# Poco::XML

# class XMLReader

Library: XML
Package: SAX
Header: Poco/SAX/XMLReader.h

## Description

Interface for reading an XML document using callbacks. XMLReader is the interface that an XML parser's SAX2 driver must implement. This interface allows an application to set and query features and properties in the parser, to register event handlers for document processing, and to initiate a document parse. All SAX interfaces are assumed to be synchronous: the parse methods must not return until parsing is complete, and readers must wait for an event-handler callback to return before reporting the next event.

## Inheritance

Known Derived Classes: DOMSerializer, SAXParser, WhitespaceFilter, XMLFilterImpl, XMLFilter

## Member Summary

Member Functions: getContentHandler, getDTDHandler, getEntityResolver, getErrorHandler, getFeature, getProperty, parse, parseMemoryNP, setContentHandler, setDTDHandler, setEntityResolver, setErrorHandler, setFeature, setProperty

## Destructor

### ~XMLReader

virtual ~XMLReader();

## Member Functions

### getContentHandler

virtual ContentHandler * getContentHandler() const = 0;

Return the current content handler.

### getDTDHandler

virtual DTDHandler * getDTDHandler() const = 0;

Return the current DTD handler.

### getEntityResolver

virtual EntityResolver * getEntityResolver() const = 0;

Return the current entity resolver.

### getErrorHandler

virtual ErrorHandler * getErrorHandler() const = 0;

Return the current error handler.

### getFeature

virtual bool getFeature(
const XMLString & featureId
) const = 0;

Look up the value of a feature.

The feature name is any fully-qualified URI. It is possible for an XMLReader to recognize a feature name but temporarily be unable to return its value. Some feature values may be available only in specific contexts, such as before, during, or after a parse. Also, some feature values may not be programmatically accessible. (In the case of an adapter for SAX1 Parser, there is no implementation-independent way to expose whether the underlying parser is performing validation, expanding external entities, and so forth.)

All XMLReaders are required to recognize the http://xml.org/sax/features/namespaces and the http://xml.org/sax/features/namespace-prefixes feature names. Implementors are free (and encouraged) to invent their own features, using names built on their own URIs.

### getProperty

virtual void * getProperty(
const XMLString & propertyId
) const = 0;

Look up the value of a property. String values are returned as XMLChar* The property name is any fully-qualified URI. It is possible for an XMLReader to recognize a property name but temporarily be unable to return its value. Some property values may be available only in specific contexts, such as before, during, or after a parse.

XMLReaders are not required to recognize any specific property names, though an initial core set is documented for SAX2.

Implementors are free (and encouraged) to invent their own properties, using names built on their own URIs.

### parse

virtual void parse(
InputSource * pSource
) = 0;

Parse an XML document.

The application can use this method to instruct the XML reader to begin parsing an XML document from any valid input source (a character stream, a byte stream, or a URI).

Applications may not invoke this method while a parse is in progress (they should create a new XMLReader instead for each nested XML document). Once a parse is complete, an application may reuse the same XMLReader object, possibly with a different input source. Configuration of the XMLReader object (such as handler bindings and values established for feature flags and properties) is unchanged by completion of a parse, unless the definition of that aspect of the configuration explicitly specifies other behavior. (For example, feature flags or properties exposing characteristics of the document being parsed.)

During the parse, the XMLReader will provide information about the XML document through the registered event handlers.

This method is synchronous: it will not return until parsing has ended. If a client application wants to terminate parsing early, it should throw an exception.

### parse

virtual void parse(
const XMLString & systemId
) = 0;

Parse an XML document from a system identifier. See also parse(InputSource*).

### parseMemoryNP

virtual void parseMemoryNP(
const char * xml,
std::size_t size
) = 0;

Parse an XML document from memory. See also parse(InputSource*).

### setContentHandler

virtual void setContentHandler(
ContentHandler * pContentHandler
) = 0;

Allow an application to register a content event handler.

If the application does not register a content handler, all content events reported by the SAX parser will be silently ignored.

Applications may register a new or different handler in the middle of a parse, and the SAX parser must begin using the new handler immediately.

### setDTDHandler

virtual void setDTDHandler(
DTDHandler * pDTDHandler
) = 0;

Allow an application to register a DTD event handler.

If the application does not register a DTD handler, all DTD events reported by the SAX parser will be silently ignored.

Applications may register a new or different handler in the middle of a parse, and the SAX parser must begin using the new handler immediately.

### setEntityResolver

virtual void setEntityResolver(
EntityResolver * pResolver
) = 0;

Allow an application to register an entity resolver.

If the application does not register an entity resolver, the XMLReader will perform its own default resolution.

Applications may register a new or different resolver in the middle of a parse, and the SAX parser must begin using the new resolver immediately.

### setErrorHandler

virtual void setErrorHandler(
ErrorHandler * pErrorHandler
) = 0;

Allow an application to register an error event handler.

If the application does not register an error handler, all error events reported by the SAX parser will be silently ignored; however, normal processing may not continue. It is highly recommended that all SAX applications implement an error handler to avoid unexpected bugs.

Applications may register a new or different handler in the middle of a parse, and the SAX parser must begin using the new handler immediately.

### setFeature

virtual void setFeature(
const XMLString & featureId,
bool state
) = 0;

Set the state of a feature.

The feature name is any fully-qualified URI. It is possible for an XMLReader to expose a feature value but to be unable to change the current value. Some feature values may be immutable or mutable only in specific contexts, such as before, during, or after a parse.

All XMLReaders are required to support setting http://xml.org/sax/features/namespaces to true and http://xml.org/sax/features/namespace-prefixes to false.

### setProperty

virtual void setProperty(
const XMLString & propertyId,
const XMLString & value
) = 0;

Set the value of a property.

The property name is any fully-qualified URI. It is possible for an XMLReader to recognize a property name but to be unable to change the current value. Some property values may be immutable or mutable only in specific contexts, such as before, during, or after a parse.

XMLReaders are not required to recognize setting any specific property names, though a core set is defined by SAX2.

This method is also the standard mechanism for setting extended handlers.

### setProperty

virtual void setProperty(
const XMLString & propertyId,
void * value
) = 0;

Set the value of a property. See also setProperty(const XMLString&, const XMLString&).

## Variables

### FEATURE_EXTERNAL_GENERAL_ENTITIES

static const XMLString FEATURE_EXTERNAL_GENERAL_ENTITIES;

### FEATURE_EXTERNAL_PARAMETER_ENTITIES

static const XMLString FEATURE_EXTERNAL_PARAMETER_ENTITIES;

### FEATURE_NAMESPACES

static const XMLString FEATURE_NAMESPACES;

### FEATURE_NAMESPACE_PREFIXES

static const XMLString FEATURE_NAMESPACE_PREFIXES;

### FEATURE_STRING_INTERNING

static const XMLString FEATURE_STRING_INTERNING;

### FEATURE_VALIDATION

static const XMLString FEATURE_VALIDATION;

### PROPERTY_DECLARATION_HANDLER

static const XMLString PROPERTY_DECLARATION_HANDLER;

### PROPERTY_LEXICAL_HANDLER

static const XMLString PROPERTY_LEXICAL_HANDLER;