QXmlStreamReader Class

   QXmlStreamReader xml;
   ...
   while (!xml.atEnd()) {
         xml.readNext();
         ... // do processing
   }
   if (xml.hasError()) {
         ... // do error handling
   }

Member Function Documentation

QXmlStreamReader::QXmlStreamReader(const char *data)

Creates a new stream reader that reads from data.

See also addData(), clear(), and setDevice().

QXmlStreamReader::QXmlStreamReader(const QString &data)

Creates a new stream reader that reads from data.

This function should only be used if the XML header either says the encoding is "UTF-8" or lacks any encoding information (the latter is the case of QXmlStreamWriter writing to a QString). Any other encoding is likely going to cause data corruption ("mojibake").

See also addData(), clear(), and setDevice().

QXmlStreamReader::QXmlStreamReader(const QByteArray &data)

Creates a new stream reader that reads from data.

See also addData(), clear(), and setDevice().

QXmlStreamReader::QXmlStreamReader(QIODevice *device)

Creates a new stream reader that reads from device.

See also setDevice() and clear().

QXmlStreamReader::QXmlStreamReader()

Constructs a stream reader.

See also setDevice() and addData().

QXmlStreamReader::~QXmlStreamReader()

Destructs the reader.

void QXmlStreamReader::addData(const QByteArray &data)

Adds more data for the reader to read. This function does nothing if the reader has a device().

See also readNext() and clear().

void QXmlStreamReader::addData(const QString &data)

Adds more data for the reader to read. This function does nothing if the reader has a device().

See also readNext() and clear().

void QXmlStreamReader::addData(const char *data)

Adds more data for the reader to read. This function does nothing if the reader has a device().

See also readNext() and clear().

void QXmlStreamReader::addExtraNamespaceDeclaration(const QXmlStreamNamespaceDeclaration &extraNamespaceDeclaration)

Adds an extraNamespaceDeclaration. The declaration will be valid for children of the current element, or - should the function be called before any elements are read - for the entire XML document.

This function was introduced in Qt 4.4.

See also namespaceDeclarations(), addExtraNamespaceDeclarations(), and setNamespaceProcessing().

void QXmlStreamReader::addExtraNamespaceDeclarations(const QXmlStreamNamespaceDeclarations &extraNamespaceDeclarations)

Adds a vector of declarations specified by extraNamespaceDeclarations.

This function was introduced in Qt 4.4.

See also namespaceDeclarations() and addExtraNamespaceDeclaration().

bool QXmlStreamReader::atEnd() const

Returns true if the reader has read until the end of the XML document, or if an error() has occurred and reading has been aborted. Otherwise, it returns false.

When atEnd() and hasError() return true and error() returns PrematureEndOfDocumentError, it means the XML has been well-formed so far, but a complete XML document has not been parsed. The next chunk of XML can be added with addData(), if the XML is being read from a QByteArray, or by waiting for more data to arrive if the XML is being read from a QIODevice. Either way, atEnd() will return false once more data is available.

See also hasError(), error(), device(), and QIODevice::atEnd().

QXmlStreamAttributes QXmlStreamReader::attributes() const

Returns the attributes of a StartElement.

qint64 QXmlStreamReader::characterOffset() const

Returns the current character offset, starting with 0.

See also lineNumber() and columnNumber().

void QXmlStreamReader::clear()

Removes any device() or data from the reader and resets its internal state to the initial state.

See also addData().

qint64 QXmlStreamReader::columnNumber() const

Returns the current column number, starting with 0.

See also lineNumber() and characterOffset().

QIODevice *QXmlStreamReader::device() const

Returns the current device associated with the QXmlStreamReader, or nullptr if no device has been assigned.

See also setDevice().

QStringRef QXmlStreamReader::documentEncoding() const

If the tokenType() is StartDocument, this function returns the encoding string as specified in the XML declaration. Otherwise an empty string is returned.

This function was introduced in Qt 4.4.

QStringRef QXmlStreamReader::documentVersion() const

If the tokenType() is StartDocument, this function returns the version string as specified in the XML declaration. Otherwise an empty string is returned.

This function was introduced in Qt 4.4.

QStringRef QXmlStreamReader::dtdName() const

If the tokenType() is DTD, this function returns the DTD's name. Otherwise an empty string is returned.

This function was introduced in Qt 4.4.

QStringRef QXmlStreamReader::dtdPublicId() const

If the tokenType() is DTD, this function returns the DTD's public identifier. Otherwise an empty string is returned.

