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.services.linktransform;
014
015import org.apache.tapestry5.Link;
016import org.apache.tapestry5.internal.services.PageRenderDispatcher;
017import org.apache.tapestry5.ioc.annotations.UsesOrderedConfiguration;
018import org.apache.tapestry5.services.ComponentEventLinkEncoder;
019import org.apache.tapestry5.services.LocalizationSetter;
020import org.apache.tapestry5.services.PageRenderRequestParameters;
021import org.apache.tapestry5.services.Request;
022
023/**
024 * Allows the default {@link Link} for a page render request to be replaced.
025 * This is a service, but also the contribution to the service, as a chain of command.
026 *
027 * A contributed implementation of this interface is expected to identify which requests it wants to transform. The
028 * {@link #transformPageRenderLink(Link, PageRenderRequestParameters)} method can return a {@link Link} that is allowed
029 * to differ from Tapestry normal default. Later, when that request is triggered,
030 * {@link #decodePageRenderRequest(Request)} is required to reverse the operation, identifying the original parameters
031 * so that request handling can continue.
032 * 
033 * @since 5.2.0
034 */
035@UsesOrderedConfiguration(PageRenderLinkTransformer.class)
036public interface PageRenderLinkTransformer
037{
038    /**
039     * Transforms a page render link.
040     * 
041     * @param defaultLink
042     *            default Link for this request
043     * @param parameters
044     *            that define the request
045     * @return replacement Link, or null
046     */
047    Link transformPageRenderLink(Link defaultLink, PageRenderRequestParameters parameters);
048
049    /**
050     * Attempts to decode the page render request, to perform the opposite action for
051     * {@link #transformPageRenderLink(Link, PageRenderRequestParameters)}. The transformer
052     * is also responsible for identifying the locale in the request (as part of the path, or as a
053     * query parameter or cookie) and setting the locale for the request.
054     *
055     * This method will be invoked from the {@link PageRenderDispatcher} and a non-null value returned from this method
056     * will prevent the default {@link ComponentEventLinkEncoder#decodePageRenderRequest(Request)} method from being
057     * invoked.
058     * 
059     * @return decoded parameters, or null to proceed normally
060     * @see LocalizationSetter#setLocaleFromLocaleName(String)
061     */
062    PageRenderRequestParameters decodePageRenderRequest(Request request);
063}