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1   /*
2    * Copyright 2009 University Corporation for Advanced Internet Development, Inc.
3    *
4    * Licensed under the Apache License, Version 2.0 (the "License");
5    * you may not use this file except in compliance with the License.
6    * You may obtain a copy of the License at
7    *
8    * http://www.apache.org/licenses/LICENSE-2.0
9    *
10   * Unless required by applicable law or agreed to in writing, software
11   * distributed under the License is distributed on an "AS IS" BASIS,
12   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13   * See the License for the specific language governing permissions and
14   * limitations under the License.
15   */
16  
17  package org.opensaml.ws.message;
18  
19  
20  /**
21   * An interface for components which evaluate a message context as the basis for extracting, calculating,
22   * or otherwise producing a specific data value.
23   * 
24   * <p>
25   * Implementations should not have side effects and should not modify any data in the 
26   * underlying message context.  For a component that is intended to allow message context
27   * modification, see {@link MessageContextMutatingFunctor}.
28   * </p>
29   * 
30   * @param <T> the type of product of the component
31   */
32  public interface MessageContextEvaluatingFunctor<T> {
33      
34      /**
35       * Using the specified MessageContext as the evaluation context,
36       * produce a data value product of the appropriate type.
37       * 
38       * @param msgContext the message context to evaluate
39       * @return value product based on the message context, or null
40       * 
41       * @throws MessageException if there is a fatal error evaluating the context
42       */
43      public T evaluate(MessageContext msgContext) throws MessageException;
44  
45  }