1 package org.codehaus.plexus.interpolation;
2
3 import java.util.List;
4
5 /*
6 * Copyright 2001-2008 Codehaus Foundation.
7 *
8 * Licensed under the Apache License, Version 2.0 (the "License");
9 * you may not use this file except in compliance with the License.
10 * You may obtain a copy of the License at
11 *
12 * http://www.apache.org/licenses/LICENSE-2.0
13 *
14 * Unless required by applicable law or agreed to in writing, software
15 * distributed under the License is distributed on an "AS IS" BASIS,
16 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
17 * See the License for the specific language governing permissions and
18 * limitations under the License.
19 */
20
21 /**
22 * Supplies one strategy for resolving a value for an interpolation expression.
23 * ValueSources may be stacked.
24 */
25 public interface ValueSource {
26
27 /**
28 * Returns a value resolved from an expression. The return value is recursively resolved via {@link Interpolator#interpolate(String)}, i.e. might contain expressions as well.
29 * @param expression The string expression.
30 * @param expressionStartDelimiter A valid start delimiter of the expression to be used with the calling {@link Interpolator} (by default <code>${</code>).
31 * @param expressionEndDelimiter A valid end delimiter of the expression to be used with the calling {@link Interpolator} (by default <code>}</code>).
32 * @return the value related to the expression, or {@code null} if not found. This value might contain other expressions separated by {@code expressionStartDelimiter} and {@code expressionEndDelimiter}
33 * @since 1.28
34 */
35 default Object getValue(String expression, String expressionStartDelimiter, String expressionEndDelimiter) {
36 return getValue(expression);
37 }
38
39 /**
40 * @param expression The string expression.
41 * @return the value related to the expression, or {@code null} if not found.
42 * @see #getValue(String, String, String)
43 */
44 public Object getValue(String expression);
45
46 /**
47 * Return the feedback about resolution failures for a particular expression.
48 *
49 * @return a combination of String and Throwable instances, where strings
50 * related to throwables are listed first.
51 */
52 List getFeedback();
53
54 /**
55 * Clear the feedback accumulated by a prior interpolation run.
56 */
57 void clearFeedback();
58 }