Java URI to Relative URI relativize(URI base, URI target)

Description

Enhanced version of URI.relativize, the target can now be in parent folder of base URI.

License

Open Source License

Parameter

Parameter	Description
base	Base uri, location from where to relativize.
target	Target uri, final destination of returned URI.

Exception

Parameter	Description
IllegalArgumentException	an exception

Return

Non-absolute URI, or target if target scheme is different than base scheme.

Declaration

public static URI relativize(URI base, URI target) 

Method Source Code

//package com.java2s;
/**/*from   w  w w.  j  av  a2s  .c  om*/
 * H2GIS is a library that brings spatial support to the H2 Database Engine
 * <http://www.h2database.com>. H2GIS is developed by CNRS
 * <http://www.cnrs.fr/>.
 *
 * This code is part of the H2GIS project. H2GIS 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;
 * version 3.0 of the License.
 *
 * H2GIS 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 <http://www.gnu.org/licenses/>.
 *
 *
 * For more information, please consult: <http://www.h2gis.org/>
 * or contact directly: info_at_h2gis.org
 */

import java.net.URI;
import java.net.URISyntaxException;

import java.util.StringTokenizer;

public class Main {
    /**
     * Enhanced version of URI.relativize, the target can now be in parent folder of base URI.
     * @param base Base uri, location from where to relativize.
     * @param target Target uri, final destination of returned URI.
     * @return Non-absolute URI, or target if target scheme is different than base scheme.
     * @throws IllegalArgumentException
     */
    public static URI relativize(URI base, URI target) {
        if (!base.getScheme().equals(target.getScheme())) {
            return target;
        }
        StringBuilder rel = new StringBuilder();
        String path = base.getPath();
        String separator = "/";
        StringTokenizer tokenizer = new StringTokenizer(target.getPath(), separator);
        String targetPart = "";
        if (tokenizer.hasMoreTokens()) {
            targetPart = tokenizer.nextToken();
        }
        if (path.startsWith(separator)) {
            path = path.substring(1);
        }
        StringTokenizer baseTokenizer = new StringTokenizer(path, separator, true);
        while (baseTokenizer.hasMoreTokens()) {
            String basePart = baseTokenizer.nextToken();
            if (baseTokenizer.hasMoreTokens()) {
                // Has a / after this folder name
                baseTokenizer.nextToken(); // return separator
                if (!basePart.isEmpty()) {
                    while (targetPart.isEmpty() && tokenizer.hasMoreTokens()) {
                        targetPart = tokenizer.nextToken();
                    }
                    if (!basePart.equals(targetPart)) {
                        rel.append("..");
                        rel.append(separator);
                    } else if (tokenizer.hasMoreTokens()) {
                        targetPart = tokenizer.nextToken();
                    }
                }
            }
        }
        // Add part of target path that is not in base path
        rel.append(targetPart);
        while (tokenizer.hasMoreTokens()) {
            targetPart = tokenizer.nextToken();
            rel.append(separator);
            rel.append(targetPart);
        }
        try {
            return new URI(null, null, rel.toString(), null, null);
        } catch (URISyntaxException ex) {
            throw new IllegalArgumentException(
                    "Illegal URI provided:\n" + base.toString() + "\n" + target.toString());
        }
    }
}

Related

1. relativeFileToURI(File file)
2. relativePath(final URI baseURI, final URI pathURI)
3. relativeURI(String basePath, String path)
4. relativize(URI base, URI child)
5. relativize(URI base, URI child)
6. relativize(URI basePath, File path)
7. relativize(URI baseUri, File f)
8. relativize(URI baseURI, URI uriToRelativize)
9. relativizeFromBase(String uri, URI base)