COBOL Tutorial

COBOL EXCEPTION-OBJECT Clause - Quick Reference

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Overview

The EXCEPTION-OBJECT clause is used in object-oriented COBOL to define and work with exception objects that encapsulate error information and provide structured exception handling capabilities.

Purpose and Usage

Exception encapsulation - Encapsulate error information in objects
Structured error handling - Provide structured exception handling
Error context preservation - Preserve error context and details
Object-oriented error management - Use object-oriented principles for error handling
Exception inheritance - Support exception class inheritance

Exception Object Concept

Exception Object: [Error Information] → [Exception Methods] → [Handling Logic]

Exception Flow: [Exception Occurs] → [Exception Object Created] → [Exception Handled]

Object Features: [Inheritance] [Polymorphism] [Encapsulation] [Methods]

EXCEPTION-OBJECT provides object-oriented exception handling capabilities

EXCEPTION-OBJECT enables structured and object-oriented exception handling in COBOL.

Syntax

The EXCEPTION-OBJECT clause follows specific syntax patterns and is used within exception handling sections and object definitions in object-oriented COBOL.

Basic Syntax

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* Basic EXCEPTION-OBJECT clause syntax
EXCEPTION-OBJECT exception-name.
    * Exception object definition
END EXCEPTION-OBJECT.
 
* Examples
EXCEPTION-OBJECT FileException.
    * File-related exception handling
END EXCEPTION-OBJECT.
 
EXCEPTION-OBJECT DataException.
    * Data-related exception handling
END EXCEPTION-OBJECT.
 
EXCEPTION-OBJECT SystemException.
    * System-related exception handling
END EXCEPTION-OBJECT.
 
* Complete example with methods
EXCEPTION-OBJECT CustomException.
    DATA DIVISION.
    WORKING-STORAGE SECTION.
    01 ERROR-CODE PIC 9(4).
    01 ERROR-MESSAGE PIC X(100).
    
    METHOD-ID GET-ERROR-CODE.
    DATA DIVISION.
    LINKAGE SECTION.
    01 RETURN-CODE PIC 9(4).
    PROCEDURE DIVISION RETURNING RETURN-CODE.
        MOVE ERROR-CODE TO RETURN-CODE
    END METHOD.
    
    METHOD-ID GET-ERROR-MESSAGE.
    DATA DIVISION.
    LINKAGE SECTION.
    01 RETURN-MESSAGE PIC X(100).
    PROCEDURE DIVISION RETURNING RETURN-MESSAGE.
        MOVE ERROR-MESSAGE TO RETURN-MESSAGE
    END METHOD.
END EXCEPTION-OBJECT.

EXCEPTION-OBJECT is used to define exception classes with methods and properties.

Exception Object Types

Exception Type	Description	Use Case
SystemException	System-level exceptions	Operating system errors
FileException	File operation exceptions	File I/O errors
DataException	Data processing exceptions	Data validation errors
CustomException	User-defined exceptions	Application-specific errors
BusinessException	Business logic exceptions	Business rule violations

Usage in Exception Handling

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* Using EXCEPTION-OBJECT in exception handling
PROCEDURE DIVISION.
    * Try block
    TRY
        * Code that may throw exceptions
        PERFORM PROCESS-DATA
    CATCH FileException AS file-ex
        * Handle file exceptions
        DISPLAY "File error: " file-ex:GET-ERROR-MESSAGE
    CATCH DataException AS data-ex
        * Handle data exceptions
        DISPLAY "Data error: " data-ex:GET-ERROR-CODE
    CATCH SystemException AS sys-ex
        * Handle system exceptions
        DISPLAY "System error: " sys-ex:GET-ERROR-MESSAGE
    END-TRY
 
* Exception object instantiation
PROCEDURE DIVISION.
    * Create exception object
    INVOKE CustomException "new" RETURNING exception-obj
    * Set exception properties
    INVOKE exception-obj "SET-ERROR-CODE" USING 1001
    INVOKE exception-obj "SET-ERROR-MESSAGE" USING "Custom error occurred"
    * Throw the exception
    RAISE exception-obj

EXCEPTION-OBJECT is used within TRY-CATCH blocks for structured exception handling.

