vaadin-framework/src/com/vaadin/terminal/gwt/server/AbstractCommunicationManager.java

/*
@ITMillApache2LicenseForJavaFiles@
 */

package com.vaadin.terminal.gwt.server;

import java.io.BufferedWriter;
import java.io.CharArrayWriter;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.io.Serializable;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.net.URL;
import java.security.GeneralSecurityException;
import java.text.DateFormat;
import java.text.DateFormatSymbols;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.Calendar;
import java.util.Collection;
import java.util.Collections;
import java.util.Comparator;
import java.util.GregorianCalendar;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Iterator;
import java.util.List;
import java.util.Locale;
import java.util.Map;
import java.util.Set;

import javax.portlet.PortletRequest;
import javax.portlet.PortletResponse;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;

import com.vaadin.Application;
import com.vaadin.Application.SystemMessages;
import com.vaadin.external.org.apache.commons.fileupload.FileItemIterator;
import com.vaadin.external.org.apache.commons.fileupload.FileItemStream;
import com.vaadin.external.org.apache.commons.fileupload.FileUpload;
import com.vaadin.external.org.apache.commons.fileupload.FileUploadException;
import com.vaadin.external.org.apache.commons.fileupload.ProgressListener;
import com.vaadin.terminal.ApplicationResource;
import com.vaadin.terminal.DownloadStream;
import com.vaadin.terminal.PaintException;
import com.vaadin.terminal.PaintTarget;
import com.vaadin.terminal.Paintable;
import com.vaadin.terminal.URIHandler;
import com.vaadin.terminal.UploadStream;
import com.vaadin.terminal.VariableOwner;
import com.vaadin.terminal.Paintable.RepaintRequestEvent;
import com.vaadin.terminal.Terminal.ErrorEvent;
import com.vaadin.terminal.Terminal.ErrorListener;
import com.vaadin.terminal.gwt.client.ApplicationConnection;
import com.vaadin.terminal.gwt.server.ComponentSizeValidator.InvalidLayout;
import com.vaadin.ui.AbstractField;
import com.vaadin.ui.Component;
import com.vaadin.ui.Upload;
import com.vaadin.ui.Window;
import com.vaadin.ui.Upload.UploadException;

/**
 * This is a common base class for the server-side implementations of the
 * communication system between the client code (compiled with GWT into
 * JavaScript) and the server side components. Its client side counterpart is
 * {@link ApplicationConnection}.
 *
 * A server side component sends its state to the client in a paint request (see
 * {@link Paintable} and {@link PaintTarget} on the server side). The client
 * widget receives these paint requests as calls to
 * {@link com.vaadin.terminal.gwt.client.Paintable#updateFromUIDL()}. The client
 * component communicates back to the server by sending a list of variable
 * changes (see {@link ApplicationConnection#updateVariable()} and
 * {@link VariableOwner#changeVariables(Object, Map)}).
 *
 * TODO Document better!
 */
@SuppressWarnings("serial")
public abstract class AbstractCommunicationManager implements
        Paintable.RepaintRequestListener, Serializable {

    /**
     * Generic interface of a (HTTP or Portlet) request to the application.
     *
     * This is a wrapper interface that allows
     * {@link AbstractCommunicationManager} to use a unified API.
     *
     * @see javax.servlet.ServletRequest
     * @see javax.portlet.PortletRequest
     *
     * @author peholmst
     */
    protected interface Request {

        /**
         * Gets a {@link Session} wrapper implementation representing the
         * session for which this request was sent.
         *
         * Multiple Vaadin applications can be associated with a single session.
         *
         * @return Session
         */
        public Session getSession();

        /**
         * Are the applications in this session running in a portlet or directly
         * as servlets.
         *
         * @return true if in a portlet
         */
        public boolean isRunningInPortlet();

        /**
         * Get the named HTTP or portlet request parameter.
         *
         * @see javax.servlet.ServletRequest#getParameter(String)
         * @see javax.portlet.PortletRequest#getParameter(String)
         *
         * @param name
         * @return
         */
        public String getParameter(String name);

        /**
         * Returns the length of the request content that can be read from the
         * input stream returned by {@link #getInputStream()}.
         *
         * @return content length in bytes
         */
        public int getContentLength();

        /**
         * Returns an input stream from which the request content can be read.
         * The request content length can be obtained with
         * {@link #getContentLength()} without reading the full stream contents.
         *
         * @return
         * @throws IOException
         */
        public InputStream getInputStream() throws IOException;

        /**
         * Returns the request identifier that identifies the target Vaadin
         * window for the request.
         *
         * @return String identifier for the request target window
         */
        public String getRequestID();

        /**
         * @see javax.servlet.ServletRequest#getAttribute(String)
         * @see javax.portlet.PortletRequest#getAttribute(String)
         */
        public Object getAttribute(String name);

        /**
         * @see javax.servlet.ServletRequest#setAttribute(String, Object)
         * @see javax.portlet.PortletRequest#setAttribute(String, Object)
         */
        public void setAttribute(String name, Object value);

        /**
         * Gets the underlying request object. The request is typically either a
         * {@link ServletRequest} or a {@link PortletRequest}.
         *
         * @return wrapped request object
         */
        public Object getWrappedRequest();

    }

    /**
     * Generic interface of a (HTTP or Portlet) response from the application.
     *
     * This is a wrapper interface that allows
     * {@link AbstractCommunicationManager} to use a unified API.
     *
     * @see javax.servlet.ServletResponse
     * @see javax.portlet.PortletResponse
     *
     * @author peholmst
     */
    protected interface Response {

        /**
         * Gets the output stream to which the response can be written.
         *
         * @return
         * @throws IOException
         */
        public OutputStream getOutputStream() throws IOException;

        /**
         * Sets the MIME content type for the response to be communicated to the
         * browser.
         *
         * @param type
         */
        public void setContentType(String type);

        /**
         * Gets the wrapped response object, usually a class implementing either
         * {@link ServletResponse} or {@link PortletResponse}.
         *
         * @return wrapped request object
         */
        public Object getWrappedResponse();

    }

    /**
     * Generic wrapper interface for a (HTTP or Portlet) session.
     *
     * Several applications can be associated with a single session.
     *
     * TODO Document me!
     *
     * @see javax.servlet.http.HttpSession
     * @see javax.portlet.PortletSession
     *
     * @author peholmst
     */
    protected interface Session {

        public boolean isNew();

        public Object getAttribute(String name);

        public void setAttribute(String name, Object o);

        public int getMaxInactiveInterval();

        public Object getWrappedSession();

