com.hedera.node.app.spi.ServiceFactory Maven / Gradle / Ivy
/*
* Copyright (C) 2022-2024 Hedera Hashgraph, LLC
*
* 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.hedera.node.app.spi;
import edu.umd.cs.findbugs.annotations.NonNull;
import java.util.Iterator;
import java.util.Objects;
import java.util.ServiceLoader;
/**
* This class provides the ability to load {@link Service} implementations at runtime. The Java SPI
* (see {@link ServiceLoader}) is used to provide such information at runtime. Since we use the Java
* module system the {@link ServiceLoader} instance can not be created in the factory. It must be
* created in the module that add "uses" information for the module to the {@code module-info.java}.
*/
public final class ServiceFactory {
private ServiceFactory() {}
/**
* This method returns a service instance of the given service that is provided by the Java SPI.
*
* @param type the service type
* @param serviceLoader the service loaded that will be used
* @param the service type
* @return the service instance
* @throws IllegalStateException if no or multiple services are found
*/
@NonNull
public static S loadService(
@NonNull final Class type, @NonNull final ServiceLoader serviceLoader) {
Objects.requireNonNull(type, "type must not be null");
Objects.requireNonNull(serviceLoader, "serviceLoader must not be null");
final Iterator iterator = serviceLoader.iterator();
if (!iterator.hasNext()) {
throw new IllegalStateException("No service implementation found for service type '" + type + "'");
}
final S serviceInstance = iterator.next();
if (iterator.hasNext()) {
throw new IllegalStateException("Multiple service implementations found for service type '" + type + "'");
}
return serviceInstance;
}
}