sync4jservlet.java

实现了SyncML无线同步协议

/**
 * Copyright (C) 2003-2004 Funambol
 *
 *  This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 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 General Public License for more details.
 *
 * You should have received a copy of the GNU 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 sync4j.transport.http.server;

import java.io.*;
import java.net.InetAddress;
import java.net.UnknownHostException;
import java.util.StringTokenizer;
import java.util.logging.Logger;
import java.util.logging.Level;

import javax.naming.*;
import javax.ejb.CreateException;
import javax.ejb.EJBException;
import javax.servlet.*;
import javax.servlet.http.*;

import sync4j.framework.core.Constants;
import sync4j.framework.core.Util;
import sync4j.framework.core.SyncML;
import sync4j.framework.core.Sync4jException;
import sync4j.framework.tools.Base64;
import sync4j.framework.tools.WBXMLTools;
import sync4j.framework.server.*;
import sync4j.framework.transport.http.SyncHolder;
import sync4j.framework.transport.http.SyncHolderCache;
import sync4j.framework.protocol.ProtocolException;

import org.apache.commons.lang.StringUtils;

import org.jibx.runtime.*;
import org.jibx.runtime.impl.*;

/**
 *  Receives the HTTP request and does session management.
 *
 *  <b>Session Management</b>
 *  <p>
 *  If the url contains a parameter {PARAM_SESSION_ID}={SESSION_ID}, the session
 *  id is used to lookup in the <i>handlerCache</i> if there is already a
 *  <i>SyncHolder</i> associated with the given session id it is used to process
 *  the incoming request. Otherwise (either if the session parameter is not
 *  specified or not cached handler is found), a new session id is created and a
 *  new <i>SyncHolder</i> object is instantiated and stored in the cache.<br>
 *  The session id is created as followed:
 *  <p>
 *  <ol>
 *    <li> the first four bytes contains the IP address of the remote client
 *    <li> a dash ('-') is appended
 *    <li> the creation timestamp is appended
 *    <li> the resulting string is encoded base 64
 *  </ol>
 *  Note that no session expiration is handled by this class. That is delegated
 *  to the <i>SyncHolderCache</i> object.
 *
 *  @author Stefano Fornari @ Funambol
 *
 *  @version $Id: Sync4jServlet.java,v 1.8 2004/05/28 16:15:14 luigiafassina Exp $
 *
 */
public final class Sync4jServlet extends javax.servlet.http.HttpServlet {
    
    // --------------------------------------------------------------- Constants
    
    public static final String LOG_NAME = "sync4j.transport.http";
    
    public static final String PARAM_SESSION_ID       = "sid"                 ;
    public static final String PARAM_SYNCHOLDER_CLASS = "sync-holder-class"   ;
    public static final String PARAM_SESSION_TTL      = "session-time-to-live";
    public static final String PARAM_SERVER_URI       = "server-uri"          ;
    
    // ------------------------------------------------------------ Private data
    
    private Logger log = Logger.getLogger(LOG_NAME);
    
    private static String          syncHolderClass = null;
    private static SyncHolderCache holderCache     = null;
    private static String          serverUri       = null;
    
    // ---------------------------------------------------------- Public methods
    
    public void init() throws ServletException {
        String value;
        long timeToLive = 0;
        
        ServletConfig config = getServletConfig();
        
        value = config.getInitParameter(PARAM_SYNCHOLDER_CLASS);
        
        if (StringUtils.isEmpty(value)) {
            String msg = "The servlet configuration parameter "
            + PARAM_SYNCHOLDER_CLASS
            + " cannot be empty ("
            + value
            + ")"
            ;
            log(msg);
            throw new ServletException(msg);
        }
        syncHolderClass = value;
        
        value = config.getInitParameter(PARAM_SESSION_TTL);
        if (!StringUtils.isEmpty(value)) {
            try {
                timeToLive = Long.parseLong(value);
            } catch (NumberFormatException e) {
                String msg = "The servlet configuration parameter "
                + PARAM_SESSION_TTL
                + " is not an integer number ("
                + value
                + ")"
                ;
                log.severe(msg);
                throw new ServletException(msg);
            }
        }
        
        holderCache = new SyncHolderCache(timeToLive);
        
