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ThreadContext.java
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ThreadContext.java
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/*
* Copyright (c) 2018 Contributors to the Eclipse Foundation
*
* See the NOTICE file(s) distributed with this work for additional
* information regarding copyright ownership.
*
* 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 org.eclipse.microprofile.concurrent;
import java.util.concurrent.CompletableFuture;
import java.util.concurrent.CompletionStage;
import java.util.concurrent.Callable;
import java.util.concurrent.Executor;
import java.util.function.Consumer;
import java.util.function.BiConsumer;
import java.util.function.BiFunction;
import java.util.function.Function;
import java.util.function.Supplier;
import org.eclipse.microprofile.concurrent.spi.ConcurrencyProvider;
/**
* This interface offers various methods for capturing the context of the current thread
* and applying it to various interfaces that are commonly used with completion stages
* and executor services. This allows you to contextualize specific actions that need
* access to the context of the creator/submitter of the stage/task.
*
* <p>Example usage:</p>
* <pre>
* <code>@Inject</code> ThreadContext threadContext;
* ...
* CompletableFuture<Integer> stage2 = stage1.thenApply(threadContext.contextualFunction(function));
* ...
* Future<Integer> future = executor.submit(threadContext.contextualCallable(callable));
* </pre>
*
* <p>This interface is intentionally kept compatible with ContextService,
* with the hope that its methods might one day be contributed to that specification.</p>
*/
public interface ThreadContext {
/**
* Creates a new {@link Builder} instance.
*
* @return a new {@link Builder} instance.
*/
public static Builder builder() {
return ConcurrencyProvider.instance().newThreadContextBuilder();
}
/**
* <p>Builder for {@link ThreadContext} instances.</p>
*
* <p>Example usage:</p>
* <pre><code> ThreadContext threadContext = ThreadContext.builder()
* .propagated(ThreadContext.APPLICATION, ThreadContext.SECURITY)
* .unchanged(ThreadContext.TRANSACTION)
* .build();
* ...
* </code></pre>
*/
interface Builder {
/**
* <p>Builds a new {@link ThreadContext} instance with the
* configuration that this builder represents as of the point in time when
* this method is invoked.</p>
*
* <p>After {@link #build} is invoked, the builder instance retains its
* configuration and may be further updated to represent different
* configurations and build additional <code>ThreadContext</code>
* instances.</p>
*
* <p>All created instances of {@link ThreadContext} are destroyed
* when the application is stopped. The container automatically shuts down these
* {@link ThreadContext} instances, cancels their remaining
* <code>CompletableFuture</code>s and <code>CompletionStage</code>s, and
* and raises <code>IllegalStateException</code> to reject subsequent attempts
* to apply previously captured thread context.</p>
*
* @return new instance of {@link ThreadContext}.
* @throws IllegalStateException for any of the following error conditions
* <ul>
* <li>if one or more of the same context types appear in multiple
* of the following sets:
* ({@link #cleared}, {@link #propagated}, {@link #unchanged})</li>
* <li>if a thread context type that is configured to be
* {@link #cleared} or {@link #propagated} is unavailable</li>
* <li>if more than one <code>ThreadContextProvider</code> has the
* same thread context
* {@link org.eclipse.microprofile.concurrent.spi.ThreadContextProvider#getThreadContextType type}
* </li>
* </ul>
*/
ThreadContext build();
/**
* <p>Defines the set of thread context types to clear from the thread
* where the action or task executes. The previous context is resumed
* on the thread after the action or task ends.</p>
*
* <p>This set replaces the <code>cleared</code> set that was
* previously specified on the builder instance, if any.</p>
*
* <p>The default set of cleared thread context types is
* {@link ThreadContext#TRANSACTION}, which means that a transaction
* is not active on the thread when the action or task runs, such
* that each action or task is able to independently start and end
* its own transactional work.</p>
*
* <p>Constants for specifying some of the core context types are provided
* on {@link ThreadContext}. Other thread context types must be defined
* by the specification that defines the context type or by a related
* MicroProfile specification.</p>
*
* @param types types of thread context to clear from threads that run
* actions and tasks.
* @return the same builder instance upon which this method is invoked.
