Classes in this File | Line Coverage | Branch Coverage | Complexity | ||||
ExpressionEngine |
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| 1.0;1 |
1 | /* | |
2 | * Licensed to the Apache Software Foundation (ASF) under one or more | |
3 | * contributor license agreements. See the NOTICE file distributed with | |
4 | * this work for additional information regarding copyright ownership. | |
5 | * The ASF licenses this file to You under the Apache License, Version 2.0 | |
6 | * (the "License"); you may not use this file except in compliance with | |
7 | * the License. You may obtain a copy of the License at | |
8 | * | |
9 | * http://www.apache.org/licenses/LICENSE-2.0 | |
10 | * | |
11 | * Unless required by applicable law or agreed to in writing, software | |
12 | * distributed under the License is distributed on an "AS IS" BASIS, | |
13 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | |
14 | * See the License for the specific language governing permissions and | |
15 | * limitations under the License. | |
16 | */ | |
17 | package org.apache.commons.configuration.tree; | |
18 | ||
19 | import java.util.List; | |
20 | ||
21 | /** | |
22 | * <p> | |
23 | * Definition of an interface for evaluating keys for hierarchical | |
24 | * configurations. | |
25 | * </p> | |
26 | * <p> | |
27 | * An <em>expression engine</em> knows how to map a key for a configuration's | |
28 | * property to a single or a set of configuration nodes. Thus it defines the way | |
29 | * how properties are addressed in this configuration. Methods of a | |
30 | * configuration that have to handle property key (e.g. | |
31 | * <code>getProperty()</code> or <code>addProperty()</code> do not interpret | |
32 | * the passed in keys on their own, but delegate this task to an associated | |
33 | * expression engine. This expression engine will then find out, which | |
34 | * configuration nodes are addressed by the key. | |
35 | * </p> | |
36 | * <p> | |
37 | * Seperating the task of evaluating property keys from the configuration object | |
38 | * has the advantage that many different expression languages (i.e. ways for | |
39 | * querying or setting properties) can be supported. Just set a suitable | |
40 | * implementation of this interface as the configuration's expression engine, | |
41 | * and you can use the syntax provided by this implementation. | |
42 | * </p> | |
43 | * | |
44 | * @since 1.3 | |
45 | * @author Oliver Heger | |
46 | */ | |
47 | public interface ExpressionEngine | |
48 | { | |
49 | /** | |
50 | * Finds the node(s) that is (are) matched by the specified key. This is the | |
51 | * main method for interpreting property keys. An implementation must | |
52 | * traverse the given root node and its children to find all nodes that are | |
53 | * matched by the given key. If the key is not correct in the syntax | |
54 | * provided by that implementation, it is free to throw a (runtime) | |
55 | * exception indicating this error condition. | |
56 | * | |
57 | * @param root the root node of a hierarchy of configuration nodes | |
58 | * @param key the key to be evaluated | |
59 | * @return a list with the nodes that are matched by the key (should never | |
60 | * be <b>null</b>) | |
61 | */ | |
62 | List query(ConfigurationNode root, String key); | |
63 | ||
64 | /** | |
65 | * Returns the key for the specified node in the expression language | |
66 | * supported by an implementation. This method is called whenever a property | |
67 | * key for a node has to be constructed, e.g. by the | |
68 | * <code>{@link org.apache.commons.configuration.Configuration#getKeys() getKeys()}</code> | |
69 | * method. | |
70 | * | |
71 | * @param node the node, for which the key must be constructed | |
72 | * @param parentKey the key of this node's parent (can be <b>null</b> for | |
73 | * the root node) | |
74 | * @return this node's key | |
75 | */ | |
76 | String nodeKey(ConfigurationNode node, String parentKey); | |
77 | ||
78 | /** | |
79 | * Returns information needed for an add operation. This method gets called | |
80 | * when new properties are to be added to a configuration. An implementation | |
81 | * has to interpret the specified key, find the parent node for the new | |
82 | * elements, and provide all information about new nodes to be added. | |
83 | * | |
84 | * @param root the root node | |
85 | * @param key the key for the new property | |
86 | * @return an object with all information needed for the add operation | |
87 | */ | |
88 | NodeAddData prepareAdd(ConfigurationNode root, String key); | |
89 | } |