org.apache.xml.internal.resolver.CatalogManager;

import com.sun.org.apache.xml.internal.resolver.helpers.FileURL;

/**
 * A SAX XMLFilter that performs catalog-based entity resolution.
 *
 * <p>This class implements a SAX XMLFilter that performs entity resolution
 * using the CatalogResolver. The actual, underlying parser is obtained
 * from a SAXParserFactory.</p>
 * </p>
 *
 * @see CatalogResolver
 * @see org.xml.sax.XMLFilter
 *
 * @author Norman Walsh
 * <a href="mailto:Norman.Walsh@Sun.COM">Norman.Walsh@Sun.COM
 *
 * @version 1.0
 */
public class ResolvingXMLFilter extends XMLFilterImpl {
  /**
   * Suppress explanatory message?
   *
   * @see #parse(InputSource)
   */
  public static boolean suppressExplanation = false;

  /** The manager for the underlying resolver. */
  CatalogManager catalogManager = CatalogManager.getStaticManager();

  /** The underlying catalog resolver. */
  private CatalogResolver catalogResolver = null;

  /** A separate resolver for oasis-xml-pi catalogs. */
  private CatalogResolver piCatalogResolver = null;

  /** Are we in the prolog? Is an oasis-xml-catalog PI valid now? */
  private boolean allowXMLCatalogPI = false;

  /** Has an oasis-xml-catalog PI been seen? */
  private boolean oasisXMLCatalogPI = false;

  /** The base URI of the input document, if known. */
  private URL baseURL = null;

  /** Construct an empty XML Filter with no parent. */
  public ResolvingXMLFilter() {
    super();
    catalogResolver = new CatalogResolver(catalogManager);
  }

  /** Construct an XML filter with the specified parent. */
  public ResolvingXMLFilter(XMLReader parent) {
    super(parent);
    catalogResolver = new CatalogResolver(catalogManager);
  }

  /** Construct an XML filter with the specified parent. */
  public ResolvingXMLFilter(CatalogManager manager) {
    super();
    catalogManager = manager;
    catalogResolver = new CatalogResolver(catalogManager);
  }

  /** Construct an XML filter with the specified parent. */
  public ResolvingXMLFilter(XMLReader parent, CatalogManager manager) {
    super(parent);
    catalogManager = manager;
    catalogResolver = new CatalogResolver(catalogManager);
  }

  /**
   * Provide accessto the underlying Catalog.
   */
  public Catalog getCatalog() {
    return catalogResolver.getCatalog();
  }

  /**
   * SAX XMLReader API.
   *
   * <p>Note that the JAXP 1.1ea2 parser crashes with an InternalError if
   * it encounters a system identifier that appears to be a relative URI
   * that begins with a slash. For example, the declaration:</p>
   *
   * <pre>
   * <!DOCTYPE book SYSTEM "/path/to/dtd/on/my/system/docbookx.dtd">
   * </pre>
   *
   * <p>would cause such an error. As a convenience, this method catches
   * that error and prints an explanation. (Unfortunately, it's not possible
   * to identify the particular system identifier that causes the problem.)
   * </p>
   *
   * <p>The underlying error is forwarded after printing the explanatory
   * message. The message is only every printed once and if
   * <code>suppressExplanation is set to false before
   * parsing, it will never be printed.</p>
   */
  public void parse(InputSource input)
    throws IOException, SAXException {
    allowXMLCatalogPI = true;

    setupBaseURI(input.getSystemId());

    try {
      super.parse(input);
    } catch (InternalError ie) {
      explain(input.getSystemId());
      throw ie;
    }
  }

  /** SAX XMLReader API.
   *
   * @see #parse(InputSource)
   */
  public void parse(String systemId)
    throws IOException, SAXException {
    allowXMLCatalogPI = true;

    setupBaseURI(systemId);

    try {
      super.parse(systemId);
    } catch (InternalError ie) {
      explain(systemId);
      throw ie;
    }
  }

  /**
   * Implements the <code>resolveEntity method
   * for the SAX interface, using an underlying CatalogResolver
   * to do the real work.
   */
  public InputSource resolveEntity (String publicId, String systemId) {
    allowXMLCatalogPI = false;
    String resolved = catalogResolver.getResolvedEntity(publicId, systemId);

    if (resolved == null && piCatalogResolver != null) {
      resolved = piCatalogResolver.getResolvedEntity(publicId, systemId);
    }

    if (resolved != null) {
      try {
        InputSource iSource = new InputSource(resolved);
        iSource.setPublicId(publicId);

