TemplateDispatcher.java

/**
 * Copyright 2005-2014 Restlet
 * 
 * The contents of this file are subject to the terms of one of the following
 * open source licenses: Apache 2.0 or or EPL 1.0 (the "Licenses"). You can
 * select the license that you prefer but you may not use this file except in
 * compliance with one of these Licenses.
 * 
 * You can obtain a copy of the Apache 2.0 license at
 * http://www.opensource.org/licenses/apache-2.0
 * 
 * You can obtain a copy of the EPL 1.0 license at
 * http://www.opensource.org/licenses/eclipse-1.0
 * 
 * See the Licenses for the specific language governing permissions and
 * limitations under the Licenses.
 * 
 * Alternatively, you can obtain a royalty free commercial license with less
 * limitations, transferable or non-transferable, directly at
 * http://restlet.com/products/restlet-framework
 * 
 * Restlet is a registered trademark of Restlet S.A.S.
 */

package org.restlet.engine.util;

import org.restlet.Request;
import org.restlet.Response;
import org.restlet.data.Protocol;
import org.restlet.routing.Filter;
import org.restlet.routing.Template;

/**
 * Filter that resolves URI templates in the target resource URI reference using
 * the request attributes.
 * 
 * Concurrency note: instances of this class or its subclasses can be invoked by
 * several threads at the same time and therefore must be thread-safe. You
 * should be especially careful when storing state as member variables.
 * 
 * @author Jerome Louvel
 */
public class TemplateDispatcher extends Filter {

    /**
     * If the response entity comes back with no identifier, automatically set
     * the request's resource reference's identifier. This is very useful to
     * resolve relative references in XSLT for example.
     */
    @Override
    protected void afterHandle(Request request, Response response) {
        if ((response.getEntity() != null)
                && (response.getEntity().getLocationRef() == null)) {
            response.getEntity().setLocationRef(
                    request.getResourceRef().getTargetRef().toString());
        }
    }

    /**
     * Handles the call after resolving any URI template on the request's target
     * resource reference.
     * 
     * @param request
     *            The request to handle.
     * @param response
     *            The response to update.
     */
    public int beforeHandle(Request request, Response response) {
        // Associate the response to the current thread
        Protocol protocol = request.getProtocol();

        if (protocol == null) {
            throw new UnsupportedOperationException(
                    "Unable to determine the protocol to use for this call.");
        }

        String targetUri = request.getResourceRef().toString(true, false);

        if (targetUri.contains("{")) {
            // Template URI detected, create the template
            Template template = new Template(targetUri);

            // Set the formatted target URI
            request.setResourceRef(template.format(request, response));
        }

        request.setOriginalRef(request.getResourceRef().getTargetRef());
        return CONTINUE;
    }

}