INVOKE Step

The INVOKE step is the most fundamental step type in Joynare Nexus. It is used to call other services, whether they are built-in system services, other Flow Services, or Adapter services.

Properties

Property	Type	Description
type	string	Must be invoke.
service	string	The fully qualified name of the service (e.g., system.string:Uppercase).
input	object	(Optional) Explicit field mappings for the service inputs.
output	object	(Optional) Explicit field mappings for the service results.

Mapping Logic

The INVOKE step uses a powerful "Mixed Mode" mapping system to move data between the Pipeline and the service.

1. Input Mapping

When calling a service, you can provide data in three ways:

• Automatic: If a pipeline field name matches a service input name.
• Explicit: Using ${pipelineField} to map a specific pipeline variable.
• Literal: Providing a fixed value directly in the YAML.

2. Output Mapping

When a service returns, its results are merged back into the pipeline:

• Full Merge (Default): If no output is defined, all results are added to the pipeline.
• Explicit Rename: Use the output property to map a result field to a different name in the pipeline.

Example: Calling a String Service

- name: "ConvertName"
  type: "invoke"
  service: "system.string:Uppercase"
  input:
    text: "${firstName}" # Explicitly map 'firstName' to 'text'
  output:
    result: "upperName"  # Map 'result' from service to 'upperName' in pipeline

Data Flow

Initial Pipeline:

{ "firstName": "john" }

Service Execution:

• Input to Uppercase: { "text": "john" }
• Result from Uppercase: { "result": "JOHN" }

Resulting Pipeline:

{
  "firstName": "john",
  "upperName": "JOHN"
}

(Note: 'firstName' remains, and 'upperName' is added based on the output mapping)

Types of Services You Can Invoke

• Built-in Services: Core functions provided by the ESB (e.g., system.math, system.json).
• Flow Services: Other YAML-defined workflows (nested flows).
• Adapter Services: Direct interactions with databases or external APIs.

Tips

• Encapsulation: Use INVOKE to call small, reusable Flow Services to keep your main flows clean.
• Validation: Ensure the service name is correctly qualified with its namespace.
• Error Handling: If an invoked service fails, the error will bubble up to the parent flow unless handled by a SEQUENCE step.