com.mgmtp.jfunk.core.config.ModulesLoader.java Source code

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Here is the source code for com.mgmtp.jfunk.core.config.ModulesLoader.java

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/*
 * Copyright (c) 2015 mgm technology partners GmbH
 *
 * Licensed 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.mgmtp.jfunk.core.config;

import java.io.IOException;
import java.io.InputStream;
import java.util.Enumeration;
import java.util.List;
import java.util.Properties;

import org.apache.commons.io.IOUtils;
import org.apache.log4j.Logger;

import com.google.common.collect.Lists;
import com.google.inject.Module;
import com.google.inject.util.Modules;
import com.mgmtp.jfunk.common.util.ResourceLoader;

/**
 * Utility class for loading Guice modules defined as properties. Automatically adds
 * {@link JFunkDefaultModule} to the list of modules. Further modules may be specified in a
 * properties file. By default, a file named "jfunk.properties" is loaded. Another file may be
 * specified with the system property "jfunk.props.file." Modules may be specified as follows:
 * 
 * <pre>
 * module.1=com.foo.bar.config.MyFirstAdditionalGuiceModule
 * module.2=com.foo.bar.config.MyVerySpecialGuiceModule
 * </pre>
 * 
 */
public final class ModulesLoader {
    private static final Logger LOG = Logger.getLogger(ModulesLoader.class);

    private ModulesLoader() {
        // nothing to do
    }

    /**
     * Loads Guice modules whose class names are specified as properties. All properties starting
     * with "module." are considered to have a fully qualified class name representing a Guice
     * module. The modules are combined and override thespecified jFunkModule.
     * 
     * @param propertiesFile
     *            The properties file
     * @return the combined module
     */
    public static Module loadModulesFromProperties(final Module jFunkModule, final String propertiesFile)
            throws ClassNotFoundException, InstantiationException, IllegalAccessException, IOException {
        final List<Module> modules = Lists.newArrayList();

        LOG.debug("Using jfunk.props.file=" + propertiesFile);
        Properties props = loadProperties(propertiesFile);

        for (final Enumeration<?> en = props.propertyNames(); en.hasMoreElements();) {
            String name = (String) en.nextElement();
            if (name.startsWith("module.")) {
                String className = props.getProperty(name);
                LOG.info("Loading " + name + "=" + className);
                Class<? extends Module> moduleClass = Class.forName(className).asSubclass(Module.class);
                Module module = moduleClass.newInstance();
                modules.add(module);
            }
        }
        return Modules.override(jFunkModule).with(modules);
    }

    private static Properties loadProperties(final String propsFileName) throws IOException {
        Properties props = new Properties();
        InputStream is = null;
        try {
            is = ResourceLoader.getConfigInputStream(propsFileName);
            props.load(is);
        } finally {
            IOUtils.closeQuietly(is);
        }
        return props;
    }
}