Java tutorial
/* * Licensed to the Apache Software Foundation (ASF) under one or more * contributor license agreements. See the NOTICE file distributed with * this work for additional information regarding copyright ownership. * The ASF licenses this file to You 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 org.apache.wicket.markup.html; import org.apache.wicket.Component; import org.apache.wicket.Page; import org.apache.wicket.markup.MarkupType; import org.apache.wicket.markup.head.IHeaderResponse; import org.apache.wicket.markup.html.internal.HtmlHeaderContainer; import org.apache.wicket.markup.html.link.BookmarkablePageLink; import org.apache.wicket.markup.parser.filter.HtmlHeaderSectionHandler; import org.apache.wicket.markup.renderStrategy.AbstractHeaderRenderStrategy; import org.apache.wicket.model.IModel; import org.apache.wicket.protocol.http.WebApplication; import org.apache.wicket.request.Request; import org.apache.wicket.request.Response; import org.apache.wicket.request.cycle.RequestCycle; import org.apache.wicket.request.http.WebRequest; import org.apache.wicket.request.http.WebResponse; import org.apache.wicket.request.mapper.parameter.PageParameters; import org.apache.wicket.response.StringResponse; import org.apache.wicket.util.string.Strings; import org.apache.wicket.util.visit.IVisit; import org.apache.wicket.util.visit.IVisitor; import org.slf4j.Logger; import org.slf4j.LoggerFactory; /** * Base class for HTML pages. This subclass of Page simply returns HTML when asked for its markup * type. It also has a method which subclasses can use to retrieve a bookmarkable link to the * application's home page. * <p> * WebPages can be constructed with any constructor when they are being used in a Wicket session, * but if you wish to link to a Page using a URL that is "bookmarkable" (which implies that the URL * will not have any session information encoded in it, and that you can call this page directly * without having a session first directly from your browser), you need to implement your Page with * a no-arg constructor or with a constructor that accepts a PageParameters argument (which wraps * any query string parameters for a request). In case the page has both constructors, the * constructor with PageParameters will be used. * * @author Jonathan Locke * @author Eelco Hillenius * @author Juergen Donnerstag * @author Gwyn Evans */ public class WebPage extends Page { private static final Logger log = LoggerFactory.getLogger(WebPage.class); private static final long serialVersionUID = 1L; /** * Constructor. * * Having this constructor public means that your page is 'bookmarkable' and hence * can be called/ created from anywhere. */ protected WebPage() { } protected WebPage(final IModel<?> model) { super(model); } /** * Constructor which receives wrapped query string parameters for a request. Having this * constructor public means that your page is 'bookmarkable' and hence can be called/ created * from anywhere. For bookmarkable pages (as opposed to when you construct page instances * yourself, this constructor will be used in preference to a no-arg constructor, if both exist. * Note that nothing is done with the page parameters argument. This constructor is provided so * that tools such as IDEs will include it their list of suggested constructors for derived * classes. * * Please call this constructor if you want to remember the pageparameters * {@link #getPageParameters()}. So that they are reused for stateless links. * * @param parameters * Wrapped query string parameters. */ protected WebPage(final PageParameters parameters) { super(parameters); } /** * Gets the markup type for a WebPage, which is "html" by default. Support for pages in another * markup language, such as VXML, would require the creation of a different Page subclass in an * appropriate package under org.apache.wicket.markup. To support VXML (voice markup), one might * create the package org.apache.wicket.markup.vxml and a subclass of Page called VoicePage. * * @return Markup type for HTML */ @Override public MarkupType getMarkupType() { return MarkupType.HTML_MARKUP_TYPE; } @Override protected void onRender() { // Configure the response such as headers etc. configureResponse((WebResponse) RequestCycle.get().getResponse()); // The rules if and when to insert an xml decl in the response are a bit tricky. Allow the // user to replace the default per page and per application. renderXmlDecl(); super.onRender(); } /** * The rules if and when to insert an xml decl in the response are a bit tricky. Allow the user * to replace the default per page and per application. */ protected void renderXmlDecl() { WebApplication.get().renderXmlDecl(this, false); } /** * Set-up response with appropriate content type, locale and encoding. The locale is set equal * to the session's locale. The content type header contains information