ContextManager.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.role;
import javax.annotation.Nonnull;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;
import java.util.Objects;
import java.util.ServiceLoader;
import java.util.function.Supplier;
import it.tidalwave.util.NotFoundException;
import it.tidalwave.util.Task;
import it.tidalwave.util.LazySupplier;
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
{
/*******************************************************************************************************************
*
* 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
{
private static final LazySupplier<ContextManager> CONTEXT_MANAGER_REF =
LazySupplier.of(Locator::findContextManager);
private static final LazySupplier<ContextManagerProvider> CONTEXT_MANAGER_PROVIDER_REF =
LazySupplier.of(Locator::findContextManagerProvider);
/***************************************************************************************************************
*
**************************************************************************************************************/
@Nonnull
public static ContextManager find()
{
return CONTEXT_MANAGER_REF.get();
}
/***************************************************************************************************************
*
* <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)
{
CONTEXT_MANAGER_REF.clear();
CONTEXT_MANAGER_PROVIDER_REF.set(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()
{
CONTEXT_MANAGER_REF.clear();
CONTEXT_MANAGER_PROVIDER_REF.clear();
}
/***************************************************************************************************************
*
**************************************************************************************************************/
@Nonnull
private static ContextManager findContextManager()
{
return Objects.requireNonNull(CONTEXT_MANAGER_PROVIDER_REF.get().getContextManager(),
"Cannot find ContextManager");
}
/***************************************************************************************************************
*
**************************************************************************************************************/
@Nonnull
private static ContextManagerProvider findContextManagerProvider()
{
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");
}
final ContextManagerProvider contextManagerProvider = Objects.requireNonNull(i.next(),
"contextManagerProvider is null");
assert contextManagerProvider != null; // for SpotBugs
log.info("ContextManagerProvider instantiated from META-INF: {}", contextManagerProvider);
return contextManagerProvider;
}
}
@FunctionalInterface
public static interface RunnableWithException<E extends Throwable>
{
public void run()
throws E;
}
@FunctionalInterface
public static interface SupplierWithException<T, E extends Throwable>
{
public T get()
throws E;
}
/*******************************************************************************************************************
*
* 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
* @deprecated Use {@link #runWithContexts(Runnable, Object...)} or {@link #runWithContexts(Supplier, Object...)}
*
******************************************************************************************************************/
@Deprecated
public default <V, T extends Throwable> V runWithContext (@Nonnull final Object context,
@Nonnull final Task<V, T> task)
throws T
{
return runWithContexts(Collections.singletonList(context), task);
}
/*******************************************************************************************************************
*
* 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
* @deprecated Use {@link #runWithContexts(Runnable, Object...)} or {@link #runWithContexts(Supplier, Object...)}
*
******************************************************************************************************************/
@Deprecated
public default <V, T extends Throwable> V runWithContexts (@Nonnull final List<Object> contexts,
@Nonnull final Task<V, T> task)
throws T
{
return runEWithContexts(task::run, contexts.toArray());
}
/*******************************************************************************************************************
*
* 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
* @deprecated Use {@link #runWithContexts(Runnable, Object...)} or {@link #runWithContexts(Supplier, Object...)}
*
******************************************************************************************************************/
@Deprecated
public default <V> V runWithContext (@Nonnull final Object context, @Nonnull final Supplier<V> task)
{
return runWithContexts(task, context);
}
/*******************************************************************************************************************
*
* 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 contexts
* @param task the task
* @return the value produced by the task
* @deprecated Use {@link #runWithContexts(Runnable, Object...)} or {@link #runWithContexts(Supplier, Object...)}
*
******************************************************************************************************************/
@Deprecated
public default <V> V runWithContexts (@Nonnull final List<Object> contexts, @Nonnull final Supplier<V> task)
{
return runWithContexts(task, contexts.toArray());
}
/*******************************************************************************************************************
*
* Calls a runnable with some local contexts. This method fits functional interfaces.
*
* @param runnable the runnable
* @param contexts the contexts
* @since 3.2-ALPHA-12
*
******************************************************************************************************************/
public default void runWithContexts (@Nonnull final Runnable runnable, @Nonnull final Object ... contexts)
{
final SupplierWithException<Void, RuntimeException> se = () ->{ runnable.run(); return null; };
runEWithContexts(se, contexts);
}
/*******************************************************************************************************************
*
* Calls a supplier with some local contexts. This method fits functional interfaces.
*
* @param <T> the type of the result
* @param supplier the supplier
* @param contexts the contexts
* @return the value returned by the supplier
* @since 3.2-ALPHA-12
*
******************************************************************************************************************/
@Nonnull
public default <T> T runWithContexts (@Nonnull final Supplier<T> supplier, @Nonnull final Object ... contexts)
{
final SupplierWithException<T, RuntimeException> se = supplier::get;
return runEWithContexts(se, contexts);
}
/*******************************************************************************************************************
*
* Calls a runnable with some local contexts. This method fits functional interfaces.
*
* @param <E> the type of the thrown exception
* @param runnable the runnable to call
* @param contexts the contexts
* @throws E the original exception thrown by task
* @since 3.2-ALPHA-12
*
******************************************************************************************************************/
public default <E extends Throwable> void runEWithContexts (@Nonnull final RunnableWithException<E> runnable,
@Nonnull final Object ... contexts)
throws E
{
final SupplierWithException<Void, E> se = () ->{ runnable.run(); return null; };
runEWithContexts(se, contexts);
}
/*******************************************************************************************************************
*
* Calls a task with some local contexts. This method fits functional interfaces.
*
* @param <T> the type of the returned value
* @param <E> the type of the thrown exception
* @param task the task to call
* @param contexts the contexts
* @return the value returned by the supplier
* @throws E the original exception thrown by task
* @since 3.2-ALPHA-12
*
******************************************************************************************************************/
@Nonnull
public <T, E extends Throwable> T runEWithContexts (@Nonnull SupplierWithException<T, E> task,
@Nonnull Object ... contexts)
throws E;
/*******************************************************************************************************************
*
* Creates a binder that makes it possible to bind a local context by means of a try-with-resources instead of a
* try/finally.
*
* <pre>
* try (final ContextManager.Binder binder = contextManager.binder(context))
* {
* ...
* }
* </pre>
*
* @param contexts the contexts
* @return a binder that can be used in try-with-resources
* @since 3.2-ALPHA-12
*
******************************************************************************************************************/
@Nonnull
public default Binder binder (@Nonnull final Object ... contexts)
{
return new Binder(this, contexts);
}
/*******************************************************************************************************************
*
* Used by
* @since 3.2-ALPHA-12
*
******************************************************************************************************************/
public static class Binder implements AutoCloseable
{
@Nonnull
private final ContextManager contextManager;
@Nonnull
private final Object[] contexts;
private Binder (@Nonnull final ContextManager contextManager, @Nonnull final Object[] contexts)
{
this.contextManager = contextManager;
this.contexts = contexts;
for (final Object context : contexts)
{
this.contextManager.addLocalContext(context);
}
}
@Override
public void close()
{
for (final Object context : contexts)
{
this.contextManager.removeLocalContext(context);
}
}
}
}