Package com.inductiveautomation.eventstream.gateway.api.expression

Interface EventStreamExpression

All Known Implementing Classes:

GatewayEventStreamExpression

public interface EventStreamExpression

Expression used in EventStreamHandler for extracting data and metadata from EventPayload. The lifecycle of the EventStreamExpression is bound to the lifecycle of the Event Stream, so no further configuration of the express is required.

Method Summary

Modifier and Type	Method	Description
QualifiedValue	evaluate(EventPayload event)	Evaluates the expression with the provided event.
<T> T	evaluateTyped(EventPayload event, Class<T> clazz)	Attempts to evaluate and coerce the express to a specific type.
String	sourceHint()	Unique key for identifying fields in diagnostics.

Method Details

sourceHint

String sourceHint()

Unique key for identifying fields in diagnostics.

Returns:

Hint representing the field, typically will be the name of the field.

evaluate

QualifiedValue evaluate(EventPayload event)
                 throws ExpressionException

Evaluates the expression with the provided event.

Parameters:

event - Current event

Throws:

ExpressionException - When the expression fails to evaluate

evaluateTyped

<T> T evaluateTyped(EventPayload event,
 Class<T> clazz)
             throws IllegalArgumentException,
ExpressionException

Attempts to evaluate and coerce the express to a specific type. Throws an exception if coercion isn't possible or the expression can't be evaluated.

Parameters:

event - Current event

clazz - Type of class to coerce to

Throws:

IllegalArgumentException

ExpressionException