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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.jxpath;
18  
19  import java.util.Iterator;
20  
21  /**
22   * Represents a compiled XPath. The interpretation of compiled XPaths
23   * may be faster, because it bypasses the compilation step. The reference
24   * implementation of {@link JXPathContext} also globally caches some of the
25   * results of compilation, so the direct use of JXPathContext is not
26   * always less efficient than the use of CompiledExpression.
27   * <p>
28   * Use CompiledExpression only when there is a need to evaluate the
29   * same expression multiple times and the CompiledExpression can be
30   * conveniently cached.
31   * <p>
32   * To acquire a CompiledExpression, call {@link JXPathContext#compile
33   * JXPathContext.compile}
34   *
35   * @author Dmitri Plotnikov
36   * @version $Revision: 652845 $ $Date: 2008-05-02 13:46:46 -0400 (Fri, 02 May 2008) $
37   */
38  public interface CompiledExpression {
39  
40      /**
41       * Evaluates the xpath and returns the resulting object. Primitive
42       * types are wrapped into objects.
43       * @param context to evaluate
44       * @return Object
45       */
46      Object getValue(JXPathContext context);
47  
48      /**
49       * Evaluates the xpath, converts the result to the specified class and
50       * returns the resulting object.
51       * @param context to evaluate
52       * @param requiredType return type
53       * @return Object
54       */
55      Object getValue(JXPathContext context, Class requiredType);
56  
57      /**
58       * Modifies the value of the property described by the supplied xpath.
59       * Will throw an exception if one of the following conditions occurs:
60       * <ul>
61       * <li>The xpath does not in fact describe an existing property
62       * <li>The property is not writable (no public, non-static set method)
63       * </ul>
64       * @param context base
65       * @param value to set
66       */
67      void setValue(JXPathContext context, Object value);
68  
69      /**
70       * Creates intermediate elements of
71       * the path by invoking an {@link AbstractFactory}, which should first be
72       * installed on the context by calling {@link JXPathContext#setFactory}.
73       * @param context base
74       * @return Pointer created
75       */
76      Pointer createPath(JXPathContext context);
77  
78      /**
79       * The same as setValue, except it creates intermediate elements of
80       * the path by invoking an {@link AbstractFactory}, which should first be
81       * installed on the context by calling {@link JXPathContext#setFactory}.
82       * <p>
83       * Will throw an exception if one of the following conditions occurs:
84       * <ul>
85       * <li>Elements of the xpath aleady exist, by the path does not in
86       *  fact describe an existing property
87       * <li>The AbstractFactory fails to create an instance for an intermediate
88       * element.
89       * <li>The property is not writable (no public, non-static set method)
90       * </ul>
91       * @param context base
92       * @param value to set
93       * @return Pointer created
94       */
95      Pointer createPathAndSetValue(JXPathContext context, Object value);
96  
97      /**
98       * Traverses the xpath and returns a Iterator of all results found
99       * for the path. If the xpath matches no properties
100      * in the graph, the Iterator will not be null.
101      * @param context base
102      * @return Iterator
103      */
104     Iterator iterate(JXPathContext context);
105 
106     /**
107      * Traverses the xpath and returns a Pointer.
108      * A Pointer provides easy access to a property.
109      * If the xpath matches no properties
110      * in the graph, the pointer will be null.
111      * @param context base
112      * @param xpath string
113      * @return Pointer found
114      */
115     Pointer getPointer(JXPathContext context, String xpath);
116 
117     /**
118      * Traverses the xpath and returns an Iterator of Pointers.
119      * A Pointer provides easy access to a property.
120      * If the xpath matches no properties
121      * in the graph, the Iterator be empty, but not null.
122      * @param context to iterate
123      * @return Iterator<Pointer>
124      */
125     Iterator iteratePointers(JXPathContext context);
126 
127     /**
128      * Remove the graph element described by this expression.
129      * @param context base
130      */
131     void removePath(JXPathContext context);
132 
133     /**
134      * Remove all graph elements described by this expression.
135      * @param context base
136      */
137     void removeAll(JXPathContext context);
138 }