Mega Code Archive
Resolve relative URIs and SystemID strings into absolute URIs
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/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you 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.
*/
/*
* $Id: SystemIDResolver.java 468655 2006-10-28 07:12:06Z minchau $
*/
import java.io.File;
import java.net.URI;
import javax.xml.transform.TransformerException;
/**
* 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>
* @xsl.usage internal
*/
public class SystemIDResolver
{
/**
* Get an absolute URI from a given relative URI (local path).
*
* <p>The relative URI is a local filesystem path. The path can be
* absolute or relative. If it is a relative path, it 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 we just return the
* relative path. The space and backslash characters are also replaced to
* generate a good absolute URI.</p>
*
* @param localPath The relative URI to resolve
*
* @return Resolved absolute URI
*/
public static String getAbsoluteURIFromRelative(String localPath)
{
if (localPath == null || localPath.length() == 0)
return "";
// If the local path is a relative path, then it is resolved against
// the "user.dir" system property.
String absolutePath = localPath;
if (!isAbsolutePath(localPath))
{
try
{
absolutePath = getAbsolutePathFromRelativePath(localPath);
}
// user.dir not accessible from applet
catch (SecurityException se)
{
return "file:" + localPath;
}
}
String urlString;
if (null != absolutePath)
{
if (absolutePath.startsWith(File.separator))
urlString = "file://" + absolutePath;
else
urlString = "file:///" + absolutePath;
}
else
urlString = "file:" + localPath;
return replaceChars(urlString);
}
/**
* Return an absolute path from a relative path.
*
* @param relativePath A relative path
* @return The absolute path
*/
private static String getAbsolutePathFromRelativePath(String relativePath)
{
return new File(relativePath).getAbsolutePath();
}
/**
* Return true if the systemId denotes an absolute URI .
*
* @param systemId The systemId string
* @return true if the systemId is an an absolute URI
*/
public static boolean isAbsoluteURI(String systemId)
{
/** http://www.ietf.org/rfc/rfc2396.txt
* Authors should be aware that a path segment which contains a colon
* character cannot be used as the first segment of a relative URI path
* (e.g., "this:that"), because it would be mistaken for a scheme name.
**/
/**
* %REVIEW% Can we assume here that systemId is a valid URI?
* It looks like we cannot ( See discussion of this common problem in
* Bugzilla Bug 22777 ).
**/
//"fix" for Bugzilla Bug 22777
if(isWindowsAbsolutePath(systemId)){
return false;
}
final int fragmentIndex = systemId.indexOf('#');
final int queryIndex = systemId.indexOf('?');
final int slashIndex = systemId.indexOf('/');
final int colonIndex = systemId.indexOf(':');
//finding substring before '#', '?', and '/'
int index = systemId.length() -1;
if(fragmentIndex > 0)
index = fragmentIndex;
if((queryIndex > 0) && (queryIndex <index))
index = queryIndex;
if((slashIndex > 0) && (slashIndex <index))
index = slashIndex;
// return true if there is ':' before '#', '?', and '/'
return ((colonIndex >0) && (colonIndex<index));
}
/**
* Return true if the local path is an absolute path.
*
* @param systemId The path string
* @return true if the path is absolute
*/
public static boolean isAbsolutePath(String systemId)
{
if(systemId == null)
return false;
final File file = new File(systemId);
return file.isAbsolute();
}
/**
* Return true if the local path is a Windows absolute path.
*
* @param systemId The path string
* @return true if the path is a Windows absolute path
*/
private static boolean isWindowsAbsolutePath(String systemId)
{
if(!isAbsolutePath(systemId))
return false;
// On Windows, an absolute path starts with "[drive_letter]:\".
if (systemId.length() > 2
&& systemId.charAt(1) == ':'
&& Character.isLetter(systemId.charAt(0))
&& (systemId.charAt(2) == '\\' || systemId.charAt(2) == '/'))
return true;
else
return false;
}
/**
* Replace spaces with "%20" and backslashes with forward slashes in
* the input string to generate a well-formed URI string.
*
* @param str The input string
* @return The string after conversion
*/
private static String replaceChars(String str)
{
StringBuffer buf = new StringBuffer(str);
int length = buf.length();
for (int i = 0; i < length; i++)
{
char currentChar = buf.charAt(i);
// Replace space with "%20"
if (currentChar == ' ')
{
buf.setCharAt(i, '%');
buf.insert(i+1, "20");
length = length + 2;
i = i + 2;
}
// Replace backslash with forward slash
else if (currentChar == '\\')
{
buf.setCharAt(i, '/');
}
}
return buf.toString();
}
/**
* Take a SystemID string and try to turn it into a good absolute URI.
*
* @param systemId A URI string, which may be absolute or relative.
*
* @return The resolved absolute URI
*/
public static String getAbsoluteURI(String systemId)
{
String absoluteURI = systemId;
if (isAbsoluteURI(systemId))
{
// Only process the systemId if it starts with "file:".
if (systemId.startsWith("file:"))
{
String str = systemId.substring(5);
// Resolve the absolute path if the systemId starts with "file:///"
// or "file:/". Don't do anything if it only starts with "file://".
if (str != null && str.startsWith("/"))
{
if (str.startsWith("///") || !str.startsWith("//"))
{
// A Windows path containing a drive letter can be relative.
// A Unix path starting with "file:/" is always absolute.
int secondColonIndex = systemId.indexOf(':', 5);
if (secondColonIndex > 0)
{
String localPath = systemId.substring(secondColonIndex-1);
try {
if (!isAbsolutePath(localPath))
absoluteURI = systemId.substring(0, secondColonIndex-1) +
getAbsolutePathFromRelativePath(localPath);
}
catch (SecurityException se) {
return systemId;
}
}
}
}
else
{
return getAbsoluteURIFromRelative(systemId.substring(5));
}
return replaceChars(absoluteURI);
}
else
return systemId;
}
else
return getAbsoluteURIFromRelative(systemId);
}
}
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