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The Object Mapper command (Command Type: 1016) enables you to map and transform data structures between different formats. This command is essential for restructuring data, mapping fields, and transforming data for downstream processing.

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Overview

The Object Mapper command provides functionality for:
  • Mapping fields between different data structures
  • Transforming data formats
  • Restructuring nested objects
  • Combining data from multiple sources
  • Creating new data structures from existing data

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Command Type

Command Type ID: 1016

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Parameters

ParameterTypeDescriptionRequired
inputstringInput data reference (e.g., @{PREVIOUS_OUTPUT})Yes
mappingobjectField mapping configurationYes
outputKeystringKey name for storing mapped resultYes
defaultValuesobjectDefault values for missing fieldsNo

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Mapping Configuration

The mapping object defines how input fields map to output fields:

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Basic Mapping

{
  "mapping": {
    "outputField": "$.inputField",
    "nestedField": "$.parent.child"
  }
}

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Array Mapping

{
  "mapping": {
    "items": "$.data.items[*]",
    "count": "$.data.items.length"
  }
}

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Usage Examples

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Basic Field Mapping

{
  "command": "object-mapper",
  "params": {
    "input": "@{PREVIOUS_OUTPUT}",
    "mapping": {
      "id": "$.data.id",
      "name": "$.data.name",
      "status": "$.data.status"
    },
    "outputKey": "mapped_data"
  }
}

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Nested Structure Mapping

{
  "command": "object-mapper",
  "params": {
    "input": "@{PREVIOUS_OUTPUT}",
    "mapping": {
      "event": {
        "id": "$.event.id",
        "title": "$.event.title",
        "date": "$.event.date"
      },
      "metadata": {
        "source": "$.metadata.source",
        "timestamp": "$.metadata.timestamp"
      }
    },
    "outputKey": "transformed_data"
  }
}

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Array Transformation

{
  "command": "object-mapper",
  "params": {
    "input": "@{PREVIOUS_OUTPUT}",
    "mapping": {
      "items": "$.data.items[*]",
      "total": "$.data.total",
      "page": "$.data.page"
    },
    "outputKey": "paginated_data"
  }
}

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Mapping with Default Values

{
  "command": "object-mapper",
  "params": {
    "input": "@{PREVIOUS_OUTPUT}",
    "mapping": {
      "id": "$.data.id",
      "name": "$.data.name",
      "status": "$.data.status"
    },
    "defaultValues": {
      "status": "unknown",
      "priority": "normal"
    },
    "outputKey": "mapped_data"
  }
}

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Variable Support

The Object Mapper command supports variable interpolation in:
  • Input: Use @{VARIABLE} to reference previous command output
  • Mapping Paths: Use JSONPath expressions in mapping configuration

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Common Variable Patterns

  • Previous Output: @{PREVIOUS_OUTPUT} - Output from previous command
  • Extracted Data: Reference data from Json Path command
  • Step Output: @{STEP_OUTPUT} - Output from previous step

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Output Structure

The Object Mapper command creates a new data structure based on the mapping configuration:

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Output Format

{
  "mapped_data": {
    "id": "123",
    "name": "Example",
    "status": "active"
  }
}

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Using Mapped Data

Mapped data can be used by subsequent commands: 
{
  "command": "sink",
  "params": {
    "exchange": "events",
    "routingKey": "data",
    "data": "@{PREVIOUS_OUTPUT}.mapped_data"
  }
}

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Best Practices

  • Use Descriptive Output Keys: Use clear, descriptive key names for mapped data
  • Handle Missing Fields: Use default values for optional fields
  • Test Mappings: Test mapping configurations with sample data
  • Document Mappings: Document complex mapping logic for maintainability
  • Validate Output: Verify mapped data structure matches expectations

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Common Use Cases

  • Data Transformation: Transform data structures for downstream processing
  • Field Mapping: Map fields between different formats
  • Data Restructuring: Restructure nested objects
  • API Response Transformation: Transform API responses to internal format
  • Data Normalization: Normalize data from different sources

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Troubleshooting

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Mapping Errors

If mapping fails:
  • Verify input data structure matches mapping paths
  • Check JSONPath expressions are correct
  • Ensure output key is unique

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Missing Fields

If mapped data has missing fields:
  • Use default values for optional fields
  • Verify input data contains expected fields
  • Check mapping paths are correct