com.linkedin.parseq.promise

Class DelegatingPromise<T>

java.lang.Object

com.linkedin.parseq.promise.DelegatingPromise<T>

All Implemented Interfaces:

Promise<T>

Direct Known Subclasses:

BaseTask

public class DelegatingPromise<T>
extends java.lang.Object
implements Promise<T>

An abstract class that makes it easy to delegate Promise method invocations to a delegate promise.

Author:

Chris Pettitt ([email protected])

Constructor Summary

Constructors

Constructor and Description
DelegatingPromise(Promise<T> delegate)

Method Summary

Modifier and Type	Method and Description
void	addListener(PromiseListener<T> listener) Adds a listener to this promise that will be notified when the promise is resolved.
void	await() Blocks the current thread for an unbounded amount of time until the promise has be resolved.
boolean	await(long time, java.util.concurrent.TimeUnit unit) Blocks the current thread for up to the specified amount of time or until the promise has been resolved.
T	get() If the promise's value is set, then this method returns the value.
protected Promise<T>	getDelegate()
java.lang.Throwable	getError() Returns the error in this promise, if there is one.
T	getOrDefault(T defaultValue) Gets the value in this promise or, if the promise contains an error, returns the given default value.
boolean	isDone() Returns true if this promise is resolved.
boolean	isFailed() Returns true if the promise has an error.

Methods inherited from class java.lang.Object

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

Constructor Detail

DelegatingPromise

public DelegatingPromise(Promise<T> delegate)

Method Detail

get

public T get()
      throws PromiseException

Description copied from interface: Promise

If the promise's value is set, then this method returns the value. If the promise has an error, the error is thrown, wrapped in a PromiseException. If the promise has not yet been resolved (i.e. it has no value and no error) then this method raises a PromiseUnresolvedException.

Specified by:

get in interface Promise<T>

Returns:

the value of the promise if it is available

Throws:

PromiseException - if the promise has an error

PromiseUnresolvedException - if the promise has not yet been resolved

getError

public java.lang.Throwable getError()

Description copied from interface: Promise

Returns the error in this promise, if there is one. If this promise contains a value, then this method will return null. If this promise has no value and no error (i.e. it is unresolved) then a PromiseUnresolvedException is thrown.

Specified by:

getError in interface Promise<T>

Returns:

the error contained in this promise, or null if the promise contains a value.

getOrDefault

public T getOrDefault(T defaultValue)

Description copied from interface: Promise

Gets the value in this promise or, if the promise contains an error, returns the given default value. This is one mechanism for gracefully handling promise failure.

If the promise has not been resolved then this method will throw PromiseUnresolvedException.

Specified by:

getOrDefault in interface Promise<T>

Parameters:

defaultValue - the default value to return if this promise contains an error.

Returns:

the value in this promise or the default value if this promise contains an error.

await

public void await()
           throws java.lang.InterruptedException

Description copied from interface: Promise

Blocks the current thread for an unbounded amount of time until the promise has be resolved.

For asynchronous workflows, use Promise.addListener(PromiseListener), which will notify the user when the promise is resolved instead of blocking the current thread.

Specified by:

await in interface Promise<T>

Throws:

java.lang.InterruptedException - if the current thread is interrupted

await

public boolean await(long time,
                     java.util.concurrent.TimeUnit unit)
              throws java.lang.InterruptedException

Description copied from interface: Promise

Blocks the current thread for up to the specified amount of time or until the promise has been resolved. If the promise was resolved before the specified time has expired, this method returns true.

For asynchronous workflows, use Promise.addListener(PromiseListener), which will notify the user when the promise is resolved instead of blocking the current thread.

Specified by:

await in interface Promise<T>

Parameters:

time - the amount of time to wait

unit - the units for the wait time

Returns:

true if the promise is resolved within the specified time

Throws:

java.lang.InterruptedException - if the current thread is interrupted

addListener

public void addListener(PromiseListener<T> listener)

Description copied from interface: Promise

Adds a listener to this promise that will be notified when the promise is resolved. If the promise has already been resolved then the listener is notified immediately.

Listener will be called on a thread that completed this promise.

The instance passed in to PromiseListener.onResolved(Promise) method does not have to be the exact same instance the PromiseListener was registered with.

Specified by:

addListener in interface Promise<T>

Parameters:

listener - the listener to add to this promise

isDone

public boolean isDone()

Description copied from interface: Promise

Returns true if this promise is resolved. A promise is resolved when it has a value or an error.

Specified by:

isDone in interface Promise<T>

Returns:

true if this promise has been resolved.

isFailed

public boolean isFailed()

Description copied from interface: Promise

Returns true if the promise has an error. Errors can retrieved using Promise.getError().

Specified by:

isFailed in interface Promise<T>

Returns:

true if the promise has en error.

getDelegate

protected Promise<T> getDelegate()