This function was introduced in Qt 4.4.

QStringRef QXmlStreamReader::dtdSystemId() const

If the tokenType() is DTD, this function returns the DTD's system identifier. Otherwise an empty string is returned.

This function was introduced in Qt 4.4.

QXmlStreamEntityDeclarations QXmlStreamReader::entityDeclarations() const

If the tokenType() is DTD, this function returns the DTD's unparsed (external) entity declarations. Otherwise an empty vector is returned.

The QXmlStreamEntityDeclarations class is defined to be a QVector of QXmlStreamEntityDeclaration.

int QXmlStreamReader::entityExpansionLimit() const

Returns the maximum amount of characters a single entity is allowed to expand into. If a single entity expands past the given limit, the document is not considered well formed.

This function was introduced in Qt 5.15.

See also setEntityExpansionLimit.

QXmlStreamEntityResolver *QXmlStreamReader::entityResolver() const

Returns the entity resolver, or nullptr if there is no entity resolver.

This function was introduced in Qt 4.4.

See also setEntityResolver().

Error QXmlStreamReader::error() const

Returns the type of the current error, or NoError if no error occurred.

See also errorString() and raiseError().

QString QXmlStreamReader::errorString() const

Returns the error message that was set with raiseError().

See also error(), lineNumber(), columnNumber(), and characterOffset().

bool QXmlStreamReader::hasError() const

Returns true if an error has occurred, otherwise false.

See also errorString() and error().

bool QXmlStreamReader::isCDATA() const

Returns true if the reader reports characters that stem from a CDATA section; otherwise returns false.

See also isCharacters() and text().

bool QXmlStreamReader::isCharacters() const

Returns true if tokenType() equals Characters; otherwise returns false.

See also isWhitespace() and isCDATA().

bool QXmlStreamReader::isComment() const

Returns true if tokenType() equals Comment; otherwise returns false.

bool QXmlStreamReader::isDTD() const

Returns true if tokenType() equals DTD; otherwise returns false.

bool QXmlStreamReader::isEndDocument() const

Returns true if tokenType() equals EndDocument; otherwise returns false.

bool QXmlStreamReader::isEndElement() const

Returns true if tokenType() equals EndElement; otherwise returns false.

bool QXmlStreamReader::isEntityReference() const

Returns true if tokenType() equals EntityReference; otherwise returns false.

bool QXmlStreamReader::isProcessingInstruction() const

Returns true if tokenType() equals ProcessingInstruction; otherwise returns false.

bool QXmlStreamReader::isStandaloneDocument() const

Returns true if this document has been declared standalone in the XML declaration; otherwise returns false.

If no XML declaration has been parsed, this function returns false.

bool QXmlStreamReader::isStartDocument() const

Returns true if tokenType() equals StartDocument; otherwise returns false.

bool QXmlStreamReader::isStartElement() const

Returns true if tokenType() equals StartElement; otherwise returns false.

bool QXmlStreamReader::isWhitespace() const

Returns true if the reader reports characters that only consist of white-space; otherwise returns false.

See also isCharacters() and text().

qint64 QXmlStreamReader::lineNumber() const

Returns the current line number, starting with 1.

See also columnNumber() and characterOffset().

QStringRef QXmlStreamReader::name() const

Returns the local name of a StartElement, EndElement, or an EntityReference.

See also namespaceUri() and qualifiedName().

QXmlStreamNamespaceDeclarations QXmlStreamReader::namespaceDeclarations() const

If the tokenType() is StartElement, this function returns the element's namespace declarations. Otherwise an empty vector is returned.

The QXmlStreamNamespaceDeclarations class is defined to be a QVector of QXmlStreamNamespaceDeclaration.

See also addExtraNamespaceDeclaration() and addExtraNamespaceDeclarations().

QStringRef QXmlStreamReader::namespaceUri() const

Returns the namespaceUri of a StartElement or EndElement.

See also name() and qualifiedName().

QXmlStreamNotationDeclarations QXmlStreamReader::notationDeclarations() const

If the tokenType() is DTD, this function returns the DTD's notation declarations. Otherwise an empty vector is returned.

The QXmlStreamNotationDeclarations class is defined to be a QVector of QXmlStreamNotationDeclaration.

QStringRef QXmlStreamReader::prefix() const

Returns the prefix of a StartElement or EndElement.

This function was introduced in Qt 4.4.

See also name() and qualifiedName().

