Package io.openems.edge.common.channel

Interface Channel<T>

Type Parameters:

T - the type of the Channel. One out of OpenemsType.

All Known Subinterfaces:

WriteChannel<T>

All Known Implementing Classes:

AbstractReadChannel, BooleanReadChannel, BooleanWriteChannel, DoubleReadChannel, DoubleWriteChannel, EnumReadChannel, EnumWriteChannel, FloatReadChannel, FloatWriteChannel, IntegerReadChannel, IntegerWriteChannel, LongReadChannel, LongWriteChannel, ShortReadChannel, ShortWriteChannel, StateChannel, StateCollectorChannel, StringReadChannel, StringWriteChannel

public interface Channel<T>

An OpenEMS Channel holds one specific piece of information of an OpenemsComponent.

A Channel has

• a Channel-ID which is unique among the OpenemsComponent. (see ChannelId)
• a Doc as static meta information. (via channelDoc())
• a system-wide unique ChannelAddress built from Component-ID and Channel-ID. (via address()
• a OpenemsType which needs to map to the generic parameter <T>. (via getType())
• an (active) Value. (via value())
• callback methods to listen on value updates and changes. (see Channel#onChange(Consumer), onUpdate(Consumer) and onSetNextValue(Consumer))

Channels implement a 'Process Image' pattern. They provide an 'active' value which should be used for any operations on the channel value. The 'next' value is filled by asynchronous workers in the background. At the 'Process Image Switch' the 'next' value is copied to the 'current' value.

The recommended implementation of an OpenEMS Channel is via AbstractReadChannel.

Field Summary

Fields

Modifier and Type	Field	Description
static int	NO_OF_PAST_VALUES	Holds the number of past values for this Channel that are kept in the 'pastValues' variable.

Method Summary

Modifier and Type	Method	Description
void	_setNextValue(T value)	Deprecated.
ChannelAddress	address()	Gets the address of this Channel.
default Doc	channelDoc()	Gets the ChannelDoc of this Channel.
ChannelId	channelId()	Gets the ChannelId of this Channel.
void	deactivate()	Deactivates the Channel and makes sure all callbacks are released for garbe collection to avoid memory-leaks.
OpenemsComponent	getComponent()	Gets the OpenemsComponent this Channel belongs to.
<META_INFO> META_INFO	getMetaInfo()	Gets the meta information object.
Value<T>	getNextValue()	Gets the 'next value'.
CircularTreeMap<java.time.LocalDateTime,Value<T>>	getPastValues()	Gets the past values for this Channel.
OpenemsType	getType()	Gets the type of this Channel, e.g.
void	nextProcessImage()	Switches to the next process image, i.e.
java.util.function.BiConsumer<Value<T>,Value<T>>	onChange(java.util.function.BiConsumer<Value<T>,Value<T>> callback)	Add an onChange callback.
java.util.function.Consumer<Value<T>>	onSetNextValue(java.util.function.Consumer<Value<T>> callback)	Add an onSetNextValue callback.
java.util.function.Consumer<Value<T>>	onUpdate(java.util.function.Consumer<Value<T>> callback)	Add an onUpdate callback.
void	removeOnChangeCallback(java.util.function.BiConsumer<?,?> callback)	Removes an onChange callback.
void	removeOnSetNextValueCallback(java.util.function.Consumer<?> callback)	Removes an onSetNextValue callback.
void	removeOnUpdateCallback(java.util.function.Consumer<Value<?>> callback)	Removes an onUpdate callback.
<META_INFO> void	setMetaInfo(META_INFO metaInfo)	Sets an object that holds meta information about the Channel, e.g.
default void	setNextValue(java.lang.Object value)	Updates the 'next value' of Channel.
Value<T>	value()	Gets the currently active value, wrapped in a @{link Value}.

Field Detail

NO_OF_PAST_VALUES

static final int NO_OF_PAST_VALUES

Holds the number of past values for this Channel that are kept in the 'pastValues' variable.

See Also:

Constant Field Values

Method Detail

channelId

ChannelId channelId()

Gets the ChannelId of this Channel.

