ContextManager.java
- /*
- * *********************************************************************************************************************
- *
- * TheseFoolishThings: Miscellaneous utilities
- * http://tidalwave.it/projects/thesefoolishthings
- *
- * Copyright (C) 2009 - 2021 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.role;
- import javax.annotation.CheckForNull;
- import javax.annotation.Nonnull;
- import java.util.Iterator;
- import java.util.List;
- import java.util.Objects;
- import java.util.ServiceLoader;
- import it.tidalwave.util.NotFoundException;
- import it.tidalwave.util.Task;
- import it.tidalwave.role.spi.ContextManagerProvider;
- import lombok.AccessLevel;
- import lombok.NoArgsConstructor;
- import lombok.extern.slf4j.Slf4j;
- /***********************************************************************************************************************
- *
- * A facility to register and unregister global and local DCI contexts.
- *
- * @author Fabrizio Giudici
- *
- **********************************************************************************************************************/
- public interface ContextManager
- {
- // We must compile with Java 7
- public static interface Supplier<V>
- {
- public V get();
- }
- /*******************************************************************************************************************
- *
- * A locator for the {@link ContextManager} which uses the {@link ServiceLoader} facility to be independent of
- * any DI framework.
- *
- * This locator caches the internal reference and this is ok for production use; during tests, since multiple
- * contexts are typically created and destroyed for each test, you should call {@link #reset()} after each test
- * has been completed.
- *
- ******************************************************************************************************************/
- @Slf4j @NoArgsConstructor(access = AccessLevel.PRIVATE)
- public static final class Locator
- {
- @CheckForNull
- private static ContextManager contextManager;
- @CheckForNull
- private static ContextManagerProvider contextManagerProvider;
- @Nonnull
- public static synchronized ContextManager find ()
- {
- if (contextManager == null)
- {
- if (contextManagerProvider == null)
- {
- final ClassLoader classLoader = Thread.currentThread().getContextClassLoader();
- final Iterator<ContextManagerProvider> i =
- ServiceLoader.load(ContextManagerProvider.class, classLoader).iterator();
- if (!i.hasNext())
- {
- throw new RuntimeException("No ServiceProvider for ContextManagerProvider");
- }
- contextManagerProvider = Objects.requireNonNull(i.next());
- assert contextManagerProvider != null : "contextManagerProvider is null";
- log.trace("ContextManagerProvider instantiated from META-INF: {}", contextManagerProvider);
- }
- contextManager = Objects.requireNonNull(contextManagerProvider.getContextManager(),
- "Cannot find ContextManager");
- }
- assert contextManager != null : "contextManager is null";
- return contextManager;
- }
- /***************************************************************************************************************
- *
- * <b>This method is for testing only.</b> Sets the global {@link ContextManagerProvider}. See note about
- * {@link #reset()}.
- *
- * @param provider the provider
- * @see #reset()
- *
- **************************************************************************************************************/
- public static void set (@Nonnull final ContextManagerProvider provider)
- {
- contextManager = null;
- contextManagerProvider = provider;
- }
- /***************************************************************************************************************
- *
- * <b>This method is for testing only.</b> Resets the global {@link ContextManagerProvider}; it must be called
- * at the test completion whenever {@link #set(ContextManagerProvider)} has been called, to avoid polluting the
- * context of further tests.
- *
- * @see #set(ContextManagerProvider)
- *
- **************************************************************************************************************/
- public static void reset()
- {
- contextManager = null;
- contextManagerProvider = null;
- }
- }
- /*******************************************************************************************************************
- *
- * Returns the list of current contexts, ordered by their priority.
- *
- * @return the list of current contexts
- *
- ******************************************************************************************************************/
- @Nonnull
- public List<Object> getContexts();
- /*******************************************************************************************************************
- *
- * Finds a current context instance of the given type.
- *
- * @param <T> the static context type
- * @param contextType the dynamic context type
- * @return the requested context
- * @throws NotFoundException if no context of that type is found
- *
- ******************************************************************************************************************/
- @Nonnull
- public <T> T findContextOfType (@Nonnull Class<T> contextType)
- throws NotFoundException;
- /*******************************************************************************************************************
- *
- * Adds a global context.
- *
- * @param context the new context
- *
- ******************************************************************************************************************/
- public void addGlobalContext (@Nonnull Object context);
- /*******************************************************************************************************************
- *
- * Removes a global context.
- *
- * @param context the context
- *
- ******************************************************************************************************************/
- public void removeGlobalContext (@Nonnull Object context);
- /*******************************************************************************************************************
- *
- * Adds a local context.
- *
- * @param context the new context
- *
- ******************************************************************************************************************/
- public void addLocalContext (@Nonnull Object context);
- /*******************************************************************************************************************
- *
- * Removes a local context.
- *
- * @param context the context
- *
- ******************************************************************************************************************/
- public void removeLocalContext (@Nonnull Object context);
- /*******************************************************************************************************************
- *
- * Runs a {@link Task} associated with a new local context.
- *
- * @param <V> the type of the returned value
- * @param <T> the type of the exception that can be thrown
- * @param context the context
- * @param task the task
- * @return the value produced by the task
- * @throws T the exception(s) thrown by the task
- *
- ******************************************************************************************************************/
- public <V, T extends Throwable> V runWithContext (@Nonnull Object context, @Nonnull Task<V, T> task)
- throws T;
- /*******************************************************************************************************************
- *
- * Runs a {@link Task} associated with a new bunch of local contexts.
- *
- * @param <V> the type of the returned value
- * @param <T> the type of the exception that can be thrown
- * @param contexts the contexts
- * @param task the task
- * @return the value produced by the task
- * @throws T the exception(s) thrown by the task
- *
- ******************************************************************************************************************/
- public <V, T extends Throwable> V runWithContexts (@Nonnull List<Object> contexts, @Nonnull Task<V, T> task)
- throws T;
- /*******************************************************************************************************************
- *
- * Runs a task associated with a new local context. This variant fits functional interfaces.
- *
- * @param <V> the type of the returned value of the task
- * @param context the context
- * @param task the task
- * @return the value produced by the task
- *
- ******************************************************************************************************************/
- public <V> V runWithContext (@Nonnull Object context, @Nonnull Supplier<V> task);
- /*******************************************************************************************************************
- *
- * Runs a task associated with a new bunch of local contexts. This variant fits functional interfaces.
- *
- * @param <V> the type of the returned value
- * @param contexts the context
- * @param task the task
- * @return the value produced by the task
- *
- ******************************************************************************************************************/
- public <V> V runWithContexts (@Nonnull List<Object> contexts, @Nonnull Supplier<V> task);
- }