about the markup type * (@see #getMarkupType()) and the encoding. The response (and request) encoding is determined * by an application setting (@see ApplicationSettings#getResponseRequestEncoding()). If null, * no xml decl will be written. * * @param response * The WebResponse object */ protected void configureResponse(final WebResponse response) { // Users may subclass setHeader() to set there own headers setHeaders(response); // The response encoding is an application setting final String encoding = getApplication().getRequestCycleSettings().getResponseRequestEncoding(); final boolean validEncoding = (Strings.isEmpty(encoding) == false); final String contentType; if (validEncoding) { contentType = getMarkupType().getMimeType() + "; charset=" + encoding; } else { contentType = getMarkupType().getMimeType(); } response.setContentType(contentType); } /** * Subclasses can override this to set there headers when the Page is being served. By default * these headers are set: * * <pre> * response.setHeader("Date", "[now]"); * response.setHeader("Expires", "[0]"); * response.setHeader("Pragma", "no-cache"); * response.setHeader("Cache-Control", "no-cache"); * </pre> * * So if a Page wants to control this or doesn't want to set this info it should override this * method and don't call super. * * @param response * The WebResponse where set(Date)Header can be called on. */ protected void setHeaders(WebResponse response) { response.disableCaching(); } /** * * @see org.apache.wicket.Component#onAfterRender() */ @Override protected void onAfterRender() { // only in development mode validate the headers if (getApplication().usesDevelopmentConfig()) { // check headers only when page was completely rendered if (wasRendered(this)) { validateHeaders(); } } super.onAfterRender(); } /** * Validate that each component which wanted to contribute to the header section actually was * able to do so. */ private void validateHeaders() { // search for HtmlHeaderContainer in the first level of children or deeper // if there are transparent resolvers used HtmlHeaderContainer header = visitChildren(new IVisitor<Component, HtmlHeaderContainer>() { @Override public void component(final Component component, final IVisit<HtmlHeaderContainer> visit) { if (component instanceof HtmlHeaderContainer) { visit.stop((HtmlHeaderContainer) component); } else if (component instanceof TransparentWebMarkupContainer == false) { visit.dontGoDeeper(); } } }); if (header == null) { // the markup must at least contain a <body> tag for wicket to automatically // create a HtmlHeaderContainer. Log an error if no header container // was created but any of the components or behaviors want to contribute // something to the header. header = new HtmlHeaderContainer(HtmlHeaderSectionHandler.HEADER_ID); add(header); RequestCycle requestCycle = getRequestCycle(); Response orgResponse = requestCycle.getResponse(); try { StringResponse tempResponse = new StringResponse(); requestCycle.setResponse(tempResponse); // Render all header sections of all components on the page AbstractHeaderRenderStrategy.get().renderHeader(header, null, getPage()); IHeaderResponse headerResponse = header.getHeaderResponse(); headerResponse.close(); CharSequence collectedHeaderOutput = tempResponse.getBuffer(); if (collectedHeaderOutput.length() > 0) { reportMissingHead(collectedHeaderOutput); } } catch (Exception e) { // just swallow this exception, there isn't much we can do about. log.error("header/body check throws exception", e); } finally { this.remove(header); requestCycle.setResponse(orgResponse); } } } /** * Reports an error that there is no <head> and/or <body> in the page and * there is no where to write the header response. * * @param collectedHeaderOutput * The collected response that should have been written to the <head> * @see #validateHeaders() */ protected void reportMissingHead(final CharSequence collectedHeaderOutput) { log.error("^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^"); log.error( "You probably forgot to add a <body> or <head> tag to your markup since no Header Container was \n" + "found but components were found which want to write to the <head> section.\n" + collectedHeaderOutput); log.error("^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^"); } /** * Creates and returns a bookmarkable link to this application's home page. * * @param id * Name of link * @return Link to home page for this application */ protected final BookmarkablePageLink<Void> homePageLink(final String id) { return new BookmarkablePageLink<>(id, getApplication().getHomePage()); } /** * Prevents page from get dirty inside an AJAX request. */ @Override public final void dirty(boolean isInitialization) { Request request = getRequest(); if (isInitialization == false && request instanceof WebRequest && ((WebRequest) request).isAjax()) { return; } super.dirty(isInitialization); } }