    }

    /**
     * TODO Document me!
     *
     * @author peholmst
     */
    protected interface Callback {

        public void criticalNotification(Request request, Response response,
                String cap, String msg, String details, String outOfSyncURL)
                throws IOException;

        public String getRequestPathInfo(Request request);

        public InputStream getThemeResourceAsStream(String themeName,
                String resource) throws IOException;

    }

    private static String GET_PARAM_REPAINT_ALL = "repaintAll";

    // flag used in the request to indicate that the security token should be
    // written to the response
    private static final String WRITE_SECURITY_TOKEN_FLAG = "writeSecurityToken";

    /* Variable records indexes */
    private static final int VAR_PID = 1;
    private static final int VAR_NAME = 2;
    private static final int VAR_TYPE = 3;
    private static final int VAR_VALUE = 0;

    private static final String VAR_RECORD_SEPARATOR = "\u001e";

    private static final String VAR_FIELD_SEPARATOR = "\u001f";

    public static final String VAR_BURST_SEPARATOR = "\u001d";

    public static final String VAR_ARRAYITEM_SEPARATOR = "\u001c";

    private final HashMap<String, OpenWindowCache> currentlyOpenWindowsInClient = new HashMap<String, OpenWindowCache>();

    private static final int MAX_BUFFER_SIZE = 64 * 1024;

    private static final String GET_PARAM_ANALYZE_LAYOUTS = "analyzeLayouts";

    private final ArrayList<Paintable> dirtyPaintables = new ArrayList<Paintable>();

    private final HashMap<Paintable, String> paintableIdMap = new HashMap<Paintable, String>();

    private final HashMap<String, Paintable> idPaintableMap = new HashMap<String, Paintable>();

    private int idSequence = 0;

    private final Application application;

    // Note that this is only accessed from synchronized block and
    // thus should be thread-safe.
    private String closingWindowName = null;

    private List<String> locales;

    private int pendingLocalesIndex;

    private int timeoutInterval = -1;

    /**
     * TODO New constructor - document me!
     *
     * @param application
     */
    public AbstractCommunicationManager(Application application) {
        this.application = application;
        requireLocale(application.getLocale().toString());
    }

    /**
     * Create an upload handler that is appropriate to the context in which the
     * application is being run (servlet or portlet).
     *
     * @return new {@link FileUpload} instance
     */
    protected abstract FileUpload createFileUpload();

    /**
     * TODO New method - document me!
     *
     * @param upload
     * @param request
     * @return
     * @throws IOException
     * @throws FileUploadException
     */
    protected abstract FileItemIterator getUploadItemIterator(FileUpload upload,
            Request request) throws IOException, FileUploadException;

    /**
     * TODO New method - document me!
     *
     * @param request
     * @param response
     * @throws IOException
     * @throws FileUploadException
     */
    protected void doHandleFileUpload(Request request, Response response)
            throws IOException, FileUploadException {
        // Create a new file upload handler
        final FileUpload upload = createFileUpload();

        final UploadProgressListener pl = new UploadProgressListener();

        upload.setProgressListener(pl);

        // Parse the request
        FileItemIterator iter;

        try {
            iter = getUploadItemIterator(upload, request);
            /*
             * ATM this loop is run only once as we are uploading one file per
             * request.
             */
            while (iter.hasNext()) {
                final FileItemStream item = iter.next();
                final String name = item.getFieldName();
                final String filename = item.getName();
                final String mimeType = item.getContentType();
                final InputStream stream = item.openStream();
                if (item.isFormField()) {
                    // ignored, upload requests contains only files
                } else {
                    final String pid = name.split("_")[0];
                    final Upload uploadComponent = (Upload) idPaintableMap
                            .get(pid);
                    if (uploadComponent == null) {
                        throw new FileUploadException(
                                "Upload component not found");
                    }
                    if (uploadComponent.isReadOnly()) {
                        throw new FileUploadException(
                                "Warning: ignored file upload because upload component is set as read-only");
                    }
                    synchronized (application) {
                        // put upload component into receiving state
                        uploadComponent.startUpload();
                    }
                    final UploadStream upstream = new UploadStream() {

                        public String getContentName() {
                            return filename;
                        }

                        public String getContentType() {
                            return mimeType;
                        }

                        public InputStream getStream() {
                            return stream;
                        }

                        public String getStreamName() {
                            return "stream";
                        }

                    };

                    // tell UploadProgressListener which component is receiving
                    // file
                    pl.setUpload(uploadComponent);

                    try {
                        uploadComponent.receiveUpload(upstream);
                    } catch (UploadException e) {
                        // error happened while receiving file. Handle the
                        // error in the same manner as it would have happened in
                        // variable change.
                        synchronized (application) {
                            handleChangeVariablesError(application,
                                    uploadComponent, e,
                                    new HashMap<String, Object>());
                        }
                    }
                }
            }
        } catch (final FileUploadException e) {
            throw e;
        }

        sendUploadResponse(request, response);
    }

    /**
     * TODO document
     *
     * @param request
     * @param response
     * @throws IOException
     */
    protected void sendUploadResponse(Request request, Response response) throws IOException {
        response.setContentType("text/html");
        final OutputStream out = response.getOutputStream();
        final PrintWriter outWriter = new PrintWriter(new BufferedWriter(
                new OutputStreamWriter(out, "UTF-8")));
        outWriter.print("<html><body>download handled</body></html>");
        outWriter.flush();
        out.close();
    }

    /**
     * Internally process a UIDL request from the client.
     *
     * This method calls
     * {@link #handleVariables(Request, Response, Callback, Application, Window)}
     * to process any changes to variables by the client and then repaints
     * affected components using {@link #paintAfterVariableChanges()}.
     *
     * Also, some cleanup is done when a request arrives for an application that
     * has already been closed.
     *
     * The method handleUidlRequest(...) in subclasses should call this method.
     *
     * TODO better documentation
     *
     * @param request
     * @param response
     * @param callback
     * @throws IOException
     * @throws InvalidUIDLSecurityKeyException
     */
    protected void doHandleUidlRequest(Request request, Response response,
            Callback callback) throws IOException,
            InvalidUIDLSecurityKeyException {

        // repaint requested or session has timed out and new one is created
        boolean repaintAll;
        final OutputStream out;

        repaintAll = (request.getParameter(GET_PARAM_REPAINT_ALL) != null);
                //|| (request.getSession().isNew()); FIXME What the h*ll is this??
        out = response.getOutputStream();

        boolean analyzeLayouts = false;
        if (repaintAll) {
            // analyzing can be done only with repaintAll
            analyzeLayouts = (request.getParameter(GET_PARAM_ANALYZE_LAYOUTS) != null);
        }

        final PrintWriter outWriter = new PrintWriter(new BufferedWriter(
                new OutputStreamWriter(out, "UTF-8")));

