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This file is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

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The source code

// $Header: /home/cvs/jakarta-jmeter/src/htmlparser/org/htmlparser/util/LinkProcessor.java,v 1.2 2004/02/11 02:16:58 woolfel Exp $
/*
 * ====================================================================
 * Copyright 2002-2004 The Apache Software Foundation.
 *
 * 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.
 * 
 */

// The developers of JMeter and Apache are greatful to the developers
// of HTMLParser for giving Apache Software Foundation a non-exclusive
// license. The performance benefits of HTMLParser are clear and the
// users of JMeter will benefit from the hard work the HTMLParser
// team. For detailed information about HTMLParser, the project is
// hosted on sourceforge at http://htmlparser.sourceforge.net/.
//
// HTMLParser was originally created by Somik Raha in 2000. Since then
// a healthy community of users has formed and helped refine the
// design so that it is able to tackle the difficult task of parsing
// dirty HTML. Derrick Oswald is the current lead developer and was kind
// enough to assist JMeter.

package org.htmlparser.util;

import java.io.Serializable;
import java.net.MalformedURLException;
import java.net.URL;

/**
 * Processor class for links, is present basically as a utility class.
 */
public class LinkProcessor implements Serializable
{
    /**
     * Overriding base URL.
     * If set, this is used instead of a provided base URL in extract().
     */
    private String baseUrl;

    /**
     * Create an HTMLLinkProcessor.
     */
    public LinkProcessor()
    {
        baseUrl = null;
    }

    /**
     * Create an absolute URL from a possibly relative link and a base URL.
     * @param link The reslative portion of a URL.
     * @param base The base URL unless overridden by the current baseURL property.
     * @return The fully qualified URL or the original link if a failure occured.
     */
    public String extract(String link, String base) throws ParserException
    {
        String path; // path portion of constructed URL
        boolean modified; // true if path is modified by us
        boolean absolute; // true if link starts with "/"
        int index;
        String ret;

        try
        {
            if (null == link)
                link = "";
            if (null != getBaseUrl())
                base = getBaseUrl();
            if ((null == base) || ("".equals(link)))
                ret = link;
            else
            {
                URL url = constructUrl(link, base);
                ret = url.toExternalForm();
            }
        }
        catch (MalformedURLException murle)
        {
            ret = link;
        }

        return (Translate.decode(ret));
    }

    public URL constructUrl(String link, String base)
        throws MalformedURLException
    {
        String path;
        boolean modified;
        boolean absolute;
        int index;
        URL url; // constructed URL combining relative link and base
        url = new URL(new URL(base), link);
        path = url.getFile();
        modified = false;
        absolute = link.startsWith("/");
        if (!absolute)
        { // we prefer to fix incorrect relative links
            // this doesn't fix them all, just the ones at the start
            while (path.startsWith("/."))
            {
                if (path.startsWith("/../"))
                {
                    path = path.substring(3);
                    modified = true;
                }
                else if (path.startsWith("/./") || path.startsWith("/."))
                {
                    path = path.substring(2);
                    modified = true;
                }
                else
                    break;
            }
        }
        // fix backslashes
        while (-1 != (index = path.indexOf("/\\")))
        {
            path = path.substring(0, index + 1) + path.substring(index + 2);
            modified = true;
        }
        if (modified)
            url = new URL(url, path);
        return url;
    }

    /**
     * Turn spaces into %20.
     * @param url The url containing spaces.
     * @return The URL with spaces as %20 sequences.
     */
    public static String fixSpaces(String url)
    {
        int index;
        int length;
        char ch;
        StringBuffer returnURL;

        index = url.indexOf(' ');
        if (-1 != index)
        {
            length = url.length();
            returnURL = new StringBuffer(length * 3);
            returnURL.append(url.substring(0, index));
            for (int i = index; i < length; i++)
            {
                ch = url.charAt(i);
                if (ch == ' ')
                    returnURL.append("%20");
                else
                    returnURL.append(ch);
            }
            url = returnURL.toString();
        }

        return (url);
    }

    /**
     * Check if a resource is a valid URL.
     * @param resourceLocn The resource to test.
     * @return true if the resource is a valid URL.
     */
    public static boolean isURL(String resourceLocn)
    {
        URL url;
        boolean ret;

        try
        {
            url = new URL(resourceLocn);
            ret = true;
        }
        catch (MalformedURLException murle)
        {
            ret = false;
        }

        return (ret);
    }

    /**
     * Returns the baseUrl.
     * @return String
     */
    public String getBaseUrl()
    {
        return baseUrl;
    }

    /**
     * Sets the baseUrl.
     * @param baseUrl The baseUrl to set
     */
    public void setBaseUrl(String baseUrl)
    {
        this.baseUrl = baseUrl;
    }

    public static String removeLastSlash(String baseUrl)
    {
        if (baseUrl.charAt(baseUrl.length() - 1) == '/')
        {
            return baseUrl.substring(0, baseUrl.length() - 1);
        }
        else
        {
            return baseUrl;
        }
    }

}
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