COBOL Tutorial

COBOL XML-EVENT - Quick Reference

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Overview

XML-EVENT in COBOL refers to the events that occur during XML document parsing. These events allow programs to respond to different parts of an XML document as it is being processed, enabling selective data extraction and custom processing logic based on the XML structure.

Key Features

Event-driven parsing - Process XML as events occur
Selective data extraction - Extract specific data based on events
Custom processing logic - Implement custom logic for different event types
Real-time processing - Process XML content as it is parsed

Syntax and Usage

XML event handling syntax and usage patterns for different XML processing scenarios.

Basic XML Event Handling

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       IDENTIFICATION DIVISION.
       PROGRAM-ID. XML-EVENT-EXAMPLE.
       DATA DIVISION.
       WORKING-STORAGE SECTION.
       01  XML-DOCUMENT    PIC X(1000) VALUE
           "John Doe12345".
       01  XML-EVENT-TYPE  PIC X(20).
       01  XML-EVENT-NAME  PIC X(30).
       01  XML-EVENT-CONTENT PIC X(100).
       01  CUSTOMER-NAME   PIC X(30).
       01  CUSTOMER-ID     PIC 9(5).
       
       PROCEDURE DIVISION.
           XML PARSE XML-DOCUMENT
               PROCESSING PROCEDURE HANDLE-XML-EVENT
           END-XML
           
           DISPLAY "Customer Name: " CUSTOMER-NAME
           DISPLAY "Customer ID: " CUSTOMER-ID
           STOP RUN.
       
       HANDLE-XML-EVENT.
           EVALUATE XML-EVENT-TYPE
               WHEN "START-OF-ELEMENT"
                   IF XML-EVENT-NAME = "name"
                       MOVE "Y" TO PROCESSING-NAME
                   END-IF
               WHEN "CHARACTER-CONTENT"
                   IF PROCESSING-NAME = "Y"
                       MOVE XML-EVENT-CONTENT TO CUSTOMER-NAME
                       MOVE "N" TO PROCESSING-NAME
                   END-IF
           END-EVALUATE
           EXIT.

Basic XML event handling to extract customer data from XML document.

XML Event with Multiple Event Types

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       IDENTIFICATION DIVISION.
       PROGRAM-ID. XML-MULTIPLE-EVENTS.
       DATA DIVISION.
       WORKING-STORAGE SECTION.
       01  XML-DOCUMENT    PIC X(1000) VALUE
           "John50000".
       01  XML-EVENT-TYPE  PIC X(20).
       01  XML-EVENT-NAME  PIC X(30).
       01  XML-EVENT-CONTENT PIC X(100).
       01  PROCESSING-FLAGS.
           05  PROCESSING-NAME   PIC X VALUE "N".
           05  PROCESSING-SALARY PIC X VALUE "N".
       01  EMPLOYEE-DATA.
           05  EMPLOYEE-NAME   PIC X(30).
           05  EMPLOYEE-SALARY PIC 9(6).
       
       PROCEDURE DIVISION.
           XML PARSE XML-DOCUMENT
               PROCESSING PROCEDURE HANDLE-EMPLOYEE-EVENTS
           END-XML
           
           DISPLAY "Employee: " EMPLOYEE-NAME
           DISPLAY "Salary: " EMPLOYEE-SALARY
           STOP RUN.
       
       HANDLE-EMPLOYEE-EVENTS.
           EVALUATE XML-EVENT-TYPE
               WHEN "START-OF-ELEMENT"
                   EVALUATE XML-EVENT-NAME
                       WHEN "name"
                           MOVE "Y" TO PROCESSING-NAME
                       WHEN "salary"
                           MOVE "Y" TO PROCESSING-SALARY
                   END-EVALUATE
               WHEN "CHARACTER-CONTENT"
                   IF PROCESSING-NAME = "Y"
                       MOVE XML-EVENT-CONTENT TO EMPLOYEE-NAME
                       MOVE "N" TO PROCESSING-NAME
                   END-IF
                   IF PROCESSING-SALARY = "Y"
                       MOVE XML-EVENT-CONTENT TO EMPLOYEE-SALARY
                       MOVE "N" TO PROCESSING-SALARY
                   END-IF
           END-EVALUATE
           EXIT.

