ExpressionEvaluator


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.services;
16  
17  /**
18   * Wrapper around the OGNL library.
19   * 
20   * @author Howard M. Lewis Ship
21   * @since 4.0
22   */
23  public interface ExpressionEvaluator
24  {
25      /**
26       * Reads a property of the target, defined by the expression.
27       * 
28       * @throws org.apache.hivemind.ApplicationRuntimeException
29       *             if the expression can not be parsed, or if some other error occurs during
30       *             evaluation of the expression.
31       */
32      public Object   read(Object   target, String   expression);
33  
34      /**
35       * Reads a property of the target, defined by the (previously compiled) expression.
36       * 
37       * @throws org.apache.hivemind.ApplicationRuntimeException
38       *             if some other error occurs during evaluation of the expression.
39       */
40      public Object   readCompiled(Object   target, Object   expression);
41  
42      /**
43       * Updates a property of the target, defined by the expression.
44       * 
45       * @throws org.apache.hivemind.ApplicationRuntimeException
46       *             if the expression can not be parsed, or if some other error occurs during
47       *             evaluation of the expression.
48       */
49      public void write(Object   target, String   expression, Object   value);
50  
51      /**
52       * Updates a property of the target, defined by the (previously compiled) expression.
53       * 
54       * @throws org.apache.hivemind.ApplicationRuntimeException
55       *             if some other error occurs during evaluation of the expression.
56       */
57      public void writeCompiled(Object   target, Object   expression, Object   value);
58  
59      /**
60       * Returns true if the expression evaluates to a constant or other literal value.
61       * 
62       * @throws org.apache.hivemind.ApplicationRuntimeException
63       *             if the expression is not valid
64       */
65      public boolean isConstant(String   expression);
66  }
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