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Class ZCL_LLM_HTTP_CLIENT_WRAPPER

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Overview

The zcl_llm_http_client_wrapper class provides a configurable abstraction layer for HTTP communication, tailored for integration with Large Language Model (LLM) services. It encapsulates the lifecycle management of an HTTP client, header/URL configuration, request execution, and error handling.

Public Methods:

  • constructor: Initializes the HTTP client using an RFC destination and validates its configuration. Raises zcx_llm_validation on errors.
  • get_client: Factory method to create a new client wrapper instance.
  • set_header: Assigns custom HTTP headers (e.g., API keys, authorization tokens).
  • set_url: Configures the target endpoint URL.
  • communicate: Executes the HTTP POST request, processes the response, logs the interaction, and handles errors.
  • close_client: Safely terminates the HTTP client connection.

Dependencies

  • cl_http_client: Core SAP HTTP client for communication.
  • zcx_llm_validation / zcx_llm_http_error: Custom exceptions for configuration/communication errors.
  • zif_llm_call_logger: Interface for logging API requests/responses.
  • zllm_clnt_config / zllm_providers: Configuration structures for client/provider settings.

Details

Key Logic Flow

sequenceDiagram  
    participant User  
    participant Wrapper as zcl_llm_http_client_wrapper  
    participant HTTP_Client as cl_http_client  
    participant Logger as zif_llm_call_logger  

    User->>Wrapper: constructor()  
    Wrapper->>HTTP_Client: create_by_destination()  
    alt Destination Invalid  
        HTTP_Client-->>Wrapper: Error  
        Wrapper->>User: Raises zcx_llm_validation  
    else Valid  
        HTTP_Client-->>Wrapper: Client instance  
    end  

    User->>Wrapper: set_header() / set_url()  
    User->>Wrapper: communicate()  
    Wrapper->>HTTP_Client: send() / receive()  
    HTTP_Client-->>Wrapper: Response  
    Wrapper->>Logger: log(request, response)  
    Wrapper->>HTTP_Client: reset_request()  
    alt HTTP Error  
        Wrapper->>User: Raises zcx_llm_http_error  
    end  
    User->>Wrapper: close_client()

Critical Implementation Aspects

  1. Header Management:
  2. Non-SAP headers (e.g., Authorization) are preserved across requests via get_header_fields and set_header_fields to avoid losing context (e.g., API keys).

  3. SAP-internal headers (prefixed with ~) are automatically excluded during reset.

  4. Error Handling:

  5. Constructor: Maps sy-subrc from cl_http_client creation to human-readable error messages (e.g., Destination Not Found).

  6. Communicate: Converts HTTP status codes ≥ 300 or communication failures into structured exceptions (zcx_llm_http_error).

  7. Logging:

  8. Captures metadata (timestamp, user, session ID), raw request/response data, and error messages via zif_llm_call_logger.

  9. Stateless Request Design:

  10. The communicate method resets the client’s request after execution to prevent URL/header conflicts in subsequent calls.

  11. Configuration-Driven:

  12. Relies on zllm_providers (RFC destination) and zllm_clnt_config for client-specific settings, enabling multi-provider support.