AsDelegateProvider.java
- /*
- * *********************************************************************************************************************
- *
- * TheseFoolishThings: Miscellaneous utilities
- * http://tidalwave.it/projects/thesefoolishthings
- *
- * Copyright (C) 2009 - 2023 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.spi;
- import javax.annotation.Nonnull;
- import java.util.ArrayList;
- import java.util.Collection;
- import java.util.Iterator;
- import java.util.ServiceLoader;
- import it.tidalwave.util.LazySupplier;
- import lombok.AccessLevel;
- import lombok.NoArgsConstructor;
- /***********************************************************************************************************************
- *
- * @author Fabrizio Giudici
- *
- **********************************************************************************************************************/
- public interface AsDelegateProvider
- {
- public static final LazySupplier<EmptyAsDelegateProvider> EMPTY_REF =
- LazySupplier.of(EmptyAsDelegateProvider::new);
- @NoArgsConstructor(access = AccessLevel.PRIVATE)
- public static final class Locator
- {
- private static final LazySupplier<AsDelegateProvider> AS_DELEGATE_PROVIDER_REF =
- LazySupplier.of(Locator::findAsSpiProvider);
- @Nonnull
- public static AsDelegateProvider find()
- {
- return AS_DELEGATE_PROVIDER_REF.get();
- }
- @Nonnull
- private static AsDelegateProvider findAsSpiProvider()
- {
- final ClassLoader classLoader = Thread.currentThread().getContextClassLoader();
- final Iterator<AsDelegateProvider> i =
- ServiceLoader.load(AsDelegateProvider.class, classLoader).iterator();
- if (!i.hasNext())
- {
- final String message = "No ServiceProvider for AsDelegateProvider found in a ServiceLoader - if " +
- "you are running tests perhaps you should first call " +
- "AsDelegateProvider.Locator.set(AsDelegateProvider.empty()) or " +
- "AsDelegateProvider.Locator.set(new MockSimpleAsDelegateProvider()) or " +
- "another appropriate AsDelegateProvider";
- throw new RuntimeException(message);
- }
- return i.next();
- }
- /***************************************************************************************************************
- *
- * <b>This method is for testing only.</b> Sets the global {@link AsDelegateProvider}.
- *
- * @param provider the provider
- * @see #reset()
- *
- **************************************************************************************************************/
- public static void set (@Nonnull final AsDelegateProvider provider)
- {
- AS_DELEGATE_PROVIDER_REF.set(provider);
- }
- /***************************************************************************************************************
- *
- * <b>This method is for testing only.</b> Resets the global {@link AsDelegateProvider}; it must be called at
- * the test completion whenever {@link #set(AsDelegateProvider)} has been called, to avoid polluting the
- * context of further tests.
- *
- * @see #set(AsDelegateProvider)
- *
- **************************************************************************************************************/
- public static void reset()
- {
- AS_DELEGATE_PROVIDER_REF.clear();
- }
- }
- /*******************************************************************************************************************
- *
- * Creates an {@link AsDelegate} for the given object
- *
- * @param datum the object
- * @return {@code AsDelegate}
- *
- ******************************************************************************************************************/
- @Nonnull
- public AsDelegate createAsDelegate (@Nonnull Object datum);
- /*******************************************************************************************************************
- *
- * Returns an empty implementation. Useful for setting up test environment.
- *
- * <pre>
- * AsDelegateProvider.Locator.set(AsDelegateProvider.empty());
- * </pre>
- *
- * @return the empty implementation
- * @since 3.2-ALPHA-1
- *
- ******************************************************************************************************************/
- @Nonnull
- public static AsDelegateProvider empty()
- {
- return EMPTY_REF.get();
- }
- /*******************************************************************************************************************
- *
- ******************************************************************************************************************/
- static class EmptyAsDelegateProvider implements AsDelegateProvider
- {
- @Override @Nonnull
- public AsDelegate createAsDelegate (@Nonnull final Object owner)
- {
- return new AsDelegate()
- {
- @Override @Nonnull
- public <T> Collection<T> as (@Nonnull final Class<T> type)
- {
- return new ArrayList<>(); // must be mutable
- }
- };
- }
- }
- }