groovyx.gpars.dataflow

Class DataflowVariable<T>

java.lang.Object

groovyx.gpars.serial.WithSerialId

groovyx.gpars.dataflow.expression.DataflowExpression<T>

groovyx.gpars.dataflow.DataflowVariable<T>

Type Parameters:

T - Type of values to bind with the DataflowVariable

All Implemented Interfaces:

groovy.lang.GroovyObject, DataflowChannel<T>, DataflowReadChannel<T>, DataflowWriteChannel<T>, Promise<T>, SelectableChannel<T>, java.io.Serializable

Direct Known Subclasses:

DataflowVariable.RemoteDataflowVariable, LazyDataflowVariable, SyncDataflowVariable

public class DataflowVariable<T>
extends DataflowExpression<T>
implements DataflowChannel<T>, Promise<T>

Represents a thread-safe single-assignment, multi-read variable. Each instance of DataflowVariable can be read repeatedly any time using the 'val' property and assigned once in its lifetime using the '<<' operator. Reads preceding assignment will be blocked until the value is assigned. For actors and Dataflow Operators the asynchronous non-blocking variants of the getValAsync() methods can be used. They register the request to read a value and will send a message to the actor or operator once the value is available.

Author:

Vaclav Pech, Alex Tkachman Date: Jun 4, 2009

See Also:

Serialized Form

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	DataflowVariable.RemoteDataflowVariable<T>

Nested classes/interfaces inherited from class groovyx.gpars.dataflow.expression.DataflowExpression

DataflowExpression.BindDataflow<T>

Field Summary

Fields

Modifier and Type	Field and Description
private static long	serialVersionUID

Fields inherited from class groovyx.gpars.dataflow.expression.DataflowExpression

error, S_INITIALIZED, S_INITIALIZING, S_NOT_INITIALIZED, state, value

Fields inherited from class groovyx.gpars.serial.WithSerialId

serialHandle

Constructor Summary

Constructors

Constructor and Description
DataflowVariable() Creates a new unbound Dataflow Variable

Method Summary

Methods

Modifier and Type	Method and Description
private DataflowWriteChannel<T>	bindDFV(DataflowReadChannel<T> ref)
T	get() Retrieves the value of the variable, blocking until a value is available
T	get(long timeout, java.util.concurrent.TimeUnit units) Retrieves the value of the variable, blocking up to given timeout, if the value has not been assigned yet.
java.lang.Throwable	getError() Returns the error bound to the promise
java.lang.Class<DataflowVariable.RemoteDataflowVariable>	getRemoteClass() Class of remote object to be created
boolean	isError() Checks if the promise is bound to an error
DataflowWriteChannel<T>	leftShift(DataflowReadChannel<T> ref) Assigns a value from one DataflowVariable instance to this variable.
DataflowWriteChannel<T>	leftShift(T value) Assigns a value to the variable.
(package private) boolean	shouldThrowTimeout()
<V> Promise<V>	then(groovy.lang.Closure<V> closure, groovy.lang.Closure<V> errorHandler) Schedule closure to be executed after data became available.
<V> Promise<V>	then(PGroup group, groovy.lang.Closure<V> closure, groovy.lang.Closure<V> errorHandler) Schedule closure to be executed after data becomes available.
<V> Promise<V>	then(Pool pool, groovy.lang.Closure<V> closure, groovy.lang.Closure<V> errorHandler) Schedule closure to be executed after data becomes available.
void	touch() May be used by lazy implementations to warm up

Methods inherited from class groovyx.gpars.dataflow.expression.DataflowExpression

binaryChoice, binaryChoice, binaryChoice, binaryChoice, binaryChoice, binaryChoice, bind, bindError, bindSafely, bindUnique, chainWith, chainWith, chainWith, chainWith, chainWith, chainWith, choice, choice, choice, choice, choice, choice, doBindImpl, doBindRemote, evaluate, filter, filter, filter, filter, filter, filter, getBindErrorManager, getEventManager, getMetaClass, getProperty, getVal, getVal, getValAsync, getValAsync, into, into, into, into, into, into, invokeMethod, isBound, join, join, length, merge, merge, merge, merge, merge, merge, merge, merge, merge, merge, merge, merge, or, or, poll, rightShift, scheduleCallback, separate, separate, separate, separate, separate, separate, setMetaClass, setProperty, split, split, split, split, split, split, split, split, split, split, split, split, subscribe, subscribe, tap, tap, tap, tap, tap, tap, then, then, then, thenForkAndJoin, thenForkAndJoin, thenForkAndJoin, toString, transform, whenBound, whenBound, whenBound, whenBound, wheneverBound, wheneverBound

Methods inherited from class groovyx.gpars.serial.WithSerialId

createRemoteHandle, getOrCreateSerialHandle, writeReplace

Methods inherited from class java.lang.Object

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

Methods inherited from interface groovyx.gpars.dataflow.DataflowReadChannel

binaryChoice, binaryChoice, binaryChoice, binaryChoice, binaryChoice, binaryChoice, chainWith, chainWith, chainWith, chainWith, chainWith, chainWith, choice, choice, choice, choice, choice, choice, filter, filter, filter, filter, filter, filter, getEventManager, getVal, getVal, getValAsync, getValAsync, into, into, into, into, into, into, isBound, length, merge, merge, merge, merge, merge, merge, merge, merge, merge, merge, merge, merge, or, or, rightShift, separate, separate, separate, separate, separate, separate, split, split, split, split, split, split, split, split, split, split, split, split, tap, tap, tap, tap, tap, tap, then, then, then, whenBound, whenBound, whenBound, whenBound

