net.yetamine.osgi.jdbc.support.DriverProviderChain Maven / Gradle / Ivy
/*
* Copyright 2016 Yetamine
*
* 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 net.yetamine.osgi.jdbc.support;
import java.sql.Driver;
import java.sql.DriverManager;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.Iterator;
import java.util.List;
import java.util.Objects;
import java.util.stream.Stream;
import net.yetamine.osgi.jdbc.DriverProvider;
import net.yetamine.osgi.jdbc.DriverSequence;
/**
* An driver provider encapsulating a chain of driver providers in the order of
* their preference.
*
*
* This class may be particularly useful for combining an implementation with
* the fallback to the {@link DriverManager} using {@link DriverManagerAdapter}.
* In such cases, it is enough to chain the implementation and the adapter with
* this class.
*/
public final class DriverProviderChain implements DriverProvider {
/** Actual chaining driver sequence. */
private final DriverSequence sequence;
/**
* Creates a new instance.
*
* @param driverProviders
* the driver providers to use. It must not be {@code null} and
* it must not contain {@code null} elements.
*/
private DriverProviderChain(Collection driverProviders) {
sequence = new Sequence(driverProviders);
}
/**
* Creates a new instance.
*
* @param driverProviders
* the driver providers to use. It must not be {@code null} and
* it must not contain {@code null} elements.
*
* @return the new instance
*/
public static DriverProvider of(DriverProvider... driverProviders) {
final List providers = Arrays.asList(driverProviders);
providers.forEach(Objects::requireNonNull);
return new DriverProviderChain(providers);
}
/**
* Creates a new instance.
*
* @param driverProviders
* the driver providers to use. It must not be {@code null} and
* it must not contain {@code null} elements.
*
* @return the new instance
*/
public static DriverProvider from(Collection driverProviders) {
final Collection providers = new ArrayList<>(driverProviders);
providers.forEach(Objects::requireNonNull);
return new DriverProviderChain(providers);
}
/**
* @see net.yetamine.osgi.jdbc.DriverProvider#drivers()
*/
public DriverSequence drivers() {
return sequence;
}
/**
* Implements the chaining sequence.
*/
private static final class Sequence implements DriverSequence {
/** Collection of the providers in their preferred order. */
private final Collection providers;
/**
* Creates a new instance.
*
* @param driverProviders
* the collection of the driver providers to use. It must not
* be {@code null}.
*/
public Sequence(Collection driverProviders) {
providers = Objects.requireNonNull(driverProviders);
}
/**
* @see net.yetamine.osgi.jdbc.DriverSequence#iterator()
*/
public Iterator iterator() {
return stream().iterator();
}
/**
* @see net.yetamine.osgi.jdbc.DriverSequence#stream()
*/
public Stream stream() {
return providers.stream().flatMap(provider -> provider.drivers().stream());
}
}
}