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Java > Open Source Codes > org > apache > commons > jxpath > CompiledExpression


1 /*
2  * Copyright 1999-2004 The Apache Software Foundation
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  * http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16 package org.apache.commons.jxpath;
17
18 import java.util.Iterator JavaDoc;
19
20 /**
21  * Represents a compiled XPath. The interpretation of compiled XPaths
22  * may be faster, because it bypasses the compilation step. The reference
23  * implementation of JXPathContext also globally caches some of the
24  * results of compilation, so the direct use of JXPathContext is not
25  * always less efficient than the use of CompiledExpression.
26  * <p>
27  * Use CompiledExpression only when there is a need to evaluate the
28  * same expression multiple times and the CompiledExpression can be
29  * conveniently cached.
30  * <p>
31  * To acqure a CompiledExpression, call {@link JXPathContext#compile
32  * JXPathContext.compile}
33  *
34  * @author Dmitri Plotnikov
35  * @version $Revision: 1.6 $ $Date: 2004/02/29 14:17:42 $
36  */
37 public interface CompiledExpression {
38
39     /**
40      * Evaluates the xpath and returns the resulting object. Primitive
41      * types are wrapped into objects.
42      */
43     Object JavaDoc getValue(JXPathContext context);
44
45     /**
46      * Evaluates the xpath, converts the result to the specified class and
47      * returns the resulting object.
48      */
49     Object JavaDoc getValue(JXPathContext context, Class JavaDoc requiredType);
50
51     /**
52      * Modifies the value of the property described by the supplied xpath.
53      * Will throw an exception if one of the following conditions occurs:
54      * <ul>
55      * <li>The xpath does not in fact describe an existing property
56      * <li>The property is not writable (no public, non-static set method)
57      * </ul>
58      */
59     void setValue(JXPathContext context, Object JavaDoc value);
60
61     /**
62      * Creates intermediate elements of
63      * the path by invoking an AbstractFactory, which should first be
64      * installed on the context by calling "setFactory".
65      */
66     Pointer createPath(JXPathContext context);
67
68     /**
69      * The same as setValue, except it creates intermediate elements of
70      * the path by invoking an AbstractFactory, which should first be
71      * installed on the context by calling "setFactory".
72      * <p>
73      * Will throw an exception if one of the following conditions occurs:
74      * <ul>
75      * <li>Elements of the xpath aleady exist, by the path does not in
76      * fact describe an existing property
77      * <li>The AbstractFactory fails to create an instance for an intermediate
78      * element.
79      * <li>The property is not writable (no public, non-static set method)
80      * </ul>
81      */
82     Pointer createPathAndSetValue(JXPathContext context, Object JavaDoc value);
83
84     /**
85      * Traverses the xpath and returns a Iterator of all results found
86      * for the path. If the xpath matches no properties
87      * in the graph, the Iterator will not be null.
88      */
89     Iterator JavaDoc iterate(JXPathContext context);
90
91     /**
92      * Traverses the xpath and returns a Pointer.
93      * A Pointer provides easy access to a property.
94      * If the xpath matches no properties
95      * in the graph, the pointer will be null.
96      */
97     Pointer getPointer(JXPathContext context, String JavaDoc xpath);
98
99     /**
100      * Traverses the xpath and returns an Iterator of Pointers.
101      * A Pointer provides easy access to a property.
102      * If the xpath matches no properties
103      * in the graph, the Iterator be empty, but not null.
104      */
105     Iterator JavaDoc iteratePointers(JXPathContext context);
106
107     /**
108      * Remove the graph element described by this expression
109      */
110     void removePath(JXPathContext context);
111
112     /**
113      * Remove all graph elements described by this expression
114      */
115     void removeAll(JXPathContext context);
116 }
117
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