Qt 5.6 | Qt XML | C++ Classes | QXmlDefaultHandler

Qt 5.6.2 Reference Documentation

# QXmlDefaultHandler Class

The QXmlDefaultHandler class provides a default implementation of all the XML handler classes. More...

Header: | #include <QXmlDefaultHandler>
qmake: | QT += xml
Inherits: | QXmlContentHandler, QXmlErrorHandler, QXmlDTDHandler, QXmlEntityResolver, QXmlLexicalHandler, and QXmlDeclHandler

- List of all members, including inherited members

Note: All functions in this class are reentrant.

## Public Functions

| QXmlDefaultHandler()
virtual | ~QXmlDefaultHandler()

## Reimplemented Public Functions

virtual bool | attributeDecl(const QString &eName, const QString &aName, const QString &type, const QString &valueDefault, const QString &value)
virtual bool | characters(const QString &ch)
virtual bool | comment(const QString &ch)
virtual bool | endCDATA()
virtual bool | endDTD()
virtual bool | endDocument()
virtual bool | endElement(const QString &namespaceURI, const QString &localName, const QString &qName)
virtual bool | endEntity(const QString &name)
virtual bool | endPrefixMapping(const QString &prefix)
virtual bool | error(const QXmlParseException &exception)
virtual QString | errorString() const
virtual bool | externalEntityDecl(const QString &name, const QString &publicId, const QString &systemId)
virtual bool | fatalError(const QXmlParseException &exception)
virtual bool | ignorableWhitespace(const QString &ch)
virtual bool | internalEntityDecl(const QString &name, const QString &value)
virtual bool | notationDecl(const QString &name, const QString &publicId, const QString &systemId)
virtual bool | processingInstruction(const QString &target, const QString &data)
virtual bool | resolveEntity(const QString &publicId, const QString &systemId, QXmlInputSource *&ret)
virtual void | setDocumentLocator(QXmlLocator *locator)
virtual bool | skippedEntity(const QString &name)
virtual bool | startCDATA()
virtual bool | startDTD(const QString &name, const QString &publicId, const QString &systemId)
virtual bool | startDocument()
virtual bool | startElement(const QString &namespaceURI, const QString &localName, const QString &qName, const QXmlAttributes &atts)
virtual bool | startEntity(const QString &name)
virtual bool | startPrefixMapping(const QString &prefix, const QString &uri)
virtual bool | unparsedEntityDecl(const QString &name, const QString &publicId, const QString &systemId, const QString &notationName)
virtual bool | warning(const QXmlParseException &exception)

- 12 public functions inherited from QXmlContentHandler
- 4 public functions inherited from QXmlErrorHandler
- 3 public functions inherited from QXmlDTDHandler
- 2 public functions inherited from QXmlEntityResolver
- 8 public functions inherited from QXmlLexicalHandler
- 4 public functions inherited from QXmlDeclHandler

## Detailed Description

The QXmlDefaultHandler class provides a default implementation of all the XML handler classes.

This class gathers together the features of the specialized handler classes, making it a convenient starting point when implementing custom handlers for subclasses of QXmlReader, particularly QXmlSimpleReader. The virtual functions from each of the base classes are reimplemented in this class, providing sensible default behavior for many common cases. By subclassing this class, and overriding these functions, you can concentrate on implementing the parts of the handler relevant to your application.

The XML reader must be told which handler to use for different kinds of events during parsing. This means that, although QXmlDefaultHandler provides default implementations of functions inherited from all its base classes, we can still use specialized handlers for particular kinds of events.

For example, QXmlDefaultHandler subclasses both QXmlContentHandler and QXmlErrorHandler, so by subclassing it we can use the same handler for both of the following reader functions:

          xmlReader.setContentHandler(handler);
          xmlReader.setErrorHandler(handler);

Since the reader will inform the handler of parsing errors, it is necessary to reimplement QXmlErrorHandler::fatalError() if, for example, we want to stop parsing when such an error occurs:

      bool Handler::fatalError (const QXmlParseException & exception)
      {
          qWarning() << "Fatal error on line" << exception.lineNumber()
                     << ", column" << exception.columnNumber() << ':'
                     << exception.message();

          return false;
      }

The above function returns `false`, which tells the reader to stop parsing. To continue to use the same reader, it is necessary to create a new handler instance, and set up the reader to use it in the manner described above.

It is useful to examine some of the functions inherited by QXmlDefaultHandler, and consider why they might be reimplemented in a custom handler. Custom handlers will typically reimplement QXmlContentHandler::startDocument() to prepare the handler for new content. Document elements and the text within them can be processed by reimplementing QXmlContentHandler::startElement(), QXmlContentHandler::endElement(), and QXmlContentHandler::characters(). You may want to reimplement QXmlContentHandler::endDocument() to perform some finalization or validation on the content once the document has been read completely.

See also QXmlDTDHandler, QXmlDeclHandler, QXmlContentHandler, QXmlEntityResolver, QXmlErrorHandler, QXmlLexicalHandler, and Introduction to SAX2.

## Member Function Documentation

### QXmlDefaultHandler::QXmlDefaultHandler()

Constructs a handler for use with subclasses of QXmlReader.

### `[virtual]` QXmlDefaultHandler::~QXmlDefaultHandler()

Destroys the handler.