*/
Builder cleared(String... types);
/**
* <p>Defines the set of thread context types to capture from the thread
* that contextualizes an action or task. This context is later
* re-established on the thread(s) where the action or task executes.</p>
*
* <p>This set replaces the <code>propagated</code> set that was
* previously specified on the builder instance, if any.</p>
*
* <p>The default set of propagated thread context types is
* {@link ThreadContext#ALL_REMAINING}, which includes all available
* thread context types that support capture and propagation to other
* threads, except for those that are explicitly {@link cleared},
* which, by default is {@link ThreadContext#TRANSACTION} context,
* in which case is suspended from the thread that runs the action or
* task.</p>
*
* <p>Constants for specifying some of the core context types are provided
* on {@link ThreadContext}. Other thread context types must be defined
* by the specification that defines the context type or by a related
* MicroProfile specification.</p>
*
* <p>Thread context types which are not otherwise included in this set or
* in the {@link #unchanged} set are cleared from the thread of execution
* for the duration of the action or task.</p>
*
* <p>A <code>ThreadContext</code> must fail to {@link #build} if the same
* context type is included in this set as well as in the {@link #unchanged}
* set.</p>
*
* @param types types of thread context to capture and propagated.
* @return the same builder instance upon which this method is invoked.
*/
Builder propagated(String... types);
/**
* <p>Defines a set of thread context types that are essentially ignored,
* in that they are neither captured nor are they propagated or cleared
* from thread(s) that execute the action or task.</p>
*
* <p>This set replaces the <code>unchanged</code> set that was previously
* specified on the builder instance.</p>
*
* <p>Constants for specifying some of the core context types are provided
* on {@link ThreadContext}. Other thread context types must be defined
* by the specification that defines the context type or by a related
* MicroProfile specification.</p>
*
* <p>The configuration of <code>unchanged</code> context is provided for
* advanced patterns where it is desirable to leave certain context types
* on the executing thread.</p>
*
* <p>For example, to run under the transaction of the thread of execution,
* with security context cleared and all other thread contexts propagated:</p>
* <pre><code> ThreadContext threadContext = ThreadContext.builder()
* .unchanged(ThreadContext.TRANSACTION)
* .cleared(ThreadContext.SECURITY)
* .propagated(ThreadContext.ALL_REMAINING)
* .build();
* ...
* task = threadContext.contextualRunnable(new MyTransactionlTask());
* ...
* // on another thread,
* tx.begin();
* ...
* task.run(); // runs under the transaction due to 'unchanged'
* tx.commit();
* </code></pre>
*
* <p>A {@link ThreadContext} must fail to {@link #build} if the same
* context type is included in this set as well as in the set specified by
* {@link #propagated}.</p>
*
* @param types types of thread context to leave unchanged on the thread.
* @return the same builder instance upon which this method is invoked.
*/
Builder unchanged(String... types);
}
/**
* <p>Identifier for all available thread context types which are
* not specified individually under <code>cleared</code>,
* <code>propagated</code>, or <code>unchanged</code>.</p>
*
* <p>When using this constant, be aware that bringing in a new
* context provider or updating levels of an existing context provider
* might change the set of available thread context types.</p>
*
* @see ManagedExecutor.Builder#cleared
* @see ManagedExecutor.Builder#propagated
* @see ManagedExecutorConfig#cleared
* @see ManagedExecutorConfig#propagated
* @see ThreadContext.Builder
* @see ThreadContextConfig
*/
static final String ALL_REMAINING = "Remaining";
/**
* Identifier for application context. Application context controls the
* application component that is associated with a thread. It can determine
* the thread context class loader as well as the set of resource references
* that are available for lookup or resource injection. An empty/default
* application context means that the thread is not associated with any
* application.
*
* @see ManagedExecutor.Builder#cleared
* @see ManagedExecutor.Builder#propagated
* @see ManagedExecutorConfig#cleared
* @see ManagedExecutorConfig#propagated
* @see ThreadContext.Builder
* @see ThreadContextConfig
*/
static final String APPLICATION = "Application";
/**
* Identifier for CDI context. CDI context controls the availability of CDI
* scopes. An empty/default CDI context means that the thread does not have
* access to the scope of the session, request, and so forth that created the
* contextualized action.
*
* @see ManagedExecutor.Builder#cleared
* @see ManagedExecutor.Builder#propagated
* @see ManagedExecutorConfig#cleared
* @see ManagedExecutorConfig#propagated
* @see ThreadContext.Builder
* @see ThreadContextConfig
*/
static final String CDI = "CDI";
/**
* Identifier for security context. Security context controls the credentials
* that are associated with the thread. An empty/default security context
* means that the thread is unauthenticated.
