TextToExpression


1   /*
2    * Copyright 2002-2006 the original author or authors.
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  package org.springframework.binding.convert.support;
17  
18  import org.springframework.binding.convert.ConversionContext;
19  import org.springframework.binding.expression.Expression;
20  import org.springframework.binding.expression.ExpressionParser;
21  import org.springframework.binding.expression.SettableExpression;
22  import org.springframework.binding.expression.support.StaticExpression;
23  import org.springframework.util.Assert;
24  
25  /**
26   * Converter that converts a String into an Expression object.
27   * 
28   * @see org.springframework.binding.expression.Expression
29   * @see org.springframework.binding.expression.SettableExpression
30   * 
31   * @author Erwin Vervaet
32   */
33  public class TextToExpression extends AbstractConverter {
34  
35      /**
36       * The expression string parser.
37       */
38      private ExpressionParser expressionParser;
39  
40      /**
41       * Creates a new string-to-expression converter.
42       * @param expressionParser the expression string parser
43       */
44      public TextToExpression(ExpressionParser expressionParser) {
45          Assert.notNull(expressionParser, "The expression parser is required");
46          this.expressionParser = expressionParser;
47      }
48  
49      /**
50       * Returns the expression parser used by this converter.
51       */
52      public ExpressionParser getExpressionParser() {
53          return expressionParser;
54      }
55  
56      public Class  [] getSourceClasses() {
57          return new Class  [] { String  .class };
58      }
59  
60      public Class  [] getTargetClasses() {
61          return new Class  [] { Expression.class, SettableExpression.class };
62      }
63  
64      protected Object   doConvert(Object   source, Class   targetClass, ConversionContext context) throws Exception   {
65          String   expressionString = (String  )source;
66          if (getExpressionParser().isDelimitedExpression(expressionString)) {
67              return getExpressionParser().parseExpression((String  )source);
68          }
69          else {
70              return new StaticExpression(expressionString);
71          }
72      }
73  }
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