Common Use Cases

EXCEPTION-OBJECT is commonly used in specific scenarios where structured exception handling and error management is needed.

File Operation Exception Handling

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* File operation exception handling with EXCEPTION-OBJECT
EXCEPTION-OBJECT FileOperationException.
    DATA DIVISION.
    WORKING-STORAGE SECTION.
    01 FILE-NAME PIC X(50).
    01 OPERATION-TYPE PIC X(10).
    01 ERROR-DETAILS PIC X(200).
    
    METHOD-ID SET-FILE-INFO.
    DATA DIVISION.
    LINKAGE SECTION.
    01 FILE-NAME-PARAM PIC X(50).
    01 OPERATION-PARAM PIC X(10).
    PROCEDURE DIVISION USING FILE-NAME-PARAM OPERATION-PARAM.
        MOVE FILE-NAME-PARAM TO FILE-NAME
        MOVE OPERATION-PARAM TO OPERATION-TYPE
    END METHOD.
    
    METHOD-ID GET-ERROR-SUMMARY.
    DATA DIVISION.
    LINKAGE SECTION.
    01 SUMMARY PIC X(100).
    PROCEDURE DIVISION RETURNING SUMMARY.
        STRING "File: " FILE-NAME " Operation: " OPERATION-TYPE
               " Error: " ERROR-DETAILS
               DELIMITED BY SIZE INTO SUMMARY
    END METHOD.
END EXCEPTION-OBJECT.
 
* Usage in file operations
PROCEDURE DIVISION.
    TRY
        OPEN INPUT data-file
        READ data-file
        CLOSE data-file
    CATCH FileOperationException AS file-ex
        INVOKE file-ex "SET-FILE-INFO" USING "data-file" "READ"
        DISPLAY "File operation failed: " file-ex:GET-ERROR-SUMMARY
    END-TRY

Define specific exception types for different file operations.

Data Validation Exception Handling

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* Data validation exception handling with EXCEPTION-OBJECT
EXCEPTION-OBJECT DataValidationException.
    DATA DIVISION.
    WORKING-STORAGE SECTION.
    01 FIELD-NAME PIC X(30).
    01 EXPECTED-VALUE PIC X(50).
    01 ACTUAL-VALUE PIC X(50).
    01 VALIDATION-RULE PIC X(100).
    
    METHOD-ID SET-VALIDATION-INFO.
    DATA DIVISION.
    LINKAGE SECTION.
    01 FIELD-NAME-PARAM PIC X(30).
    01 EXPECTED-VAL PIC X(50).
    01 ACTUAL-VAL PIC X(50).
    01 RULE-PARAM PIC X(100).
    PROCEDURE DIVISION USING FIELD-NAME-PARAM EXPECTED-VAL ACTUAL-VAL RULE-PARAM.
        MOVE FIELD-NAME-PARAM TO FIELD-NAME
        MOVE EXPECTED-VAL TO EXPECTED-VALUE
        MOVE ACTUAL-VAL TO ACTUAL-VALUE
        MOVE RULE-PARAM TO VALIDATION-RULE
    END METHOD.
    
    METHOD-ID GET-VALIDATION-REPORT.
    DATA DIVISION.
    LINKAGE SECTION.
    01 REPORT PIC X(200).
    PROCEDURE DIVISION RETURNING REPORT.
        STRING "Field: " FIELD-NAME " Expected: " EXPECTED-VALUE
               " Actual: " ACTUAL-VALUE " Rule: " VALIDATION-RULE
               DELIMITED BY SIZE INTO REPORT
    END METHOD.
END EXCEPTION-OBJECT.
 