*
* @see ManagedExecutor.Builder#cleared
* @see ManagedExecutor.Builder#propagated
* @see ManagedExecutorConfig#cleared
* @see ManagedExecutorConfig#propagated
* @see ThreadContext.Builder
* @see ThreadContextConfig
*/
static final String SECURITY = "Security";
/**
* Identifier for transaction context. Transaction context controls the
* active transaction scope that is associated with the thread.
* Implementations are not expected to propagate transaction context across
* threads. Instead, the concept of transaction context is provided for its
* cleared context, which means the active transaction on the thread
* is suspended such that a new transaction can be started if so desired.
* In most cases, the most desirable behavior will be to leave transaction
* context defaulted to cleared (suspended),
* in order to prevent dependent actions and tasks from accidentally
* enlisting in transactions that are on the threads where they happen to
* run.
*
* @see ManagedExecutor.Builder#cleared
* @see ManagedExecutor.Builder#propagated
* @see ManagedExecutorConfig#cleared
* @see ManagedExecutorConfig#propagated
* @see ThreadContext.Builder
* @see ThreadContextConfig
*/
static final String TRANSACTION = "Transaction";
/**
* <p>Creates an <code>Executor</code>that runs tasks on the same thread from which
* <code>execute</code>is invoked but with context that is captured from the thread
* that invokes <code>currentContextExecutor</code>.</p>
*
* <p>Example usage:</p>
* <pre>
* <code>Executor contextSnapshot = threadContext.currentContextExecutor();
* ...
* // from another thread, or after thread context has changed,
* contextSnapshot.execute(() -> obj.doSomethingThatNeedsContext());
* contextSnapshot.execute(() -> doSomethingElseThatNeedsContext(x, y));
* </code></pre>
*
* @return an executor that wraps the <code>execute</code> method with context.
*/
Executor currentContextExecutor();
/**
* <p>Wraps a <code>Callable</code> with context that is captured from the thread that invokes
* <code>contextualCallable</code>.</p>
*
* <p>When <code>call</code> is invoked on the proxy instance,
* context is first established on the thread that will run the <code>call</code> method,
* then the <code>call</code> method of the provided <code>Callable</code> is invoked.
* Finally, the previous context is restored on the thread, and the result of the
* <code>Callable</code> is returned to the invoker.</p>
*
* @param <R> callable result type.
* @param callable instance to contextualize.
* @return contextualized proxy instance that wraps execution of the <code>call</code> method with context.
*/
<R> Callable<R> contextualCallable(Callable<R> callable);
/**
* <p>Wraps a <code>BiConsumer</code> with context that is captured from the thread that invokes
* <code>contextualConsumer</code>.</p>
*
* <p>When <code>accept</code> is invoked on the proxy instance,
* context is first established on the thread that will run the <code>accept</code> method,
* then the <code>accept</code> method of the provided <code>BiConsumer</code> is invoked.
* Finally, the previous context is restored on the thread, and control is returned to the invoker.</p>
*
* @param <T> type of first parameter to consumer.
* @param <U> type of second parameter to consumer.
* @param consumer instance to contextualize.
* @return contextualized proxy instance that wraps execution of the <code>accept</code> method with context.
*/
<T, U> BiConsumer<T, U> contextualConsumer(BiConsumer<T, U> consumer);
/**
* <p>Wraps a <code>Consumer</code> with context that is captured from the thread that invokes
* <code>contextualConsumer</code>.</p>
*
* <p>When <code>accept</code> is invoked on the proxy instance,
* context is first established on the thread that will run the <code>accept</code> method,
* then the <code>accept</code> method of the provided <code>Consumer</code> is invoked.
* Finally, the previous context is restored on the thread, and control is returned to the invoker.</p>
*
* @param <T> type of parameter to consumer.
* @param consumer instance to contextualize.
* @return contextualized proxy instance that wraps execution of the <code>accept</code> method with context.
*/
<T> Consumer<T> contextualConsumer(Consumer<T> consumer);
/**
* <p>Wraps a <code>BiFunction</code> with context that is captured from the thread that invokes
* <code>contextualFunction</code>.</p>
*
* <p>When <code>apply</code> is invoked on the proxy instance,
* context is first established on the thread that will run the <code>apply</code> method,
* then the <code>apply</code> method of the provided <code>BiFunction</code> is invoked.
* Finally, the previous context is restored on the thread, and the result of the
* <code>BiFunction</code> is returned to the invoker.</p>
*
* @param <T> type of first parameter to function.
* @param <U> type of second parameter to function.
* @param <R> function result type.