        // The rest of the process is synchronized with the application
        // in order to guarantee that no parallel variable handling is
        // made
        synchronized (application) {

            // Finds the window within the application
            Window window = null;
            if (application.isRunning()) {
                window = doGetApplicationWindow(request, callback, application,
                        null);
                // Returns if no window found
                if (window == null) {
                    // This should not happen, no windows exists but
                    // application is still open.
                    System.err
                            .println("Warning, could not get window for application with request ID "
                                    + request.getRequestID());
                    return;
                }
            } else {
                // application has been closed
                endApplication(request, response, application);
                return;
            }

            // Change all variables based on request parameters
            if (!handleVariables(request, response, callback, application,
                    window)) {

                // var inconsistency; the client is probably out-of-sync
                SystemMessages ci = null;
                try {
                    Method m = application.getClass().getMethod(
                            "getSystemMessages", (Class[]) null);
                    ci = (Application.SystemMessages) m.invoke(null,
                            (Object[]) null);
                } catch (Exception e2) {
                    // FIXME: Handle exception
                    // Not critical, but something is still wrong; print
                    // stacktrace
                    e2.printStackTrace();
                }
                if (ci != null) {
                    String msg = ci.getOutOfSyncMessage();
                    String cap = ci.getOutOfSyncCaption();
                    if (msg != null || cap != null) {
                        callback.criticalNotification(request, response, cap,
                                msg, null, ci.getOutOfSyncURL());
                        // will reload page after this
                        return;
                    }
                }
                // No message to show, let's just repaint all.
                repaintAll = true;

            }

            paintAfterVariableChanges(request, response, callback, repaintAll,
                    outWriter, window, analyzeLayouts);

            if (closingWindowName != null) {
                currentlyOpenWindowsInClient.remove(closingWindowName);
                closingWindowName = null;
            }
        }

        //out.flush(); - this line will cause errors when deployed on GateIn.
        out.close();
    }

    /**
     * TODO document
     *
     * @param request
     * @param response
     * @param callback
     * @param repaintAll
     * @param outWriter
     * @param window
     * @param analyzeLayouts
     * @throws PaintException
     * @throws IOException
     */
    private void paintAfterVariableChanges(Request request, Response response,
            Callback callback, boolean repaintAll, final PrintWriter outWriter,
            Window window, boolean analyzeLayouts) throws PaintException,
            IOException {

        if (repaintAll) {
            // If repaint is requested, clean all ids in this root window
            for (final Iterator<String> it = idPaintableMap.keySet().iterator(); it
                    .hasNext();) {
                final Component c = (Component) idPaintableMap.get(it.next());
                if (isChildOf(window, c)) {
                    it.remove();
                    paintableIdMap.remove(c);
                }
            }
            // clean WindowCache
            OpenWindowCache openWindowCache = currentlyOpenWindowsInClient
                    .get(window.getName());
            if (openWindowCache != null) {
                openWindowCache.clear();
            }
        }

        // Removes application if it has stopped during variable changes
        if (!application.isRunning()) {
            endApplication(request, response, application);
            return;
        }

        // Sets the response type
        response.setContentType("application/json; charset=UTF-8");
        // some dirt to prevent cross site scripting
        outWriter.print("for(;;);[{");

        // security key
        Object writeSecurityTokenFlag = request
                .getAttribute(WRITE_SECURITY_TOKEN_FLAG);

        if (writeSecurityTokenFlag != null) {
            String seckey = (String) request.getSession().getAttribute(
                    ApplicationConnection.UIDL_SECURITY_TOKEN_ID);
            if (seckey == null) {
                seckey = "" + (int) (Math.random() * 1000000);
                request.getSession().setAttribute(
                        ApplicationConnection.UIDL_SECURITY_TOKEN_ID, seckey);
            }
            outWriter.print("\"" + ApplicationConnection.UIDL_SECURITY_TOKEN_ID
                    + "\":\"");
            outWriter.print(seckey);
            outWriter.print("\",");
        }

        outWriter.print("\"changes\":[");

        ArrayList<Paintable> paintables = null;

        // If the browser-window has been closed - we do not need to paint it at
        // all
        if (!window.getName().equals(closingWindowName)) {

            List<InvalidLayout> invalidComponentRelativeSizes = null;

            // re-get window - may have been changed
            Window newWindow = doGetApplicationWindow(request, callback,
                    application, window);
            if (newWindow != window) {
                window = newWindow;
                repaintAll = true;
            }

            JsonPaintTarget paintTarget = new JsonPaintTarget(this, outWriter,
                    !repaintAll);
            OpenWindowCache windowCache = currentlyOpenWindowsInClient
                    .get(window.getName());
            if (windowCache == null) {
                windowCache = new OpenWindowCache();
                currentlyOpenWindowsInClient.put(window.getName(), windowCache);
            }

            // Paints components
            if (repaintAll) {
                paintables = new ArrayList<Paintable>();
                paintables.add(window);

                // Reset sent locales
                locales = null;
                requireLocale(application.getLocale().toString());

            } else {
                // remove detached components from paintableIdMap so they
                // can be GC'ed
                for (Iterator<Paintable> it = paintableIdMap.keySet()
                        .iterator(); it.hasNext();) {
                    Component p = (Component) it.next();
                    if (p.getApplication() == null) {
                        idPaintableMap.remove(paintableIdMap.get(p));
                        it.remove();
                        dirtyPaintables.remove(p);
                        p.removeListener(this);
                    }
                }
                paintables = getDirtyVisibleComponents(window);
            }
            if (paintables != null) {

                // We need to avoid painting children before parent.
                // This is ensured by ordering list by depth in component
                // tree
                Collections.sort(paintables, new Comparator<Paintable>() {
                    public int compare(Paintable o1, Paintable o2) {
                        Component c1 = (Component) o1;
                        Component c2 = (Component) o2;
                        int d1 = 0;
                        while (c1.getParent() != null) {
                            d1++;
                            c1 = c1.getParent();
                        }
                        int d2 = 0;
                        while (c2.getParent() != null) {
                            d2++;
                            c2 = c2.getParent();
                        }
                        if (d1 < d2) {
                            return -1;
                        }
                        if (d1 > d2) {
                            return 1;
                        }
                        return 0;
                    }
                });

                for (final Iterator<Paintable> i = paintables.iterator(); i
                        .hasNext();) {
                    final Paintable p = i.next();

