org.apache.tamaya.inject

Interface DynamicValue<T>

Type Parameters:

T - The type of the value.

All Known Implementing Classes:

BaseDynamicValue, DefaultDynamicValue

public interface DynamicValue<T>

A accessor for a single configured value. This can be used to support values that may change during runtime, reconfigured or final. Hereby external code (could be Tamaya configuration listners or client code), can set a new value. Depending on the DynamicValue.UpdatePolicy the new value is immedeately active or it requires an active commit by client code. Similarly an instance also can ignore all later changes to the value.
Types of this interface can be used as injection targets in injected beans or as template resiult on configuration templates.

Implementation Specification

Implementation of this interface must be

• Serializable, when also the item stored is serializable
• Thread safe

Nested Class Summary

Nested Classes

Modifier and Type	Interface and Description
static class	DynamicValue.UpdatePolicy Policy to control how new values are applied to this instance.

Method Summary

Modifier and Type	Method and Description
void	addListener(PropertyChangeListener l) Add a listener to be called as weak reference, when this value has been changed.
void	commit() Commits a new value that has not been committed yet, make it the new value of the instance.
T	commitAndGet() Performs a commit, if necessary, and returns the current value.
void	discard() Discards a new value that was published.
T	evaluateValue() Evaluates the current value dynamically from the underlying configuration.
T	get() If a value is present in this DynamicValue, returns the value, otherwise throws ConfigException.
T	getNewValue() Access a new value that has not yet been committed.
DynamicValue.UpdatePolicy	getUpdatePolicy() Access the DynamicValue.UpdatePolicy used for updating this value.
boolean	isPresent() Return true if there is a value present, otherwise false.
T	orElse(T other) Return the value if present, otherwise return other.
T	orElseGet(ConfiguredItemSupplier<? extends T> other) Return the value if present, otherwise invoke other and return the result of that invocation.
<X extends Throwable> T	orElseThrow(ConfiguredItemSupplier<? extends X> exceptionSupplier) Return the contained value, if present, otherwise throw an exception to be created by the provided supplier.
void	removeListener(PropertyChangeListener l) Removes a listener to be called, when this value has been changed.
void	setUpdatePolicy(DynamicValue.UpdatePolicy updatePolicy) Sets a new DynamicValue.UpdatePolicy.
boolean	updateValue() Method to check for and apply a new value.

Method Detail

commitAndGet

T commitAndGet()

Performs a commit, if necessary, and returns the current value.

Returns:

the non-null value held by this DynamicValue

Throws:

ConfigException - if there is no value present

See Also:

isPresent()

commit

void commit()

Commits a new value that has not been committed yet, make it the new value of the instance. On change any registered listeners will be triggered.

discard

void discard()

Discards a new value that was published. No listeners will be informed.

getUpdatePolicy

DynamicValue.UpdatePolicy getUpdatePolicy()

Access the DynamicValue.UpdatePolicy used for updating this value.

Returns:

the update policy, never null.

addListener

void addListener(PropertyChangeListener l)

Add a listener to be called as weak reference, when this value has been changed.

Parameters:

l - the listener, not null

removeListener

void removeListener(PropertyChangeListener l)

Removes a listener to be called, when this value has been changed.

Parameters:

l - the listner to be removed, not null

get

T get()

If a value is present in this DynamicValue, returns the value, otherwise throws ConfigException.

Returns:

the non-null value held by this Optional

Throws:

ConfigException - if there is no value present

See Also:

isPresent()

updateValue

boolean updateValue()

Method to check for and apply a new value. Depending on the DynamicValue.UpdatePolicy the value is immediately or deferred visible (or it may even be ignored completely).

Returns:

true, if a new value has been detected. The value may not be visible depending on the current DynamicValue.UpdatePolicy in place.

evaluateValue

T evaluateValue()

Evaluates the current value dynamically from the underlying configuration.

Returns:

the current actual value, or null.

setUpdatePolicy

void setUpdatePolicy(DynamicValue.UpdatePolicy updatePolicy)

Sets a new DynamicValue.UpdatePolicy.

Parameters:

updatePolicy - the new policy, not null.

getNewValue

T getNewValue()

Access a new value that has not yet been committed.

Returns:

the uncommitted new value, or null.

isPresent

boolean isPresent()

Return true if there is a value present, otherwise false.

Returns:

true if there is a value present, otherwise false

orElse

T orElse(T other)

Return the value if present, otherwise return other.

Parameters:

other - the value to be returned if there is no value present, may be null

Returns:

the value, if present, otherwise other

orElseGet

T orElseGet(ConfiguredItemSupplier<? extends T> other)

Return the value if present, otherwise invoke other and return the result of that invocation.

Parameters:

other - a ConfiguredItemSupplier whose result is returned if no value is present

Returns:

the value if present otherwise the result of other.get()

Throws:

NullPointerException - if value is not present and other is null

orElseThrow

<X extends Throwable> T orElseThrow(ConfiguredItemSupplier<? extends X> exceptionSupplier)
                             throws X extends Throwable

Return the contained value, if present, otherwise throw an exception to be created by the provided supplier. NOTE A method reference to the exception constructor with an empty argument list can be used as the supplier. For example, IllegalStateException::new

Type Parameters:

X - Type of the exception to be thrown

Parameters:

exceptionSupplier - The supplier which will return the exception to be thrown

Returns:

the present value

Throws:

X - if there is no value present

NullPointerException - if no value is present and exceptionSupplier is null

X extends Throwable