atomservlet.java

这个weblogging 设计得比较精巧

/*
 * Copyright 2005 David M Johnson (For RSS and Atom In Action)
 *
 * 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.
 */
package org.roller.presentation.atomapi;

import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.Reader;
import java.io.Writer;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.apache.commons.lang.StringUtils;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.jdom.Document;
import org.jdom.Element;
import org.jdom.JDOMException;
import org.jdom.input.SAXBuilder;
import org.jdom.output.Format;
import org.jdom.output.XMLOutputter;
import org.roller.util.Utilities;

import com.sun.syndication.feed.atom.Entry;
import com.sun.syndication.feed.atom.Feed;
import com.sun.syndication.feed.atom.Link;
import com.sun.syndication.io.FeedException;
import com.sun.syndication.io.WireFeedInput;
import com.sun.syndication.io.WireFeedOutput;

/**
 * Atom Servlet implements Atom by calling a Roller independent handler.
 * @web.servlet name="AtomServlet"
 * @web.servlet-mapping url-pattern="/atom/*"
 * @author David M Johnson
 */
public class AtomServlet extends HttpServlet
{
    /** We use Rome to parse/generate Atom feeds and it does Atom format 0.3 */
    public static final String FEED_TYPE = "atom_0.3"; 
    
    private static Log mLogger = 
        LogFactory.getFactory().getInstance(AtomServlet.class);

    //-----------------------------------------------------------------------------
    /**
     * Create an Atom request handler.
     * TODO: make AtomRequestHandler implementation configurable.
     */
    private AtomHandler createAtomRequestHandler(HttpServletRequest request)
    {
        return new RollerAtomHandler(request);   
    }
    
    //-----------------------------------------------------------------------------
    /**
     * Handles an Atom GET by calling handler and writing results to response.
     */
    protected void doGet(HttpServletRequest req, HttpServletResponse res)
        throws ServletException, IOException
    {
        AtomHandler handler = createAtomRequestHandler(req);
        String userName = handler.getAuthenticatedUsername();
        if (userName != null) 
        {
            String[] pathInfo = getPathInfo(req);
            try
            {
                if (handler.isIntrospectionURI(pathInfo)) 
                {
                    // return an Atom Service document
                    AtomService service = handler.getIntrospection(pathInfo);                   
                    Document doc = AtomService.serviceToDocument(service);
                    Writer writer = res.getWriter();
                    XMLOutputter outputter = new XMLOutputter();
                    outputter.setFormat(Format.getPrettyFormat());
                    outputter.output(doc, writer);
                    writer.close();
                    res.setStatus(HttpServletResponse.SC_OK);
                }
                else if (handler.isCollectionURI(pathInfo))
                {
                    // return a collection
                    String ranges = req.getHeader("Range");
                    if (ranges == null) req.getParameter("Range");
                    AtomCollection col = null;
                    if (ranges != null) 
                    {
                        AtomCollection.Range range = 
                            AtomCollection.parseRange(req.getHeader("Range"));
                        int offset = 0;
                        String offsetString = req.getParameter("offset");
                        if (offsetString != null) 
                        {
                            offset = Integer.parseInt(offsetString);
                        }
                        col= handler.getCollection(
                            pathInfo, range.start, range.end, offset);
                    }
                    else 
                    {
                        col= handler.getCollection(pathInfo);
                    }
                    Document doc = AtomCollection.collectionToDocument(col);
                    Writer writer = res.getWriter();
                    XMLOutputter outputter = new XMLOutputter();
                    outputter.setFormat(Format.getPrettyFormat());
                    outputter.output(doc, writer);
                    writer.close();
                    res.setStatus(HttpServletResponse.SC_OK);
                }
                else if (handler.isEntryURI(pathInfo)) 
                {
                    // return an entry
                    Entry entry = handler.getEntry(pathInfo);                    
                    Writer writer = res.getWriter(); 
                    serializeEntry(entry, writer);                    
                    writer.close();
                }
                else if (handler.isResourceURI(pathInfo))
                {
                    // return a resource
                    String absPath = handler.getResourceFilePath(pathInfo);
                    String type = getServletContext().getMimeType(absPath);
                    res.setContentType(type);
                    Utilities.copyInputToOutput(
                        new FileInputStream(absPath), res.getOutputStream());
                }
                else
                {
                    res.setStatus(HttpServletResponse.SC_NOT_FOUND);
                }
            }
            catch (Exception e)
            {
                res.setStatus(HttpServletResponse.SC_INTERNAL_SERVER_ERROR);
                e.printStackTrace(res.getWriter());
                mLogger.error(e);
            }
        }
        else 
        {
            res.setStatus(HttpServletResponse.SC_UNAUTHORIZED);
        }
    }
    
    //-----------------------------------------------------------------------------  
    /**
     * Handles an Atom POST by calling handler to identify URI, reading/parsing
     * data, calling handler and writing results to response.
     */
    protected void doPost(HttpServletRequest req, HttpServletResponse res)
        throws ServletException, IOException
    {
        AtomHandler handler = createAtomRequestHandler(req);
        String userName = handler.getAuthenticatedUsername();
        if (userName != null) 
        {
            String[] pathInfo = getPathInfo(req);
            try
            {
                if (handler.isEntryCollectionURI(pathInfo)) 
                {
                    // parse incoming entry
                    Entry unsavedEntry = parseEntry(
                        new InputStreamReader(req.getInputStream()));
                    
                    // call handler to post it
                    Entry savedEntry = handler.postEntry(pathInfo, unsavedEntry);
                    Iterator links = savedEntry.getAlternateLinks().iterator();
                    while (links.hasNext()) {
                        Link link = (Link) links.next();
                        if (link.getRel().equals("alternate")) {
                            res.addHeader("Location", link.getHref());
                            break;
                        }