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COBOL SERVICE Clause - Quick Reference

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Overview

The SERVICE clause is used to call external services, web services, and APIs from COBOL programs. It enables integration with modern systems and provides a standardized way to invoke external services with proper parameter handling.

Purpose and Usage

  • External service calls - Call web services and APIs
  • System integration - Integrate with external systems
  • Modern architecture - Support service-oriented architecture
  • Parameter handling - Handle service parameters and responses
  • Error management - Manage service call errors

Syntax

The SERVICE clause is used in the PROCEDURE DIVISION for external service calls.

Basic Syntax

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* Basic SERVICE syntax
SERVICE service-name
    [USING parameter-1 parameter-2...]
    [RETURNING result-field].
 
* Complete example
IDENTIFICATION DIVISION.
PROGRAM-ID. SERVICE-EXAMPLE.
 
DATA DIVISION.
WORKING-STORAGE SECTION.
01  SERVICE-PARAMETERS.
    05  INPUT-DATA    PIC X(100).
    05  OUTPUT-DATA   PIC X(100).
01  SERVICE-RESULT    PIC XX.
 
PROCEDURE DIVISION.
MAIN-LOGIC.
    MOVE "Request data" TO INPUT-DATA
    SERVICE "EXTERNAL-SERVICE"
        USING INPUT-DATA
        RETURNING SERVICE-RESULT
    DISPLAY "Service result: " SERVICE-RESULT
    STOP RUN.

SERVICE calls external services with parameters.

Practical Examples

Examples of using the SERVICE clause in different scenarios.

Web Service Call

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* Call web service
01  WEB-SERVICE-PARAMS.
    05  USER-ID        PIC X(10).
    05  REQUEST-TYPE   PIC X(20).
    05  RESPONSE-DATA  PIC X(200).
 
PROCEDURE DIVISION.
CALL-WEB-SERVICE.
    MOVE "USER123" TO USER-ID
    MOVE "GET-PROFILE" TO REQUEST-TYPE
    
    SERVICE "USER-PROFILE-SERVICE"
        USING USER-ID REQUEST-TYPE
        RETURNING RESPONSE-DATA
    
    DISPLAY "Profile data: " RESPONSE-DATA.

SERVICE for web service calls.

Database Service Call

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* Call database service
01  DB-SERVICE-PARAMS.
    05  QUERY-TEXT     PIC X(200).
    05  RESULT-SET     PIC X(500).
    05  STATUS-CODE    PIC XX.
 
PROCEDURE DIVISION.
CALL-DB-SERVICE.
    MOVE "SELECT * FROM CUSTOMERS" TO QUERY-TEXT
    
    SERVICE "DATABASE-SERVICE"
        USING QUERY-TEXT
        RETURNING RESULT-SET STATUS-CODE
    
    IF STATUS-CODE = "00"
        DISPLAY "Query successful"
        DISPLAY "Results: " RESULT-SET
    ELSE
        DISPLAY "Query failed with status: " STATUS-CODE
    END-IF.

SERVICE for database service calls.

API Integration

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* Call external API
01  API-PARAMETERS.
    05  API-ENDPOINT   PIC X(100).
    05  API-METHOD     PIC X(10).
    05  API-DATA       PIC X(300).
    05  API-RESPONSE   PIC X(500).
 
PROCEDURE DIVISION.
CALL-EXTERNAL-API.
    MOVE "https://api.example.com/data" TO API-ENDPOINT
    MOVE "POST" TO API-METHOD
    MOVE "{"key":"value"}" TO API-DATA
    
    SERVICE "HTTP-API-SERVICE"
        USING API-ENDPOINT API-METHOD API-DATA
        RETURNING API-RESPONSE
    
    DISPLAY "API Response: " API-RESPONSE.

SERVICE for external API integration.

Best Practices

Understanding best practices ensures effective use of the SERVICE clause.

Best Practices

  • Handle errors properly - Always check service return codes
  • Validate parameters - Validate input parameters before service calls
  • Use timeouts - Implement timeout handling for service calls
  • Document service interfaces - Document service parameters and responses
  • Test thoroughly - Test service calls with various scenarios

Test Your Knowledge

1. What is the primary purpose of the SERVICE clause in COBOL?

  • To provide customer service
  • To call external services and APIs
  • To service hardware
  • To service files

2. In which COBOL division is the SERVICE clause typically used?

  • IDENTIFICATION DIVISION
  • ENVIRONMENT DIVISION
  • DATA DIVISION
  • PROCEDURE DIVISION

3. What types of services can be called using the SERVICE clause?

  • Only database services
  • Only file services
  • Web services, APIs, and external programs
  • Only hardware services

4. Is the SERVICE clause commonly used in modern COBOL applications?

  • Yes, in all applications
  • No, it is obsolete
  • Yes, in service-oriented and modern COBOL applications
  • Only in legacy systems

5. What is the relationship between SERVICE and CALL statements?

  • They are the same thing
  • SERVICE calls external services, CALL calls subprograms
  • SERVICE is for modern systems, CALL is for legacy
  • They cannot be used together

Frequently Asked Questions

Related Concepts

Service-Oriented Architecture

Service-oriented architecture concepts in COBOL.

Web Services Integration

Web services integration techniques.

API Integration

API integration methods in COBOL.

SEQUENTIAL ClauseSET Statement