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1   package org.codehaus.plexus.interpolation.fixed;
2   
3   /*
4    * Copyright 2014 Codehaus Foundation.
5    *
6    * Licensed under the Apache License, Version 2.0 (the "License");
7    * you may not use this file except in compliance with the License.
8    * You may obtain a copy of the License at
9    *
10   *      http://www.apache.org/licenses/LICENSE-2.0
11   *
12   * Unless required by applicable law or agreed to in writing, software
13   * distributed under the License is distributed on an "AS IS" BASIS,
14   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
15   * See the License for the specific language governing permissions and
16   * limitations under the License.
17   */
18  
19  import org.codehaus.plexus.interpolation.util.ValueSourceUtils;
20  
21  import java.util.List;
22  
23  /**
24   * {@link org.codehaus.plexus.interpolation.fixed.FixedValueSource} implementation which simply wraps another
25   * value source, and trims any of a set of possible expression prefixes before delegating the
26   * modified expression to be resolved by the real value source.
27   *
28   * @author jdcasey
29   * @author krosenvold
30   * @version $Id$
31   */
32  public class PrefixedValueSourceWrapper implements FixedValueSource
33  {
34  
35      private final FixedValueSource valueSource;
36  
37      private final String[] possiblePrefixes;
38  
39      private boolean allowUnprefixedExpressions;
40  
41      private String lastExpression;
42  
43      /**
44       * Wrap the given value source, but first trim the given prefix from any
45       * expressions before they are passed along for resolution. If an expression
46       * doesn't start with the given prefix, do not resolve it.
47       *
48       * @param valueSource The {@link org.codehaus.plexus.interpolation.ValueSource} to wrap.
49       * @param prefix      The expression prefix to trim.
50       */
51      public PrefixedValueSourceWrapper( FixedValueSource valueSource, String prefix )
52      {
53          this.valueSource = valueSource;
54          possiblePrefixes = new String[]{ prefix };
55      }
56  
57      /**
58       * Wrap the given value source, but first trim the given prefix from any
59       * expressions before they are passed along for resolution. If an expression
60       * doesn't start with the given prefix and the allowUnprefixedExpressions flag
61       * is set to true, simply pass the expression through to the nested value source
62       * unchanged. If this flag is false, only allow resolution of those expressions
63       * that start with the specified prefix.
64       *
65       * @param valueSource                The {@link org.codehaus.plexus.interpolation.ValueSource} to wrap.
66       * @param prefix                     The expression prefix to trim.
67       * @param allowUnprefixedExpressions Flag telling the wrapper whether to
68       *                                   continue resolving expressions that don't start with the prefix it tracks.
69       */
70      public PrefixedValueSourceWrapper( FixedValueSource valueSource, String prefix, boolean allowUnprefixedExpressions )
71      {
72          this.valueSource = valueSource;
73          possiblePrefixes = new String[]{ prefix };
74          this.allowUnprefixedExpressions = allowUnprefixedExpressions;
75      }
76  
77      /**
78       * Wrap the given value source, but first trim one of the given prefixes from any
79       * expressions before they are passed along for resolution. If an expression
80       * doesn't start with one of the given prefixes, do not resolve it.
81       *
82       * @param valueSource      The {@link org.codehaus.plexus.interpolation.ValueSource} to wrap.
83       * @param possiblePrefixes The List of expression prefixes to trim.
84       */
85      public PrefixedValueSourceWrapper( FixedValueSource valueSource, List<String> possiblePrefixes )
86      {
87          this.valueSource = valueSource;
88          this.possiblePrefixes = possiblePrefixes.toArray( new String[possiblePrefixes.size()] );
89      }
90  
91      /**
92       * Wrap the given value source, but first trim one of the given prefixes from any
93       * expressions before they are passed along for resolution. If an expression
94       * doesn't start with the given prefix and the allowUnprefixedExpressions flag
95       * is set to true, simply pass the expression through to the nested value source
96       * unchanged. If this flag is false, only allow resolution of those expressions
97       * that start with the specified prefix.
98       *
99       * @param valueSource                The {@link org.codehaus.plexus.interpolation.ValueSource} to wrap.
100      * @param possiblePrefixes           The List of expression prefixes to trim.
101      * @param allowUnprefixedExpressions Flag telling the wrapper whether to
102      *                                   continue resolving expressions that don't start with one of the prefixes it tracks.
103      */
104     public PrefixedValueSourceWrapper( FixedValueSource valueSource, List<String> possiblePrefixes,
105                                        boolean allowUnprefixedExpressions )
106     {
107         this.valueSource = valueSource;
108         this.possiblePrefixes = possiblePrefixes.toArray( new String[possiblePrefixes.size()] );
109         this.allowUnprefixedExpressions = allowUnprefixedExpressions;
110     }
111 
112 
113     public Object getValue( String expression, InterpolationState interpolationState )
114     {
115         expression = ValueSourceUtils.trimPrefix( expression, possiblePrefixes, allowUnprefixedExpressions );
116 
117         if ( expression == null )
118         {
119             return null;
120         }
121 
122         return valueSource.getValue( expression, interpolationState );
123     }
124 }