com.holonplatform.core

Interface Context

All Known Implementing Classes:

DefaultContext

public interface Context

Main interface to access global platform context resources.

A context resource is an object instance identified by a String key.

Resources are organized in ContextScopes, each of them characterized by a resource data source and a resource retrieval strategy. A scope can be manageable, i.e. supporting resource addition and removal, or not.

Context scope can be registered either by using standard Java extension service loading using ContextScope class name files under META-INF/services, or by direct registration using ContextManager.registerScope(ClassLoader, ContextScope).

When asking for a context resource using resource(String, Class) and similar methods, all registered context scopes are invoked, in the order defined by ContextScope.getOrder() precedence value. The first not null resource instance obtained from a scope is the one returned to caller, if any.

Every Context resource set is bound to a ClassLoader. If not specified, the default classloader is obtained from ClassUtils.getDefaultClassLoader().

Two default context scope are registered by default:

• A ClassLoader bound scope named CLASSLOADER_SCOPE_NAME, registering and providing resources as singleton instances for the reference ClassLoader. This scope is registered with a low precedence order;
• A thread-bound scope named THREAD_SCOPE_NAME, using current Thread local data set to register and provide context resources. This scope is registered with a high precedence order.

Since:

5.0.0

Field Summary

Fields

Modifier and Type	Field and Description
static String	CLASSLOADER_SCOPE_NAME Default classloader-bound scope name
static String	THREAD_SCOPE_NAME Default thread-bound scope name

Method Summary

Modifier and Type	Method and Description
default Optional<ContextScope>	classLoaderScope() Shortcut method to obtain the ClassLoader-bound context scope, i.e.
default Optional<ContextScope>	classLoaderScope(ClassLoader classLoader) Shortcut method to obtain the ClassLoader-bound context scope, i.e.
default <V> V	executeThreadBound(String resourceKey, Object resource, Callable<V> operation) Execute given Callable operation, binding given Context resource key and value to current Thread, and removing the binding after operation execution.
default void	executeThreadBound(String resourceKey, Object resource, Runnable operation) Execute given Runnable operation, binding given Context resource key and value to current Thread, and removing the binding after operation execution.
static Context	get() Obtain the default Context implementation instance.
default <T> Optional<T>	resource(Class<T> resourceType) Shortcut method to obtain a Context resource using the resourceType class name as resource key.
default <T> Optional<T>	resource(Class<T> resourceType, ClassLoader classLoader) Shortcut method to obtain a Context resource using the resourceType class name as resource key and given classLoader.
default <T> Optional<T>	resource(String resourceKey, Class<T> resourceType) Lookup a context resource of resourceType class using given resourceKey and the default ClassLoader.
<T> Optional<T>	resource(String resourceKey, Class<T> resourceType, ClassLoader classLoader) Lookup a context resource of resourceType class using given resourceKey.
default Optional<ContextScope>	scope(String name) Gets a registered ContextScope with the given name and bound to default ClassLoader.
Optional<ContextScope>	scope(String name, ClassLoader classLoader) Gets a registered ContextScope with the given name and bound to given classLoader.
default Optional<ContextScope>	threadScope() Shortcut method to obtain the thread-bound context scope, i.e.
default Optional<ContextScope>	threadScope(ClassLoader classLoader) Shortcut method to obtain the thread-bound context scope, i.e.

Field Detail

THREAD_SCOPE_NAME

static final String THREAD_SCOPE_NAME

Default thread-bound scope name

See Also:

Constant Field Values

CLASSLOADER_SCOPE_NAME

static final String CLASSLOADER_SCOPE_NAME

Default classloader-bound scope name

See Also:

Constant Field Values

Method Detail

resource

<T> Optional<T> resource(String resourceKey,
                         Class<T> resourceType,
                         ClassLoader classLoader)

Lookup a context resource of resourceType class using given resourceKey.

All registered context scopes are invoked, in the order defined by ContextScope.getOrder() precedence value. The first not null resource instance obtained from a scope is the one returned to caller, if any.

Type Parameters:

T - Resource type

Parameters:

resourceKey - Resource key (not null)

resourceType - Required resource type (not null)

classLoader - ClassLoader to use. If null, the default ClassLoader is used.

Returns:

Optional resource instance, empty if not available from context

Throws:

TypeMismatchException - If a context resource with given key was found but it is not of required type

resource

default <T> Optional<T> resource(String resourceKey,
                                 Class<T> resourceType)

Lookup a context resource of resourceType class using given resourceKey and the default ClassLoader.

