Expression


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2   * Licensed to the Apache Software Foundation (ASF) under one or more
3   * contributor license agreements.  See the NOTICE file distributed with
4   * this work for additional information regarding copyright ownership.
5   * The ASF licenses this file to You under the Apache License, Version 2.0
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8   *
9   *     http://www.apache.org/licenses/LICENSE-2.0
10  *
11  * Unless required by applicable law or agreed to in writing, software
12  * distributed under the License is distributed on an "AS IS" BASIS,
13  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14  * See the License for the specific language governing permissions and
15  * limitations under the License.
16  */
17  
18  
19  package javax.servlet.jsp.el;
20  
21  
22  /**
23   * <p>The abstract class for a prepared expression.</p>
24   *
25   * <p>An instance of an Expression can be obtained via from an 
26   * ExpressionEvaluator instance.</p>
27   *
28   * <p>An Expression may or not have done a syntactic parse of the expression.
29   * A client invoking the evaluate() method should be ready for the case 
30   * where ELParseException exceptions are raised. </p>
31   *
32   * @since 2.0
33   * @deprecated
34   */
35  public abstract class Expression {
36  
37      /** 
38       * Evaluates an expression that was previously prepared.  In some 
39       * implementations preparing an expression involves full syntactic 
40       * validation, but others may not do so.  Evaluating the expression may 
41       * raise an ELParseException as well as other ELExceptions due to 
42       * run-time evaluation.
43       *
44       * @param vResolver A VariableResolver instance that can be used at 
45       *   runtime to resolve the name of implicit objects into Objects.
46       * @return The result of the expression evaluation.
47       *
48       * @exception ELException Thrown if the expression evaluation failed.
49       */ 
50      public abstract Object   evaluate( VariableResolver   vResolver )
51          throws ELException  ;
52  }
53  
54
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