    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.functions;
    018
    019    import java.lang.reflect.Constructor;
    020    import java.lang.reflect.InvocationTargetException;
    021
    022    import org.apache.commons.jxpath.ExpressionContext;
    023    import org.apache.commons.jxpath.Function;
    024    import org.apache.commons.jxpath.JXPathInvalidAccessException;
    025    import org.apache.commons.jxpath.util.TypeUtils;
    026
    027    /**
    028     * An extension function that creates an instance using a constructor.
    029     *
    030     * @author Dmitri Plotnikov
    031     * @version $Revision: 652845 $ $Date: 2008-05-02 12:46:46 -0500 (Fri, 02 May 2008) $
    032     */
    033    public class ConstructorFunction implements Function {
    034        private static final Object[] EMPTY_ARRAY = new Object[0];
    035
    036        private Constructor constructor;
    037
    038        /**
    039         * Create a new ConstructorFunction.
    040         * @param constructor the constructor to call.
    041         */
    042        public ConstructorFunction(Constructor constructor) {
    043            this.constructor = constructor;
    044        }
    045
    046        /**
    047         * Converts parameters to suitable types and invokes the constructor.
    048         * @param context evaluation context
    049         * @param parameters constructor args
    050         * @return new instance
    051         */
    052        public Object invoke(ExpressionContext context, Object[] parameters) {
    053            try {
    054                Object[] args;
    055                if (parameters == null) {
    056                    parameters = EMPTY_ARRAY;
    057                }
    058                int pi = 0;
    059                Class[] types = constructor.getParameterTypes();
    060                if (types.length > 0
    061                    && ExpressionContext.class.isAssignableFrom(types[0])) {
    062                    pi = 1;
    063                }
    064                args = new Object[parameters.length + pi];
    065                if (pi == 1) {
    066                    args[0] = context;
    067                }
    068                for (int i = 0; i < parameters.length; i++) {
    069                    args[i + pi] = TypeUtils.convert(parameters[i], types[i + pi]);
    070                }
    071                return constructor.newInstance(args);
    072            }
    073            catch (Throwable ex) {
    074                if (ex instanceof InvocationTargetException) {
    075                    ex = ((InvocationTargetException) ex).getTargetException();
    076                }
    077                throw new JXPathInvalidAccessException(
    078                    "Cannot invoke constructor " + constructor,
    079                    ex);
    080            }
    081        }
    082    }