        // Ideally this method would not attempt to open the
        // InputStream, but there is a bug (in Xerces, at least)
        // that causes the parser to mistakenly open the wrong
        // system identifier if the returned InputSource does
        // not have a byteStream.
        //
        // It could be argued that we still shouldn't do this here,
        // but since the purpose of calling the entityResolver is
        // almost certainly to open the input stream, it seems to
        // do little harm.
        //
        URL url = new URL(resolved);
        InputStream iStream = url.openStream();
        iSource.setByteStream(iStream);

        return iSource;
      } catch (Exception e) {
        catalogManager.debug.message(1, "Failed to create InputSource", resolved);
        return null;
      }
    } else {
      return null;
    }
  }

  /** SAX DTDHandler API.
   *
   * <p>Captured here only to detect the end of the prolog so that
   * we can ignore subsequent oasis-xml-catalog PIs. Otherwise
   * the events are just passed through.</p>
   */
  public void notationDecl (String name, String publicId, String systemId)
    throws SAXException {
    allowXMLCatalogPI = false;
    super.notationDecl(name,publicId,systemId);
  }

  /** SAX DTDHandler API.
   *
   * <p>Captured here only to detect the end of the prolog so that
   * we can ignore subsequent oasis-xml-catalog PIs. Otherwise
   * the events are just passed through.</p>
   */
  public void unparsedEntityDecl (String name,
                                  String publicId,
                                  String systemId,
                                  String notationName)
    throws SAXException {
    allowXMLCatalogPI = false;
    super.unparsedEntityDecl (name, publicId, systemId, notationName);
  }

  /** SAX ContentHandler API.
   *
   * <p>Captured here only to detect the end of the prolog so that
   * we can ignore subsequent oasis-xml-catalog PIs. Otherwise
   * the events are just passed through.</p>
   */
  public void startElement (String uri, String localName, String qName,
                            Attributes atts)
    throws SAXException {
    allowXMLCatalogPI = false;
    super.startElement(uri,localName,qName,atts);
  }

  /** SAX ContentHandler API.
   *
   * <p>Detect and use the oasis-xml-catalog PI if it occurs.

   */
  public void processingInstruction(String target, String pidata)
    throws SAXException {
    if (target.equals("oasis-xml-catalog")) {
      URL catalog = null;
      String data = pidata;

      int pos = data.indexOf("catalog=");
      if (pos >= 0) {
        data = data.substring(pos+8);
        if (data.length() > 1) {
          String quote = data.substring(0,1);
          data = data.substring(1);
          pos = data.indexOf(quote);
          if (pos >= 0) {
            data = data.substring(0, pos);
            try {
              if (baseURL != null) {
                catalog = new URL(baseURL, data);
              } else {
                catalog = new URL(data);
              }
            } catch (MalformedURLException mue) {
              // nevermind
            }
          }
        }
      }

      if (allowXMLCatalogPI) {
        if (catalogManager.getAllowOasisXMLCatalogPI()) {
          catalogManager.debug.message(4,"oasis-xml-catalog PI", pidata);

          if (catalog != null) {
            try {
              catalogManager.debug.message(4,"oasis-xml-catalog", catalog.toString());
              oasisXMLCatalogPI = true;

              if (piCatalogResolver == null) {
                piCatalogResolver = new CatalogResolver(true);
              }

              piCatalogResolver.getCatalog().parseCatalog(catalog.toString());
            } catch (Exception e) {
              catalogManager.debug.message(3, "Exception parsing oasis-xml-catalog: "
                            + catalog.toString());
            }
          } else {
            catalogManager.debug.message(3, "PI oasis-xml-catalog unparseable: " + pidata);
          }
        } else {
          catalogManager.debug.message(4,"PI oasis-xml-catalog ignored: " + pidata);
        }
      } else {
        catalogManager.debug.message(3, "PI oasis-xml-catalog occurred in an invalid place: "
                      + pidata);
      }
    } else {
      super.processingInstruction(target, pidata);
    }
  }

  /** Save the base URI of the document being parsed. */
  private void setupBaseURI(String systemId) {
    URL cwd = null;

    try {
      cwd = FileURL.makeURL("basename");
    } catch (MalformedURLException mue) {
      cwd = null;
    }

    try {
      baseURL = new URL(systemId);
    } catch (MalformedURLException mue) {
      if (cwd != null) {
        try {
          baseURL = new URL(cwd, systemId);
        } catch (MalformedURLException mue2) {
          // give up
          baseURL = null;
        }
      } else {
        // give up
        baseURL = null;
      }
    }
  }

  /** Provide one possible explanation for an InternalError. */
  private void explain(String systemId) {
    if (!suppressExplanation) {
      System.out.println("XMLReader probably encountered bad URI in " + systemId);
      System.out.println("For example, replace '/some/uri' with 'file:/some/uri'.");
    }
    suppressExplanation = true;
  }
}