001 /*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements. See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License. You may obtain a copy of the License at
008 *
009 * http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017 package org.apache.commons.jxpath;
018
019 import java.lang.reflect.Constructor;
020 import java.lang.reflect.Method;
021 import java.util.Collections;
022 import java.util.Set;
023
024 import org.apache.commons.jxpath.functions.ConstructorFunction;
025 import org.apache.commons.jxpath.functions.MethodFunction;
026 import org.apache.commons.jxpath.util.MethodLookupUtils;
027
028 /**
029 * Extension functions provided by a Java class.
030 *
031 * Let's say we declared a ClassFunction like this:
032 * <blockquote><pre>
033 * new ClassFunctions(Integer.class, "int")
034 * </pre></blockquote>
035 *
036 * We can now use XPaths like:
037 * <dl>
038 * <dt><code>"int:new(3)"</code></dt>
039 * <dd>Equivalent to <code>new Integer(3)</code></dd>
040 * <dt><code>"int:getInteger('foo')"</code></dt>
041 * <dd>Equivalent to <code>Integer.getInteger("foo")</code></dd>
042 * <dt><code>"int:floatValue(int:new(4))"</code></dt>
043 * <dd>Equivalent to <code>new Integer(4).floatValue()</code></dd>
044 * </dl>
045 *
046 * <p>
047 * If the first argument of a method is {@link ExpressionContext}, the
048 * expression context in which the function is evaluated is passed to
049 * the method.
050 *
051 * @author Dmitri Plotnikov
052 * @version $Revision: 652845 $ $Date: 2008-05-02 12:46:46 -0500 (Fri, 02 May 2008) $
053 */
054 public class ClassFunctions implements Functions {
055 private static final Object[] EMPTY_ARRAY = new Object[0];
056
057 private Class functionClass;
058 private String namespace;
059
060 /**
061 * Create a new ClassFunctions.
062 * @param functionClass Class providing the functions
063 * @param namespace assigned ns
064 */
065 public ClassFunctions(Class functionClass, String namespace) {
066 this.functionClass = functionClass;
067 this.namespace = namespace;
068 }
069
070 /**
071 * Returns a set of one namespace - the one specified in the constructor.
072 *
073 * @return a singleton
074 */
075 public Set getUsedNamespaces() {
076 return Collections.singleton(namespace);
077 }
078
079 /**
080 * Returns a {@link Function}, if any, for the specified namespace,
081 * name and parameter types.
082 *
083 * @param namespace if it is not the namespace specified in the constructor,
084 * the method returns null
085 * @param name is a function name or "new" for a constructor.
086 * @param parameters Object[] of parameters
087 *
088 * @return a MethodFunction, a ConstructorFunction or null if there is no
089 * such function.
090 */
091 public Function getFunction(
092 String namespace,
093 String name,
094 Object[] parameters) {
095 if (namespace == null) {
096 if (this.namespace != null) {
097 return null;
098 }
099 }
100 else if (!namespace.equals(this.namespace)) {
101 return null;
102 }
103
104 if (parameters == null) {
105 parameters = EMPTY_ARRAY;
106 }
107
108 if (name.equals("new")) {
109 Constructor constructor =
110 MethodLookupUtils.lookupConstructor(functionClass, parameters);
111 if (constructor != null) {
112 return new ConstructorFunction(constructor);
113 }
114 }
115 else {
116 Method method = MethodLookupUtils.
117 lookupStaticMethod(functionClass, name, parameters);
118 if (method != null) {
119 return new MethodFunction(method);
120 }
121
122 method = MethodLookupUtils.
123 lookupMethod(functionClass, name, parameters);
124 if (method != null) {
125 return new MethodFunction(method);
126 }
127 }
128
129 return null;
130 }
131 }