        value = config.getInitParameter(PARAM_SERVER_URI);
        if (StringUtils.isEmpty(value)) {
            String msg = "The servlet configuration parameter "
            + PARAM_SERVER_URI
            + " cannot be empty ("
            + value
            + ")"
            ;
            log(msg);
            throw new ServletException(msg);
        }
        
        serverUri = value;
    }
    
    
    public void doPost(
    final HttpServletRequest httpRequest,
    final HttpServletResponse httpResponse)
    throws ServletException, IOException {
        
        final String contentType = httpRequest.getContentType().split(";")[0];
        final int contentLength  = httpRequest.getContentLength();
        
        if (log.isLoggable(Level.FINE)) {
            log("contentType: " + contentType);
            log("contentLength: " + contentLength);
        }
        
        if (contentLength < 1) {
            throw new Error("Content length < 1 (" + contentLength + ")");
        }
        
        byte[] requestData = new byte[contentLength];
        
        InputStream in = httpRequest.getInputStream();
        int n = 0;
        int bytesRead = 0;
        
        try {
            do {
                n = in.read(requestData,
                bytesRead,
                requestData.length - bytesRead);
                if (n > 0) {
                    bytesRead += n;
                }
            } while (n != -1);
        } catch (IOException ex) {
            handleError(httpRequest, httpResponse, "Error reading the request", ex);
            return;
        } finally {
            try {
                if (in != null) {
                    in.close();
                }
            } catch (Exception ex) {
                handleError(httpRequest, httpResponse, ex.getClass().getName(), ex);
                return;
            }
            in = null;
        }
        
        if (bytesRead != contentLength) {
            handleError(httpRequest, httpResponse, "bytesRead != contentLength", null);
            return;
        }
        
        //
        // If the session id is not specified in the URL, a new remote object
        // will be created. Otherwise the session id specifies which remote
        // object shall handles the request.
        //
        SyncHolder holder = null;
        try {
            holder = createHolder(httpRequest);
        } catch (Exception e) {
            handleError(httpRequest, httpResponse, "Error creating SyncBean", e);
            return;
        }
        
        SyncResponse resp = null;
        try {
            resp = holder.processMessage(requestData, contentType);
        } catch (Exception e) {
            Throwable cause = e.getCause();
            
            if (  (cause != null)
            && (  (cause instanceof ProtocolException)
            || (cause instanceof Sync4jException  )
            )
            ) {
                handleError(httpRequest, httpResponse, "Protocol error", cause);
                return;
            } else {
                throw new ServletException(e);
            }
        }
        
        //
        // Set the <RespURI> tag to the server uri plus the session id parameter
        //
        SyncML responseMessage = resp.getMessage();
        responseMessage.getSyncHdr().setRespURI(
        serverUri                    +
        httpRequest.getContextPath() +
        httpRequest.getServletPath() +
        '?'                          +
        PARAM_SESSION_ID             +
        '='                          +
        holder.getSessionId()
        );
        
        OutputStream out = null;
        try {
            out = httpResponse.getOutputStream();
            httpResponse.setContentType(resp.getMimeType());
            
            byte[] response = null;
            if (Constants.MIMETYPE_SYNCML_XML.equals(resp.getMimeType())) {
                
                if (log.isLoggable(Level.FINE)) {
                    log.fine("Sending back XML");
                }
                
                try {
                    
                    if (log.isLoggable(Level.FINE)) {
                        log.info("Marshalling response message SyncML");
                    }
                    
                    ByteArrayOutputStream bout = new ByteArrayOutputStream();
                    
                    IBindingFactory f = BindingDirectory.getFactory(SyncML.class);
                    IMarshallingContext c = f.createMarshallingContext();
                    c.setIndent(0);
                    c.marshalDocument(responseMessage, "UTF-8", null, bout);
                    
                    String msgOut = new String(bout.toByteArray());
                    response = msgOut.getBytes();
                    
                } catch(Exception e) {
                    e.printStackTrace();
                }                
                
            } else if (Constants.MIMETYPE_SYNCML_WBXML.equals(resp.getMimeType())){
                if (log.isLoggable(Level.FINE)) {
                    log.fine("Sending back WBXML");
                }
                
                try {
                    //
                    // The marshalling is doing directly into WBXMLTools because
                    // that method is calling in the other code too
                    //
                    response = WBXMLTools.toWBXML(responseMessage);
                    
