com.thruzero.common.web.servlet.RssFeedPublisherServlet.java Source code

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Here is the source code for com.thruzero.common.web.servlet.RssFeedPublisherServlet.java

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/*
 *   Copyright 2012 George Norman
 *
 *   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 com.thruzero.common.web.servlet;

import java.io.IOException;
import java.io.Writer;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

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

import org.apache.commons.lang3.StringUtils;

import com.thruzero.common.core.infonode.InfoNodeElement;
import com.thruzero.common.core.locator.ProviderLocator;
import com.thruzero.common.core.locator.ServiceLocator;
import com.thruzero.common.core.support.ContainerPath;
import com.thruzero.common.core.support.EntityPath;
import com.thruzero.domain.model.DataStoreInfo;
import com.thruzero.domain.provider.DataStoreInfoProvider;
import com.thruzero.domain.service.InfoNodeService;
import com.thruzero.domain.service.RssFeedService;

/**
 * A servlet that generates RSS 2.0 feeds for a given request. The request must contain the feed id as a request parameter
 * with the following format: {@code <username>.<feedName>}
 * <p>
 * Example feed link: http://www.thruzero.com/jcat3/rss?id=dilbert.test1
 *
 * @author George Norman
 */
public class RssFeedPublisherServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;

    /** Valid userName and entityName pattern (components of a feedId). */
    private Pattern namePattern = Pattern.compile("^[a-z0-9_-]{1,60}$");

    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        // feed id is <userName>.<entityName>
        String feedId = request.getParameter("id");
        String[] feedInfo = StringUtils.split(feedId, '.');

        if (feedInfo == null || feedInfo.length != 2) {
            throw new IllegalArgumentException(
                    "Invalid Feed ID. Verify the format matches this: \"id=userName.feedName\"");
        }

        // get and validate userName
        String userName = feedInfo[0];
        Matcher userNameMatcher = namePattern.matcher(userName);
        if (!userNameMatcher.matches()) {
            throw new IllegalArgumentException("Invalid Feed ID");
        }

        // get and validate entityName
        String entityName = feedInfo[1];
        Matcher entityNameMatcher = namePattern.matcher(entityName);
        if (!entityNameMatcher.matches()) {
            throw new IllegalArgumentException("Invalid Feed ID");
        }

        // load the user that has published the requested feed
        DataStoreInfo dataStoreInfo = ProviderLocator.locate(DataStoreInfoProvider.class)
                .getDataStoreInfo(userName);
        if (dataStoreInfo == null) {
            throw new IllegalArgumentException("Feed Not Found");
        }

        // load the InfoNode from the user's datastore for the requested feed
        EntityPath entityPath = new EntityPath(
                ContainerPath.CONTAINER_PATH_SEPARATOR + userName + ContainerPath.CONTAINER_PATH_SEPARATOR + "rss"
                        + ContainerPath.CONTAINER_PATH_SEPARATOR + entityName + ".xml");
        InfoNodeService infoNodeService = ServiceLocator.locate(InfoNodeService.class);
        InfoNodeElement rssFeedNode = infoNodeService.getInfoNode(entityPath, dataStoreInfo);

        if (rssFeedNode == null) {
            throw new IllegalArgumentException("Feed Not Found");
        } else {
            rssFeedNode.enableRootNode();
        }

        // publish the feed
        RssFeedService rssFeedService = ServiceLocator.locate(RssFeedService.class);
        Writer writer = response.getWriter();
        response.setContentType("application/xml; charset=UTF-8");
        rssFeedService.writeRssFeed(rssFeedNode, writer);
    }
}