Module jakarta.concurrency

Package jakarta.enterprise.concurrent.spi

Interface ThreadContextProvider

public interface ThreadContextProvider

Third party providers of thread context implement this interface to participate in thread context capture and propagation.

Application code must never access the classes within this spi package. Instead, application code uses the various interfaces that are defined by the Jakarta Concurrency specification, such as ManagedExecutorService and ContextService.

The ThreadContextProvider implementation and related classes are packaged within the third party provider's JAR file. The implementation is made discoverable via the ServiceLoader mechanism. The JAR file that packages it must include a file with the following name and location,

META-INF/services/jakarta.enterprise.concurrent.spi.ThreadContextProvider

The content of the aforementioned file must be one or more lines, each specifying the fully qualified name of a ThreadContextProvider implementation that is provided within the JAR file.

The Jakarta EE Product Provider must use the ServiceLoader to identify all available implementations of ThreadContextProvider that can participate in thread context capture and propagation and must invoke them either to capture current thread context or establish default thread context per the configuration of the ContextServiceDefinition, or vendor-specific configuration, and execution properties such as ManagedTask.TRANSACTION that override context propagation configuration.

Since:

3.0

Method Summary

Modifier and Type	Method	Description
ThreadContextSnapshot	clearedContext(Map<String,String> props)	Returns empty/cleared context of the provided type.
ThreadContextSnapshot	currentContext(Map<String,String> props)	Captures from the current thread a snapshot of the provided thread context type.
String	getThreadContextType()	Returns a human readable identifier for the type of thread context that is captured by this ThreadContextProvider implementation.

Method Details

currentContext

ThreadContextSnapshot currentContext(Map<String,String> props)

Captures from the current thread a snapshot of the provided thread context type.

Parameters:

props - execution properties, which are optionally provided by some types of tasks and contextual proxies. Thread context providers that do not supply or use execution properties can ignore this parameter.

Returns:

immutable snapshot of the provided type of context, captured from the current thread.

clearedContext

ThreadContextSnapshot clearedContext(Map<String,String> props)

Returns empty/cleared context of the provided type. This context is not captured from the current thread, but instead represents the behavior that you get for this context type when no particular context has been applied to the thread.

This is used in cases where the provided type of thread context should not be propagated from the requesting thread or inherited from the thread of execution, in which case it is necessary to establish an empty/cleared context in its place, so that an action does not unintentionally inherit context of the thread that happens to run it.

For example, a security context provider's empty/cleared context ensures there is no authenticated user on the thread. A transaction context provider's empty/cleared context ensures that any active transaction is suspended. And so forth.

Parameters:

props - execution properties, which are optionally provided by some types of tasks and contextual proxies. Thread context providers that do not supply or use execution properties can ignore this parameter.

Returns:

immutable empty/default context of the provided type.

getThreadContextType

String getThreadContextType()

Returns a human readable identifier for the type of thread context that is captured by this ThreadContextProvider implementation.

To ensure portability of applications, this is typically be a keyword that is defined by the same specification that defines the thread context type.

ContextServiceDefinition defines identifiers for built-in thread context types, including Application, Security, and Transaction, as well as the Remaining identifer which covers all remaining context. These identifiers must not be returned from this method.

Applications use a combination of built-in identifiers and those that are defined by other specifications and third-party context types when configuring a ContextServiceDefinition to capture and propagate only specific types of thread context.

For example:

 @ContextServiceDefinition(
    name = "java:module/concurrent/MyCustomContext",
    propagated = MyCustomContextProvider.CONTEXT_NAME,
    cleared = { ContextServiceDefinition.SECURITY, ContextServiceDefinition.TRANSACTION },
    unchanged = ContextServiceDefinition.ALL_REMAINING)
 

It is an error for multiple thread context providers of an identical type to be simultaneously available.

Returns:

identifier for the provided type of thread context.