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
018package org.apache.commons.jxpath.functions;
019
020import java.lang.reflect.Constructor;
021import java.lang.reflect.InvocationTargetException;
022
023import org.apache.commons.jxpath.ExpressionContext;
024import org.apache.commons.jxpath.Function;
025import org.apache.commons.jxpath.JXPathInvalidAccessException;
026import org.apache.commons.jxpath.util.TypeUtils;
027
028/**
029 * An extension function that creates an instance using a constructor.
030 */
031public class ConstructorFunction implements Function {
032
033    private static final Object[] EMPTY_ARRAY = {};
034    private final Constructor constructor;
035
036    /**
037     * Constructs a new ConstructorFunction.
038     *
039     * @param constructor the constructor to call.
040     */
041    public ConstructorFunction(final Constructor constructor) {
042        this.constructor = constructor;
043    }
044
045    /**
046     * Converts parameters to suitable types and invokes the constructor.
047     *
048     * @param context    evaluation context
049     * @param parameters constructor args
050     * @return new instance
051     */
052    @Override
053    public Object invoke(final ExpressionContext context, Object[] parameters) {
054        try {
055            Object[] args;
056            if (parameters == null) {
057                parameters = EMPTY_ARRAY;
058            }
059            int pi = 0;
060            final Class[] types = constructor.getParameterTypes();
061            if (types.length > 0 && 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        } catch (Throwable ex) {
073            if (ex instanceof InvocationTargetException) {
074                ex = ((InvocationTargetException) ex).getTargetException();
075            }
076            throw new JXPathInvalidAccessException("Cannot invoke constructor " + constructor, ex);
077        }
078    }
079}