aws-cdk-lib.aws_stepfunctions_tasks.EvaluateExpression

class EvaluateExpression (construct)

LanguageType name
.NETAmazon.CDK.AWS.StepFunctions.Tasks.EvaluateExpression
Gogithub.com/aws/aws-cdk-go/awscdk/v2/awsstepfunctionstasks#EvaluateExpression
Javasoftware.amazon.awscdk.services.stepfunctions.tasks.EvaluateExpression
Pythonaws_cdk.aws_stepfunctions_tasks.EvaluateExpression
TypeScript (source)aws-cdk-lib » aws_stepfunctions_tasks » EvaluateExpression

Implements IConstruct, IDependable, IChainable, INextable

A Step Functions Task to evaluate an expression.

OUTPUT: the output of this task is the evaluated expression.

Example

const convertToSeconds = new tasks.EvaluateExpression(this, 'Convert to seconds', {
  expression: '$.waitMilliseconds / 1000',
  resultPath: '$.waitSeconds',
});

const createMessage = new tasks.EvaluateExpression(this, 'Create message', {
  // Note: this is a string inside a string.
  expression: '`Now waiting ${$.waitSeconds} seconds...`',
  runtime: lambda.Runtime.NODEJS_16_X,
  resultPath: '$.message',
});

const publishMessage = new tasks.SnsPublish(this, 'Publish message', {
  topic: new sns.Topic(this, 'cool-topic'),
  message: sfn.TaskInput.fromJsonPathAt('$.message'),
  resultPath: '$.sns',
});

const wait = new sfn.Wait(this, 'Wait', {
  time: sfn.WaitTime.secondsPath('$.waitSeconds'),
});

new sfn.StateMachine(this, 'StateMachine', {
  definition: convertToSeconds
    .next(createMessage)
    .next(publishMessage)
    .next(wait),
});

Initializer

new EvaluateExpression(scope: Construct, id: string, props: EvaluateExpressionProps)

Parameters

  • scope Construct
  • id string — Descriptive identifier for this chainable.
  • props EvaluateExpressionProps

Construct Props

NameTypeDescription
expressionstringThe expression to evaluate. The expression may contain state paths.
comment?stringAn optional description for this state.
credentials?CredentialsCredentials for an IAM Role that the State Machine assumes for executing the task.
heartbeat?⚠️DurationTimeout for the heartbeat.
heartbeatTimeout?TimeoutTimeout for the heartbeat.
inputPath?stringJSONPath expression to select part of the state to be the input to this state.
integrationPattern?IntegrationPatternAWS Step Functions integrates with services directly in the Amazon States Language.
outputPath?stringJSONPath expression to select select a portion of the state output to pass to the next state.
resultPath?stringJSONPath expression to indicate where to inject the state's output.
resultSelector?{ [string]: any }The JSON that will replace the state's raw result and become the effective result before ResultPath is applied.
runtime?RuntimeThe runtime language to use to evaluate the expression.
taskTimeout?TimeoutTimeout for the task.
timeout?⚠️DurationTimeout for the task.

expression

Type: string

The expression to evaluate. The expression may contain state paths.

Example value: '$.a + $.b'


comment?

Type: string (optional, default: No comment)

An optional description for this state.


credentials?

Type: Credentials (optional, default: None (Task is executed using the State Machine's execution role))

Credentials for an IAM Role that the State Machine assumes for executing the task.

This enables cross-account resource invocations.

See also: https://docs.aws.amazon.com/step-functions/latest/dg/concepts-access-cross-acct-resources.html


heartbeat?⚠️

⚠️ Deprecated: use heartbeatTimeout

Type: Duration (optional, default: None)

Timeout for the heartbeat.


heartbeatTimeout?

Type: Timeout (optional, default: None)

Timeout for the heartbeat.

[disable-awslint:duration-prop-type] is needed because all props interface in aws-stepfunctions-tasks extend this interface


inputPath?

Type: string (optional, default: The entire task input (JSON path '$'))

JSONPath expression to select part of the state to be the input to this state.

May also be the special value JsonPath.DISCARD, which will cause the effective input to be the empty object {}.


integrationPattern?

Type: IntegrationPattern (optional, default: IntegrationPattern.REQUEST_RESPONSE for most tasks. IntegrationPattern.RUN_JOB for the following exceptions: BatchSubmitJob, EmrAddStep, EmrCreateCluster, EmrTerminationCluster, and EmrContainersStartJobRun.)

AWS Step Functions integrates with services directly in the Amazon States Language.

You can control these AWS services using service integration patterns

See also: https://docs.aws.amazon.com/step-functions/latest/dg/connect-to-resource.html#connect-wait-token


outputPath?

Type: string (optional, default: The entire JSON node determined by the state input, the task result, and resultPath is passed to the next state (JSON path '$'))

JSONPath expression to select select a portion of the state output to pass to the next state.

May also be the special value JsonPath.DISCARD, which will cause the effective output to be the empty object {}.


resultPath?

Type: string (optional, default: Replaces the entire input with the result (JSON path '$'))

JSONPath expression to indicate where to inject the state's output.

May also be the special value JsonPath.DISCARD, which will cause the state's input to become its output.


resultSelector?

Type: { [string]: any } (optional, default: None)

The JSON that will replace the state's raw result and become the effective result before ResultPath is applied.

You can use ResultSelector to create a payload with values that are static or selected from the state's raw result.

See also: https://docs.aws.amazon.com/step-functions/latest/dg/input-output-inputpath-params.html#input-output-resultselector


runtime?

