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COBOL XML PARSE - Quick Reference

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Overview

XML PARSE is a COBOL feature that allows you to parse and process XML data using an event-driven approach. It provides a structured way to handle XML documents by calling specific procedures for different XML events such as start tags, end tags, and content, enabling efficient processing of XML data in COBOL applications.

Purpose and Usage

  • XML data processing and parsing
  • Event-driven XML handling
  • Memory-efficient processing
  • Web service integration
  • Configuration file processing

Syntax

XML PARSE follows specific syntax patterns for parsing XML data:

Basic XML PARSE Syntax

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* Basic XML PARSE syntax
XML PARSE xml-data
    PROCESSING PROCEDURE xml-parser
    ON EXCEPTION
        PERFORM xml-error-handling
END-XML.
 
* XML PARSE with event handlers
XML PARSE xml-content
    PROCESSING PROCEDURE xml-event-handler
    ON EXCEPTION
        DISPLAY "XML parsing error"
        PERFORM error-recovery
END-XML.
 
* XML PARSE with specific handlers
XML PARSE xml-document
    PROCESSING PROCEDURE xml-parser
    ON EXCEPTION
        PERFORM xml-exception-handling
    NOT ON EXCEPTION
        PERFORM xml-success-processing
END-XML.

XML PARSE uses event-driven processing with specific handlers.

Event Handler Procedures

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* XML event handler procedures
XML-PARSER.
    * Handle different XML events
    EVALUATE XML-EVENT
        WHEN "START-OF-ELEMENT"
            PERFORM handle-start-element
        WHEN "END-OF-ELEMENT"
            PERFORM handle-end-element
        WHEN "CONTENT-OF-ELEMENT"
            PERFORM handle-content
        WHEN "START-OF-DOCUMENT"
            PERFORM handle-document-start
        WHEN "END-OF-DOCUMENT"
            PERFORM handle-document-end
        WHEN OTHER
            PERFORM handle-other-event
    END-EVALUATE.
 
HANDLE-START-ELEMENT.
    * Process start tag
    DISPLAY "Start element: " XML-ELEMENT-NAME.
    PERFORM process-element-attributes.
 
HANDLE-END-ELEMENT.
    * Process end tag
    DISPLAY "End element: " XML-ELEMENT-NAME.
 
HANDLE-CONTENT.
    * Process element content
    DISPLAY "Content: " XML-CONTENT.

Practical Examples

Here are some practical uses of XML PARSE in COBOL:

Configuration File Parsing

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* Parsing XML configuration file
DATA DIVISION.
WORKING-STORAGE SECTION.
01  xml-config PIC X(1000).
01  current-element PIC X(50).
01  config-values.
    05  database-url PIC X(100).
    05  max-connections PIC 9(3).
    05  timeout PIC 9(3).
 
PROCEDURE DIVISION.
PARSE-CONFIG-FILE.
    * Load XML configuration
    MOVE xml-config-data TO xml-config.
    
    * Parse the XML configuration
    XML PARSE xml-config
        PROCESSING PROCEDURE config-parser
        ON EXCEPTION
            DISPLAY "Error parsing config file"
            PERFORM use-default-config
    END-XML.
    
    DISPLAY "Database URL: " database-url.
    DISPLAY "Max connections: " max-connections.
    DISPLAY "Timeout: " timeout.
    
    STOP RUN.
 
* Configuration parser
CONFIG-PARSER.
    EVALUATE XML-EVENT
        WHEN "START-OF-ELEMENT"
            MOVE XML-ELEMENT-NAME TO current-element
        WHEN "CONTENT-OF-ELEMENT"
            EVALUATE current-element
                WHEN "database-url"
                    MOVE XML-CONTENT TO database-url
                WHEN "max-connections"
                    MOVE XML-CONTENT TO max-connections
                WHEN "timeout"
                    MOVE XML-CONTENT TO timeout
            END-EVALUATE
    END-EVALUATE.

Parsing XML configuration files using XML PARSE.

Customer Data Processing

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* Processing customer XML data
DATA DIVISION.
WORKING-STORAGE SECTION.
01  customer-xml PIC X(2000).
01  customer-data.
    05  customer-id PIC X(10).
    05  customer-name PIC X(50).
    05  customer-email PIC X(100).
01  current-field PIC X(20).
01  record-count PIC 9(4) VALUE 0.
 
PROCEDURE DIVISION.
PROCESS-CUSTOMER-XML.
    * Load customer XML data
    MOVE customer-xml-data TO customer-xml.
    
    * Parse customer XML
    XML PARSE customer-xml
        PROCESSING PROCEDURE customer-parser
        ON EXCEPTION
            DISPLAY "Error processing customer XML"
            STOP RUN
    END-XML.
    
    DISPLAY "Processed " record-count " customer records".
    STOP RUN.
 
* Customer data parser
CUSTOMER-PARSER.
    EVALUATE XML-EVENT
        WHEN "START-OF-ELEMENT"
            MOVE XML-ELEMENT-NAME TO current-field
            IF current-field = "customer"
                * Start of new customer record
                INITIALIZE customer-data
            END-IF
        WHEN "CONTENT-OF-ELEMENT"
            EVALUATE current-field
                WHEN "id"
                    MOVE XML-CONTENT TO customer-id
                WHEN "name"
                    MOVE XML-CONTENT TO customer-name
                WHEN "email"
                    MOVE XML-CONTENT TO customer-email
            END-EVALUATE
        WHEN "END-OF-ELEMENT"
            IF XML-ELEMENT-NAME = "customer"
                * End of customer record
                ADD 1 TO record-count
                PERFORM process-customer-record
            END-IF
    END-EVALUATE.
 
PROCESS-CUSTOMER-RECORD.
    * Process the complete customer record
    DISPLAY "Customer: " customer-id " - " customer-name.
    * Additional processing logic here.

Processing customer XML data with structured parsing.

Best Practices

  • Always provide exception handling for XML parsing errors.
  • Use meaningful procedure names for event handlers.
  • Validate XML content before processing.
  • Handle all relevant XML events appropriately.
  • Consider memory usage when processing large XML documents.
  • Document the expected XML structure and event handling logic.

Common Pitfalls

  • Not handling XML parsing exceptions properly.
  • Ignoring important XML events in event handlers.
  • Not validating XML content before processing.
  • Creating overly complex event handling logic.
  • Not considering XML namespace handling.

Test Your Knowledge

1. What is XML PARSE in COBOL?

  • A file operation
  • An XML parsing mechanism
  • A data declaration
  • A program structure

2. What type of parsing does XML PARSE use?

  • DOM parsing
  • SAX-like event-driven parsing
  • Stream parsing
  • Tree parsing

3. What events does XML PARSE handle?

  • Only start and end tags
  • Start tags, end tags, and content
  • Only content
  • Only attributes

4. Where are XML PARSE event handlers defined?

  • In the PROCEDURE DIVISION
  • In the DATA DIVISION
  • In the ENVIRONMENT DIVISION
  • In the WORKING-STORAGE SECTION

5. What is the primary benefit of using XML PARSE?

  • Faster processing
  • Memory efficiency
  • Structured XML processing
  • Better error handling

Frequently Asked Questions

Related Concepts

XML GENERATE

Generating XML data in COBOL.

XML Processing

Comprehensive XML processing in COBOL.

Web Services

Integrating with web services using XML.

Data Processing

Processing various data formats.

Event-Driven Programming

Event-driven programming patterns.

WITH NO ADVANCINGXML GENERATE