All registered context scopes are invoked, in the order defined by ContextScope.getOrder() precedence value. The first not null resource instance obtained from a scope is the one returned to caller, if any.

Type Parameters:

T - Resource type

Parameters:

resourceKey - Resource key (not null)

resourceType - Required resource type (not null)

Returns:

Optional resource instance, empty if not available from context

Throws:

TypeMismatchException - If a context resource with given key was found but it is not of required type

resource

default <T> Optional<T> resource(Class<T> resourceType)

Shortcut method to obtain a Context resource using the resourceType class name as resource key.

Type Parameters:

T - Resource type

Parameters:

resourceType - Resource type (not null)

Returns:

Optional resource instance, empty if not available from context

resource

default <T> Optional<T> resource(Class<T> resourceType,
                                 ClassLoader classLoader)

Shortcut method to obtain a Context resource using the resourceType class name as resource key and given classLoader.

Type Parameters:

T - Resource type

Parameters:

resourceType - Resource type (not null)

classLoader - ClassLoader to use. If null, the default ClassLoader is used.

Returns:

Optional resource instance, empty if not available from context

scope

Optional<ContextScope> scope(String name,
                             ClassLoader classLoader)

Gets a registered ContextScope with the given name and bound to given classLoader.

Parameters:

name - Scope name (not null)

classLoader - ClassLoader, if null, the default ClassLoader is used

Returns:

The registered ContextScope with given name, or an empty Optional if a scope with such name is not registered in context

scope

default Optional<ContextScope> scope(String name)

Gets a registered ContextScope with the given name and bound to default ClassLoader.

Parameters:

name - Scope name (not null)

Returns:

The registered ContextScope with given name, or an empty Optional if a scope with such name is not registered in context

classLoaderScope

default Optional<ContextScope> classLoaderScope(ClassLoader classLoader)

Shortcut method to obtain the ClassLoader-bound context scope, i.e. the default ContextScope named CLASSLOADER_SCOPE_NAME.

Parameters:

classLoader - ClassLoader, if null, the default ClassLoader is used

Returns:

The ClassLoader-bound context scope, or an empty Optional if scope is not registered

classLoaderScope

default Optional<ContextScope> classLoaderScope()

Shortcut method to obtain the ClassLoader-bound context scope, i.e. the default ContextScope named CLASSLOADER_SCOPE_NAME, using the default ClassLoader.

Returns:

The ClassLoader-bound context scope, or an empty Optional if scope is not registered

threadScope

default Optional<ContextScope> threadScope(ClassLoader classLoader)

Shortcut method to obtain the thread-bound context scope, i.e. the default ContextScope named THREAD_SCOPE_NAME.

Parameters:

classLoader - ClassLoader, if null, the default ClassLoader is used

Returns:

The thread-bound context scope, or an empty Optional if scope is not registered

threadScope

default Optional<ContextScope> threadScope()

Shortcut method to obtain the thread-bound context scope, i.e. the default ContextScope named THREAD_SCOPE_NAME, using the default ClassLoader.

Returns:

The thread-bound context scope, or an empty Optional if scope is not registered

executeThreadBound

default void executeThreadBound(String resourceKey,
                                Object resource,
                                Runnable operation)
                         throws RuntimeException

Execute given Runnable operation, binding given Context resource key and value to current Thread, and removing the binding after operation execution.

The THREAD_SCOPE_NAME context scope is used.

Parameters:

resourceKey - Context resource key (not null)

resource - Context resource value to bind to current Thread (not null)

operation - Operation to execute (not null)

Throws:

RuntimeException - Exception during operation execution

executeThreadBound

default <V> V executeThreadBound(String resourceKey,
                                 Object resource,
                                 Callable<V> operation)
                          throws RuntimeException

Execute given Callable operation, binding given Context resource key and value to current Thread, and removing the binding after operation execution.

The THREAD_SCOPE_NAME context scope is used.

Type Parameters:

V - Operation result type

Parameters:

resourceKey - Context resource key (not null)

resource - Context resource value to bind to current Thread (not null)

operation - Operation to execute

Returns:

Operation result

Throws:

RuntimeException - Exception during operation execution

get

static Context get()

Obtain the default Context implementation instance.

Returns:

Default Context