src/org/apache/xml/utils/SystemIDResolver.java

/*
 * The Apache Software License, Version 1.1
 *
 *
 * Copyright (c) 1999 The Apache Software Foundation.  All rights 
 * reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer. 
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
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 *    distribution.
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 * 3. The end-user documentation included with the redistribution,
 *    if any, must include the following acknowledgment:  
 *       "This product includes software developed by the
 *        Apache Software Foundation (http://www.apache.org/)."
 *    Alternately, this acknowledgment may appear in the software itself,
 *    if and wherever such third-party acknowledgments normally appear.
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 * 4. The names "Xalan" and "Apache Software Foundation" must
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 * 5. Products derived from this software may not be called "Apache",
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 * SUCH DAMAGE.
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of the Apache Software Foundation and was
 * originally based on software copyright (c) 1999, Lotus
 * Development Corporation., http://www.lotus.com.  For more
 * information on the Apache Software Foundation, please see
 * <http://www.apache.org/>.
 */
package org.apache.xml.utils;

import javax.xml.transform.TransformerException;

import org.apache.xml.utils.URI;
import org.apache.xml.utils.URI.MalformedURIException;

import java.io.*;

import java.lang.StringBuffer;

/**
 * <meta name="usage" content="internal"/>
 * This class is used to resolve relative URIs and SystemID 
 * strings into absolute URIs.
 *
 * <p>This is a generic utility for resolving URIs, other than the 
 * fact that it's declared to throw TransformerException.  Please 
 * see code comments for details on how resolution is performed.</p>
 */
public class SystemIDResolver
{

  /**
   * Get absolute URI from a given relative URI. 
   * 
   * <p>The URI is resolved relative to the system property "user.dir" 
   * if it is available; if not (i.e. in an Applet perhaps which 
   * throws SecurityException) then it is currently resolved 
   * relative to "" or a blank string.  Also replaces all 
   * backslashes with forward slashes.</p>
   *
   * @param uri Relative URI to resolve
   *
   * @return Resolved absolute URI or the input relative URI if 
   * it could not be resolved.
   */
  public static String getAbsoluteURIFromRelative(String uri)
  {

    String curdir = "";
    try {
      curdir = System.getProperty("user.dir");
    }
    catch (SecurityException se) {}// user.dir not accessible from applet

    if (null != curdir)
    {
      String base;
      if (curdir.startsWith(File.separator))
        base = "file://" + curdir;
      else
        base = "file:///" + curdir;
        
      if (uri != null)
        // Note: this should arguably stick in a '/' forward 
        //  slash character instead of the file separator, 
        //  since we're effectively assuming it's a hierarchical 
        //  URI and adding in the abs_path separator -sc
        uri = base + System.getProperty("file.separator") + uri;
      else
        uri = base + System.getProperty("file.separator");
    }

    if (null != uri && (uri.indexOf('\\') > -1))
      uri = uri.replace('\\', '/');

    return uri;
  }
  
  /**
   * Take a SystemID string and try and turn it into a good absolute URL.
   *
   * @param urlString url A URL string, which may be relative or absolute.
   *
   * @return The resolved absolute URI
   * @throws TransformerException thrown if the string can't be turned into a URL.
   */
  public static String getAbsoluteURI(String url)
          throws TransformerException
  {
    if (url.startsWith(".."))
      url = new File(url).getAbsolutePath();
      
    if (url.startsWith(File.separator))
    {
      // If the url starts with a path separator, we assume it's 
      //  a reference to a file: scheme (why do we do this? -sc)
      url = "file://" + url;
    }
    else if (url.indexOf(':') < 0)
    {
      // If the url does not have a colon: character (which 
      //  separates the scheme part from the rest) then it 
      //  must be a relative one, so go get an absolute one -sc
      url = getAbsoluteURIFromRelative(url);
    }

    // Bugzilla#5701: the below else if is incorrect, if you read 
    //  section 5.2 of RFC 2396.  If the url did start with file:, 
    //  it implies we should assume it's absolute and be done 
    //  with resolving.  Note that I'm not even sure why we put 
    //  in the second check for '/' anyways -sc
    //else if (url.startsWith("file:") && url.charAt(5) != '/') 
    //{
    //  url = getAbsoluteURIFromRelative(url.substring(5));
    //}
    // Bugzilla#5701 comment out code end 

    return url;
  }


  /**
   * Take a SystemID string and try and turn it into a good absolute URL.
   *
   * @param urlString SystemID string
   * @param base Base URI to use to resolve the given systemID
   *
   * @return The resolved absolute URI
   * @throws TransformerException thrown if the string can't be turned into a URL.
   */
  public static String getAbsoluteURI(String urlString, String base)
          throws TransformerException
  {
    boolean isAbsouteUrl = false;
    boolean needToResolve = false;    
 
    // Bugzilla#5701: the below if is incorrect, if you read 
    //  section 5.2 of RFC 2396.  If the url did start with file:, 
    //  it implies we should assume it's absolute and be done 
    //  with resolving.  Note that I'm not even sure why we put 
    //  in the second check for '/' anyways -sc
    //if(urlString.startsWith("file:") && urlString.charAt(5) != '/') 
    //{
    //  needToResolve = true;
    //}
    //else if (urlString.indexOf(':') > 0)
    // Bugzilla#5701 comment out code end 
    if (urlString.indexOf(':') > 0)
    {
      // If there is a colon to separate the scheme from the rest, 
      //  it should be an absolute URL
      isAbsouteUrl = true;
    }
    else if (urlString.startsWith(File.separator))
    {
      // If the url starts with a path separator, we assume it's 
      //  a reference to a file: scheme (why do we do this? -sc)
      urlString = "file://" + urlString;
      isAbsouteUrl = true;
    }

    if ((!isAbsouteUrl) && ((null == base)
            || (base.indexOf(':') < 0)))
    {
      if (base != null && base.startsWith(File.separator))
        base = "file://" + base;
      else
        base = getAbsoluteURIFromRelative(base);
    }

    // bit of a hack here.  Need to talk to URI person to see if this can be fixed.
    if ((null != base) && needToResolve) 
         
    {
      if(base.equals(urlString))
      {
        base = "";
      }
      else
      {
        urlString = urlString.substring(5);
        isAbsouteUrl = false;
      }
    }   

    // This is probably a bad idea, we should at least check for quotes...
    if (null != base && (base.indexOf('\\') > -1))
      base = base.replace('\\', '/');

    if (null != urlString && (urlString.indexOf('\\') > -1))
      urlString = urlString.replace('\\', '/');

    URI uri;

    try
    {
      if ((null == base) || (base.length() == 0) || (isAbsouteUrl))
      {
        uri = new URI(urlString);
      }
      else
      {
        URI baseURI = new URI(base);

        uri = new URI(baseURI, urlString);
      }
    }
    catch (MalformedURIException mue)
    {
      throw new TransformerException(mue);
    }

    String uriStr = uri.toString();
    
    // Not so sure if this is good.  But, for now, I'll try it. We really must 
    // make sure the return from this function is a URL!
    if((Character.isLetter(uriStr.charAt(0)) && (uriStr.charAt(1) == ':') 
     && (uriStr.charAt(2) == '/') && (uriStr.charAt(3) != '/'))
       || ((uriStr.charAt(0) == '/') && (uriStr.charAt(1) != '/')))
    {
    	uriStr = "file:///"+uriStr;
    }
    return uriStr;
  }
}