* Usage in data validation
PROCEDURE DIVISION.
    TRY
        IF customer-age < 18
            INVOKE DataValidationException "new" RETURNING validation-ex
            INVOKE validation-ex "SET-VALIDATION-INFO" 
                USING "customer-age" ">= 18" customer-age "Age must be 18 or older"
            RAISE validation-ex
        END-IF
    CATCH DataValidationException AS val-ex
        DISPLAY "Validation failed: " val-ex:GET-VALIDATION-REPORT
    END-TRY

Create structured validation exceptions with detailed error information.

Business Logic Exception Handling

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* Business logic exception handling with EXCEPTION-OBJECT
EXCEPTION-OBJECT BusinessRuleException.
    DATA DIVISION.
    WORKING-STORAGE SECTION.
    01 RULE-ID PIC X(20).
    01 BUSINESS-CONTEXT PIC X(100).
    01 VIOLATION-DETAILS PIC X(200).
    01 SEVERITY-LEVEL PIC X(10).
    
    METHOD-ID SET-BUSINESS-INFO.
    DATA DIVISION.
    LINKAGE SECTION.
    01 RULE-ID-PARAM PIC X(20).
    01 CONTEXT-PARAM PIC X(100).
    01 DETAILS-PARAM PIC X(200).
    01 SEVERITY-PARAM PIC X(10).
    PROCEDURE DIVISION USING RULE-ID-PARAM CONTEXT-PARAM DETAILS-PARAM SEVERITY-PARAM.
        MOVE RULE-ID-PARAM TO RULE-ID
        MOVE CONTEXT-PARAM TO BUSINESS-CONTEXT
        MOVE DETAILS-PARAM TO VIOLATION-DETAILS
        MOVE SEVERITY-PARAM TO SEVERITY-LEVEL
    END METHOD.
    
    METHOD-ID GET-BUSINESS-REPORT.
    DATA DIVISION.
    LINKAGE SECTION.
    01 REPORT PIC X(300).
    PROCEDURE DIVISION RETURNING REPORT.
        STRING "Rule: " RULE-ID " Context: " BUSINESS-CONTEXT
               " Details: " VIOLATION-DETAILS " Severity: " SEVERITY-LEVEL
               DELIMITED BY SIZE INTO REPORT
    END METHOD.
END EXCEPTION-OBJECT.
 
* Usage in business logic
PROCEDURE DIVISION.
    TRY
        IF account-balance < minimum-balance
            INVOKE BusinessRuleException "new" RETURNING business-ex
            INVOKE business-ex "SET-BUSINESS-INFO" 
                USING "MIN_BALANCE" "Account maintenance" 
                      "Balance below minimum" "HIGH"
            RAISE business-ex
        END-IF
    CATCH BusinessRuleException AS bus-ex
        DISPLAY "Business rule violation: " bus-ex:GET-BUSINESS-REPORT
    END-TRY

Handle business rule violations with structured exception objects.

Best Practices and Tips

Following these best practices ensures effective use of the EXCEPTION-OBJECT clause for proper exception handling.

EXCEPTION-OBJECT Design Principles

Create specific exception types - Define specific exception classes for different error types
Include relevant information - Store all relevant error information in exception objects
Provide useful methods - Include methods for accessing and formatting error information
Use inheritance appropriately - Create exception hierarchies for related error types
Document exception behavior - Clearly document what each exception type represents
Handle exceptions at appropriate levels - Catch exceptions at the right level in your program

Common Pitfalls to Avoid

Pitfall	Problem	Solution
Generic exception handling	Loss of specific error information	Create specific exception types for different error categories
Empty exception objects	No useful error information	Always populate exception objects with relevant error details
Exception swallowing	Errors hidden from debugging	Always log or handle exceptions appropriately
Overly complex exception hierarchies	Difficult to maintain and understand	Keep exception hierarchies simple and logical
Performance impact of exceptions	Slow performance with frequent exceptions	Use exceptions for exceptional cases, not normal flow control

Performance Considerations

Exception object creation overhead - Creating exception objects has overhead
Exception handling stack - Exception handling involves stack unwinding
Memory usage - Exception objects consume memory
Exception frequency - Frequent exceptions can impact performance
Exception object size - Large exception objects use more memory
Exception propagation - Exception propagation can be expensive

