Package org.apache.commons.lang3.concurrent

Class AbstractCircuitBreaker<T>

java.lang.Object

org.apache.commons.lang3.concurrent.AbstractCircuitBreaker<T>

Type Parameters:

T - the type of the value monitored by this circuit breaker

All Implemented Interfaces:

CircuitBreaker<T>

Direct Known Subclasses:

EventCountCircuitBreaker, ThresholdCircuitBreaker

public abstract class AbstractCircuitBreaker<T>
extends Object
implements CircuitBreaker<T>

Base class for circuit breakers.

Since:

3.5

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
protected static enum	AbstractCircuitBreaker.State	An internal enumeration representing the different states of a circuit breaker.

Field Summary

Fields

Modifier and Type	Field	Description
static final String	PROPERTY_NAME	The name of the open property as it is passed to registered change listeners.
protected final AtomicReference<AbstractCircuitBreaker.State>	state	The current state of this circuit breaker.

Constructor Summary

Constructors

Constructor	Description
AbstractCircuitBreaker()	Creates an AbstractCircuitBreaker.

Method Summary

Modifier and Type	Method	Description
void	addChangeListener(PropertyChangeListener listener)	Adds a change listener to this circuit breaker.
protected void	changeState(AbstractCircuitBreaker.State newState)	Changes the internal state of this circuit breaker.
abstract boolean	checkState()	Checks the state of this circuit breaker and changes it if necessary.
void	close()	Closes this circuit breaker.
abstract boolean	incrementAndCheckState(T increment)	Increments the monitored value and performs a check of the current state of this circuit breaker.
boolean	isClosed()	Tests the current closed state of this circuit breaker.
boolean	isOpen()	Tests the current open state of this circuit breaker.
protected static boolean	isOpen(AbstractCircuitBreaker.State state)	Converts the given state value to a boolean open property.
void	open()	Opens this circuit breaker.
void	removeChangeListener(PropertyChangeListener listener)	Removes the specified change listener from this circuit breaker.

Methods inherited from class java.lang.Object

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

Field Details

PROPERTY_NAME

public static final String PROPERTY_NAME

The name of the open property as it is passed to registered change listeners.

See Also:

• Constant Field Values

state

protected final AtomicReference<AbstractCircuitBreaker.State> state

The current state of this circuit breaker.

Constructor Details

AbstractCircuitBreaker

public AbstractCircuitBreaker()

Creates an AbstractCircuitBreaker. It also creates an internal PropertyChangeSupport.

Method Details

isOpen

protected static boolean isOpen(AbstractCircuitBreaker.State state)

Converts the given state value to a boolean open property.

Parameters:

state - the state to be converted

Returns:

the boolean open flag

addChangeListener

public void addChangeListener(PropertyChangeListener listener)

Adds a change listener to this circuit breaker. This listener is notified whenever the state of this circuit breaker changes. If the listener is null, it is silently ignored.

Parameters:

listener - the listener to be added

changeState

protected void changeState(AbstractCircuitBreaker.State newState)

Changes the internal state of this circuit breaker. If there is actually a change of the state value, all registered change listeners are notified.

Parameters:

newState - the new state to be set

checkState

public abstract boolean checkState()

Checks the state of this circuit breaker and changes it if necessary. The return value indicates whether the circuit breaker is now in state closed; a value of true typically means that the current operation can continue.

Specified by:

checkState in interface CircuitBreaker<T>

Returns:

true if the circuit breaker is now closed; false otherwise.

close

public void close()

Closes this circuit breaker. Its state is changed to closed. If this circuit breaker is already closed, this method has no effect.

Specified by:

close in interface CircuitBreaker<T>

incrementAndCheckState

public abstract boolean incrementAndCheckState(T increment)

Increments the monitored value and performs a check of the current state of this circuit breaker. This method works like CircuitBreaker.checkState(), but the monitored value is incremented before the state check is performed.

Specified by:

incrementAndCheckState in interface CircuitBreaker<T>

Parameters:

increment - value to increment in the monitored value of the circuit breaker

Returns:

true if the circuit breaker is now closed; false otherwise

isClosed

public boolean isClosed()

Tests the current closed state of this circuit breaker. A return value of true means that the circuit breaker is currently closed. This means that everything is okay with the monitored subsystem.

Specified by:

isClosed in interface CircuitBreaker<T>

Returns:

the current closed state of this circuit breaker.

isOpen

public boolean isOpen()

Tests the current open state of this circuit breaker. A return value of true means that the circuit breaker is currently open indicating a problem in the monitored subsystem.

Specified by:

isOpen in interface CircuitBreaker<T>

Returns:

the current open state of this circuit breaker.

open

public void open()

Opens this circuit breaker. Its state is changed to open. Depending on a concrete implementation, it may close itself again if the monitored subsystem becomes available. If this circuit breaker is already open, this method has no effect.

Specified by:

open in interface CircuitBreaker<T>

removeChangeListener

public void removeChangeListener(PropertyChangeListener listener)

Removes the specified change listener from this circuit breaker.

Parameters:

listener - the listener to be removed