Methods inherited from interface groovyx.gpars.dataflow.SelectableChannel

poll, wheneverBound, wheneverBound

Methods inherited from interface groovyx.gpars.dataflow.DataflowWriteChannel

bind

Methods inherited from interface groovyx.gpars.dataflow.Promise

isBound, join, join, rightShift, then, then, then, thenForkAndJoin, thenForkAndJoin, thenForkAndJoin, whenBound, whenBound, whenBound, whenBound

Field Detail

serialVersionUID

private static final long serialVersionUID

See Also:

Constant Field Values

Constructor Detail

DataflowVariable

public DataflowVariable()

Creates a new unbound Dataflow Variable

Method Detail

leftShift

public DataflowWriteChannel<T> leftShift(T value)

Assigns a value to the variable. Can only be invoked once on each instance of DataflowVariable

Specified by:

leftShift in interface DataflowWriteChannel<T>

Parameters:

value - The value to assign

Returns:

The current channel instance

leftShift

public DataflowWriteChannel<T> leftShift(DataflowReadChannel<T> ref)

Assigns a value from one DataflowVariable instance to this variable. Can only be invoked once on each instance of DataflowVariable

Specified by:

leftShift in interface DataflowWriteChannel<T>

Parameters:

ref - The DataflowVariable instance the value of which to bind

Returns:

The current channel instance

bindDFV

private DataflowWriteChannel<T> bindDFV(DataflowReadChannel<T> ref)

get

public final T get()
            throws java.lang.Throwable

Retrieves the value of the variable, blocking until a value is available

Specified by:

get in interface Promise<T>

Returns:

The value stored in the variable

Throws:

java.lang.Throwable - If the stored value is an exception instance it gets re-thrown

get

public final T get(long timeout,
    java.util.concurrent.TimeUnit units)
            throws java.lang.Throwable

Retrieves the value of the variable, blocking up to given timeout, if the value has not been assigned yet.

Specified by:

get in interface Promise<T>

Parameters:

timeout - The timeout value

units - Units for the timeout

Returns:

The value stored in the variable

Throws:

java.lang.Throwable - If the stored value is an exception instance it gets re-thrown

shouldThrowTimeout

boolean shouldThrowTimeout()

isError

public boolean isError()

Checks if the promise is bound to an error

Specified by:

isError in interface Promise<T>

Returns:

True, if an error has been bound

getError

public java.lang.Throwable getError()

Returns the error bound to the promise

Specified by:

getError in interface Promise<T>

Returns:

The error

Throws:

java.lang.IllegalStateException - If not bound or not bound to an error

touch

public void touch()

Description copied from interface: Promise

May be used by lazy implementations to warm up

Specified by:

touch in interface Promise<T>

then

public <V> Promise<V> then(groovy.lang.Closure<V> closure,
                  groovy.lang.Closure<V> errorHandler)

Schedule closure to be executed after data became available. It is important to notice that even if the expression is already bound the execution of closure will not happen immediately but will be scheduled

Specified by:

then in interface Promise<T>

Parameters:

closure - closure to execute when data becomes available. The closure should take at most one argument.

errorHandler - closure to execute when an error (instance of Throwable) gets bound. The closure should take at most one argument.

Returns:

A promise for the results of the supplied closure. This allows for chaining of then() method calls.

then

public <V> Promise<V> then(Pool pool,
                  groovy.lang.Closure<V> closure,
                  groovy.lang.Closure<V> errorHandler)

Schedule closure to be executed after data becomes available. It is important to notice that even if the expression is already bound the execution of closure will not happen immediately but will be scheduled.

Specified by:

then in interface Promise<T>

Parameters:

pool - The thread pool to use for task scheduling for asynchronous message delivery

closure - closure to execute when data becomes available. The closure should take at most one argument.

errorHandler - closure to execute when an error (instance of Throwable) gets bound. The closure should take at most one argument.

Returns:

A promise for the results of the supplied closure. This allows for chaining of then() method calls.

then

public <V> Promise<V> then(PGroup group,
                  groovy.lang.Closure<V> closure,
                  groovy.lang.Closure<V> errorHandler)

Schedule closure to be executed after data becomes available. It is important to notice that even if the expression is already bound the execution of closure will not happen immediately but will be scheduled.

Specified by:

then in interface Promise<T>

Parameters:

group - The PGroup to use for task scheduling for asynchronous message delivery

closure - closure to execute when data becomes available. The closure should take at most one argument.

errorHandler - closure to execute when an error (instance of Throwable) gets bound. The closure should take at most one argument.

Returns:

A promise for the results of the supplied closure. This allows for chaining of then() method calls.

getRemoteClass

public java.lang.Class<DataflowVariable.RemoteDataflowVariable> getRemoteClass()

Description copied from class: WithSerialId

Class of remote object to be created

Overrides:

getRemoteClass in class WithSerialId

Returns:

Throws UnsupportedOperationException