FragmentRequestParserBase.java

package org.linkeddatafragments.fragments;

import javax.servlet.http.HttpServletRequest;

import org.linkeddatafragments.config.ConfigReader;

/**
 * Base class for implementations of {@link IFragmentRequestParser}.
 *
 * @author <a href="http://olafhartig.de">Olaf Hartig</a>
 */
abstract public class FragmentRequestParserBase implements
		IFragmentRequestParser {
	@Override
	final public ILinkedDataFragmentRequest parseIntoFragmentRequest(
			final HttpServletRequest httpRequest, final ConfigReader config)
			throws IllegalArgumentException {
		return getWorker(httpRequest, config).createFragmentRequest();
	}

	/**
	 *
	 * @param httpRequest
	 * @param config
	 * @return
	 * @throws IllegalArgumentException
	 */
	abstract protected Worker getWorker(final HttpServletRequest httpRequest,
			final ConfigReader config) throws IllegalArgumentException;

	/**
     *
     */
	abstract static protected class Worker {

		/**
         *
         */
		public final HttpServletRequest request;

		/**
         *
         */
		public final ConfigReader config;

		/**
         *
         */
		public final boolean pageNumberWasRequested;

		/**
         *
         */
		public final long pageNumber;

		/**
		 *
		 * @param request
		 * @param config
		 */
		public Worker(final HttpServletRequest request,
				final ConfigReader config) {
			this.request = request;
			this.config = config;

			final String givenPageNumber = request
					.getParameter(ILinkedDataFragmentRequest.PARAMETERNAME_PAGE);
			if (givenPageNumber != null) {
				long pageNumber;
				try {
					pageNumber = Long.parseLong(givenPageNumber);
				} catch (final NumberFormatException ex) {
					pageNumber = 1L;
				}
				this.pageNumber = (pageNumber > 0) ? pageNumber : 1L;
				this.pageNumberWasRequested = true;
			} else {
				this.pageNumber = 1L;
				this.pageNumberWasRequested = false;
			}
		}

		/**
		 *
		 * @return
		 * @throws IllegalArgumentException
		 */
		abstract public ILinkedDataFragmentRequest createFragmentRequest()
				throws IllegalArgumentException;

		/**
		 *
		 * @return
		 */
		public String getFragmentURL() {
			final String datasetURL = getDatasetURL();
			final String query = this.request.getQueryString();
			return query == null ? datasetURL : (datasetURL + "?" + query);
		}

		/**
		 * Returns the dataset URL
		 * 
		 * @return the dataset URL. This consists of the base URL of the
		 *         application, the servlet path and the pathinfo as supplied by
		 *         request.getPathInfo()
		 */
		public String getDatasetURL() {
			return extractBaseURL(this.request, this.config)
					+ this.request.getServletPath()
					+ this.request.getPathInfo();
		}

	} // end of class Worker

	// ----- HELPERS ---------

	/**
	 *
	 * @param request
	 * @param config
	 * @return
	 */

	public static String extractBaseURL(final HttpServletRequest request,
			final ConfigReader config) {
		final String contextPath = request.getServletContext().getContextPath();
		if (config.getBaseURL() != null) {
			return config.getBaseURL();
		} else if ((request.getServerPort() == 80)
				|| (request.getServerPort() == 443)) {
			return request.getScheme() + "://" + request.getServerName()
					+ contextPath;
		} else {
			return request.getScheme() + "://" + request.getServerName() + ":"
					+ request.getServerPort() + contextPath;
		}
	}

}