GpioFactory.java

package com.pi4j.io.gpio;

/*
 * #%L
 * **********************************************************************
 * ORGANIZATION  :  Pi4J
 * PROJECT       :  Pi4J :: Java Library (Core)
 * FILENAME      :  GpioFactory.java  
 * 
 * This file is part of the Pi4J project. More information about 
 * this project can be found here:  http://www.pi4j.com/
 * **********************************************************************
 * %%
 * Copyright (C) 2012 - 2013 Pi4J
 * %%
 * 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.
 * #L%
 */


import com.pi4j.concurrent.DefaultExecutorServiceFactory;
import com.pi4j.concurrent.ExecutorServiceFactory;
import com.pi4j.io.gpio.impl.GpioControllerImpl;

/**
 * <p>This factory class provides a static method to create new 'GpioController' instances. </p>
 * 
 * <p>
 * Before using the Pi4J library, you need to ensure that the Java VM in configured with access to
 * the following system libraries:
 * <ul>
 * <li>pi4j</li>
 * <li>wiringPi</li>
 * </ul>
 * 
 * <blockquote> This library depends on the wiringPi native system library.</br> (developed by
 * Gordon Henderson @ <a href="https://projects.drogon.net/">https://projects.drogon.net/</a>)
 * </blockquote>
 * </p>
 * 
 * @see #com.pi4j.io.gpio.Gpio
 * 
 * @see <a href="http://www.pi4j.com/">http://www.pi4j.com/</a>
 * @author Robert Savage (<a
 *         href="http://www.savagehomeautomation.com">http://www.savagehomeautomation.com</a>)
 */
public class GpioFactory {

    // we only allow a single controller to exists
    private static GpioController controller = null;

    // we only allow a single default provider to exists
    private static GpioProvider provider = null;

    // we only allow a single default scheduled executor service factory to exists
    private static ExecutorServiceFactory executorServiceFactory = null;
    
    // private constructor 
    private GpioFactory() {
        // forbid object construction 
    }
    
    /**
     * <p>Return default instance of {@link GpioController}.</p>
     * <p>Note: this is not thread safe singleton pattern implementation. 
     *    Implementation does not provide any synchronization or mechanisms to prevent
     *    instantiation of two instances.</p>
     * 
     * @return Return a new GpioController impl instance.
     */
    public static GpioController getInstance() {
        // if a controller has not been created, then create a new instance
        // Note: this is not thread safe singleton 
        if (controller == null) {
            controller = new GpioControllerImpl();
        }
        // else return a copy of the existing controller
        return controller;
    }
    
    /**
     * <p>Return default instance of {@link GpioProvider}.</p>
     * <p>Note: this is not thread safe singleton pattern implementation. 
     *    Implementation does not provide any synchronization or mechanisms to prevent
     *    instantiation of two instances.</p>
     * 
     * @return Return a new GpioController impl instance.
     */
    public static GpioProvider getDefaultProvider() {
        // if a provider has not been created, then create a new instance
        if (provider == null) {
            provider = new RaspiGpioProvider();
        }
        // return the provider instance
        return provider;
    }

    /**
     * Sets default {@link GpioProvider}.
     * 
     * @param provider default gpio provider
     */
    public static void setDefaultProvider(GpioProvider provider) {
        // set the default provider instance
        GpioFactory.provider = provider;
    }
    
    
    /**
     * <p>Return instance of {@link ExecutorServiceFactory}.</p>
     * <p>Note: .</p>
     * 
     * @return Return a new GpioController impl instance.
     */
    public static ExecutorServiceFactory getExecutorServiceFactory() {
        // if an executor service provider factory has not been created, then create a new default instance
        if (executorServiceFactory == null) {
            executorServiceFactory = new DefaultExecutorServiceFactory();
        }
        // return the provider instance
        return executorServiceFactory;
    }

    /**
     * Sets default {@link ExecutorServiceFactory}.
     * 
     * @param executor service factory instance
     */
    public static void setExecutorServiceFactory(ExecutorServiceFactory executorServiceFactory) {
        // set the default factory instance
        GpioFactory.executorServiceFactory = executorServiceFactory;
    }    
}