com.vaadin.util

Class CurrentInstance

java.lang.Object

com.vaadin.util.CurrentInstance

All Implemented Interfaces:

Serializable

public class CurrentInstance
extends Object
implements Serializable

Keeps track of various current instances for the current thread. All the instances are automatically cleared after handling a request from the client to avoid leaking memory. The inheritable values are also maintained when execution is moved to another thread, both when a new thread is created and when VaadinSession.access(Runnable) or UI.access(Runnable) is used.

Please note that the instances are stored using WeakReference. This means that the a current instance value may suddenly disappear if there a no other references to the object.

Currently the framework uses the following instances:

Inheritable: UI, VaadinService, VaadinSession.

Non-inheritable: VaadinRequest, VaadinResponse.

Since:

7.0.0

Author:

Vaadin Ltd

See Also:

Serialized Form

Method Summary

Modifier and Type	Method and Description
static void	clearAll() Clears all current instances.
static <T> void	defineFallbackResolver(Class<T> type, CurrentInstanceFallbackResolver<T> fallbackResolver) Adds a CurrentInstanceFallbackResolver, that is triggered when get(Class) can't find a suitable instance for the given type parameter.
static <T> T	get(Class<T> type) Gets the current instance of a specific type if available.
static Map<Class<?>,CurrentInstance>	getInstances(boolean onlyInheritable) Gets the currently set instances so that they can later be restored using restoreInstances(Map).
static void	restoreInstances(Map<Class<?>,CurrentInstance> old) Restores the given instances to the given values.
static <T> void	set(Class<T> type, T instance) Sets the current instance of the given type.
static Map<Class<?>,CurrentInstance>	setCurrent(UI ui) Sets current instances for the UI and all related classes.
static Map<Class<?>,CurrentInstance>	setCurrent(VaadinSession session) Sets current instances for the VaadinSession and all related classes.
static <T> void	setInheritable(Class<T> type, T instance) Sets the current inheritable instance of the given type.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Detail

get

public static <T> T get(Class<T> type)

Gets the current instance of a specific type if available.

When a current instance of the specific type is not found, the CurrentInstanceFallbackResolver registered via defineFallbackResolver(Class, CurrentInstanceFallbackResolver) (if any) is invoked.

Parameters:

type - the class to get an instance of

Returns:

the current instance or the provided type, or null if there is no current instance.

defineFallbackResolver

public static <T> void defineFallbackResolver(Class<T> type,
                                              CurrentInstanceFallbackResolver<T> fallbackResolver)

Adds a CurrentInstanceFallbackResolver, that is triggered when get(Class) can't find a suitable instance for the given type parameter.

Parameters:

type - the class used on get(Class) invocations to retrieve the current instance

fallbackResolver - the resolver, not null

Throws:

IllegalArgumentException - if there's already a defined fallback resolver for the given type

Since:

7.7.14

set

public static <T> void set(Class<T> type,
                           T instance)

Sets the current instance of the given type.

Parameters:

type - the class that should be used when getting the current instance back

instance - the actual instance

See Also:

setInheritable(Class, Object), ThreadLocal

setInheritable

public static <T> void setInheritable(Class<T> type,
                                      T instance)

Sets the current inheritable instance of the given type. A current instance that is inheritable will be available for child threads and in code run by VaadinSession.access(Runnable) and UI.access(Runnable).

Parameters:

type - the class that should be used when getting the current instance back

instance - the actual instance

See Also:

set(Class, Object), InheritableThreadLocal

clearAll

public static void clearAll()

Clears all current instances.

restoreInstances

public static void restoreInstances(Map<Class<?>,CurrentInstance> old)

Restores the given instances to the given values. Note that this should only be used internally to restore Vaadin classes.

Parameters:

old - A Class -> CurrentInstance map to set as current instances

Since:

7.1

getInstances

public static Map<Class<?>,CurrentInstance> getInstances(boolean onlyInheritable)

Gets the currently set instances so that they can later be restored using restoreInstances(Map).

Parameters:

onlyInheritable - true if only the inheritable instances should be included; false to get all instances.

Returns:

a map containing the current instances

Since:

7.1

setCurrent

public static Map<Class<?>,CurrentInstance> setCurrent(UI ui)

Sets current instances for the UI and all related classes. The previously defined values can be restored by passing the returned map to restoreInstances(Map).

Parameters:

ui - The UI

Returns:

A map containing the old values of the instances that this method updated.

Since:

7.1

setCurrent

public static Map<Class<?>,CurrentInstance> setCurrent(VaadinSession session)

Sets current instances for the VaadinSession and all related classes. The previously defined values can be restored by passing the returned map to restoreInstances(Map).

Parameters:

session - The VaadinSession

Returns:

A map containing the old values of the instances this method updated.

Since:

7.1