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The source code

/*
 * 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:
 * 
 *     new ClassFunctions(Integer.class, "int")
 * 
* * We can now use XPaths like: *
*
"int:new(3)"
*
Equivalent to new Integer(3)
*
"int:getInteger('foo')"
*
Equivalent to Integer.getInteger("foo")
*
"int:floatValue(int:new(4))"
*
Equivalent to new Integer(4).floatValue()
*
* *

* 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; } }

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