org.jdag.config.ConfigurationProvider.java Source code

Introduction

Here is the source code for org.jdag.config.ConfigurationProvider.java

Source

/*******************************************************************************
 * jDAG is a project to build acyclic dataflow graphs for processing massive datasets.
 *
 *     Copyright (C) 2011, Author: Balraja,Subbiah
 *
 *     This program is free software: you can redistribute it and/or modify
 *     it under the terms of the GNU General Public License as published by
 *     the Free Software Foundation, either version 3 of the License, or
 *     (at your option) any later version.
 *
 *     This program is distributed in the hope that it will be useful,
 *     but WITHOUT ANY WARRANTY; without even the implied warranty of
 *     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *     GNU General Public License for more details.
 */

package org.jdag.config;

import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import java.net.InetSocketAddress;

import org.apache.commons.configuration.ConfigurationException;
import org.apache.commons.configuration.PropertiesConfiguration;

/**
 * A class that proxies the configuration interface and provides configuration
 * details from the underlying properties file using apache configuration.
 *
 * @author Balraja Subbiah
 * @version $Id:$
 */
public final class ConfigurationProvider implements InvocationHandler {
    private final String myBasePrefix;

    private final PropertiesConfiguration myPropertiesConfiguration;

    private final Class<?> myConfigDefnClass;

    /**
     * CTOR
     */
    private ConfigurationProvider(String src, String basePrefix, Class<?> configDefinitionClass)
            throws ConfigurationException {
        myPropertiesConfiguration = new PropertiesConfiguration(src);
        myBasePrefix = basePrefix;
        myConfigDefnClass = configDefinitionClass;
    }

    /**
     * CTOR
     */
    private ConfigurationProvider(String basePrefix, Class<?> configDefinitionClass) {
        myBasePrefix = basePrefix;
        myPropertiesConfiguration = null;
        myConfigDefnClass = configDefinitionClass;
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public Object invoke(Object proxy, Method method, Object[] args) {
        try {
            Method actualDefnMethod = myConfigDefnClass.getDeclaredMethod(method.getName());
            PropertyDef def = actualDefnMethod.getAnnotation(PropertyDef.class);
            String property = myBasePrefix + "." + def.name();
            String value = System.getProperty(property);
            switch (def.resultType()) {
            case INT:
                return value != null ? Integer.parseInt(value)
                        : myPropertiesConfiguration != null ? myPropertiesConfiguration.getInt(property) : null;
            case STRING:
                return value != null ? value
                        : myPropertiesConfiguration != null ? myPropertiesConfiguration.getProperty(property)
                                : null;
            case BOOLEAN:
                return value != null ? Boolean.parseBoolean(value)
                        : myPropertiesConfiguration != null ? myPropertiesConfiguration.getBoolean(property) : null;
            case SOCKET_ADDRESS:
                return value != null ? new InetSocketAddress(Integer.parseInt(value))
                        : myPropertiesConfiguration != null
                                ? new InetSocketAddress(myPropertiesConfiguration.getInt(property))
                                : null;
            }
            return null;
        } catch (SecurityException e) {
            throw new RuntimeException(e);
        } catch (NoSuchMethodException e) {
            throw new RuntimeException(e);
        }
    }

    /**
     *  A factory method that creates a proxy to read from underlying
     *  property configuration.
     */
    @SuppressWarnings("unchecked")
    public static <T> T makeConfiguration(Class<T> configDefinitionClass, String propertyFile) {
        Source s = configDefinitionClass.getAnnotation(Source.class);
        try {
            ConfigurationProvider provider = propertyFile != null
                    ? new ConfigurationProvider(propertyFile, s.prefix(), configDefinitionClass)
                    : new ConfigurationProvider(s.prefix(), configDefinitionClass);

            return (T) Proxy.newProxyInstance(configDefinitionClass.getClassLoader(),
                    new Class<?>[] { configDefinitionClass }, provider);
        } catch (IllegalArgumentException e) {
            throw new RuntimeException(e);
        } catch (ConfigurationException e) {
            throw new RuntimeException(e);
        }
    }
}