* @param function instance to contextualize.
* @return contextualized proxy instance that wraps execution of the <code>apply</code> method with context.
*/
<T, U, R> BiFunction<T, U, R> contextualFunction(BiFunction<T, U, R> function);
/**
* <p>Wraps a <code>Function</code> with context that is captured from the thread that invokes
* <code>contextualFunction</code>.</p>
*
* <p>When <code>apply</code> is invoked on the proxy instance,
* context is first established on the thread that will run the <code>apply</code> method,
* then the <code>apply</code> method of the provided <code>Function</code> is invoked.
* Finally, the previous context is restored on the thread, and the result of the
* <code>Function</code> is returned to the invoker.</p>
*
* @param <T> type of parameter to function.
* @param <R> function result type.
* @param function instance to contextualize.
* @return contextualized proxy instance that wraps execution of the <code>apply</code> method with context.
*/
<T, R> Function<T, R> contextualFunction(Function<T, R> function);
/**
* <p>Wraps a <code>Runnable</code> with context that is captured from the thread that invokes
* <code>ContextualRunnable</code>.</p>
*
* <p>When <code>run</code> is invoked on the proxy instance,
* context is first established on the thread that will run the <code>run</code> method,
* then the <code>run</code> method of the provided <code>Runnable</code> is invoked.
* Finally, the previous context is restored on the thread, and control is returned to the invoker.</p>
*
* @param runnable instance to contextualize.
* @return contextualized proxy instance that wraps execution of the <code>run</code> method with context.
*/
Runnable contextualRunnable(Runnable runnable);
/**
* <p>Wraps a <code>Supplier</code> with context captured from the thread that invokes
* <code>contextualSupplier</code>.</p>
*
* <p>When <code>supply</code> is invoked on the proxy instance,
* context is first established on the thread that will run the <code>supply</code> method,
* then the <code>supply</code> method of the provided <code>Supplier</code> is invoked.
* Finally, the previous context is restored on the thread, and the result of the
* <code>Supplier</code> is returned to the invoker.</p>
*
* @param <R> supplier result type.
* @param supplier instance to contextualize.
* @return contextualized proxy instance that wraps execution of the <code>supply</code> method with context.
*/
<R> Supplier<R> contextualSupplier(Supplier<R> supplier);
/**
* <p>Returns a new <code>CompletableFuture</code> that is completed by the completion of the
* specified stage.</p>
*
* <p>The container supplies the default asynchronous execution facility for the new completable
* future that is returned by this method and all dependent stages that are created from it,
* and all dependent stages that are created from those, and so forth.</p>
*
* <p>When dependent stages are created from the new completable future, thread context is captured
* from the thread that creates the dependent stage and is applied to the thread that runs the
* action, being removed afterward. When dependent stages are created from these dependent stages,
* and likewise from any dependent stages created from those, and so on, thread context is captured
* from the respective thread that creates each dependent stage. This guarantees that the action
* performed by each stage always runs under the thread context of the code that creates the stage.
* </p>
*
* <p>Invocation of this method does not impact thread context propagation for the supplied
* completable future or any dependent stages created from it, other than the new dependent
* completable future that is created by this method.</p>
*
* @param stage a completable future whose completion triggers completion of the new completable
* future that is created by this method.
* @return the new completable future.
*/
<T> CompletableFuture<T> withContextCapture(CompletableFuture<T> stage);
/**
* <p>Returns a new <code>CompletionStage</code> that is completed by the completion of the
* specified stage.</p>
*
* <p>The container supplies the default asynchronous execution facility for the new completion
* stage that is returned by this method and all dependent stages that are created from it,
* and all dependent stages that are created from those, and so forth.</p>
*
* <p>When dependent stages are created from the new completion stage, thread context is captured
* from the thread that creates the dependent stage and is applied to the thread that runs the
* action, being removed afterward. When dependent stages are created from these dependent stages,
* and likewise from any dependent stages created from those, and so on, thread context is captured
* from the respective thread that creates each dependent stage. This guarantees that the action
* performed by each stage always runs under the thread context of the code that creates the stage.
* </p>
*
* <p>Invocation of this method does not impact thread context propagation for the supplied
* stage or any dependent stages created from it, other than the new dependent
* completion stage that is created by this method.</p>
*
* @param stage a completion stage whose completion triggers completion of the new stage
* that is created by this method.
* @return the new completion stage.
*/
<T> CompletionStage<T> withContextCapture(CompletionStage<T> stage);
}