hu.akarnokd.reactive4java.util

Class DefaultObserver<T>

java.lang.Object

hu.akarnokd.reactive4java.util.DefaultObserver<T>

Type Parameters:

T - the element type to observe

All Implemented Interfaces:

BaseObserver, Observer<T>, java.io.Closeable, java.lang.AutoCloseable

Direct Known Subclasses:

DefaultObserverEx

public abstract class DefaultObserver<T>
extends java.lang.Object
implements Observer<T>, java.io.Closeable

The default implementation of the Observer interface used by the Reactive operators.

This implementation ensures that its onNext, onError and onFinish methods are never interleaved and won't be executed after an error or finish message. In addition, a Throwable thrown from the onNext() method is routed through the error() method.

The close method is idempotent and can be called multiple times.

Extend this class when you need something more than a decorator or filter around some Observer passed to the custom register method, e.g., observers with multiple sub-observers registered to multiple sources or observers with an accompanied scheduled task.

Field Summary

Fields

Modifier and Type	Field and Description
protected boolean	closeOnTermination Should the observer close() itself on error or finish()?
protected boolean	completed The completion flag, it will be set by the close method once.
protected java.util.concurrent.locks.Lock	lock The lock that ensures sequential and exclusive runs for the observer's methods.

Constructor Summary

Constructors

Constructor and Description
DefaultObserver(boolean complete) Constructor.
DefaultObserver(java.util.concurrent.locks.Lock lock, boolean complete) Constructor.

Method Summary

Modifier and Type	Method and Description
void	close()
void	error(java.lang.Throwable ex) An exception is received.
void	finish() No more values to expect.
java.util.concurrent.locks.Lock	getLock() Returns the internal lock which might be shared among multiple instances.
boolean	isCompleted()
void	next(T value) The next value is received.
protected void	onClose() Called by close to close down any associated resources with this instance.
protected abstract void	onError(java.lang.Throwable ex) The alternative error() method, which is called by the original error() method.
protected abstract void	onFinish() The alternative finish() method, which is called by the original finish() method.
protected abstract void	onNext(T value) The alternative next() method, which is called by the original next() method under lock.

Methods inherited from class java.lang.Object

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

Field Detail

lock

@Nonnull
protected final java.util.concurrent.locks.Lock lock

The lock that ensures sequential and exclusive runs for the observer's methods.

completed

protected boolean completed

The completion flag, it will be set by the close method once.

closeOnTermination

protected final boolean closeOnTermination

Should the observer close() itself on error or finish()?

Constructor Detail

DefaultObserver

public DefaultObserver(boolean complete)

Constructor. Initializes the class with a fair reentrant lock.

Parameters:

complete - should set the completion status on an error or finish?

DefaultObserver

public DefaultObserver(@Nonnull
                       java.util.concurrent.locks.Lock lock,
                       boolean complete)

Constructor. Initializes the class with a shared lock instance.

Parameters:

lock - the lock instance, nonnul

complete - should set the completion status on an error or finish?

Method Detail

onNext

protected abstract void onNext(T value)

The alternative next() method, which is called by the original next() method under lock.

Parameters:

value - the value

onError

protected abstract void onError(@Nonnull
                                java.lang.Throwable ex)

The alternative error() method, which is called by the original error() method.

Parameters:

ex - the exception

onFinish

protected abstract void onFinish()

The alternative finish() method, which is called by the original finish() method.

onClose

protected void onClose()

Called by close to close down any associated resources with this instance.

The close() method ensures that the lock is held this code executes.

next

public final void next(T value)

Description copied from interface: Observer

The next value is received.

Specified by:

next in interface Observer<T>

Parameters:

value - the next value

close

public final void close()

Specified by:

close in interface java.io.Closeable

Specified by:

close in interface java.lang.AutoCloseable

error

public final void error(@Nonnull
                        java.lang.Throwable ex)

Description copied from interface: BaseObserver

An exception is received.

Specified by:

error in interface BaseObserver

Parameters:

ex - the exception

finish

public final void finish()

Description copied from interface: BaseObserver

No more values to expect.

Specified by:

finish in interface BaseObserver

getLock

public java.util.concurrent.locks.Lock getLock()

Returns the internal lock which might be shared among multiple instances.

Returns:

the lock

isCompleted

public boolean isCompleted()

Returns:

the completion status.