When to Use EXCEPTION-OBJECT

Use Case	EXCEPTION-OBJECT Suitability	Reasoning
Complex error handling	Excellent	Perfect for structured exception handling
Object-oriented applications	Excellent	Natural fit for object-oriented programming
Error information preservation	Excellent	Excellent for preserving error context
Simple error handling	Poor	Overkill for simple error conditions
Performance-critical code	Poor	Exception handling overhead may be too high

EXCEPTION-OBJECT Clause Quick Reference

Usage	Syntax	Example
Basic exception object	EXCEPTION-OBJECT exception-name	EXCEPTION-OBJECT MyException
Exception with methods	EXCEPTION-OBJECT exception-name with METHOD-ID	EXCEPTION-OBJECT MyException with GET-ERROR-INFO method
Exception instantiation	INVOKE exception-name "new"	INVOKE MyException "new" RETURNING ex-obj
Exception raising	RAISE exception-object	RAISE ex-obj
Exception catching	CATCH exception-name AS variable	CATCH MyException AS my-ex

Test Your Knowledge

1. What is the primary purpose of the EXCEPTION-OBJECT clause in COBOL?

To define data types
To handle and manage exception objects in object-oriented COBOL
To control file operations
To perform calculations

2. Where is the EXCEPTION-OBJECT clause typically used?

In DATA DIVISION
In exception handling sections and object definitions
In PROCEDURE DIVISION
In ENVIRONMENT DIVISION

3. What information does EXCEPTION-OBJECT provide?

Only error codes
Only error messages
Comprehensive exception information including error details, context, and handling methods
Only program flow

4. When is EXCEPTION-OBJECT most useful?

In simple programs
In complex applications requiring robust error handling and exception management
Only during compilation
Only during program termination

5. How does EXCEPTION-OBJECT relate to exception handling?

They are completely independent
EXCEPTION-OBJECT is essential for modern exception handling in object-oriented COBOL
EXCEPTION-OBJECT overrides other exception handling features
They serve the same purpose

COBOL Tutorial

COBOL EXCEPTION-OBJECT Clause - Quick Reference

Overview

Purpose and Usage

Exception Object Concept

Syntax

Basic Syntax

Exception Object Types

Usage in Exception Handling

Common Use Cases

File Operation Exception Handling

Data Validation Exception Handling

Business Logic Exception Handling

Best Practices and Tips

EXCEPTION-OBJECT Design Principles

Common Pitfalls to Avoid

Performance Considerations

When to Use EXCEPTION-OBJECT

EXCEPTION-OBJECT Clause Quick Reference

Test Your Knowledge

Frequently Asked Questions

Related Concepts

EXCEPTION Clause

RAISE Statement

TRY-CATCH Blocks

Object-Oriented COBOL

Error Handling

Related Pages

COBOL Tutorial

COBOL EXCEPTION-OBJECT Clause - Quick Reference

Overview

Purpose and Usage

Exception Object Concept

Syntax

Basic Syntax

Exception Object Types

Usage in Exception Handling

Common Use Cases

File Operation Exception Handling

Data Validation Exception Handling

Business Logic Exception Handling

Best Practices and Tips

EXCEPTION-OBJECT Design Principles

Common Pitfalls to Avoid

Performance Considerations

When to Use EXCEPTION-OBJECT

EXCEPTION-OBJECT Clause Quick Reference

Test Your Knowledge

Frequently Asked Questions

What is the difference between EXCEPTION-OBJECT and traditional error handling?

Can EXCEPTION-OBJECT be used in traditional COBOL programs?

What types of exception information can EXCEPTION-OBJECT provide?

How do you create and use EXCEPTION-OBJECT instances?

Are there performance implications when using EXCEPTION-OBJECT?

Related Concepts

EXCEPTION Clause

RAISE Statement

TRY-CATCH Blocks

Object-Oriented COBOL

Error Handling

Related Pages