ServiceLoaderLocator.java
- /*
- * *************************************************************************************************************************************************************
- *
- * TheseFoolishThings: Miscellaneous utilities
- * http://tidalwave.it/projects/thesefoolishthings
- *
- * Copyright (C) 2009 - 2025 by Tidalwave s.a.s. (http://tidalwave.it)
- *
- * *************************************************************************************************************************************************************
- *
- * 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.
- *
- * *************************************************************************************************************************************************************
- *
- * git clone https://bitbucket.org/tidalwave/thesefoolishthings-src
- * git clone https://github.com/tidalwave-it/thesefoolishthings-src
- *
- * *************************************************************************************************************************************************************
- */
- package it.tidalwave.util.impl;
- import jakarta.annotation.Nonnull;
- import java.util.ServiceLoader;
- import java.util.Spliterators;
- import java.util.stream.StreamSupport;
- import org.slf4j.Logger;
- import org.slf4j.LoggerFactory;
- import it.tidalwave.util.LazySupplier;
- import it.tidalwave.util.PreferencesHandler;
- import it.tidalwave.role.spi.annotation.DefaultProvider;
- import lombok.AccessLevel;
- import lombok.NoArgsConstructor;
- import static java.util.stream.Collectors.*;
- /***************************************************************************************************************************************************************
- *
- * @author Fabrizio Giudici
- *
- **************************************************************************************************************************************************************/
- @NoArgsConstructor(access = AccessLevel.PRIVATE)
- // PreferencesHandler can be used to programmatically set the log folder, so don't inject logger
- public class ServiceLoaderLocator
- {
- public static final String PROPS_BASE_NAME = PreferencesHandler.class.getPackage().getName();
- /** Suppress any console output. @since 3.2-ALPHA-21 */
- public static final String PROP_SUPPRESS_CONSOLE = PROPS_BASE_NAME + ".suppressConsoleOutput";
- /***********************************************************************************************************************************************************
- *
- **********************************************************************************************************************************************************/
- @Nonnull
- public static <T> T findService (@Nonnull final Class<? extends T> serviceClass)
- {
- final var serviceClassName = serviceClass.getSimpleName();
- final var classLoader = Thread.currentThread().getContextClassLoader();
- final var iterator = ServiceLoader.load(serviceClass, classLoader).iterator();
- final var spliterator = Spliterators.spliteratorUnknownSize(iterator, 0);
- var providers = StreamSupport.stream(spliterator, false).collect(toList());
- if (providers.isEmpty())
- {
- throw new RuntimeException("No ServiceProvider for " + serviceClassName);
- }
- if (providers.size() > 1) // filter out the default one
- {
- getLogger().info("Too many instances of {}, using @DefaultProvider ...", serviceClassName);
- providers = providers.stream()
- .filter(p -> p.getClass().getAnnotation(DefaultProvider.class) == null)
- .collect(toList());
- }
- if (providers.size() > 1)
- {
- throw new RuntimeException("Too many instances of " + serviceClassName + " : " + providers);
- }
- final var provider = providers.get(0);
-
- // PreferencesHandler can be used to programmatically set the log folder, so don't log yet
- if (!serviceClass.equals(PreferencesHandler.class))
- {
- getLogger().info("{} instantiated from META-INF/services: {}", serviceClassName, provider);
- }
- else if (!Boolean.getBoolean(PROP_SUPPRESS_CONSOLE))
- {
- System.out.printf("%s instantiated from META-INF/services: %s%n", serviceClassName, provider);
- }
- return provider;
- }
- @Nonnull
- public static <T> LazySupplier<T> lazySupplierOf (@Nonnull final Class<? extends T> clazz)
- {
- return LazySupplier.of(() -> findService(clazz));
- }
- @Nonnull
- private static Logger getLogger()
- {
- return LoggerFactory.getLogger(ServiceLoaderLocator.class);
- }
- }