Package com.inductiveautomation.perspective.gateway.binding

Class AbstractPollingBinding<P>

java.lang.Object

com.inductiveautomation.perspective.gateway.binding.AbstractPollingBinding<P>

All Implemented Interfaces:

Binding

Direct Known Subclasses:

HttpBinding, QueryBinding

public abstract class AbstractPollingBinding<P>
extends Object
implements Binding

Abstract base class which takes care of executing bindings which have a polling option in a thread-safe manner. Also has a debouncing feature built in.

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
protected static enum	AbstractPollingBinding.State

Field Summary

Fields

Modifier and Type	Field	Description
protected final BindingContext	context
protected AbstractPollingBinding.State	state

Fields inherited from interface com.inductiveautomation.perspective.gateway.api.Binding

BAD_CONFIG, BAD_REF, BIDIRECTIONAL_KEY, COALESCE_KEY, INITIAL_VALUE, MDC_BINDING_TARGET, NOT_FOUND

Constructor Summary

Constructors

Modifier	Constructor	Description
protected	AbstractPollingBinding(BindingContext bindingContext, String pollingRateExpression, Function<P,QualifiedValue> fetchFunction, boolean valueCacheEnabled)

Method Summary

Modifier and Type	Method	Description
protected abstract P	buildFetchParameters()	This method will be called when it is time to fetch a new value.
protected abstract boolean	isDirty()	If any dependencies of the implementation have changed, this method should return true, which will kick off another execution if dependencies have changed while the execution was running.
protected abstract boolean	isReady()	Indicates whether or not the instance of the underlying implementation is ready for execution.
void	onUserRefresh()	Called to prompt the binding to produce a value as soon as possible.
Collection<PropertyReference>	resolveReferences()
protected void	scheduleNow()	Schedule the next execution immediately.
void	shutdown()	Shut down the binding.
void	startup()	Start up the binding.

Methods inherited from class java.lang.Object

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

Methods inherited from interface com.inductiveautomation.perspective.gateway.api.Binding

isBidirectional, onTargetUpdated, shouldCoalesce

Field Details

context

protected final BindingContext context

state

protected volatile AbstractPollingBinding.State state

Constructor Details

AbstractPollingBinding

protected AbstractPollingBinding(@Nonnull
 BindingContext bindingContext,
 @Nullable
 String pollingRateExpression,
 @Nonnull
 Function<P,QualifiedValue> fetchFunction,
 boolean valueCacheEnabled)
                          throws ConfigurationException

Parameters:

fetchFunction - A function to retrieve a new value. Must be a pure function of P - this function may not use anything but what is available through the parameter object, otherwise a memory leak will occur because the param object and the fetch function may outlive this binding instance in the ValueCache.

Throws:

ConfigurationException

Method Details

resolveReferences

public Collection<PropertyReference> resolveReferences()

Specified by:

resolveReferences in interface Binding

startup

public void startup()

Description copied from interface: Binding

Start up the binding. Will be called on-queue

Specified by:

startup in interface Binding

shutdown

public void shutdown()

Description copied from interface: Binding

Shut down the binding. Will be called on-queue

Specified by:

shutdown in interface Binding

isReady

protected abstract boolean isReady()

Indicates whether or not the instance of the underlying implementation is ready for execution.

isDirty

protected abstract boolean isDirty()

If any dependencies of the implementation have changed, this method should return true, which will kick off another execution if dependencies have changed while the execution was running.

buildFetchParameters

protected abstract P buildFetchParameters()

This method will be called when it is time to fetch a new value. The parameter object must implement hashcode and equals, and must contain everything needed to run this parameter's fetch function. The parameter object will be given to the ValueCache, which will then execute the fetch function if a new value is needed. This method will be called within a synchronized block holding this lock.

scheduleNow

protected void scheduleNow()

Schedule the next execution immediately. This method is debounced.

onUserRefresh

public void onUserRefresh()

Description copied from interface: Binding

Called to prompt the binding to produce a value as soon as possible. This _not_ the normal way that bindings work. Bindings are expected to produce a value un-prompted after startup, and then again whenever they feel is appropriate. This is there to allow the user to call component.refreshBinding(property) and prompt a non-polling binding to run.

Specified by:

onUserRefresh in interface Binding