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1   /*
2    * $Id: FreemarkerUtil.java 1360343 2012-07-11 18:35:52Z nlebas $
3    *
4    * Licensed to the Apache Software Foundation (ASF) under one
5    * or more contributor license agreements.  See the NOTICE file
6    * distributed with this work for additional information
7    * regarding copyright ownership.  The ASF licenses this file
8    * to you under the Apache License, Version 2.0 (the
9    * "License"); you may not use this file except in compliance
10   * with the License.  You may obtain a copy of the License at
11   *
12   * http://www.apache.org/licenses/LICENSE-2.0
13   *
14   * Unless required by applicable law or agreed to in writing,
15   * software distributed under the License is distributed on an
16   * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
17   * KIND, either express or implied.  See the License for the
18   * specific language governing permissions and limitations
19   * under the License.
20   */
21  
22  package org.apache.tiles.request.freemarker.autotag;
23  
24  import freemarker.template.TemplateModel;
25  import freemarker.template.TemplateModelException;
26  import freemarker.template.utility.DeepUnwrap;
27  
28  /**
29   * Utilities for FreeMarker usage in Tiles.
30   *
31   * @version $Rev: 1360343 $ $Date: 2012-07-12 04:35:52 +1000 (Thu, 12 Jul 2012) $
32   */
33  public final class FreemarkerUtil {
34  
35      /**
36       * Private constructor to avoid instantiation.
37       */
38      private FreemarkerUtil() {
39      }
40  
41      /**
42       * Unwraps a TemplateModel to extract an object.
43       *
44       * @param model The TemplateModel to unwrap.
45       * @param defaultValue The default value, as specified in the template
46       * model, or null if not specified.
47       * @return The unwrapped object.
48       */
49      public static <T> T getAsObject(TemplateModel model, Class<T> type, T defaultValue) {
50          try {
51              T retValue = defaultValue;
52              if (model != null) {
53                  @SuppressWarnings("unchecked")
54                  T value = (T) DeepUnwrap.unwrap(model);
55                  if (value != null) {
56                      retValue = value;
57                  }
58              }
59              return retValue;
60          } catch (TemplateModelException e) {
61              throw new FreemarkerAutotagException("Cannot unwrap a model", e);
62          }
63      }
64  }