Coverage Report - org.apache.commons.configuration.tree.ExpressionEngine
 
Classes in this File Line Coverage Branch Coverage Complexity
ExpressionEngine
N/A
N/A
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>
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  * 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()} or {@code addProperty()} 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  
  * Separating 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 <a
 46  
  * href="http://commons.apache.org/configuration/team-list.html">Commons
 47  
  * Configuration team</a>
 48  
  * @version $Id: ExpressionEngine.java 1206474 2011-11-26 16:14:09Z oheger $
 49  
  */
 50  
 public interface ExpressionEngine
 51  
 {
 52  
     /**
 53  
      * Finds the node(s) that is (are) matched by the specified key. This is the
 54  
      * main method for interpreting property keys. An implementation must
 55  
      * traverse the given root node and its children to find all nodes that are
 56  
      * matched by the given key. If the key is not correct in the syntax
 57  
      * provided by that implementation, it is free to throw a (runtime)
 58  
      * exception indicating this error condition.
 59  
      *
 60  
      * @param root the root node of a hierarchy of configuration nodes
 61  
      * @param key the key to be evaluated
 62  
      * @return a list with the nodes that are matched by the key (should never
 63  
      * be <b>null</b>)
 64  
      */
 65  
     List<ConfigurationNode> query(ConfigurationNode root, String key);
 66  
 
 67  
     /**
 68  
      * Returns the key for the specified node in the expression language
 69  
      * supported by an implementation. This method is called whenever a property
 70  
      * key for a node has to be constructed, e.g. by the
 71  
      * {@link org.apache.commons.configuration.Configuration#getKeys() getKeys()}
 72  
      * method.
 73  
      *
 74  
      * @param node the node, for which the key must be constructed
 75  
      * @param parentKey the key of this node's parent (can be <b>null</b> for
 76  
      * the root node)
 77  
      * @return this node's key
 78  
      */
 79  
     String nodeKey(ConfigurationNode node, String parentKey);
 80  
 
 81  
     /**
 82  
      * Returns information needed for an add operation. This method gets called
 83  
      * when new properties are to be added to a configuration. An implementation
 84  
      * has to interpret the specified key, find the parent node for the new
 85  
      * elements, and provide all information about new nodes to be added.
 86  
      *
 87  
      * @param root the root node
 88  
      * @param key the key for the new property
 89  
      * @return an object with all information needed for the add operation
 90  
      */
 91  
     NodeAddData prepareAdd(ConfigurationNode root, String key);
 92  
 }