1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one
3 * or more contributor license agreements. See the NOTICE file
4 * distributed with this work for additional information
5 * regarding copyright ownership. The ASF licenses this file
6 * to you under the Apache License, Version 2.0 (the
7 * "License"); you may not use this file except in compliance
8 * with the License. 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,
13 * software distributed under the License is distributed on an
14 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
15 * KIND, either express or implied. See the License for the
16 * specific language governing permissions and limitations
17 * under the License.
18 */
19 package org.apache.maven.model.interpolation;
20
21 /*
22 * Copyright 2007 The Codehaus Foundation.
23 *
24 * Licensed under the Apache License, Version 2.0 (the "License");
25 * you may not use this file except in compliance with the License.
26 * You may obtain a copy of the License at
27 *
28 * http://www.apache.org/licenses/LICENSE-2.0
29 *
30 * Unless required by applicable law or agreed to in writing, software
31 * distributed under the License is distributed on an "AS IS" BASIS,
32 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
33 * See the License for the specific language governing permissions and
34 * limitations under the License.
35 */
36
37 import org.apache.maven.model.interpolation.reflection.ReflectionValueExtractor;
38 import org.codehaus.plexus.interpolation.AbstractValueSource;
39
40 /**
41 * Wraps an object, providing reflective access to the object graph of which the
42 * supplied object is the root. Expressions like 'child.name' will translate into
43 * 'rootObject.getChild().getName()' for non-boolean properties, and
44 * 'rootObject.getChild().isName()' for boolean properties.
45 */
46 public class ObjectBasedValueSource extends AbstractValueSource {
47
48 private final Object root;
49
50 /**
51 * Construct a new value source, using the supplied object as the root from
52 * which to start, and using expressions split at the dot ('.') to navigate
53 * the object graph beneath this root.
54 * @param root the root of the graph.
55 */
56 public ObjectBasedValueSource(Object root) {
57 super(true);
58 this.root = root;
59 }
60
61 /**
62 * <p>Split the expression into parts, tokenized on the dot ('.') character. Then,
63 * starting at the root object contained in this value source, apply each part
64 * to the object graph below this root, using either 'getXXX()' or 'isXXX()'
65 * accessor types to resolve the value for each successive expression part.
66 * Finally, return the result of the last expression part's resolution.</p>
67 *
68 * <p><b>NOTE:</b> The object-graph nagivation actually takes place via the
69 * {@link ReflectionValueExtractor} class.</p>
70 */
71 public Object getValue(String expression) {
72 if (expression == null || expression.trim().isEmpty()) {
73 return null;
74 }
75
76 try {
77 return ReflectionValueExtractor.evaluate(expression, root, false);
78 } catch (Exception e) {
79 addFeedback("Failed to extract \'" + expression + "\' from: " + root, e);
80 }
81
82 return null;
83 }
84 }