/*
* Copyright 1999-2004 The Apache Software Foundation
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.commons.jxpath;
import java.lang.reflect.Constructor;
import java.lang.reflect.Method;
import java.util.Collections;
import java.util.Set;
import org.apache.commons.jxpath.functions.ConstructorFunction;
import org.apache.commons.jxpath.functions.MethodFunction;
import org.apache.commons.jxpath.util.MethodLookupUtils;
/**
* Extension functions provided by a Java class.
*
* Let's say, we declared a ClassFunction like this:
* <blockquote><pre>
* new ClassFunctions(Integer.class, "int")
* </pre></blockquote>
*
* We can now use XPaths like:
* <dl>
* <dt><code>"int:new(3)"</code></dt>
* <dd>Equivalent to <code>new Integer(3)</code></dd>
* <dt><code>"int:getInteger('foo')"</code></dt>
* <dd>Equivalent to <code>Integer.getInteger("foo")</code></dd>
* <dt><code>"int:floatValue(int:new(4))"</code></dt>
* <dd>Equivalent to <code>new Integer(4).floatValue()</code></dd>
* </dl>
*
* <p>
* If the first argument of a method is ExpressionContext, the
* expression context in which the function is evaluated is passed to
* the method.
*
* @author Dmitri Plotnikov
* @version $Revision: 1.9 $ $Date: 2004/02/29 14:17:42 $
*/
public class ClassFunctions implements Functions {
private Class functionClass;
private String namespace;
private static final Object[] EMPTY_ARRAY = new Object[0];
public ClassFunctions(Class functionClass, String namespace) {
this.functionClass = functionClass;
this.namespace = namespace;
}
/**
* Returns a set of one namespace - the one specified in the constructor.
*
* @returns a singleton
*/
public Set getUsedNamespaces() {
return Collections.singleton(namespace);
}
/**
* Returns a Function, if any, for the specified namespace,
* name and parameter types.
*
* @param namespace if it is not the namespace specified in the constructor,
* the method returns null
* @param name is a function name or "new" for a constructor.
*
* @return a MethodFunction, a ConstructorFunction or null if there is no
* such function.
*/
public Function getFunction(
String namespace,
String name,
Object[] parameters)
{
if (!namespace.equals(this.namespace)) {
return null;
}
if (parameters == null) {
parameters = EMPTY_ARRAY;
}
if (name.equals("new")) {
Constructor constructor =
MethodLookupUtils.lookupConstructor(functionClass, parameters);
if (constructor != null) {
return new ConstructorFunction(constructor);
}
}
else {
Method method = MethodLookupUtils.
lookupStaticMethod(functionClass, name, parameters);
if (method != null) {
return new MethodFunction(method);
}
method = MethodLookupUtils.
lookupMethod(functionClass, name, parameters);
if (method != null) {
return new MethodFunction(method);
}
}
return null;
}
}