                    // TODO CLEAN
                    if (p instanceof Window) {
                        final Window w = (Window) p;
                        if (w.getTerminal() == null) {
                            w.setTerminal(application.getMainWindow()
                                    .getTerminal());
                        }
                    }
                    /*
                     * This does not seem to happen in tk5, but remember this
                     * case: else if (p instanceof Component) { if (((Component)
                     * p).getParent() == null || ((Component)
                     * p).getApplication() == null) { // Component requested
                     * repaint, but is no // longer attached: skip
                     * paintablePainted(p); continue; } }
                     */

                    // TODO we may still get changes that have been
                    // rendered already (changes with only cached flag)
                    if (paintTarget.needsToBePainted(p)) {
                        paintTarget.startTag("change");
                        paintTarget.addAttribute("format", "uidl");
                        final String pid = getPaintableId(p);
                        paintTarget.addAttribute("pid", pid);

                        p.paint(paintTarget);

                        paintTarget.endTag("change");
                    }
                    paintablePainted(p);

                    if (analyzeLayouts) {
                        Window w = (Window) p;
                        invalidComponentRelativeSizes = ComponentSizeValidator
                                .validateComponentRelativeSizes(w.getContent(),
                                        null, null);

                        // Also check any existing subwindows
                        if (w.getChildWindows() != null) {
                            for (Window subWindow : w.getChildWindows()) {
                                invalidComponentRelativeSizes = ComponentSizeValidator
                                        .validateComponentRelativeSizes(
                                                subWindow.getContent(),
                                                invalidComponentRelativeSizes,
                                                null);
                            }
                        }
                    }
                }
            }

            paintTarget.close();
            outWriter.print("]"); // close changes

            outWriter.print(", \"meta\" : {");
            boolean metaOpen = false;

            if (repaintAll) {
                metaOpen = true;
                outWriter.write("\"repaintAll\":true");
                if (analyzeLayouts) {
                    outWriter.write(", \"invalidLayouts\":");
                    outWriter.write("[");
                    if (invalidComponentRelativeSizes != null) {
                        boolean first = true;
                        for (InvalidLayout invalidLayout : invalidComponentRelativeSizes) {
                            if (!first) {
                                outWriter.write(",");
                            } else {
                                first = false;
                            }
                            invalidLayout.reportErrors(outWriter, this,
                                    System.err);
                        }
                    }
                    outWriter.write("]");
                }
            }

            SystemMessages ci = null;
            try {
                Method m = application.getClass().getMethod(
                        "getSystemMessages", (Class[]) null);
                ci = (Application.SystemMessages) m.invoke(null,
                        (Object[]) null);
            } catch (NoSuchMethodException e1) {
                e1.printStackTrace();
            } catch (IllegalArgumentException e) {
                e.printStackTrace();
            } catch (IllegalAccessException e) {
                e.printStackTrace();
            } catch (InvocationTargetException e) {
                e.printStackTrace();
            }

            // meta instruction for client to enable auto-forward to
            // sessionExpiredURL after timer expires.
            if (ci != null && ci.getSessionExpiredMessage() == null
                    && ci.getSessionExpiredCaption() == null
                    && ci.isSessionExpiredNotificationEnabled()) {
                int newTimeoutInterval = request.getSession()
                        .getMaxInactiveInterval();
                if (repaintAll || (timeoutInterval != newTimeoutInterval)) {
                    String escapedURL = ci.getSessionExpiredURL() == null ? ""
                            : ci.getSessionExpiredURL().replace("/", "\\/");
                    if (metaOpen) {
                        outWriter.write(",");
                    }
                    outWriter.write("\"timedRedirect\":{\"interval\":"
                            + (newTimeoutInterval + 15) + ",\"url\":\""
                            + escapedURL + "\"}");
                    metaOpen = true;
                }
                timeoutInterval = newTimeoutInterval;
            }

            outWriter.print("}, \"resources\" : {");

            // Precache custom layouts
            String themeName = window.getTheme();
            String requestThemeName = request.getParameter("theme");

            if (requestThemeName != null) {
                themeName = requestThemeName;
            }
            if (themeName == null) {
                themeName = AbstractApplicationServlet.getDefaultTheme();
            }

            // TODO We should only precache the layouts that are not
            // cached already (plagiate from usedPaintableTypes)
            int resourceIndex = 0;
            for (final Iterator<Object> i = paintTarget.getUsedResources()
                    .iterator(); i.hasNext();) {
                final String resource = (String) i.next();
                InputStream is = null;
                try {
                    is = callback.getThemeResourceAsStream(themeName, resource);
                } catch (final Exception e) {
                    // FIXME: Handle exception
                    e.printStackTrace();
                }
                if (is != null) {

                    outWriter.print((resourceIndex++ > 0 ? ", " : "") + "\""
                            + resource + "\" : ");
                    final StringBuffer layout = new StringBuffer();

                    try {
                        final InputStreamReader r = new InputStreamReader(is,
                                "UTF-8");
                        final char[] buffer = new char[20000];
                        int charsRead = 0;
                        while ((charsRead = r.read(buffer)) > 0) {
                            layout.append(buffer, 0, charsRead);
                        }
                        r.close();
                    } catch (final java.io.IOException e) {
                        // FIXME: Handle exception
                        System.err.println("Resource transfer failed:  "
                                + request.getRequestID() + ". ("
                                + e.getMessage() + ")");
                    }
                    outWriter.print("\""
                            + JsonPaintTarget.escapeJSON(layout.toString())
                            + "\"");
                } else {
                    // FIXME: Handle exception
                    System.err.println("CustomLayout not found");
                }
            }
            outWriter.print("}");

            Collection<Class<? extends Paintable>> usedPaintableTypes = paintTarget
                    .getUsedPaintableTypes();
            boolean typeMappingsOpen = false;
            for (Class<? extends Paintable> class1 : usedPaintableTypes) {
                if (windowCache.cache(class1)) {
                    // client does not know the mapping key for this type, send
                    // mapping to client
                    if (!typeMappingsOpen) {
                        typeMappingsOpen = true;
                        outWriter.print(", \"typeMappings\" : { ");
                    } else {
                        outWriter.print(" , ");
                    }
                    String canonicalName = class1.getCanonicalName();
                    outWriter.print("\"");
                    outWriter.print(canonicalName);
                    outWriter.print("\" : ");
                    outWriter.print(getTagForType(class1));
                }
            }
            if (typeMappingsOpen) {
                outWriter.print(" }");
            }

            // add any pending locale definitions requested by the client
            printLocaleDeclarations(outWriter);

            outWriter.print("}]");
        }
        outWriter.flush();
        outWriter.close();

