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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;
19  import java.util.HashMap;
20  import java.util.Iterator;
21  import java.util.List;
22  import java.util.Set;
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 allFunctions = new ArrayList();
35      private HashMap 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 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 namespace,
70          String name,
71          Object[] parameters) 
72      {
73          if (byNamespace == null) {
74              prepareCache();
75          }
76          Object 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) {
84              List list = (List) 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();
102         int count = allFunctions.size();
103         for (int i = 0; i < count; i++) {
104             Functions funcs = (Functions) allFunctions.get(i);
105             Set namespaces = funcs.getUsedNamespaces();
106             for (Iterator it = namespaces.iterator(); it.hasNext();) {
107                 String ns = (String) it.next();
108                 Object candidates = byNamespace.get(ns);
109                 if (candidates == null) {
110                     byNamespace.put(ns, funcs);
111                 }
112                 else if (candidates instanceof Functions) {
113                     List lst = new ArrayList();
114                     lst.add(candidates);
115                     lst.add(funcs);
116                     byNamespace.put(ns, lst);
117                 }
118                 else {
119                     ((List) candidates).add(funcs);
120                 }
121             }
122         }
123     }
124 }