Type: Runtime (optional, default: lambda.Runtime.NODEJS_16_X)

The runtime language to use to evaluate the expression.


taskTimeout?

Type: Timeout (optional, default: None)

Timeout for the task.

[disable-awslint:duration-prop-type] is needed because all props interface in aws-stepfunctions-tasks extend this interface


timeout?⚠️

⚠️ Deprecated: use taskTimeout

Type: Duration (optional, default: None)

Timeout for the task.

Properties

NameTypeDescription
endStatesINextable[]Continuable states of this Chainable.
idstringDescriptive identifier for this chainable.
nodeNodeThe tree node.
startStateStateFirst state of this Chainable.
stateIdstringTokenized string that evaluates to the state's ID.
taskMetrics?TaskMetricsConfig
taskPolicies?PolicyStatement[]

endStates

Type: INextable[]

Continuable states of this Chainable.


id

Type: string

Descriptive identifier for this chainable.


node

Type: Node

The tree node.


startState

Type: State

First state of this Chainable.


stateId

Type: string

Tokenized string that evaluates to the state's ID.


taskMetrics?

Type: TaskMetricsConfig (optional)


taskPolicies?

Type: PolicyStatement[] (optional)

Methods

NameDescription
addCatch(handler, props?)Add a recovery handler for this state.
addPrefix(x)Add a prefix to the stateId of this state.
addRetry(props?)Add retry configuration for this state.
bindToGraph(graph)Register this state as part of the given graph.
metric(metricName, props?)Return the given named metric for this Task.
metricFailed(props?)Metric for the number of times this activity fails.
metricHeartbeatTimedOut(props?)Metric for the number of times the heartbeat times out for this activity.
metricRunTime(props?)The interval, in milliseconds, between the time the Task starts and the time it closes.
metricScheduleTime(props?)The interval, in milliseconds, for which the activity stays in the schedule state.
metricScheduled(props?)Metric for the number of times this activity is scheduled.
metricStarted(props?)Metric for the number of times this activity is started.
metricSucceeded(props?)Metric for the number of times this activity succeeds.
metricTime(props?)The interval, in milliseconds, between the time the activity is scheduled and the time it closes.
metricTimedOut(props?)Metric for the number of times this activity times out.
next(next)Continue normal execution with the given state.
toStateJson()Return the Amazon States Language object for this state.
toString()Returns a string representation of this construct.

addCatch(handler, props?)

public addCatch(handler: IChainable, props?: CatchProps): TaskStateBase

Parameters

  • handler IChainable
  • props CatchProps

Returns

  • TaskStateBase

Add a recovery handler for this state.

When a particular error occurs, execution will continue at the error handler instead of failing the state machine execution.


addPrefix(x)

public addPrefix(x: string): void

Parameters

  • x string

Add a prefix to the stateId of this state.


addRetry(props?)

public addRetry(props?: RetryProps): TaskStateBase

Parameters

  • props RetryProps

Returns

  • TaskStateBase

Add retry configuration for this state.

This controls if and how the execution will be retried if a particular error occurs.


bindToGraph(graph)

public bindToGraph(graph: StateGraph): void

Parameters

  • graph StateGraph

Register this state as part of the given graph.

Don't call this. It will be called automatically when you work with states normally.


metric(metricName, props?)

public metric(metricName: string, props?: MetricOptions): Metric

Parameters

  • metricName string
  • props MetricOptions

Returns

  • Metric

Return the given named metric for this Task.


metricFailed(props?)

public metricFailed(props?: MetricOptions): Metric

Parameters

  • props MetricOptions

Returns

  • Metric

Metric for the number of times this activity fails.


metricHeartbeatTimedOut(props?)

public metricHeartbeatTimedOut(props?: MetricOptions): Metric

Parameters

  • props MetricOptions

Returns

  • Metric

Metric for the number of times the heartbeat times out for this activity.


metricRunTime(props?)

public metricRunTime(props?: MetricOptions): Metric

Parameters

  • props MetricOptions

Returns

  • Metric

The interval, in milliseconds, between the time the Task starts and the time it closes.


metricScheduleTime(props?)

public metricScheduleTime(props?: MetricOptions): Metric

Parameters

  • props MetricOptions

Returns

  • Metric

The interval, in milliseconds, for which the activity stays in the schedule state.


metricScheduled(props?)

public metricScheduled(props?: MetricOptions): Metric

Parameters

  • props MetricOptions

Returns

  • Metric

Metric for the number of times this activity is scheduled.


metricStarted(props?)

public metricStarted(props?: MetricOptions): Metric

Parameters

  • props MetricOptions

Returns

  • Metric

Metric for the number of times this activity is started.


metricSucceeded(props?)

public metricSucceeded(props?: MetricOptions): Metric

Parameters

  • props MetricOptions

Returns

  • Metric

Metric for the number of times this activity succeeds.


metricTime(props?)

public metricTime(props?: MetricOptions): Metric

Parameters

  • props MetricOptions

Returns

  • Metric

The interval, in milliseconds, between the time the activity is scheduled and the time it closes.


metricTimedOut(props?)

public metricTimedOut(props?: MetricOptions): Metric

Parameters

  • props MetricOptions

Returns

  • Metric

Metric for the number of times this activity times out.


next(next)

public next(next: IChainable): Chain

Parameters

  • next IChainable

Returns

  • Chain

Continue normal execution with the given state.


toStateJson()

public toStateJson(): json

Returns

  • json

Return the Amazon States Language object for this state.


toString()

public toString(): string

Returns

  • string

Returns a string representation of this construct.