    }

    /**
     * TODO document
     *
     * If this method returns false, something was submitted that we did not
     * expect; this is probably due to the client being out-of-sync and sending
     * variable changes for non-existing pids
     *
     * @return true if successful, false if there was an inconsistency
     */
    private boolean handleVariables(Request request, Response response,
            Callback callback, Application application2, Window window)
            throws IOException, InvalidUIDLSecurityKeyException {
        boolean success = true;
        int contentLength = request.getContentLength();

        if (contentLength > 0) {
            String changes = readRequest(request);

            // Manage bursts one by one
            final String[] bursts = changes.split(VAR_BURST_SEPARATOR);

            // Security: double cookie submission pattern unless disabled by
            // property
            if (!"true"
                    .equals(application2
                            .getProperty(AbstractApplicationServlet.SERVLET_PARAMETER_DISABLE_XSRF_PROTECTION))) {
                if (bursts.length == 1 && "init".equals(bursts[0])) {
                    // init request; don't handle any variables, key sent in
                    // response.
                    request.setAttribute(WRITE_SECURITY_TOKEN_FLAG, true);
                    return true;
                } else {
                    // ApplicationServlet has stored the security token in the
                    // session; check that it matched the one sent in the UIDL
                    String sessId = (String) request.getSession().getAttribute(
                            ApplicationConnection.UIDL_SECURITY_TOKEN_ID);

                    if (sessId == null || !sessId.equals(bursts[0])) {
                        throw new InvalidUIDLSecurityKeyException(
                                "Security key mismatch");
                    }
                }

            }

            for (int bi = 1; bi < bursts.length; bi++) {

                // extract variables to two dim string array
                final String[] tmp = bursts[bi].split(VAR_RECORD_SEPARATOR);
                final String[][] variableRecords = new String[tmp.length][4];
                for (int i = 0; i < tmp.length; i++) {
                    variableRecords[i] = tmp[i].split(VAR_FIELD_SEPARATOR);
                }

                for (int i = 0; i < variableRecords.length; i++) {
                    String[] variable = variableRecords[i];
                    String[] nextVariable = null;
                    if (i + 1 < variableRecords.length) {
                        nextVariable = variableRecords[i + 1];
                    }
                    final VariableOwner owner = (VariableOwner) idPaintableMap
                            .get(variable[VAR_PID]);
                    if (owner != null && owner.isEnabled()) {
                        // TODO this should be Map<String, Object>, but the
                        // VariableOwner API does not guarantee the key is a
                        // string
                        Map<Object, Object> m;
                        if (nextVariable != null
                                && variable[VAR_PID]
                                        .equals(nextVariable[VAR_PID])) {
                            // we have more than one value changes in row for
                            // one variable owner, collect em in HashMap
                            m = new HashMap<Object, Object>();
                            m.put(variable[VAR_NAME], convertVariableValue(
                                    variable[VAR_TYPE].charAt(0),
                                    variable[VAR_VALUE]));
                        } else {
                            // use optimized single value map
                            m = Collections.singletonMap(
                                    (Object) variable[VAR_NAME],
                                    convertVariableValue(variable[VAR_TYPE]
                                            .charAt(0), variable[VAR_VALUE]));
                        }

                        // collect following variable changes for this owner
                        while (nextVariable != null
                                && variable[VAR_PID]
                                        .equals(nextVariable[VAR_PID])) {
                            i++;
                            variable = nextVariable;
                            if (i + 1 < variableRecords.length) {
                                nextVariable = variableRecords[i + 1];
                            } else {
                                nextVariable = null;
                            }
                            m.put(variable[VAR_NAME], convertVariableValue(
                                    variable[VAR_TYPE].charAt(0),
                                    variable[VAR_VALUE]));
                        }
                        try {
                            owner.changeVariables(request, m);

                            // Special-case of closing browser-level windows:
                            // track browser-windows currently open in client
                            if (owner instanceof Window
                                    && ((Window) owner).getParent() == null) {
                                final Boolean close = (Boolean) m.get("close");
                                if (close != null && close.booleanValue()) {
                                    closingWindowName = ((Window) owner)
                                            .getName();
                                }
                            }
                        } catch (Exception e) {
                            handleChangeVariablesError(application2,
                                    (Component) owner, e, m);
                        }
                    } else {

                        // Handle special case where window-close is called
                        // after the window has been removed from the
                        // application or the application has closed
                        if ("close".equals(variable[VAR_NAME])
                                && "true".equals(variable[VAR_VALUE])) {
                            // Silently ignore this
                            continue;
                        }

                        // Ignore variable change
                        String msg = "Warning: Ignoring variable change for ";
                        if (owner != null) {
                            msg += "disabled component " + owner.getClass();
                            String caption = ((Component) owner).getCaption();
                            if (caption != null) {
                                msg += ", caption=" + caption;
                            }
                        } else {
                            msg += "non-existent component, VAR_PID="
                                    + variable[VAR_PID];
                            success = false;
                        }
                        System.err.println(msg);
                        continue;
                    }
                }

                // In case that there were multiple bursts, we know that this is
                // a special synchronous case for closing window. Thus we are
                // not interested in sending any UIDL changes back to client.
                // Still we must clear component tree between bursts to ensure
                // that no removed components are updated. The painting after
                // the last burst is handled normally by the calling method.
                if (bi < bursts.length - 1) {

                    // We will be discarding all changes
                    final PrintWriter outWriter = new PrintWriter(
                            new CharArrayWriter());

                    paintAfterVariableChanges(request, response, callback,
                            true, outWriter, window, false);

                }

            }
        }
        return success;
    }

    /**
     * Reads the request data from the Request and returns it converted to an
     * UTF-8 string.
     *
     * @param request
     * @return
     * @throws IOException
     */
    private static String readRequest(Request request) throws IOException {

        int requestLength = request.getContentLength();

        byte[] buffer = new byte[requestLength];
        InputStream inputStream = request.getInputStream();

        int bytesRemaining = requestLength;
        while (bytesRemaining > 0) {
            int bytesToRead = Math.min(bytesRemaining, MAX_BUFFER_SIZE);
            int bytesRead = inputStream.read(buffer, requestLength
                    - bytesRemaining, bytesToRead);
            if (bytesRead == -1) {
                break;
            }

            bytesRemaining -= bytesRead;
        }

        String result = new String(buffer, "utf-8");

        return result;
    }

    public class ErrorHandlerErrorEvent implements ErrorEvent, Serializable {
        private final Throwable throwable;

        public ErrorHandlerErrorEvent(Throwable throwable) {
            this.throwable = throwable;
        }

