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Java > Open Source Codes > org > apache > commons > jxpath > ri > compiler > ExtensionFunction


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.ri.compiler;
17
18 import java.util.Arrays JavaDoc;
19
20 import org.apache.commons.jxpath.Function;
21 import org.apache.commons.jxpath.JXPathException;
22 import org.apache.commons.jxpath.ri.EvalContext;
23 import org.apache.commons.jxpath.ri.QName;
24
25 /**
26  * Represents an element of the parse tree representing an extension function
27  * call.
28  *
29  * @author Dmitri Plotnikov
30  * @version $Revision: 1.13 $ $Date: 2004/03/25 05:42:01 $
31  */
32 public class ExtensionFunction extends Operation {
33
34     private QName functionName;
35
36     public ExtensionFunction(QName functionName, Expression args[]) {
37         super(args);
38         this.functionName = functionName;
39     }
40
41     public QName getFunctionName() {
42         return functionName;
43     }
44
45     /**
46      * An extension function gets the current context, therefore it MAY be
47      * context dependent.
48      */
49     public boolean computeContextDependent() {
50         return true;
51     }
52
53     public String JavaDoc toString() {
54         StringBuffer JavaDoc buffer = new StringBuffer JavaDoc();
55         buffer.append(functionName);
56         buffer.append('(');
57         Expression args[] = getArguments();
58         if (args != null) {
59             for (int i = 0; i < args.length; i++) {
60                 if (i > 0) {
61                     buffer.append(", ");
62                 }
63                 buffer.append(args[i]);
64             }
65         }
66         buffer.append(')');
67         return buffer.toString();
68     }
69     
70     public Object JavaDoc compute(EvalContext context) {
71         return computeValue(context);
72     }
73
74     public Object JavaDoc computeValue(EvalContext context) {
75         Object JavaDoc[] parameters = null;
76         if (args != null) {
77             parameters = new Object JavaDoc[args.length];
78             for (int i = 0; i < args.length; i++) {
79                 parameters[i] = convert(args[i].compute(context));
80             }
81         }
82
83         Function function =
84             context.getRootContext().getFunction(functionName, parameters);
85         if (function == null) {
86             throw new JXPathException(
87                 "No such function: "
88                     + functionName
89                     + Arrays.asList(parameters));
90         }
91
92         return function.invoke(context, parameters);
93     }
94     
95     private Object JavaDoc convert(Object JavaDoc object) {
96         if (object instanceof EvalContext) {
97             return ((EvalContext) object).getValue();
98         }
99         return object;
100     }
101 }
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