trackbackservlet.java

这个weblogging 设计得比较精巧

/*
 * Created on Apr 13, 2003
 */
package org.roller.presentation.weblog;

import org.roller.pojos.WeblogEntryData;
import org.roller.presentation.RollerRequest;

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.UnsupportedEncodingException;


/**
 * Roller's Trackback server implementation. POSTing to this Servlet will add a
 * Trackback to a Weblog Entrty. For more info on Trackback, read the spec: 
 * <a href="http://www.movabletype.org/docs/mttrackback.html>MT Trackback</a>.
 * 
 * @web.servlet name="TrackbackServlet"
 * @web.servlet-mapping url-pattern="/trackback/*"
 * 
 * @author David M Johnson
 */
public class TrackbackServlet extends HttpServlet
{
    /** Request parameter to indicate a trackback "tb" */
    //private static final String TRACKBACK_PARAM = "tb";

    /** Request parameter for the trackback "title" */
    private static final String TRACKBACK_TITLE_PARAM = "title";

    /** Request parameter for the trackback "excerpt" */
    private static final String TRACKBACK_EXCERPT_PARAM = "excerpt";

    /** Request parameter for the trackback "url" */
    private static final String TRACKBACK_URL_PARAM = "url";

    /** Request parameter for the trackback "blog_name" */
    private static final String TRACKBACK_BLOG_NAME_PARAM = "blog_name";

    /** Key under which the trackback return code will be placed
     * (example: on the request for the JSPDispatcher) */
    public static final String BLOJSOM_TRACKBACK_RETURN_CODE = 
            "BLOJSOM_TRACKBACK_RETURN_CODE";

    /** Key under which the trackback error message will be placed
     * (example: on the request for the JSPDispatcher) */
    public static final String BLOJSOM_TRACKBACK_MESSAGE = 
            "BLOJSOM_TRACKBACK_MESSAGE";

    /** Trackback success page */
    //private static final String TRACKBACK_SUCCESS_PAGE = "trackback-success";

    /** Trackback failure page */
    //private static final String TRACKBACK_FAILURE_PAGE = "trackback-failure";

    /**
     * Constructor.
     */
    public TrackbackServlet()
    {
        super();
    }

    /** 
     * POSTing to this Servlet will add a Trackback to a Weblog Entrty.
     */
    protected void doGet(HttpServletRequest req, HttpServletResponse res)
                   throws ServletException, IOException
    {
        doPost(req,res);
    }
    
    /** 
     * POSTing to this Servlet will add a Trackback to a Weblog Entrty.
     */
    protected void doPost(HttpServletRequest req, HttpServletResponse res)
                   throws ServletException, IOException
    {
        try
        {
            // insure that incoming data is parsed as UTF-8
            req.setCharacterEncoding("UTF-8");
        }
        catch (UnsupportedEncodingException e)
        {
            throw new ServletException("Can't set incoming encoding to UTF-8");
        }

        String url = req.getParameter(TRACKBACK_URL_PARAM);
        String title = req.getParameter(TRACKBACK_TITLE_PARAM);
        String excerpt = req.getParameter(TRACKBACK_EXCERPT_PARAM);
        String blogName = req.getParameter(TRACKBACK_BLOG_NAME_PARAM);

        if ((title == null) || "".equals(title))
        {
            title = url;
        }

        if (excerpt == null)
        {
            excerpt = "";
        }
        else
        {
            if (excerpt.length() >= 255)
            {
                excerpt = excerpt.substring(0, 252);
                excerpt += "...";
            }
        }
               
        String error = null;
        PrintWriter pw = new PrintWriter(res.getOutputStream());
        try
        {
            if ( title==null || url==null || excerpt==null || blogName==null )
            {
                error = "title, url, excerpt, and blog_name not specified.";
            }
            else
            {
                RollerRequest rreq = RollerRequest.getRollerRequest(req);
                WeblogEntryData entry = rreq.getWeblogEntry();
                
                if (entry!=null && entry.getCommentsStillAllowed())
                {
                    entry.addTrackback(url,title,excerpt,blogName);
                    rreq.getRoller().commit();
            
                    pw.println("<?xml version=\"1.0\" encoding=\"iso-8859-1\"?>");
                    pw.println("<response>");
                    pw.println("<error>0</error>");
                    pw.println("</response>");
                    pw.flush();
                }
                else if (entry!=null)
                {
                    error = "Comments and Trackbacks are disabled for the entry you specified.";
                }                
                else
                {
                    error = "Entry not specified.";
                }                
            }
            
        }
        catch (Exception e)
        {
            error = e.getMessage();
            if ( error == null )
            {   
                error = e.getClass().getName();
            }
        }
        
        if ( error!= null )
        {
            pw.println("<?xml version=\"1.0\" encoding=\"iso-8859-1\"?>");
            pw.println("<response>");
            pw.println("<error>1</error>");
            pw.println("<message>ERROR: "+error+"</message>");
            pw.println("</response>");
            pw.flush();
        }
        res.flushBuffer();
        
        // TODO : FindBugs thinks 'pw' should close
    }
}