DriverFinder.java

/*-
 *
 *  * Copyright 2015 Skymind,Inc.
 *  *
 *  *    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 org.nd4j.jdbc.driverfinder;

import org.reflections.Reflections;

import java.io.IOException;
import java.io.InputStream;
import java.lang.reflect.Modifier;
import java.sql.Driver;
import java.util.HashSet;
import java.util.Properties;
import java.util.Set;

/**
 * JDBC Driver finder
 *
 * @author Adam Gibson
 */
public class DriverFinder {

    public final static String ND4j_JDBC_PROPERTIES = "nd4j.jdbc.properties";
    public final static String JDBC_KEY = "jdbc.driver";
    private static Class<? extends Driver> clazz;
    private static Driver driver;

    public static Driver getDriver() {
        if (driver == null) {
            if (clazz == null)
                discoverDriverClazz();
            try {
                driver = clazz.newInstance();
            } catch (InstantiationException e) {
                e.printStackTrace();
            } catch (IllegalAccessException e) {
                e.printStackTrace();
            }
        }
        return driver;
    }


    private static void discoverDriverClazz() {
        Reflections r = new Reflections();
        Set<Class<? extends Driver>> clazzes = new HashSet<>(r.getSubTypesOf(Driver.class));
        if (clazzes.isEmpty()) {
            throw new IllegalStateException("No org.nd4j.jdbc drivers found.");
        } else if (clazzes.size() != 1) {
            Set<Class<? extends Driver>> remove = new HashSet<>();
            for (Class<? extends Driver> clazz : clazzes) {
                if (Modifier.isAbstract(clazz.getModifiers())) {
                    remove.add(clazz);
                } else if (Modifier.isInterface(clazz.getModifiers())) {
                    remove.add(clazz);
                }
            }

            clazzes.removeAll(remove);
            if (clazzes.size() != 1) {
                InputStream i = DriverFinder.class.getResourceAsStream("/" + ND4j_JDBC_PROPERTIES);
                if (i == null)
                    throw new IllegalStateException("Only one jdbc driver allowed on the class path");
                else {
                    Properties props = new Properties();
                    try {
                        props.load(i);
                    } catch (IOException e) {
                        throw new RuntimeException(e);
                    }

                    String clazz = props.getProperty(JDBC_KEY);
                    if (clazz == null)
                        throw new IllegalStateException("Unable to find jdbc driver. Please specify a "
                                        + ND4j_JDBC_PROPERTIES + " with the key " + JDBC_KEY);
                    try {
                        DriverFinder.clazz = (Class<? extends Driver>) Class.forName(clazz);
                    } catch (ClassNotFoundException e) {
                        throw new IllegalStateException("Unable to find jdbc driver. Please specify a "
                                        + ND4j_JDBC_PROPERTIES + " with the key " + JDBC_KEY);

                    }

                }

            }
        }
    }


}