An Introduction to DBMS_XMLPARSE in Oracle PL/SQL
Tags: oracle, sql, apacheage
Published: 2023-07-28 12:24:54

XML (eXtensible Markup Language) has become a popular format for storing and exchanging data due to its flexibility and self-descriptive nature. Oracle provides a powerful package called DBMS_XMLPARSER that allows developers to work with XML documents in the PL/SQL language. This package enables you to access the contents and structure of XML documents, manipulate them, and validate their data against defined rules.

In this article, we will explore the DBMS_XMLPARSER package and its essential subprograms, which provide various functionalities to handle XML data in Oracle PL/SQL.

## Understanding XML and DBMS_XMLPARSER

### What is XML?
XML is a markup language used for describing structured data. It consists of storage units called entities, which contain parsed or unparsed data. Parsed data includes both character data and markup that encodes the document's storage layout and logical structure. XML documents conform to the SGML (Standard Generalized Markup Language) standard, and they can impose constraints on storage layout and logical structure.

### Introducing DBMS_XMLPARSER
DBMS_XMLPARSER is an Oracle PL/SQL package designed to work with XML documents. It provides an XML processor, which reads XML documents and grants access to their content and structure. The package follows the W3C XML specification REC-xml-19980210 and adheres to the required behavior of an XML processor as specified by the W3C.

## Key Subprograms of DBMS_XMLPARSER
The DBMS_XMLPARSER package offers various subprograms that allow developers to perform different tasks related to XML processing. Let's take a closer look at some of the essential subprograms provided by this package:

### FREEPARSER
The FREEPARSER procedure frees a parser object, making it available for garbage collection. It helps manage resources efficiently when you are done processing XML data.

### GETDOCTYPE

The GETDOCTYPE function returns the parsed DTD (Document Type Definition). This function should be called only after parsing a DTD.

### GETDOCUMENT
The GETDOCUMENT function retrieves the document node of a DOM (Document Object Model) tree built by the parser. It should be called after parsing an XML document.

### GETRELEASEVERSION
The GETRELEASEVERSION function returns the release version of the Oracle XML Parser for PL/SQL.

### GETVALIDATIONMODE
The GETVALIDATIONMODE function retrieves the validation mode used by the parser. It returns TRUE if the parser is set to validate XML documents, and FALSE otherwise

### NEWPARSER
The NEWPARSER function creates a new parser instance. It should be called before changing the default behavior of the parser or when using other parse methods.

### PARSE
The PARSE function parses XML data stored in a given URL or file. It returns the built DOM document. If parsing fails, an application error is raised.

### PARSEBUFFER
The PARSEBUFFER procedure parses XML data stored in a buffer. It allows you to modify the default parser behavior before calling the procedure. If parsing fails, an application error is raised.

### PARSECLOB
The PARSECLOB procedure parses XML data stored in a CLOB (Character Large Object). Like PARSEBUFFER, it enables changes to the default parser behavior before parsing.

### PARSEDTD
The PARSEDTD procedure parses the DTD stored in a given URL or file. It is essential to set the DTD before parsing the XML document.

### PARSEDTDBUFFER
The PARSEDTDBUFFER procedure parses the DTD stored in a buffer. As with other parsing methods, changes to the default behavior can be applied before parsing.

### PARSEDTDCLOB
The PARSEDTDCLOB procedure parses the DTD stored in a CLOB. It allows you to specify the root element for parsing.

### SETBASEDIR
The SETBASEDIR procedure sets the base directory used to resolve relative URLs. It helps in parsing XML documents that refer to external entities or resources.

### SETDOCTYPE
The SETDOCTYPE procedure sets the DTD to be used by the parser for validation. It should be called before parsing the document.

### SETERRORLOG
The SETERRORLOG procedure sets errors to be sent to a specified file, aiding in error tracking and debugging.

### SETPRESERVEWHITESPACE
The SETPRESERVEWHITESPACE procedure sets the whitespace preserving mode for the parser. This can be useful when preserving whitespace formatting is crucial.

### SETVALIDATIONMODE
The SETVALIDATIONMODE procedure sets the validation mode for the parser. It enables or disables XML validation during parsing.

### SHOWWWARNINGS
The SHOWWARNINGS procedure turns warnings on or off for the parser. Warnings can help identify potential issues during XML processing.

## In Conclusion 
The DBMS_XMLPARSER package in Oracle PL/SQL provides a robust set of subprograms to handle XML documents efficiently. It allows developers to parse XML data, access their content and structure, and apply validation rules when needed. By utilizing the functionalities offered by DBMS_XMLPARSER, developers can effectively work with XML data in their Oracle database applications, enhancing the versatility and power of their systems.