                } catch(Exception e) {
                    e.printStackTrace();
                }
            }
            
            httpResponse.setContentLength(response.length);
            out.write(response);
            
            out.flush();
        } finally {
            if (log.isLoggable(Level.FINE)) {
                log.fine("Finally");
            }
            if (out != null) out.close();
        }
        
        //
        // If the message completed the SyncML communication, the holder
        // must be closed and discarded.
        //
        if (resp.isCompleted()) {
            releaseHolder(holder);
        }
    }
    
    // --------------------------------------------------------- Private methods
    
    
    /**
     * Factory method for <i>SyncHolder</i> objects. If the session id is
     * passed as a CGI parameter, it is transformed in a EJB handle. If the
     * handle is not valid, it is considered expired. If the session id is not
     * specified, a new EJB is created
     *
     * @param request the associated HTTP request object
     *
     * @return a new <i>SyncHolder</i>
     *
     */
    private SyncHolder createHolder(HttpServletRequest request)
    throws Exception {
        String sessionId = request.getParameter(PARAM_SESSION_ID);
        
        SyncHolder holder = null;
        
        if (log.isLoggable(Level.FINE)) {
            log.fine("cache: " + holderCache);
        }
        
        if (!StringUtils.isEmpty(sessionId)) {
            holder = (SyncHolder)holderCache.get(sessionId);
        }
        
        if (holder == null) {
            holder = (SyncHolder)getClass().forName(syncHolderClass).newInstance();
            
            sessionId = createSessionId(request);
            holder.setSessionId(sessionId);
            holderCache.put(holder);
        }
        
        return holder;
    }
    
    /**
     * Closes the given <i>SyncHolder</i> and removes it from the cache.
     *
     * @param holder the holder to releases
     */
    private void releaseHolder(SyncHolder holder) {
        try {
            holder.close();
        } catch (Exception e) {
            log.severe(e.getMessage());
            log.throwing(getClass().getName(), "releaseHolder", e.getCause());
        }
        holderCache.remove(holder.getSessionId());
    }
    
    /**
     * Handles errors conditions returning an appropriate content to the client.
     *
     * @param request the request object
     * @param response the response object
     * @msg   a desctiptive message
     * @t     a throwable object
     *
     */
    private void handleError(final HttpServletRequest   request,
    final HttpServletResponse response,
    String                   msg,
    final Throwable                  t) {
        
        if (msg == null) {
            msg = "";
        }
        
        if (t == null) {
            log.severe(msg);
        } else {
            log.severe(msg);
            log.throwing(getClass().getName(), "unknown", t);
        }
        try {
            response.sendError(response.SC_BAD_REQUEST, msg);
        } catch (IOException e) {
            log.severe(e.getMessage());
            log.throwing(getClass().getName(), "unknown", t);
        }
    }
    
    /**
     * Creates the session id (see the class description for details).
     *
     * @param request the HTTP request object
     *
     * @return a newly created session id
     */
    private String createSessionId(HttpServletRequest request) {
        String clientIP  = request.getRemoteAddr()   ;
        long   timestamp = System.currentTimeMillis();
        
        StringBuffer sb = new StringBuffer();
        
        byte[] ip = null;
        
        try {
            ip = InetAddress.getByName(clientIP).getAddress();
        } catch (UnknownHostException e) {
            ip = new byte[] {0, 0, 0, 0};
        }
        
        sb.append(ip).append('-').append(timestamp);
        
        String stringSessionId = new String(Base64.encode(sb.toString().getBytes()));
        
        //
        // strips out tailing '='
        //
        int i = stringSessionId.lastIndexOf('=');
        
        return ((i>0) ? stringSessionId.substring(0, i-1) : stringSessionId);
    }
    
    /**
     * The same as <i>handleError(reqest, response, msg, t, null)</i>.
     *
     * @param request the request object
     * @param response the response object
     * @msg   a desctiptive message
     * @t     a throwable object
     *
     */
    private void handleError(final HttpServletRequest   request,
    final HttpServletResponse response,
    final String                   msg) {
        this.handleError(request, response, msg, null);
    }
}