import java.io.*; import java.util.*; public class AlbumServlet extends PhotoApplicationServlet { protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { User user = getCurrentUser(request); if (user == null) { response.sendRedirect(LOGIN_PAGE_URL); return; } PrintWriter out = startWritingPage(response); String albumName = request.getParameter("album"); if (!validateAlbumName(albumName, out)) return; Album album = loadAlbumByName(albumName); if (!validateAlbum(album, out)) return; AlbumPageModel model = new AlbumPageModel(album, request.getParameter("page")); new AlbumPage(model).printPage(out); out.flush(); } private boolean validateAlbum(Album album, PrintWriter out) { boolean valid = true; if (album == null) { new ErrorPage("Could not load album '" + album.getName() + "'").printError(out); valid = false; } return valid; } private boolean validateAlbumName(String albumName, PrintWriter out) { boolean valid = true; if (albumName == null || albumName.equals("")) { new ErrorPage("Missing parameter: album").printError(out); valid = false; } return valid; } private PrintWriter startWritingPage(HttpServletResponse response) { response.setContentType("text/html"); disableCache(response); PrintWriter out = response.getWriter(); return out; } User getCurrentUser(HttpServletRequest request) { return (User) (request.getSession(true).getAttribute(CURRENT_USER_SESSION_ATTRIBUTE)); } private void disableCache(HttpServletResponse response) { response.setHeader("Cache-Control", "no-cache"); //HTTP 1.1 response.setHeader("Pragma", "no-cache"); //HTTP 1.0 // prevents caching at the proxy server response.setHeader("Expires", "Thu, 01 Jan 1970 00:00:00 GMT"); } } class Page { protected void printHead(PrintWriter out, String title) { out.println(""); out.println(""); out.println(""); out.println("" + title + ""); out.println(""); } } class AlbumPageModel { private Album album; private String pageParameter; public AlbumPageModel(Album album, String pageParameter) { this.album = album; this.pageParameter = pageParameter; } public Album getAlbum() { return album; } public void setAlbum(Album album) { this.album = album; } public int getPicturesPerPage() { return PICTURES_PER_PAGE; } private static final int PICTURES_PER_PAGE = 20; public int getPageNumber() { int page; if (pageParameter == null || pageParameter.equals("")) { page = 0; } else { page = Integer.parseInt(pageParameter); } return page; } public List getPictures() { List pictures = new ArrayList(); int start = getStart(); int end = getEnd(); end = Math.min(end, getAlbum().getPictures().size()); for (int i = start; i < end; ++i) { pictures.add(getAlbum().getPictures().get(i)); } return pictures; } public int getEnd() { int end = getStart() + getPicturesPerPage(); return end; } public int getStart() { int start = getPageNumber() * getPicturesPerPage(); return start; } public int getTotalPictures() { return getAlbum().getPictures().size(); } } class AlbumPage extends Page { private AlbumPageModel model; public AlbumPage(AlbumPageModel model) { this.setModel(model); } public AlbumPageModel getModel() { return model; } public void setModel(AlbumPageModel model) { this.model = model; } public void printPage(PrintWriter out) { String title = "Album: " + getModel().getAlbum().getName(); printHead(out, title); out.println(""); out.println("

" + title + "

"); printPictureTable(out); printPreviousAndNextLinks(out, getModel().getPageNumber()); } private void printPreviousAndNextLinks(PrintWriter out, int pageNumber) { // todo: refactor me! out.println(""); if (pageNumber > 0) { out.print("<< previous "); } if (getModel().getEnd() < getModel().getTotalPictures()) { out.print(" next >>"); } out.println(""); } private void printPictureTable(PrintWriter out) { out.println(""); List pictures = getModel().getPictures(); for (Iterator pictureIterator = pictures.iterator(); pictureIterator.hasNext(); ) { Picture picture = (Picture) pictureIterator.next(); printPicture(out, picture); } out.println("

"); } private void printPicture(PrintWriter out, Picture picture) { out.print(""); out.print("

"); out.print(""); out.print(""); out.print(""); out.print(picture.getCaption()); out.print(""); out.println(""); } public void printError(PrintWriter out, String message) { printHead(out, "Error"); out.println("

"); out.print(message); out.print("

"); out.println(""); } } class ErrorPage extends Page { String message; public ErrorPage(String message) { this.message = message; } // todo: rename to "printPage" and make it an abstract method of Page public void printError(PrintWriter out) { printHead(out, "Error"); out.println("

"); out.print(message); out.print("

"); out.println(""); } }