    001// Licensed under the Apache License, Version 2.0 (the "License");
    002// you may not use this file except in compliance with the License.
    003// You may obtain a copy of the License at
    004//
    005//     http://www.apache.org/licenses/LICENSE-2.0
    006//
    007// Unless required by applicable law or agreed to in writing, software
    008// distributed under the License is distributed on an "AS IS" BASIS,
    009// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    010// See the License for the specific language governing permissions and
    011// limitations under the License.
    012
    013package org.apache.tapestry5.corelib.components;
    014
    015import org.apache.tapestry5.BindingConstants;
    016import org.apache.tapestry5.MarkupWriter;
    017import org.apache.tapestry5.annotations.Parameter;
    018import org.apache.tapestry5.commons.util.CommonsUtils;
    019import org.apache.tapestry5.corelib.base.AbstractLink;
    020import org.apache.tapestry5.http.Link;
    021import org.apache.tapestry5.ioc.annotations.Inject;
    022import org.apache.tapestry5.services.PageRenderLinkSource;
    023
    024/**
    025 * Generates a render request link to some other page in the application. If an activation context is supplied (as the
    026 * context parameter), then the context values will be encoded into the URL. If no context is supplied, then the target
    027 * page itself will supply the context via a passivate event.
    028 *
    029 * Pages are not required to have an activation context. When a page does have an activation context, the value
    030 * typically represents the identity of some object displayed or otherwise manipulated by the page.
    031 *
    032 * @tapestrydoc
    033 */
    034public class PageLink extends AbstractLink
    035{
    036    /**
    037     * The page to link to. If a <code>String</code>, as usual, it should be the page logical name.
    038     * If it's a <code>Class</code> instance, it's treated as the target page.
    039     * If it's not a <code>String</code> nor an <code>Class</code>, the target page will be
    040     * the result of calling <code>page.getClass()</code>.
    041     * Notice you'll need to use the <code>prop</code> binding when passing a value which
    042     * isn't a <code>String</code>.
    043     */
    044    @Parameter(required = true, allowNull = false, defaultPrefix = BindingConstants.LITERAL)
    045    private Object page;
    046
    047    /**
    048     * If provided, this is the activation context for the target page (the information will be encoded into the URL).
    049     * If not provided, then the target page will provide its own activation context.
    050     */
    051    @Parameter
    052    private Object[] context;
    053
    054    @Inject
    055    private PageRenderLinkSource linkSource;
    056
    057    void beginRender(MarkupWriter writer)
    058    {
    059        if (isDisabled()) return;
    060
    061        Link link;
    062        if (page instanceof String) {
    063            final String pageName = (String) page;
    064            link = resources.isBound("context")
    065                ? linkSource.createPageRenderLinkWithContext(pageName, context == null ? CommonsUtils.EMPTY_STRING_ARRAY : context)
    066                : linkSource.createPageRenderLink(pageName);
    067        }
    068        else {
    069            // If page is a Class, use it directly. If not, use its class (type)
    070            Class<?> clasz = page instanceof Class<?> ? (Class<?>) page : page.getClass();
    071            link = resources.isBound("context")
    072                    ? linkSource.createPageRenderLinkWithContext(clasz, context == null ? CommonsUtils.EMPTY_STRING_ARRAY : context)
    073                    : linkSource.createPageRenderLink(clasz);
    074        }
    075
    076        writeLink(writer, link);
    077    }
    078
    079    void afterRender(MarkupWriter writer)
    080    {
    081        if (isDisabled()) return;
    082
    083        writer.end(); // <a>
    084    }
    085}