001// Copyright 2005 The Apache Software Foundation
002//
003// Licensed under the Apache License, Version 2.0 (the "License");
004// you may not use this file except in compliance with the License.
005// You may obtain a copy of the License at
006//
007//     http://www.apache.org/licenses/LICENSE-2.0
008//
009// Unless required by applicable law or agreed to in writing, software
010// distributed under the License is distributed on an "AS IS" BASIS,
011// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
012// See the License for the specific language governing permissions and
013// limitations under the License.
014
015package org.apache.hivemind.util;
016
017import org.apache.hivemind.ApplicationRuntimeException;
018import org.apache.hivemind.HiveMind;
019import org.apache.hivemind.Location;
020import org.apache.hivemind.internal.Module;
021
022/**
023 * Code for creating an instance, possibly setting its {@link org.apache.hivemind.Location}, and
024 * possibly initializing its properties.
025 * 
026 * @author Howard M. Lewis Ship
027 * @since 1.1
028 */
029public class InstanceCreationUtils
030{
031    /**
032     * Creates an instance.
033     * 
034     * @param module
035     *            the referencing module, used to resolve partial class names
036     * @param initializer
037     *            The name of the class to instantiate, possibly followed by a list of properties
038     *            and values. I.e. <code>com.examples.MyBean,property=value</code>.
039     * @param location
040     *            The location to assign to the newly created instance, if it implements
041     *            {@link org.apache.hivemind.LocationHolder}. Also the location used to report
042     *            errors creating or configuring the instance.
043     */
044    public static Object createInstance(Module module, String initializer, Location location)
045    {
046        int commax = initializer.indexOf(',');
047
048        String className = (commax < 0) ? initializer : initializer.substring(0, commax);
049
050        Class objectClass = module.resolveType(className);
051
052        try
053        {
054            Object result = objectClass.newInstance();
055
056            HiveMind.setLocation(result, location);
057
058            if (commax > 0)
059                PropertyUtils.configureProperties(result, initializer.substring(commax + 1));
060
061            return result;
062        }
063        catch (Exception ex)
064        {
065            // JDK 1.4 produces a good message here, but JDK 1.3 does not, so we
066            // create our own.
067
068            throw new ApplicationRuntimeException(UtilMessages.unableToInstantiateInstanceOfClass(
069                    objectClass,
070                    ex), location, ex);
071        }
072
073    }
074}