Returns:

channelDoc

default Doc channelDoc()

Gets the ChannelDoc of this Channel.

Returns:

getComponent

OpenemsComponent getComponent()

Gets the OpenemsComponent this Channel belongs to.

Returns:

address

ChannelAddress address()

Gets the address of this Channel.

Returns:

nextProcessImage

void nextProcessImage()

Switches to the next process image, i.e. copies the "next"-value into "current"-value.

getType

OpenemsType getType()

Gets the type of this Channel, e.g. INTEGER, BOOLEAN,..

Returns:

setNextValue

default void setNextValue(java.lang.Object value)

Updates the 'next value' of Channel.

Parameters:

value - the 'next value'. It is going to be the 'value' after the next ProcessImage gets activated.

getNextValue

Value<T> getNextValue()

Gets the 'next value'.

Note that usually you should prefer the value() method.

Returns:

the 'next value'

onSetNextValue

java.util.function.Consumer<Value<T>> onSetNextValue(java.util.function.Consumer<Value<T>> callback)

Add an onSetNextValue callback. It is called, after a new NextValue was set. Note that usually you should prefer the onUpdate() callback.

Remember to remove the callback using removeOnSetNextValueCallback(Consumer) once it is not needed anymore, e.g. on deactivate().

Parameters:

callback - the callback Consumer

Returns:

the callback to enable fluent programming

See Also:

onUpdate(java.util.function.Consumer<io.openems.edge.common.channel.value.Value<T>>)

removeOnSetNextValueCallback

void removeOnSetNextValueCallback(java.util.function.Consumer<?> callback)

Removes an onSetNextValue callback.

Parameters:

callback - the callback Consumer

See Also:

onSetNextValue(Consumer)

_setNextValue

@Deprecated
void _setNextValue(T value)

Deprecated.

Internal method. Do not call directly.

Parameters:

value - the 'next value'

value

Value<T> value()
        throws java.lang.IllegalArgumentException

Gets the currently active value, wrapped in a @{link Value}.

Throws:

java.lang.IllegalArgumentException - if value cannot be access, e.g. because the Channel is Write-Only.

getPastValues

CircularTreeMap<java.time.LocalDateTime,Value<T>> getPastValues()

Gets the past values for this Channel.

Returns:

a map of recording time and historic value at that time

onUpdate

java.util.function.Consumer<Value<T>> onUpdate(java.util.function.Consumer<Value<T>> callback)

Add an onUpdate callback. It is called, after the active value was updated by nextProcessImage().

removeOnUpdateCallback

void removeOnUpdateCallback(java.util.function.Consumer<Value<?>> callback)

Removes an onUpdate callback.

Parameters:

callback - the callback Consumer

See Also:

onUpdate(Consumer)

onChange

java.util.function.BiConsumer<Value<T>,Value<T>> onChange(java.util.function.BiConsumer<Value<T>,Value<T>> callback)

Add an onChange callback. It is called, after a new, different active value was set by nextProcessImage().

Parameters:

callback - old value and new value

removeOnChangeCallback

void removeOnChangeCallback(java.util.function.BiConsumer<?,?> callback)

Removes an onChange callback.

Parameters:

callback - the callback BiConsumer

See Also:

onChange(BiConsumer)

deactivate

void deactivate()

Deactivates the Channel and makes sure all callbacks are released for garbe collection to avoid memory-leaks.

setMetaInfo

<META_INFO> void setMetaInfo(META_INFO metaInfo)
                      throws java.lang.IllegalArgumentException

Sets an object that holds meta information about the Channel, e.g. a read source or write target of this Channel, like a Modbus Register or REST-Api endpoint address. Defaults to null.

Type Parameters:

META_INFO - the type of the meta info

Parameters:

metaInfo - the meta info object

Throws:

java.lang.IllegalArgumentException - if there is already a different meta-info registered with the Channel

getMetaInfo

<META_INFO> META_INFO getMetaInfo()

Gets the meta information object. Defaults to null.

Type Parameters:

META_INFO - the type of the meta info attachment

Returns:

the meta info object