XML event handling for multiple data elements with processing flags.

XML Event with Error Handling

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       IDENTIFICATION DIVISION.
       PROGRAM-ID. XML-EVENT-ERROR.
       DATA DIVISION.
       WORKING-STORAGE SECTION.
       01  XML-DOCUMENT    PIC X(1000) VALUE
           "John Doedata".
       01  XML-EVENT-TYPE  PIC X(20).
       01  XML-EVENT-NAME  PIC X(30).
       01  ERROR-COUNT     PIC 9(3) VALUE 0.
       
       PROCEDURE DIVISION.
           XML PARSE XML-DOCUMENT
               PROCESSING PROCEDURE HANDLE-XML-WITH-ERRORS
           END-XML
           
           DISPLAY "Total errors: " ERROR-COUNT
           STOP RUN.
       
       HANDLE-XML-WITH-ERRORS.
           EVALUATE XML-EVENT-TYPE
               WHEN "START-OF-ELEMENT"
                   IF XML-EVENT-NAME = "invalid"
                       ADD 1 TO ERROR-COUNT
                       DISPLAY "Invalid element found: " XML-EVENT-NAME
                   END-IF
               WHEN "XML-EXCEPTION"
                   ADD 1 TO ERROR-COUNT
                   DISPLAY "XML parsing error occurred"
           END-EVALUATE
           EXIT.

XML event handling with error detection and processing.

Event Types

Start of Element

Triggered when an opening tag is encountered.

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WHEN "START-OF-ELEMENT"
    * Handle opening tag

End of Element

Triggered when a closing tag is encountered.

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WHEN "END-OF-ELEMENT"
    * Handle closing tag

Character Content

Triggered when text content is found.

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WHEN "CHARACTER-CONTENT"
    * Handle text content

XML Exception

Triggered when parsing errors occur.

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WHEN "XML-EXCEPTION"
    * Handle parsing errors

Best Practices

Use processing flags - Track which elements are being processed
Handle all event types - Provide handlers for all relevant event types
Validate event data - Check event data before processing
Error handling - Always provide error handling for XML events
Performance optimization - Only process events that are needed

XML-EVENT Quick Reference

Event Type	When Triggered	Use Case
START-OF-ELEMENT	Opening tag found	Begin element processing
END-OF-ELEMENT	Closing tag found	Complete element processing
CHARACTER-CONTENT	Text content found	Extract text data
XML-EXCEPTION	Parsing error occurs	Handle errors

Test Your Knowledge

1. What is the primary purpose of XML-EVENT in COBOL?

To generate XML documents
To handle events that occur during XML parsing and processing
To validate XML schemas
To format XML output

2. Which statement is used to handle XML events in COBOL?

XML PARSE
XML EVENT
XML HANDLE
XML PROCESS

3. What types of XML events can be handled?

Only start and end element events
Only text content events
Start element, end element, text content, and other parsing events
Only error events

4. How do you specify an event handler for XML parsing?

Using the EVENT clause
Using the PROCESSING PROCEDURE clause
Using the HANDLER clause
Using the CALL clause

5. What is the purpose of XML event handling?

To validate XML structure
To process XML content as it is parsed and extract specific data
To generate XML output
To format XML documents

Frequently Asked Questions

Related Concepts

XML Processing

XML and JSON processing in COBOL.

XML-INFORMATION

XML information and context.

Event Handling

Handle program events and exceptions.

Data Extraction

Extract and process data.

String Operations

String manipulation for XML content.

XML-CODE XML-INFORMATION

COBOL Tutorial

COBOL XML-EVENT - Quick Reference

Overview

Key Features

Syntax and Usage

Basic XML Event Handling

XML Event with Multiple Event Types

XML Event with Error Handling

Event Types

Start of Element

End of Element

Character Content

XML Exception

Best Practices

XML-EVENT Quick Reference

Test Your Knowledge

Frequently Asked Questions

Is XML-EVENT available in all COBOL compilers?

What are the main XML event types?

How do you access event data in an XML event handler?

Can you handle multiple event types in one procedure?

What is the difference between XML-EVENT and XML-INFORMATION?

Related Concepts

XML Processing

XML-INFORMATION

Event Handling

Data Extraction

String Operations

Related Pages