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.

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:

UI, VaadinService, VaadinSession, 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() 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> CurrentInstance	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.

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:

8.5.2

set

public static <T> CurrentInstance 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:

ThreadLocal

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()

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

Returns:

a map containing the current instances

Since:

8.0

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