ValueConverter


1   // Copyright 2004, 2005 The Apache Software Foundation
2   //
3   // Licensed under the Apache License, Version 2.0 (the "License");
4   // you may not use this file except in compliance with the License.
5   // You may obtain a copy of the License at
6   //
7   //     http://www.apache.org/licenses/LICENSE-2.0
8   //
9   // Unless required by applicable law or agreed to in writing, software
10  // distributed under the License is distributed on an "AS IS" BASIS,
11  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12  // See the License for the specific language governing permissions and
13  // limitations under the License.
14  
15  package org.apache.tapestry.coerce;
16  
17  /**
18   * Converts a value (possibly null) to an alternate data type; typically from String to boolean or a
19   * number type.
20   * <p>
21   * Typically, a ValueConverter will select a particular
22   * {@link org.apache.tapestry.coerce.TypeConverter}to perform the conversion. The
23   * {@link org.apache.tapestry.coerce.ValueConverterImpl}implementation also makes use of built-in
24   * {@link java.beans.PropertyEditor}s.
25   * 
26   * @author Howard M. Lewis Ship
27   * @since 4.0
28   */
29  public interface ValueConverter
30  {
31      /**
32       * Performs a conversion of a value to a particular type.
33       * 
34       * @param value
35       *            The value to be converted (may be null)
36       * @param desiredType
37       *            the type that will be converted to
38       * @returns the value converted to the indicated type. May return the input value if it is
39       *          already assignable to the desiredType.
40       * @throws org.apache.hivemind.ApplicationRuntimeException
41       *             if the value can not be converted
42       */
43      public Object   coerceValue(Object   value, Class   desiredType);
44  }
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