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Commons JXPath example source code file (ClassFunctions.java)

This example Commons JXPath source code file (ClassFunctions.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Java - Commons JXPath tags/keywords

classfunctions, classfunctions, empty_array, function, functions, method, methodfunction, methodfunction, methodlookuputils, object, object, reflection, set, string, string, util

The Commons JXPath ClassFunctions.java source code

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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>
 *     new ClassFunctions(Integer.class, "int")
 * </pre>
 *
 * We can now use XPaths like:
 * <dl>
 *  <dt>"int:new(3)"
 *  <dd>Equivalent to new Integer(3)
 *  <dt>"int:getInteger('foo')"
 *  <dd>Equivalent to Integer.getInteger("foo")
 *  <dt>"int:floatValue(int:new(4))"
 *  <dd>Equivalent to new Integer(4).floatValue()
 * </dl>
 *
 * <p>
 * If the first argument of a method is {@link ExpressionContext}, the
 * expression context in which the function is evaluated is passed to
 * the method.
 *
 * @author Dmitri Plotnikov
 * @version $Revision: 652845 $ $Date: 2008-05-02 12:46:46 -0500 (Fri, 02 May 2008) $
 */
public class ClassFunctions implements Functions {
    private static final Object[] EMPTY_ARRAY = new Object[0];

    private Class functionClass;
    private String namespace;

    /**
     * Create a new ClassFunctions.
     * @param functionClass Class providing the functions
     * @param namespace assigned ns
     */
    public ClassFunctions(Class functionClass, String namespace) {
        this.functionClass = functionClass;
        this.namespace = namespace;
    }

    /**
     * Returns a set of one namespace - the one specified in the constructor.
     *
     * @return a singleton
     */
    public Set getUsedNamespaces() {
        return Collections.singleton(namespace);
    }

    /**
     * Returns a {@link 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.
     * @param parameters Object[] of parameters
     *
     * @return a MethodFunction, a ConstructorFunction or null if there is no
     *      such function.
     */
    public Function getFunction(
        String namespace,
        String name,
        Object[] parameters) {
        if (namespace == null) {
            if (this.namespace != null) {
                return null;
            }
        }
        else 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;
    }
}

Other Commons JXPath examples (source code examples)

Here is a short list of links related to this Commons JXPath ClassFunctions.java source code file:

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