001    package org.apache.turbine.services.template;
002    
003    
004    /*
005     * Licensed to the Apache Software Foundation (ASF) under one
006     * or more contributor license agreements.  See the NOTICE file
007     * distributed with this work for additional information
008     * regarding copyright ownership.  The ASF licenses this file
009     * to you under the Apache License, Version 2.0 (the
010     * "License"); you may not use this file except in compliance
011     * with the License.  You may obtain a copy of the License at
012     *
013     *   http://www.apache.org/licenses/LICENSE-2.0
014     *
015     * Unless required by applicable law or agreed to in writing,
016     * software distributed under the License is distributed on an
017     * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
018     * KIND, either express or implied.  See the License for the
019     * specific language governing permissions and limitations
020     * under the License.
021     */
022    
023    
024    import java.util.Hashtable;
025    
026    /**
027     * This is the interface that all template engine services must adhere
028     * to. This includes the Velocity, WebMacro, FreeMarker, and JSP
029     * services.
030     *
031     * @author <a href="mailto:jvanzyl@apache.org">Jason van Zyl</a>
032     * @author <a href="mailto:dlr@finemaltcoding.com">Daniel Rall</a>
033     * @version $Id: TemplateEngineService.java 1078552 2011-03-06 19:58:46Z tv $ */
034    public interface TemplateEngineService
035    {
036        static final String TEMPLATE_EXTENSIONS = "template.extension";
037        static final String DEFAULT_TEMPLATE_EXTENSION = "template.default.extension";
038        static final String DEFAULT_PAGE = "default.page";
039        static final String DEFAULT_SCREEN = "default.screen";
040        static final String DEFAULT_LAYOUT = "default.layout";
041        static final String DEFAULT_NAVIGATION = "default.navigation";
042        static final String DEFAULT_ERROR_SCREEN = "default.error.screen";
043        static final String DEFAULT_LAYOUT_TEMPLATE = "default.layout.template";
044        static final String DEFAULT_SCREEN_TEMPLATE = "default.screen.template";
045        static final String DEFAULT_NAVIGATION_TEMPLATE = "default.navigation.template";
046    
047        /**
048         * Return the configuration of the template engine in
049         * the form of a Hashtable.
050         */
051        Hashtable<String, Object> getTemplateEngineServiceConfiguration();
052    
053        /**
054         * Initializes file extension associations and registers with the
055         * template service.
056         *
057         * @param defaultExt The default file extension association to use
058         *                   in case of properties file misconfiguration.
059         */
060        void registerConfiguration(String defaultExt);
061    
062        /**
063         * Supplies the file extension to key this engine in {@link
064         * org.apache.turbine.services.template.TemplateService}'s
065         * registry with.
066         */
067        String[] getAssociatedFileExtensions();
068    
069        /**
070         * Use the specific template engine to determine whether
071         * a given template exists. This allows Turbine the TemplateService
072         * to delegate the search for a template to the template
073         * engine being used for the view. This gives us the
074         * advantage of fully utilizing the capabilities of
075         * template engine with respect to retrieving templates
076         * from arbitrary sources.
077         *
078         * @param template The name of the template to check the existance of.
079         * @return         Whether the specified template exists.
080         */
081        boolean templateExists(String template);
082    }