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


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.ArrayList JavaDoc;
19 import java.util.HashMap JavaDoc;
20 import java.util.Iterator JavaDoc;
21 import java.util.List JavaDoc;
22 import java.util.Set JavaDoc;
23
24 /**
25  * An object that aggregates Functions objects into a group Functions object.
26  * Since JXPathContext can only register a single Functions object,
27  * FunctionLibrary should always be used to group all Functions objects
28  * that need to be registered.
29  *
30  * @author Dmitri Plotnikov
31  * @version $Revision: 1.5 $ $Date: 2004/02/29 14:17:42 $
32  */
33 public class FunctionLibrary implements Functions {
34     private List JavaDoc allFunctions = new ArrayList JavaDoc();
35     private HashMap JavaDoc byNamespace = null;
36
37     /**
38      * Add functions to the library
39      */
40     public void addFunctions(Functions functions) {
41         allFunctions.add(functions);
42         byNamespace = null;
43     }
44
45     /**
46      * Remove functions from the library.
47      */
48     public void removeFunctions(Functions functions) {
49         allFunctions.remove(functions);
50         byNamespace = null;
51     }
52
53     /**
54      * Returns a set containing all namespaces used by the aggregated
55      * Functions.
56      */
57     public Set JavaDoc getUsedNamespaces() {
58         if (byNamespace == null) {
59             prepareCache();
60         }
61         return byNamespace.keySet();
62     }
63
64     /**
65      * Returns a Function, if any, for the specified namespace,
66      * name and parameter types.
67      */
68     public Function getFunction(
69         String JavaDoc namespace,
70         String JavaDoc name,
71         Object JavaDoc[] parameters)
72     {
73         if (byNamespace == null) {
74             prepareCache();
75         }
76         Object JavaDoc candidates = byNamespace.get(namespace);
77         if (candidates instanceof Functions) {
78             return ((Functions) candidates).getFunction(
79                 namespace,
80                 name,
81                 parameters);
82         }
83         else if (candidates instanceof List JavaDoc) {
84             List JavaDoc list = (List JavaDoc) candidates;
85             int count = list.size();
86             for (int i = 0; i < count; i++) {
87                 Function function =
88                     ((Functions) list.get(i)).getFunction(
89                         namespace,
90                         name,
91                         parameters);
92                 if (function != null) {
93                     return function;
94                 }
95             }
96         }
97         return null;
98     }
99
100     private void prepareCache() {
101         byNamespace = new HashMap JavaDoc();
102         int count = allFunctions.size();
103         for (int i = 0; i < count; i++) {
104             Functions funcs = (Functions) allFunctions.get(i);
105             Set JavaDoc namespaces = funcs.getUsedNamespaces();
106             for (Iterator JavaDoc it = namespaces.iterator(); it.hasNext();) {
107                 String JavaDoc ns = (String JavaDoc) it.next();
108                 Object JavaDoc candidates = byNamespace.get(ns);
109                 if (candidates == null) {
110                     byNamespace.put(ns, funcs);
111                 }
112                 else if (candidates instanceof Functions) {
113                     List JavaDoc lst = new ArrayList JavaDoc();
114                     lst.add(candidates);
115                     lst.add(funcs);
116                     byNamespace.put(ns, lst);
117                 }
118                 else {
119                     ((List JavaDoc) candidates).add(funcs);
120                 }
121             }
122         }
123     }
124 }
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