QStringRef QXmlStreamReader::processingInstructionData() const

Returns the data of a ProcessingInstruction.

QStringRef QXmlStreamReader::processingInstructionTarget() const

Returns the target of a ProcessingInstruction.

QStringRef QXmlStreamReader::qualifiedName() const

Returns the qualified name of a StartElement or EndElement;

A qualified name is the raw name of an element in the XML data. It consists of the namespace prefix, followed by colon, followed by the element's local name. Since the namespace prefix is not unique (the same prefix can point to different namespaces and different prefixes can point to the same namespace), you shouldn't use qualifiedName(), but the resolved namespaceUri() and the attribute's local name().

See also name(), prefix(), and namespaceUri().

void QXmlStreamReader::raiseError(const QString &message = QString())

Raises a custom error with an optional error message.

See also error() and errorString().

QString QXmlStreamReader::readElementText(ReadElementTextBehaviour behaviour = ErrorOnUnexpectedElement)

Convenience function to be called in case a StartElement was read. Reads until the corresponding EndElement and returns all text in-between. In case of no error, the current token (see tokenType()) after having called this function is EndElement.

The function concatenates text() when it reads either Characters or EntityReference tokens, but skips ProcessingInstruction and Comment. If the current token is not StartElement, an empty string is returned.

The behaviour defines what happens in case anything else is read before reaching EndElement. The function can include the text from child elements (useful for example for HTML), ignore child elements, or raise an UnexpectedElementError and return what was read so far (default).

This function was introduced in Qt 4.6.

TokenType QXmlStreamReader::readNext()

Reads the next token and returns its type.

With one exception, once an error() is reported by readNext(), further reading of the XML stream is not possible. Then atEnd() returns true, hasError() returns true, and this function returns QXmlStreamReader::Invalid.

The exception is when error() returns PrematureEndOfDocumentError. This error is reported when the end of an otherwise well-formed chunk of XML is reached, but the chunk doesn't represent a complete XML document. In that case, parsing can be resumed by calling addData() to add the next chunk of XML, when the stream is being read from a QByteArray, or by waiting for more data to arrive when the stream is being read from a device().

See also tokenType() and tokenString().

bool QXmlStreamReader::readNextStartElement()

Reads until the next start element within the current element. Returns true when a start element was reached. When the end element was reached, or when an error occurred, false is returned.

The current element is the element matching the most recently parsed start element of which a matching end element has not yet been reached. When the parser has reached the end element, the current element becomes the parent element.

This is a convenience function for when you're only concerned with parsing XML elements. The QXmlStream Bookmarks Example makes extensive use of this function.

This function was introduced in Qt 4.6.

See also readNext().

void QXmlStreamReader::setDevice(QIODevice *device)

Sets the current device to device. Setting the device resets the stream to its initial state.

See also device() and clear().

void QXmlStreamReader::setEntityExpansionLimit(int limit)

Sets the maximum amount of characters a single entity is allowed to expand into to limit. If a single entity expands past the given limit, the document is not considered well formed.

The limit is there to prevent DoS attacks when loading unknown XML documents where recursive entity expansion could otherwise exhaust all available memory.

The default value for this property is 4096 characters.

This function was introduced in Qt 5.15.

See also entityExpansionLimit.

void QXmlStreamReader::setEntityResolver(QXmlStreamEntityResolver *resolver)

Makes resolver the new entityResolver().

The stream reader does not take ownership of the resolver. It's the callers responsibility to ensure that the resolver is valid during the entire life-time of the stream reader object, or until another resolver or nullptr is set.

This function was introduced in Qt 4.4.

See also entityResolver().

void QXmlStreamReader::skipCurrentElement()

Reads until the end of the current element, skipping any child nodes. This function is useful for skipping unknown elements.

The current element is the element matching the most recently parsed start element of which a matching end element has not yet been reached. When the parser has reached the end element, the current element becomes the parent element.

This function was introduced in Qt 4.6.

QStringRef QXmlStreamReader::text() const

Returns the text of Characters, Comment, DTD, or EntityReference.

QString QXmlStreamReader::tokenString() const

Returns the reader's current token as string.

See also tokenType().

TokenType QXmlStreamReader::tokenType() const

Returns the type of the current token.

The current token can also be queried with the convenience functions isStartDocument(), isEndDocument(), isStartElement(), isEndElement(), isCharacters(), isComment(), isDTD(), isEntityReference(), and isProcessingInstruction().

See also tokenString().