        public Throwable getThrowable() {
            return throwable;
        }

    }

    /**
     * Handles an error (exception) that occurred when processing variable
     * changes from the client or a failure of a file upload.
     *
     * For {@link AbstractField} components,
     * {@link AbstractField#handleError(com.vaadin.ui.AbstractComponent.ComponentErrorEvent)}
     * is called. In all other cases (or if the field does not handle the
     * error), {@link ErrorListener#terminalError(ErrorEvent)} for the
     * application error handler is called.
     *
     * @param application
     * @param owner
     *            component that the error concerns
     * @param e
     *            exception that occurred
     * @param m
     *            map from variable names to values
     */
    private void handleChangeVariablesError(Application application,
            Component owner, Exception e, Map<? extends Object, Object> m) {
        boolean handled = false;
        ChangeVariablesErrorEvent errorEvent = new ChangeVariablesErrorEvent(
                owner, e, m);

        if (owner instanceof AbstractField) {
            try {
                handled = ((AbstractField) owner).handleError(errorEvent);
            } catch (Exception handlerException) {
                /*
                 * If there is an error in the component error handler we pass
                 * the that error to the application error handler and continue
                 * processing the actual error
                 */
                application.getErrorHandler().terminalError(
                        new ErrorHandlerErrorEvent(handlerException));
                handled = false;
            }
        }

        if (!handled) {
            application.getErrorHandler().terminalError(errorEvent);
        }

    }

    private Object convertVariableValue(char variableType, String strValue) {
        Object val = null;
        switch (variableType) {
        case 'a':
            val = strValue.split(VAR_ARRAYITEM_SEPARATOR);
            break;
        case 's':
            val = strValue;
            break;
        case 'i':
            val = Integer.valueOf(strValue);
            break;
        case 'l':
            val = Long.valueOf(strValue);
            break;
        case 'f':
            val = Float.valueOf(strValue);
            break;
        case 'd':
            val = Double.valueOf(strValue);
            break;
        case 'b':
            val = Boolean.valueOf(strValue);
            break;
        case 'p':
            val = idPaintableMap.get(strValue);
            break;
        }

        return val;
    }

    /**
     * Prints the queued (pending) locale definitions to a {@link PrintWriter} in
     * a (UIDL) format that can be sent to the client and used there in formatting
     * dates, times etc.
     *
     * @param outWriter
     */
    private void printLocaleDeclarations(PrintWriter outWriter) {
        /*
         * ----------------------------- Sending Locale sensitive date
         * -----------------------------
         */

        // Send locale informations to client
        outWriter.print(", \"locales\":[");
        for (; pendingLocalesIndex < locales.size(); pendingLocalesIndex++) {

            final Locale l = generateLocale(locales.get(pendingLocalesIndex));
            // Locale name
            outWriter.print("{\"name\":\"" + l.toString() + "\",");

            /*
             * Month names (both short and full)
             */
            final DateFormatSymbols dfs = new DateFormatSymbols(l);
            final String[] short_months = dfs.getShortMonths();
            final String[] months = dfs.getMonths();
            outWriter.print("\"smn\":[\""
                    + // ShortMonthNames
                    short_months[0] + "\",\"" + short_months[1] + "\",\""
                    + short_months[2] + "\",\"" + short_months[3] + "\",\""
                    + short_months[4] + "\",\"" + short_months[5] + "\",\""
                    + short_months[6] + "\",\"" + short_months[7] + "\",\""
                    + short_months[8] + "\",\"" + short_months[9] + "\",\""
                    + short_months[10] + "\",\"" + short_months[11] + "\""
                    + "],");
            outWriter.print("\"mn\":[\""
                    + // MonthNames
                    months[0] + "\",\"" + months[1] + "\",\"" + months[2]
                    + "\",\"" + months[3] + "\",\"" + months[4] + "\",\""
                    + months[5] + "\",\"" + months[6] + "\",\"" + months[7]
                    + "\",\"" + months[8] + "\",\"" + months[9] + "\",\""
                    + months[10] + "\",\"" + months[11] + "\"" + "],");

            /*
             * Weekday names (both short and full)
             */
            final String[] short_days = dfs.getShortWeekdays();
            final String[] days = dfs.getWeekdays();
            outWriter.print("\"sdn\":[\""
                    + // ShortDayNames
                    short_days[1] + "\",\"" + short_days[2] + "\",\""
                    + short_days[3] + "\",\"" + short_days[4] + "\",\""
                    + short_days[5] + "\",\"" + short_days[6] + "\",\""
                    + short_days[7] + "\"" + "],");
            outWriter.print("\"dn\":[\""
                    + // DayNames
                    days[1] + "\",\"" + days[2] + "\",\"" + days[3] + "\",\""
                    + days[4] + "\",\"" + days[5] + "\",\"" + days[6] + "\",\""
                    + days[7] + "\"" + "],");

            /*
             * First day of week (0 = sunday, 1 = monday)
             */
            final Calendar cal = new GregorianCalendar(l);
            outWriter.print("\"fdow\":" + (cal.getFirstDayOfWeek() - 1) + ",");

            /*
             * Date formatting (MM/DD/YYYY etc.)
             */

            DateFormat dateFormat = DateFormat.getDateTimeInstance(
                    DateFormat.SHORT, DateFormat.SHORT, l);
            if (!(dateFormat instanceof SimpleDateFormat)) {
                System.err
                        .println("Unable to get default date pattern for locale "
                                + l.toString());
                dateFormat = new SimpleDateFormat();
            }
            final String df = ((SimpleDateFormat) dateFormat).toPattern();

            int timeStart = df.indexOf("H");
            if (timeStart < 0) {
                timeStart = df.indexOf("h");
            }
            final int ampm_first = df.indexOf("a");
            // E.g. in Korean locale AM/PM is before h:mm
            // TODO should take that into consideration on client-side as well,
            // now always h:mm a
            if (ampm_first > 0 && ampm_first < timeStart) {
                timeStart = ampm_first;
            }
            // Hebrew locale has time before the date
            final boolean timeFirst = timeStart == 0;
            String dateformat;
            if (timeFirst) {
                int dateStart = df.indexOf(' ');
                if (ampm_first > dateStart) {
                    dateStart = df.indexOf(' ', ampm_first);
                }
                dateformat = df.substring(dateStart + 1);
            } else {
                dateformat = df.substring(0, timeStart - 1);
            }

            outWriter.print("\"df\":\"" + dateformat.trim() + "\",");

