difflinktag.java

JSPWiki,100%Java开发的一套完整WIKI程序

/* 
    JSPWiki - a JSP-based WikiWiki clone.

    Copyright (C) 2001-2002 Janne Jalkanen ([e-mail])

    This program 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 program 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 program; if not, write to the Free Software
    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */
package com.ecyrd.jspwiki.tags;

import java.io.IOException;
import javax.servlet.jsp.JspWriter;

import com.ecyrd.jspwiki.WikiEngine;
import com.ecyrd.jspwiki.WikiPage;
import com.ecyrd.jspwiki.WikiProvider;

/**
 *  Writes a diff link.  Body of the link becomes the link text.
 *  <P><B>Attributes</B></P>
 *  <UL>
 *    <LI>page - Page name to refer to.  Default is the current page.</LI>
 *    <LI>version - The older of these versions.  May be an integer to
 *        signify a version number, or the text "latest" to signify the latest version.
 *        If not specified, will default to "latest".  May also be "previous" to signify
 *        a version prior to this particular version.</LI>
 *    <LI>newVersion - The newer of these versions.  Can also be "latest", or "previous".  Defaults to "latest".</LI>
 *  </UL>
 *
 *  If the page does not exist, this tag will fail silently, and not evaluate
 *  its body contents.
 *
 *  @author Janne Jalkanen
 *  @since 2.0
 */
public class DiffLinkTag
    extends WikiLinkTag
{
    public static final String VER_LATEST   = "latest";
    public static final String VER_PREVIOUS = "previous";

    private String m_version    = VER_LATEST;
    private String m_newVersion = VER_LATEST;

    public final String getVersion()
    {
        return m_version;
    }

    public void setVersion( String arg )
    {
        m_version = arg;
    }

    public final String getNewVersion()
    {
        return m_newVersion;
    }

    public void setNewVersion( String arg )
    {
        m_newVersion = arg;
    }

    public final int doWikiStartTag()
        throws IOException
    {
        WikiEngine engine   = m_wikiContext.getEngine();
        String     pageName = m_pageName;

        if( m_pageName == null )
        {
            if( m_wikiContext.getPage() != null )
            {
                pageName = m_wikiContext.getPage().getName();
            }
            else
            {
                return SKIP_BODY;
            }
        }

        JspWriter out = pageContext.getOut();
        String encodedlink = engine.encodeName( pageName );

        int r1 = 0;
        int r2 = 0;

        //
        //  In case the page does not exist, we fail silently.
        //
        if(!engine.pageExists(pageName))
        {
            return SKIP_BODY;
        }

        if( VER_LATEST.equals(getVersion()) )
        {
            WikiPage latest = engine.getPage( pageName, 
                                              WikiProvider.LATEST_VERSION );

            r1 = latest.getVersion();
        }
        else if( VER_PREVIOUS.equals(getVersion()) )
        {
            r1 = m_wikiContext.getPage().getVersion() - 1;
            r1 = (r1 < 1 ) ? 1 : r1;
        }
        else
        {
            r1 = Integer.parseInt( getVersion() );
        }

        if( VER_LATEST.equals(getNewVersion()) )
        {
            WikiPage latest = engine.getPage( pageName,
                                              WikiProvider.LATEST_VERSION );

            r2 = latest.getVersion();
        }
        else if( VER_PREVIOUS.equals(getNewVersion()) )
        {
            r2 = m_wikiContext.getPage().getVersion() - 1;
            r2 = (r2 < 1 ) ? 1 : r2;
        }
        else
        {
            r2 = Integer.parseInt( getNewVersion() );
        }

        switch( m_format )
        {
          case ANCHOR:
            out.print("<a href=\""+engine.getBaseURL()+"Diff.jsp?page="+encodedlink+"&amp;r1="+r1+"&amp;r2="+r2+"\">");
            break;

          case URL:
            out.print( engine.getBaseURL()+"Diff.jsp?page="+encodedlink+"&amp;r1="+r1+"&amp;r2="+r2 );
            break;
        }

        return EVAL_BODY_INCLUDE;
    }
}