com.holonplatform.core

Interface ContextScope

All Known Implementing Classes:

ClassLoaderScope, ExampleContext.MyContextScope, ThreadScope

public interface ContextScope

A Context scope to hold, manage and access context resources. Every resource is identified by a String key.

Each scope is identified by a name which must be unique among all registered context scopes and may implement a specific strategy to store and provide resources.

Every concrete scope must provide the get(String, Class) operation. Resource management operations (put/remove) are optional and may not be available, throwing an UnsupportedOperationException.

A ContextScope must be registered in ContextManager to be accessibile from Context façade and join generic context resource retrieval chain. Scope registration can be performed using default Java extension through ServiceLoader or directly using ContextManager.registerScope(ClassLoader, ContextScope).

The getOrder() method can be used to assign a order to the scope within the scopes chain for context resource resolution. Lower order values mean highest precedence.

Since:

5.0.0

Method Summary

Modifier and Type	Method and Description
<T> Optional<T>	get(String resourceKey, Class<T> resourceType) Try to obtain the resource identified by given resourceKey and with expected resourceType.
String	getName() Gets the scope name.
int	getOrder() Gets the scope order.
<T> Optional<T>	put(String resourceKey, T value) Stores a resource reference identified by given resourceKey.
<T> Optional<T>	putIfAbsent(String resourceKey, T value) Stores a resource reference identified by given resourceKey, only if there is not a resource instance already bound to given key.
boolean	remove(String resourceKey) Removes the resource reference bound to the given resourceKey from scope, if any.

Method Detail

getName

String getName()

Gets the scope name. Scope name must be unique among all registered context scopes.

Returns:

the scope name

getOrder

int getOrder()

Gets the scope order. Lower order values mean highest precedence.

Returns:

the scope order

get

<T> Optional<T> get(String resourceKey,
                    Class<T> resourceType)
             throws TypeMismatchException

Try to obtain the resource identified by given resourceKey and with expected resourceType.

Type Parameters:

T - Resource type

Parameters:

resourceKey - Resource key (not null)

resourceType - Expected resource type (not null)

Returns:

Optional resource instance, an empty Optional if resource is not available from scope according to scope resource provisioning strategy

Throws:

TypeMismatchException - If a resource is available but the expected type is not compatible with the resource type

put

<T> Optional<T> put(String resourceKey,
                    T value)
             throws UnsupportedOperationException

Stores a resource reference identified by given resourceKey.

Type Parameters:

T - Resource instance type

Parameters:

resourceKey - Resource key (not null)

value - Resource instance. If null, if a previous resource was bound to given resource key, it will be removed from scope.

Returns:

Optional previous resource instance bound to given key

Throws:

UnsupportedOperationException - If the concrete scope implementation does not support this operation

putIfAbsent

<T> Optional<T> putIfAbsent(String resourceKey,
                            T value)
                     throws UnsupportedOperationException

Stores a resource reference identified by given resourceKey, only if there is not a resource instance already bound to given key.

Type Parameters:

T - Resource instance type

Parameters:

resourceKey - Resource key (not null)

value - Resource instance, if null, this method should do nothing.

Returns:

Optional previous resource instance bound to given key. If there was no resource already bound to the key, an empty Optional is returned, meaning the given value has been associated to the resource key.

Throws:

UnsupportedOperationException - If the concrete scope implementation does not support this operation

remove

boolean remove(String resourceKey)
        throws UnsupportedOperationException

Removes the resource reference bound to the given resourceKey from scope, if any.

Parameters:

resourceKey - Resource key (not null)

Returns:

true if a resource instance was bound to the given key and it's been removed, false otherwise.

Throws:

UnsupportedOperationException - If the concrete scope implementation does not support this operation