com.acciente.induction.init.ConfigLoaderInitializer.java Source code

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Here is the source code for com.acciente.induction.init.ConfigLoaderInitializer.java

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/*
 * Copyright 2008-2013 Acciente, LLC
 *
 * Acciente, LLC 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 com.acciente.induction.init;

import com.acciente.commons.reflect.ParameterProviderException;
import com.acciente.induction.init.config.ConfigLoader;
import com.acciente.induction.init.config.xmlconfigloader.XMLConfigLoader;
import com.acciente.induction.util.ConstructorNotFoundException;
import com.acciente.induction.util.ObjectFactory;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import javax.servlet.ServletConfig;
import java.lang.reflect.InvocationTargetException;

/**
 * This class manages the loading of a config loader (yes, the config loader itself
 * is configurable, and the parameter specifying its name is in a sense a bootstrap
 * parameter value).
 *
 * This class also defines the names of any config parameters that may defined
 * directly in the web.xml where the dispatcher servlet is defined. There are few
 * parameters that can be defined directly in the web.xml, since most of the
 * configuration used to initialize the displatcher is expected to be in an XML
 * file named using the convention [servlet-name]-induction.xml residing in the
 * same location as the web.xml file.
 *
 * Currently the only parameter that may be defined in the web.xml is one that
 * allows reading the configuration using a custom configuration reader class
 * in which case no [servlet-name]-induction.xml is expected. In fact the
 * [servlet-name]-induction.xml is what is loaded by the default configuration
 * reader implementation.
 *
 * Any parameter are expected to be
 * prefixed by the name of given to the dispatcher servlet. For example if the
 * dispatcher servlet is named myapp, the an example of a parameter name
 * in the web.xml would look like: myapp.config-loader-class
 *
 * @created Mar 15, 2008
 *
 * @author Adinath Raveendra Raj
 */
public class ConfigLoaderInitializer {
    public static final String CONFIG_LOADER_CLASS = "config-loader-class";

    /**
     * Loads the configuration parameters used to configure every module in this dispatcher servlet.
     *
     * @param oServletConfig provides access to the dispatcher's servlet config
     *
     * @return a container with configuration values
     *
     * @throws ClassNotFoundException propagated exception
     * @throws ConstructorNotFoundException propagated exception
     * @throws IllegalAccessException propagated exception
     * @throws InstantiationException propagated exception
     * @throws InvocationTargetException propagated exception
     *
     * Log
     * Mar 15, 2008 APR  -  created
     */
    public static ConfigLoader getConfigLoader(ServletConfig oServletConfig)
            throws ClassNotFoundException, InvocationTargetException, ConstructorNotFoundException,
            ParameterProviderException, IllegalAccessException, InstantiationException {
        ConfigLoader oConfigLoader;
        String sConfigLoaderClassName;
        Log oLog;

        oLog = LogFactory.getLog(ConfigLoaderInitializer.class);

        sConfigLoaderClassName = oServletConfig.getInitParameter(
                oServletConfig.getServletName() + "." + ConfigLoaderInitializer.CONFIG_LOADER_CLASS);

        // first check if there is custom config loader defined
        if (sConfigLoaderClassName == null) {
            // no custom loader defined, use the default XML loader (this is the typical case)
            oConfigLoader = new XMLConfigLoader("induction-" + oServletConfig.getServletName() + ".xml",
                    oServletConfig);

            oLog.info("using default XML config loader");
        } else {
            oLog.info("loading user-defined config loader class: " + sConfigLoaderClassName);

            // note that to load this class we use the default class loader since any of our
            // custom classloaders have to wait until we load in the configuration
            Class oConfigLoaderClass = Class.forName(sConfigLoaderClassName);

            // attempt to find and call the single public constructor
            oConfigLoader = (ConfigLoader) ObjectFactory.createObject(oConfigLoaderClass,
                    new Object[] { oServletConfig }, null);
        }

        return oConfigLoader;
    }
}

// EOF