001// Copyright 2010 The Apache Software Foundation
002//
003// Licensed under the Apache License, Version 2.0 (the "License");
004// you may not use this file except in compliance with the License.
005// You may obtain a copy of the License at
006//
007// http://www.apache.org/licenses/LICENSE-2.0
008//
009// Unless required by applicable law or agreed to in writing, software
010// distributed under the License is distributed on an "AS IS" BASIS,
011// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
012// See the License for the specific language governing permissions and
013// limitations under the License.
014
015package org.apache.tapestry5.services.linktransform;
016
017import org.apache.tapestry5.Link;
018import org.apache.tapestry5.internal.services.PageRenderDispatcher;
019import org.apache.tapestry5.ioc.annotations.UsesOrderedConfiguration;
020import org.apache.tapestry5.services.ComponentEventLinkEncoder;
021import org.apache.tapestry5.services.LocalizationSetter;
022import org.apache.tapestry5.services.PageRenderRequestParameters;
023import org.apache.tapestry5.services.Request;
024
025/**
026 * Allows the default {@link Link} for a page render request to be replaced.
027 * This is a service, but also the contribution to the service, as a chain of command.
028 * <p>
029 * A contributed implementation of this interface is expected to identify which requests it wants to transform. The
030 * {@link #transformPageRenderLink(Link, PageRenderRequestParameters)} method can return a {@link Link} that is allowed
031 * to differ from Tapestry normal default. Later, when that request is triggered,
032 * {@link #decodePageRenderRequest(Request)} is required to reverse the operation, identifying the original parameters
033 * so that request handling can continue.
034 * 
035 * @since 5.2.0
036 */
037@UsesOrderedConfiguration(PageRenderLinkTransformer.class)
038public interface PageRenderLinkTransformer
039{
040    /**
041     * Transforms a page render link.
042     * 
043     * @param defaultLink
044     *            default Link for this request
045     * @param parameters
046     *            that define the request
047     * @return replacement Link, or null
048     */
049    Link transformPageRenderLink(Link defaultLink, PageRenderRequestParameters parameters);
050
051    /**
052     * Attempts to decode the page render request, to perform the opposite action for
053     * {@link #transformPageRenderLink(Link, PageRenderRequestParameters)}. The transformer
054     * is also responsible for identifying the locale in the request (as part of the path, or as a
055     * query parameter or cookie) and setting the locale for the request.
056     * <p>
057     * This method will be invoked from the {@link PageRenderDispatcher} and a non-null value returned from this method
058     * will prevent the default {@link ComponentEventLinkEncoder#decodePageRenderRequest(Request)} method from being
059     * invoked.
060     * 
061     * @return decoded parameters, or null to proceed normally
062     * @see LocalizationSetter#setLocaleFromLocaleName(String)
063     */
064    PageRenderRequestParameters decodePageRenderRequest(Request request);
065}