1 package org.codehaus.plexus.interpolation;
2
3 /*
4 * Copyright 2001-2008 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 java.util.Collections;
20 import java.util.List;
21
22 import org.codehaus.plexus.interpolation.util.ValueSourceUtils;
23
24 /**
25 * {@link ValueSource} implementation which simply wraps another value source,
26 * and trims any of a set of possible expression prefixes before delegating the
27 * modified expression to be resolved by the real value source.
28 *
29 * @author jdcasey
30 */
31 public class PrefixedValueSourceWrapper implements FeedbackEnabledValueSource, QueryEnabledValueSource {
32
33 private final ValueSource valueSource;
34
35 private final String[] possiblePrefixes;
36
37 private boolean allowUnprefixedExpressions;
38
39 private String lastExpression;
40
41 /**
42 * Wrap the given value source, but first trim the given prefix from any
43 * expressions before they are passed along for resolution. If an expression
44 * doesn't start with the given prefix, do not resolve it.
45 *
46 * @param valueSource The {@link ValueSource} to wrap.
47 * @param prefix The expression prefix to trim.
48 */
49 public PrefixedValueSourceWrapper(ValueSource valueSource, String prefix) {
50 this.valueSource = valueSource;
51 possiblePrefixes = new String[] {prefix};
52 }
53
54 /**
55 * Wrap the given value source, but first trim the given prefix from any
56 * expressions before they are passed along for resolution. If an expression
57 * doesn't start with the given prefix and the allowUnprefixedExpressions flag
58 * is set to true, simply pass the expression through to the nested value source
59 * unchanged. If this flag is false, only allow resolution of those expressions
60 * that start with the specified prefix.
61 *
62 * @param valueSource The {@link ValueSource} to wrap.
63 * @param prefix The expression prefix to trim.
64 * @param allowUnprefixedExpressions Flag telling the wrapper whether to
65 * continue resolving expressions that don't start with the prefix it tracks.
66 */
67 public PrefixedValueSourceWrapper(ValueSource valueSource, String prefix, boolean allowUnprefixedExpressions) {
68 this.valueSource = valueSource;
69 possiblePrefixes = new String[] {prefix};
70 this.allowUnprefixedExpressions = allowUnprefixedExpressions;
71 }
72
73 /**
74 * Wrap the given value source, but first trim one of the given prefixes from any
75 * expressions before they are passed along for resolution. If an expression
76 * doesn't start with one of the given prefixes, do not resolve it.
77 *
78 * @param valueSource The {@link ValueSource} to wrap.
79 * @param possiblePrefixes The List of expression prefixes to trim.
80 */
81 public PrefixedValueSourceWrapper(ValueSource valueSource, List<String> possiblePrefixes) {
82 this.valueSource = valueSource;
83 this.possiblePrefixes = possiblePrefixes.toArray(new String[possiblePrefixes.size()]);
84 }
85
86 /**
87 * Wrap the given value source, but first trim one of the given prefixes from any
88 * expressions before they are passed along for resolution. If an expression
89 * doesn't start with the given prefix and the allowUnprefixedExpressions flag
90 * is set to true, simply pass the expression through to the nested value source
91 * unchanged. If this flag is false, only allow resolution of those expressions
92 * that start with the specified prefix.
93 *
94 * @param valueSource The {@link ValueSource} to wrap.
95 * @param possiblePrefixes The List of expression prefixes to trim.
96 * @param allowUnprefixedExpressions Flag telling the wrapper whether to
97 * continue resolving expressions that don't start with one of the prefixes it tracks.
98 */
99 public PrefixedValueSourceWrapper(
100 ValueSource valueSource, List<String> possiblePrefixes, boolean allowUnprefixedExpressions) {
101 this.valueSource = valueSource;
102 this.possiblePrefixes = possiblePrefixes.toArray(new String[possiblePrefixes.size()]);
103 this.allowUnprefixedExpressions = allowUnprefixedExpressions;
104 }
105
106 /**
107 * Uses {@link ValueSourceUtils#trimPrefix(String, java.util.Collection, boolean)} to
108 * get the trimmed expression. If this expression is null (because the original
109 * expression was null, or because the expression is unprefixed and unprefixed
110 * expressions are not allowed here), then return null; otherwise, return the
111 * nested {@link ValueSource#getValue(String)} result.
112 */
113 public Object getValue(String expression) {
114 lastExpression = ValueSourceUtils.trimPrefix(expression, possiblePrefixes, allowUnprefixedExpressions);
115
116 if (lastExpression == null) {
117 return null;
118 }
119
120 return valueSource.getValue(lastExpression);
121 }
122
123 /**
124 * If the nested {@link ValueSource} implements {@link FeedbackEnabledValueSource},
125 * then return that source's feedback list. Otherwise, return {@link Collections#EMPTY_LIST}.
126 */
127 public List getFeedback() {
128 return (valueSource instanceof FeedbackEnabledValueSource) ? valueSource.getFeedback() : Collections.EMPTY_LIST;
129 }
130
131 /**
132 * If the nested {@link ValueSource} implements {@link QueryEnabledValueSource},
133 * then return that source's last expression. Otherwise, return the last expression
134 * that was processed by the wrapper itself.
135 */
136 public String getLastExpression() {
137 return (valueSource instanceof QueryEnabledValueSource)
138 ? ((QueryEnabledValueSource) valueSource).getLastExpression()
139 : lastExpression;
140 }
141
142 /**
143 * If the nested {@link ValueSource} implements {@link FeedbackEnabledValueSource},
144 * then clear that source's feedback list.
145 */
146 public void clearFeedback() {
147 valueSource.clearFeedback();
148 }
149 }