            /*
             * Time formatting (24 or 12 hour clock and AM/PM suffixes)
             */
            final String timeformat = df.substring(timeStart, df.length());
            /*
             * Doesn't return second or milliseconds.
             *
             * We use timeformat to determine 12/24-hour clock
             */
            final boolean twelve_hour_clock = timeformat.indexOf("a") > -1;
            // TODO there are other possibilities as well, like 'h' in french
            // (ignore them, too complicated)
            final String hour_min_delimiter = timeformat.indexOf(".") > -1 ? "."
                    : ":";
            // outWriter.print("\"tf\":\"" + timeformat + "\",");
            outWriter.print("\"thc\":" + twelve_hour_clock + ",");
            outWriter.print("\"hmd\":\"" + hour_min_delimiter + "\"");
            if (twelve_hour_clock) {
                final String[] ampm = dfs.getAmPmStrings();
                outWriter.print(",\"ampm\":[\"" + ampm[0] + "\",\"" + ampm[1]
                        + "\"]");
            }
            outWriter.print("}");
            if (pendingLocalesIndex < locales.size() - 1) {
                outWriter.print(",");
            }
        }
        outWriter.print("]"); // Close locales
    }

    /**
     * TODO New method - document me!
     *
     * @param request
     * @param callback
     * @param application
     * @param assumedWindow
     * @return
     */
    protected Window doGetApplicationWindow(Request request, Callback callback,
            Application application, Window assumedWindow) {

        Window window = null;

        // If the client knows which window to use, use it if possible
        String windowClientRequestedName = request.getParameter("windowName");

        if (assumedWindow != null
                && application.getWindows().contains(assumedWindow)) {
            windowClientRequestedName = assumedWindow.getName();
        }
        if (windowClientRequestedName != null) {
            window = application.getWindow(windowClientRequestedName);
            if (window != null) {
                return window;
            }
        }

        // If client does not know what window it wants
        if (window == null && !request.isRunningInPortlet()) {
            // This is only supported if the application is running inside a
            // servlet

            // Get the path from URL
            String path = callback.getRequestPathInfo(request);
            if (path != null && path.startsWith("/UIDL")) {
                path = path.substring("/UIDL".length());
            }

            // If the path is specified, create name from it
            if (path != null && path.length() > 0 && !path.equals("/")) {
                String windowUrlName = null;
                if (path.charAt(0) == '/') {
                    path = path.substring(1);
                }
                final int index = path.indexOf('/');
                if (index < 0) {
                    windowUrlName = path;
                    path = "";
                } else {
                    windowUrlName = path.substring(0, index);
                    path = path.substring(index + 1);
                }

                window = application.getWindow(windowUrlName);
            }
        }

        // By default, use mainwindow
        if (window == null) {
            window = application.getMainWindow();
            // Return null if no main window was found
            if (window == null) {
                return null;
            }
        }

        // If the requested window is already open, resolve conflict
        if (currentlyOpenWindowsInClient.containsKey(window.getName())) {
            String newWindowName = window.getName();
            while (currentlyOpenWindowsInClient.containsKey(newWindowName)) {
                newWindowName = window.getName() + "_"
                        + ((int) (Math.random() * 100000000));
            }

            window = application.getWindow(newWindowName);

            // If everything else fails, use main window even in case of
            // conflicts
            if (window == null) {
                window = application.getMainWindow();
            }
        }

        return window;
    }

    /**
     * Ends the Application.
     *
     * The browser is redirected to the Application logout URL set with
     * {@link Application#setLogoutURL(String)}, or to the application URL if no
     * logout URL is given.
     *
     * @param request
     *            the request instance.
     * @param response
     *            the response to write to.
     * @param application
     *            the Application to end.
     * @throws IOException
     *             if the writing failed due to input/output error.
     */
    private void endApplication(Request request, Response response,
            Application application) throws IOException {

        String logoutUrl = application.getLogoutURL();
        if (logoutUrl == null) {
            logoutUrl = application.getURL().toString();
        }
        // clients JS app is still running, send a special json file to tell
        // client that application has quit and where to point browser now
        // Set the response type
        final OutputStream out = response.getOutputStream();
        response.setContentType("application/json; charset=UTF-8");
        final PrintWriter outWriter = new PrintWriter(new BufferedWriter(
                new OutputStreamWriter(out, "UTF-8")));
        outWriter.print("for(;;);[{");
        outWriter.print("\"redirect\":{");
        outWriter.write("\"url\":\"" + logoutUrl + "\"}}]");
        outWriter.flush();
        outWriter.close();
        out.flush();
    }

    /**
     * Gets the Paintable Id. If Paintable has debug id set it will be used
     * prefixed with "PID_S". Otherwise a sequenced ID is created.
     *
     * @param paintable
     * @return the paintable Id.
     */
    public String getPaintableId(Paintable paintable) {

        String id = paintableIdMap.get(paintable);
        if (id == null) {
            // use testing identifier as id if set
            id = paintable.getDebugId();
            if (id == null) {
                id = "PID" + Integer.toString(idSequence++);
            } else {
                id = "PID_S" + id;
            }
            Paintable old = idPaintableMap.put(id, paintable);
            if (old != null && old != paintable) {
                /*
                 * Two paintables have the same id. We still make sure the old
                 * one is a component which is still attached to the
                 * application. This is just a precaution and should not be
                 * absolutely necessary.
                 */

                if (old instanceof Component
                        && ((Component) old).getApplication() != null) {
                    throw new IllegalStateException("Two paintables ("
                            + paintable.getClass().getSimpleName() + ","
                            + old.getClass().getSimpleName()
                            + ") have been assigned the same id: "
                            + paintable.getDebugId());
                }
            }
            paintableIdMap.put(paintable, id);
        }

        return id;
    }

    public boolean hasPaintableId(Paintable paintable) {
        return paintableIdMap.containsKey(paintable);
    }

    /**
     * Returns dirty components which are in given window. Components in an
     * invisible subtrees are omitted.
     *
     * @param w
     *            root window for which dirty components is to be fetched
     * @return
     */
    private ArrayList<Paintable> getDirtyVisibleComponents(Window w) {
        final ArrayList<Paintable> resultset = new ArrayList<Paintable>(
                dirtyPaintables);

        // The following algorithm removes any components that would be painted
        // as a direct descendant of other components from the dirty components
        // list. The result is that each component should be painted exactly
        // once and any unmodified components will be painted as "cached=true".

        for (final Iterator<Paintable> i = dirtyPaintables.iterator(); i
                .hasNext();) {
            final Paintable p = i.next();
            if (p instanceof Component) {
                final Component component = (Component) p;
                if (component.getApplication() == null) {
                    // component is detached after requestRepaint is called
                    resultset.remove(p);
                    i.remove();
                } else {
                    Window componentsRoot = component.getWindow();
                    if (componentsRoot.getParent() != null) {
                        // this is a subwindow
                        componentsRoot = (Window) componentsRoot.getParent();
                    }
                    if (componentsRoot != w) {
                        resultset.remove(p);
                    } else if (component.getParent() != null
                            && !component.getParent().isVisible()) {
                        /*
                         * Do not return components in an invisible subtree.
                         *
                         * Components that are invisible in visible subree, must
                         * be rendered (to let client know that they need to be
                         * hidden).
                         */
                        resultset.remove(p);
                    }
                }
            }
        }

        return resultset;
    }

    /**
     * @see com.vaadin.terminal.Paintable.RepaintRequestListener#repaintRequested(com.vaadin.terminal.Paintable.RepaintRequestEvent)
     */
    public void repaintRequested(RepaintRequestEvent event) {
        final Paintable p = event.getPaintable();
        if (!dirtyPaintables.contains(p)) {
            dirtyPaintables.add(p);
        }
    }

