Make a URL from the given string : URL « Network « Java Tutorial

1. Java Tutorial
2. Network
3. URL

import java.io.File;
import java.io.IOException;
import java.io.UnsupportedEncodingException;
import java.net.MalformedURLException;
import java.net.URI;
import java.net.URISyntaxException;
import java.net.URL;
import java.net.URLDecoder;
import java.util.Map;


/*
  * JBoss, Home of Professional Open Source
  * Copyright 2005, JBoss Inc., and individual contributors as indicated
  * by the @authors tag. See the copyright.txt in the distribution for a
  * full listing of individual contributors.
  *
  * This is free software; you can redistribute it and/or modify it
  * under the terms of the GNU Lesser General Public License as
  * published by the Free Software Foundation; either version 2.1 of
  * the License, or (at your option) any later version.
  *
  * This software is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  * Lesser General Public License for more details.
  *
  * You should have received a copy of the GNU Lesser General Public
  * License along with this software; if not, write to the Free
  * Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
  * 02110-1301 USA, or see the FSF site: http://www.fsf.org.
  */



public class Main{


  /**
   * Make a URL from the given string.
   *
   * <p>
   * If the string is a properly formatted file URL, then the file
   * portion will be made canonical.
   *
   * <p>
   * If the string is an invalid URL then it will be converted into a
   * file URL.
   *
   * @param urlspec           The string to construct a URL for.
   * @param relativePrefix    The string to prepend to relative file
   *                          paths, or null to disable prepending.
   * @return                  A URL for the given string.
   *
   * @throws MalformedURLException  Could not make a URL for the given string.
   */
  public static URL toURL(String urlspec, final String relativePrefix) throws MalformedURLException
  {
     urlspec = urlspec.trim();

     URL url;

     try
     {
        url = new URL(urlspec);
        if (url.getProtocol().equals("file"))
        {
           url = makeURLFromFilespec(url.getFile(), relativePrefix);
        }
     }
     catch (Exception e)
     {
        // make sure we have a absolute & canonical file url
        try
        {
           url = makeURLFromFilespec(urlspec, relativePrefix);
        }
        catch (IOException n)
        {
           //
           // jason: or should we rethrow e?
           //
           throw new MalformedURLException(n.toString());
        }
     }

     return url;
  }

  public static URI toURI(String urispec, final String relativePrefix)
     throws URISyntaxException
  {
     urispec = urispec.trim();

     URI uri;

     if( urispec.startsWith("file:") )
     {
        uri = makeURIFromFilespec(urispec.substring(5), relativePrefix);
     }
     else
     {
        uri = new URI(urispec);
     }

     return uri;
  }

  /** A helper to make a URL from a filespec. */
  private static URL makeURLFromFilespec(final String filespec, final String relativePrefix)
     throws IOException
  {
     // make sure the file is absolute & canonical file url
     File file = new File(decode(filespec));
     
     // if we have a prefix and the file is not abs then prepend
     if (relativePrefix != null && !file.isAbsolute())
     {
        file = new File(relativePrefix, filespec);
     }
     
     // make sure it is canonical (no ../ and such)
     file = file.getCanonicalFile();

     return file.toURI().toURL();
  }
  
  private static String decode(String filespec)
  {
     try
     {
        return URLDecoder.decode(filespec, "UTF-8");
     }
     catch (UnsupportedEncodingException e)
     {
        throw new RuntimeException("Error decoding filespec: " + filespec, e);
     }
  }
  
  private static URI makeURIFromFilespec(final String filespec, final String relativePrefix)
  {
     // make sure the file is absolute & canonical file url
     File file = new File(decode(filespec));
     
     // if we have a prefix and the file is not abs then prepend
     if (relativePrefix != null && !file.isAbsolute())
     {
        file = new File(relativePrefix, filespec);
     }
     
     return file.toURI();
  }

  /**
   * Make a URL from the given string.
   *
   * @see #toURL(String,String)
   *
   * @param urlspec    The string to construct a URL for.
   * @return           A URL for the given string.
   *
   * @throws MalformedURLException  Could not make a URL for the given string.
   */
  public static URL toURL(final String urlspec) throws MalformedURLException
  {
     return toURL(urlspec, null);
  }

  /**
   * 
   * @param urispec
   * @return the uri
   * @throws URISyntaxException for any error
   */
  public static URI toURI(final String urispec)
     throws URISyntaxException
  {
     return toURI(urispec, null);
  }

}