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    
015    package org.apache.tapestry5.services.linktransform;
016    
017    import org.apache.tapestry5.Link;
018    import org.apache.tapestry5.internal.services.PageRenderDispatcher;
019    import org.apache.tapestry5.ioc.annotations.UsesOrderedConfiguration;
020    import org.apache.tapestry5.services.ComponentEventLinkEncoder;
021    import org.apache.tapestry5.services.LocalizationSetter;
022    import org.apache.tapestry5.services.PageRenderRequestParameters;
023    import 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)
038    public 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    }