    /**
     * Internally mark a {@link Paintable} as painted and start collecting new
     * repaint requests for it.
     *
     * @param paintable
     */
    private void paintablePainted(Paintable paintable) {
        dirtyPaintables.remove(paintable);
        paintable.requestRepaintRequests();
    }

    /**
     * Implementation of {@link URIHandler.ErrorEvent} interface.
     */
    public class URIHandlerErrorImpl implements URIHandler.ErrorEvent,
            Serializable {

        private final URIHandler owner;

        private final Throwable throwable;

        /**
         *
         * @param owner
         * @param throwable
         */
        private URIHandlerErrorImpl(URIHandler owner, Throwable throwable) {
            this.owner = owner;
            this.throwable = throwable;
        }

        /**
         * @see com.vaadin.terminal.Terminal.ErrorEvent#getThrowable()
         */
        public Throwable getThrowable() {
            return throwable;
        }

        /**
         * @see com.vaadin.terminal.URIHandler.ErrorEvent#getURIHandler()
         */
        public URIHandler getURIHandler() {
            return owner;
        }
    }

    /**
     * Queues a locale to be sent to the client (browser) for date and time
     * entry etc. All locale specific information is derived from server-side
     * {@link Locale} instances and sent to the client when needed, eliminating
     * the need to use the {@link Locale} class and all the framework behind
     * it on the client.
     *
     * @see Locale#toString()
     *
     * @param value
     */
    public void requireLocale(String value) {
        if (locales == null) {
            locales = new ArrayList<String>();
            locales.add(application.getLocale().toString());
            pendingLocalesIndex = 0;
        }
        if (!locales.contains(value)) {
            locales.add(value);
        }
    }

    /**
     * Constructs a {@link Locale} instance to be sent to the client based on a
     * short locale description string.
     *
     * @see #requireLocale(String)
     *
     * @param value
     * @return
     */
    private Locale generateLocale(String value) {
        final String[] temp = value.split("_");
        if (temp.length == 1) {
            return new Locale(temp[0]);
        } else if (temp.length == 2) {
            return new Locale(temp[0], temp[1]);
        } else {
            return new Locale(temp[0], temp[1], temp[2]);
        }
    }

    /*
     * Upload progress listener notifies upload component once when Jakarta
     * FileUpload can determine content length. Used to detect files total size,
     * uploads progress can be tracked inside upload.
     */
    private class UploadProgressListener implements ProgressListener,
            Serializable {

        Upload uploadComponent;

        boolean updated = false;

        public void setUpload(Upload u) {
            uploadComponent = u;
        }

        public void update(long bytesRead, long contentLength, int items) {
            if (!updated && uploadComponent != null) {
                uploadComponent.setUploadSize(contentLength);
                updated = true;
            }
        }
    }

    /**
     * Helper method to test if a component contains another
     *
     * @param parent
     * @param child
     */
    private static boolean isChildOf(Component parent, Component child) {
        Component p = child.getParent();
        while (p != null) {
            if (parent == p) {
                return true;
            }
            p = p.getParent();
        }
        return false;
    }

    protected class InvalidUIDLSecurityKeyException extends
            GeneralSecurityException {

        InvalidUIDLSecurityKeyException(String message) {
            super(message);
        }

    }

    /**
     * Calls the Window URI handler for a request and returns the
     * {@link DownloadStream} returned by the handler.
     *
     * If the window is the main window of an application, the (deprecated)
     * {@link Application#handleURI(java.net.URL, String)} is called first to
     * handle {@link ApplicationResource}s, and the window handler is only
     * called if it returns null.
     *
     * @param window
     *            the target window of the request
     * @param request
     *            the request instance
     * @param response
     *            the response to write to
     * @return DownloadStream if the request was handled and further processing
     *         should be suppressed, null otherwise.
     * @see com.vaadin.terminal.URIHandler
     */
    protected DownloadStream handleURI(Window window, Request request,
            Response response, Callback callback) {

        String uri = callback.getRequestPathInfo(request);

        // If no URI is available
        if (uri == null) {
            uri = "";
        } else {
            // Removes the leading /
            while (uri.startsWith("/") && uri.length() > 0) {
                uri = uri.substring(1);
            }
        }

        // Handles the uri
        try {
            URL context = application.getURL();
            if (window == application.getMainWindow()) {
                DownloadStream stream = null;
                /*
                 * Application.handleURI run first. Handles possible
                 * ApplicationResources.
                 */
                stream = application.handleURI(context, uri);
                if (stream == null) {
                    stream = window.handleURI(context, uri);
                }
                return stream;
            } else {
                // Resolve the prefix end inded
                final int index = uri.indexOf('/');
                if (index > 0) {
                    String prefix = uri.substring(0, index);
                    URL windowContext;
                    windowContext = new URL(context, prefix + "/");
                    final String windowUri = (uri.length() > prefix.length() + 1) ? uri
                            .substring(prefix.length() + 1)
                            : "";
                    return window.handleURI(windowContext, windowUri);
                } else {
                    return null;
                }
            }

        } catch (final Throwable t) {
            application.getErrorHandler().terminalError(
                    new URIHandlerErrorImpl(application, t));
            return null;
        }
    }

    private static HashMap<Class<? extends Paintable>, Integer> typeToKey = new HashMap<Class<? extends Paintable>, Integer>();
    private static int nextTypeKey = 0;

    static String getTagForType(Class<? extends Paintable> class1) {
        synchronized (typeToKey) {
            Integer object = typeToKey.get(class1);
            if (object == null) {
                object = nextTypeKey++;
                typeToKey.put(class1, object);
            }
            return object.toString();
        }
    }

    /**
     * Helper class for terminal to keep track of data that client is expected
     * to know.
     *
     * TODO make customlayout templates (from theme) to be cached here.
     */
    class OpenWindowCache implements Serializable {

        private Set<Object> res = new HashSet<Object>();

        /**
         *
         * @param paintable
         * @return true if the given class was added to cache
         */
        boolean cache(Object object) {
            return res.add(object);
        }

        public void clear() {
            res.clear();
        }

    }
}