org.openmrs.module.atomfeed.web.AtomFeedDownloadServlet.java Source code

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Here is the source code for org.openmrs.module.atomfeed.web.AtomFeedDownloadServlet.java

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/**
 * The contents of this file are subject to the OpenMRS Public License
 * Version 1.0 (the "License"); you may not use this file except in
 * compliance with the License. You may obtain a copy of the License at
 * http://license.openmrs.org
 *
 * Software distributed under the License is distributed on an "AS IS"
 * basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See the
 * License for the specific language governing rights and limitations
 * under the License.
 *
 * Copyright (C) OpenMRS, LLC.  All Rights Reserved.
 */
package org.openmrs.module.atomfeed.web;

import java.io.IOException;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;

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.openmrs.api.context.Context;
import org.openmrs.module.atomfeed.AtomFeedUtil;

/**
 * Download ability for the atom feed
 */
public class AtomFeedDownloadServlet extends HttpServlet {

    private static final long serialVersionUID = 1L;

    private static Log log = LogFactory.getLog(AtomFeedUtil.class);

    /**
     * @see javax.servlet.http.HttpServlet#doGet(javax.servlet.http.HttpServletRequest,
     *      javax.servlet.http.HttpServletResponse)
     * @should exclude entries before the asOfDate value
     * @should include all entries if no valid asOfDate is specified
     */
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

        Date asOfDate = null;
        String asOfDateString = req.getParameter("asOfDate");
        if (!StringUtils.isBlank(asOfDateString)) {
            try {
                asOfDate = new SimpleDateFormat(AtomFeedUtil.RFC_3339_DATE_FORMAT).parse(asOfDateString);
            } catch (ParseException ex) {
                try {
                    asOfDate = Context.getDateFormat().parse(asOfDateString);
                } catch (ParseException e) {
                    log.error(asOfDateString + ": for asOfDate parameter is not in the correct date format", ex);
                }
            }
        }

        AtomFeedUtil.getAtomFeedStream(resp.getOutputStream(), asOfDate);
    }

    /**
     * This method is called by the servlet container to process a HEAD request made by RSS readers
     * against the /atomfeed URI
     * 
     * @see javax.servlet.http.HttpServlet#doHead(javax.servlet.http.HttpServletRequest,
     *      javax.servlet.http.HttpServletResponse)
     * @should send not modified error if atom feed has not changed
     * @should send valid headers if atom feed has changed
     */
    public void doHead(HttpServletRequest req, HttpServletResponse resp) throws IOException {
        // read atomfeed header specific information from the header file
        String headerFileContent = AtomFeedUtil.readFeedHeaderFile();
        int contentLength = 0;
        String etagToken = "";
        Date lastModified = null;
        if (StringUtils.isNotBlank(headerFileContent)) {
            contentLength = headerFileContent.length() + Integer
                    .valueOf(StringUtils.substringBetween(headerFileContent, "<entriesSize>", "</entriesSize>"));
            etagToken = StringUtils.substringBetween(headerFileContent, "<versionId>", "</versionId>");
            try {
                lastModified = new SimpleDateFormat(AtomFeedUtil.RFC_3339_DATE_FORMAT)
                        .parse(StringUtils.substringBetween(headerFileContent, "<updated>", "</updated>"));
            } catch (ParseException e) {
                // ignore it here
            }
        }

        // set the content length and type
        resp.setContentLength(contentLength);
        resp.setContentType("application/atom+xml");
        resp.setCharacterEncoding("UTF-8");

        // compare previous ETag token with current one
        String previousEtagToken = req.getHeader("If-None-Match");
        Calendar ifModifiedSince = Calendar.getInstance();
        long ifModifiedSinceInMillis = req.getDateHeader("If-Modified-Since");
        ifModifiedSince.setTimeInMillis(ifModifiedSinceInMillis);
        if (((etagToken != null) && (previousEtagToken != null && previousEtagToken.equals('"' + etagToken + '"')))
                || (ifModifiedSinceInMillis > 0 && ifModifiedSince.getTime().compareTo(lastModified) >= 0)) {
            // send 304 status code that indicates that resource has not been modified
            resp.sendError(HttpServletResponse.SC_NOT_MODIFIED);
            // re-use original last modified time-stamp
            resp.setHeader("Last-Modified", req.getHeader("If-Modified-Since"));
            // no further processing required
            return;
        }

        // set header for the next time the client calls
        if (etagToken != null) {
            resp.setHeader("ETag", '"' + etagToken + '"');
            // set the last modified time if it's already specified
            if (lastModified == null) {
                // otherwise set the last modified time to now
                Calendar cal = Calendar.getInstance();
                cal.set(Calendar.MILLISECOND, 0);
                lastModified = cal.getTime();
            }
            resp.setDateHeader("Last-Modified", lastModified.getTime());
        }
    }

}