/*

  * $Id: DefaultAttributeResolver.java 836174 2009-11-14 13:40:31Z apetrelli $

  *

  * Licensed to the Apache Software Foundation (ASF) under one

  * or more contributor license agreements.  See the NOTICE file

  * distributed with this work for additional information

  * regarding copyright ownership.  The ASF licenses this file

  * to you under the Apache License, Version 2.0 (the

  * "License"); you may not use this file except in compliance

  * with the License.  You may obtain a copy of the License at

  *

  * http://www.apache.org/licenses/LICENSE-2.0

  *

  * Unless required by applicable law or agreed to in writing,

  * software distributed under the License is distributed on an

  * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY

  * KIND, either express or implied.  See the License for the

  * specific language governing permissions and limitations

  * under the License.

  */

 package org.apache.tiles.template;

 import org.apache.tiles.Attribute;

 import org.apache.tiles.AttributeContext;

 import org.apache.tiles.Expression;

 import org.apache.tiles.TilesContainer;

 import org.apache.tiles.request.Request;

 /**

  * The default implementation of AttributeResolver.

  *

  * @version $Rev: 836174 $ $Date: 2009-11-15 00:40:31 +1100 (Sun, 15 Nov 2009) $

  * @since 2.2.0

  */

 public class DefaultAttributeResolver implements AttributeResolver {

     /** {@inheritDoc} */

     public Attribute computeAttribute(TilesContainer container, Attribute attribute,

             String name, String role, boolean ignore,

             Object defaultValue, String defaultValueRole, String defaultValueType, Request request) {

         if (attribute == null) {

             AttributeContext evaluatingContext = container

                     .getAttributeContext(request);

             attribute = evaluatingContext.getAttribute(name);

             if (attribute == null) {

                 attribute = computeDefaultAttribute(defaultValue,

                         defaultValueRole, defaultValueType);

                 if (attribute == null && !ignore) {

                     throw new NoSuchAttributeException("Attribute '" + name

                             + "' not found.");

                 }

             }

         }

         if (attribute != null && role != null && !"".equals(role.trim())) {

             attribute = new Attribute(attribute);

             attribute.setRole(role);

         }

         return attribute;

     }

     /**

      * Computes the default attribute.

      *

      * @param defaultValue The default value of the attribute.

      * @param defaultValueRole The default role of tha attribute.

      * @param defaultValueType The default type of the attribute.

      * @return The default attribute.

      */

     private Attribute computeDefaultAttribute(Object defaultValue,

             String defaultValueRole, String defaultValueType) {

         Attribute attribute = null;

         if (defaultValue != null) {

             if (defaultValue instanceof Attribute) {

                 attribute = (Attribute) defaultValue;

             } else if (defaultValue instanceof String) {

                 attribute = new Attribute(defaultValue, (Expression) null,

                         defaultValueRole, defaultValueType);

             }

         }

         return attribute;

     }

 }