The Net: Ultimate Internet Guide/WWLCD1.ISO/pc/java/un2maiq4/pjjava/src/pj/net/remoteurl.java

Java Source | 1996-08-14 | 5.9 KB | 219 lines

/*---------------------------------------------------------------------------

    Written by the Personal Journal developers of Dow Jones & Company, Inc.

    Dow Jones makes no representations or warranties about
    the suitability of this software, either express or
    implied, including but not limited to the implied warranties
    of merchantability, fitness for a particular purpose,
    or non-infringement.  Dow Jones will not be liable for
    any damages suffered by a user as a result of using,
    modifying or distributing this software or its derivatives.


    @(#)RemoteURL.java  0.00 rphall

    A RemoteURL is a URL stored at a URL.

    Authors:

    rphall          Rick Hall
    jlee            James Lee

    Version Ident:
    $Header$

    History:

    16-Jan-1996 rphall     Initial Creation
    21-Mar-1996 jlee       Modified getURL so that it can process URL's title and URL at the same time.

---------------------------------------------------------------------------*/

package pj.net;

import pj.net.RemoteString;

import java.net.MalformedURLException;
import java.net.URL;
import java.util.StringTokenizer;
import java.util.NoSuchElementException;

/**
 * A RemoteURL is a URL stored at a URL.  The source
 * implementation assumes the URL is stored in a file
 * and represented as an ANSI string.
 * <P>
 * This class is totally unrelated to RemoteObject and subclasses
 * defined in the sun.tools.debug package.
 * <P>
 * This class is related to RemoteImage and RemoteString defined
 * in this package (pj.net).
 *
 * @see pj.net.RemoteImage
 * @see pj.net.RemoteString
 * @version 0.00 16-Jan-1996
 * @author Rick Hall
*/
public class RemoteURL
    {

    // --- Instance variables

    private final int GETURL = 0;
    private final int GETURLTITLE = 1;


    /**
     * The source URL from which a string representation of a URL is loaded.
    */
    private URL urlSource;

    /**
     * A URL resolved from the source url.
     * May be null if the source url or its contents are invalid.
    */
    private URL urlResolved;


    /**
     * A URL title resolved from the source url.
     * May be null if the source url or its contents are invalid.
    */
    private String urlTitleResolved;
    // --- Public constructors

    /**
     * Constructs an RemoteURL based on the specified source URL.
    */
    public RemoteURL(URL u)
        {
        urlSource = u;
        urlResolved = null;
        urlTitleResolved = null;
        }

    // --- Public operations

    /**
     * @return The source URL of this RemoteURL.
    */
    public URL getSourceURL()
        {
        return urlSource;
        }

    /**
     * Get a URL resolved from a source url.
     * <P>
     * This operation does not automatically force a new resolution.
     * If the current URL is not null, the current URL is returned.
     * If the current URL is null, this operation resolves a new URL from
     * the source URL.  The returned URL is null if the source URL
     * or its contents are invalid.
     * @return A resolved URL, or null if the source url or its contents
     * are invalid.
    */
    public URL getURL()
        {
        if (urlResolved == null)
            urlResolved = (URL)resolveURL( GETURL );

        return urlResolved;
        }

    public String getURLTitle()
        {
        if (urlTitleResolved == null)
            urlTitleResolved = (String)resolveURL( GETURLTITLE );

        return urlTitleResolved;
        }

    // --- Private operations

    /**
     * Resolve a URL from the source url.
     * The URL data is loaded immediately.
     * This operation blocks until the url string is finished loading.
     * @return May be null if url or its contents are invalid;
    */
    private Object resolveURL( int type )
        {
        URL     urlMoreAd = null;
        String  strURLTitle = null;

        try {
            switch ( type )
                {
                case GETURL:
                        urlMoreAd = (URL)getURLData(urlSource, type);
                    return urlMoreAd;
                case GETURLTITLE:
                    strURLTitle = (String)getURLData(urlSource, type);
                    return strURLTitle;
                default:
                    break;
                }
            }
        catch(MalformedURLException e)
            {
            System.out.println("RemoteURL resolveURL, exception = " + e.toString());
            }

        return null;
        }

    private Object getURLData(URL u, int type) throws MalformedURLException
        {
        URL             u_ = null;
        String          strURLTitle = null;
        String          strURL = null;
        RemoteString    rs = new RemoteString(u);
        String          s = rs.getString();
        StringTokenizer st = new StringTokenizer( s, "\r\n" );

        try {
            strURLTitle = st.nextToken();
            }
        catch (NoSuchElementException e)
            {
            return null;
            }

        try {
            strURL = st.nextToken();
            }
        catch (NoSuchElementException e)
            {
            strURL = strURLTitle;
            }


        switch ( type )
            {
            case GETURL:
                try {
                    u_ = new URL( strURL );
                    }
                catch ( MalformedURLException e )
                    {
                    System.out.println("Debug-RemoteURL-getURLData:MalformedURLException" );
                    return null;
                    }
                return u_;

            case GETURLTITLE:
                return strURLTitle;

            default:
                break;
            }

        return null;
        } // getURLData



    } // RemoteURL