### `[virtual]` bool QXmlDefaultHandler::attributeDecl(const QString &eName, const QString &aName, const QString &type, const QString &valueDefault, const QString &value)

Reimplemented from QXmlDeclHandler::attributeDecl().

This reimplementation does nothing.

### `[virtual]` bool QXmlDefaultHandler::characters(const QString &ch)

Reimplemented from QXmlContentHandler::characters().

This reimplementation does nothing.

### `[virtual]` bool QXmlDefaultHandler::comment(const QString &ch)

Reimplemented from QXmlLexicalHandler::comment().

This reimplementation does nothing.

### `[virtual]` bool QXmlDefaultHandler::endCDATA()

Reimplemented from QXmlLexicalHandler::endCDATA().

This reimplementation does nothing.

### `[virtual]` bool QXmlDefaultHandler::endDTD()

Reimplemented from QXmlLexicalHandler::endDTD().

This reimplementation does nothing.

### `[virtual]` bool QXmlDefaultHandler::endDocument()

Reimplemented from QXmlContentHandler::endDocument().

This reimplementation does nothing.

### `[virtual]` bool QXmlDefaultHandler::endElement(const QString &namespaceURI, const QString &localName, const QString &qName)

Reimplemented from QXmlContentHandler::endElement().

This reimplementation does nothing.

### `[virtual]` bool QXmlDefaultHandler::endEntity(const QString &name)

Reimplemented from QXmlLexicalHandler::endEntity().

This reimplementation does nothing.

### `[virtual]` bool QXmlDefaultHandler::endPrefixMapping(const QString &prefix)

Reimplemented from QXmlContentHandler::endPrefixMapping().

This reimplementation does nothing.

### `[virtual]` bool QXmlDefaultHandler::error(const QXmlParseException &exception)

Reimplemented from QXmlErrorHandler::error().

This reimplementation does nothing.

### `[virtual]` QString QXmlDefaultHandler::errorString() const

Reimplemented from QXmlContentHandler::errorString().

Returns the default error string.

### `[virtual]` bool QXmlDefaultHandler::externalEntityDecl(const QString &name, const QString &publicId, const QString &systemId)

Reimplemented from QXmlDeclHandler::externalEntityDecl().

This reimplementation does nothing.

### `[virtual]` bool QXmlDefaultHandler::fatalError(const QXmlParseException &exception)

Reimplemented from QXmlErrorHandler::fatalError().

This reimplementation does nothing.

### `[virtual]` bool QXmlDefaultHandler::ignorableWhitespace(const QString &ch)

Reimplemented from QXmlContentHandler::ignorableWhitespace().

This reimplementation does nothing.

### `[virtual]` bool QXmlDefaultHandler::internalEntityDecl(const QString &name, const QString &value)

Reimplemented from QXmlDeclHandler::internalEntityDecl().

This reimplementation does nothing.

### `[virtual]` bool QXmlDefaultHandler::notationDecl(const QString &name, const QString &publicId, const QString &systemId)

Reimplemented from QXmlDTDHandler::notationDecl().

This reimplementation does nothing.

### `[virtual]` bool QXmlDefaultHandler::processingInstruction(const QString &target, const QString &data)

Reimplemented from QXmlContentHandler::processingInstruction().

This reimplementation does nothing.

### `[virtual]` bool QXmlDefaultHandler::resolveEntity(const QString &publicId, const QString &systemId, QXmlInputSource *&ret)

Reimplemented from QXmlEntityResolver::resolveEntity().

Sets ret to 0, so that the reader uses the system identifier provided in the XML document.

### `[virtual]` void QXmlDefaultHandler::setDocumentLocator(QXmlLocator *locator)

Reimplemented from QXmlContentHandler::setDocumentLocator().

This reimplementation does nothing.

### `[virtual]` bool QXmlDefaultHandler::skippedEntity(const QString &name)

Reimplemented from QXmlContentHandler::skippedEntity().

This reimplementation does nothing.

### `[virtual]` bool QXmlDefaultHandler::startCDATA()

Reimplemented from QXmlLexicalHandler::startCDATA().

This reimplementation does nothing.

### `[virtual]` bool QXmlDefaultHandler::startDTD(const QString &name, const QString &publicId, const QString &systemId)

Reimplemented from QXmlLexicalHandler::startDTD().

This reimplementation does nothing.

### `[virtual]` bool QXmlDefaultHandler::startDocument()

Reimplemented from QXmlContentHandler::startDocument().

This reimplementation does nothing.

### `[virtual]` bool QXmlDefaultHandler::startElement(const QString &namespaceURI, const QString &localName, const QString &qName, const QXmlAttributes &atts)

Reimplemented from QXmlContentHandler::startElement().

This reimplementation does nothing.

### `[virtual]` bool QXmlDefaultHandler::startEntity(const QString &name)

Reimplemented from QXmlLexicalHandler::startEntity().

This reimplementation does nothing.

### `[virtual]` bool QXmlDefaultHandler::startPrefixMapping(const QString &prefix, const QString &uri)

Reimplemented from QXmlContentHandler::startPrefixMapping().

This reimplementation does nothing.

### `[virtual]` bool QXmlDefaultHandler::unparsedEntityDecl(const QString &name, const QString &publicId, const QString &systemId, const QString &notationName)

Reimplemented from QXmlDTDHandler::unparsedEntityDecl().

This reimplementation does nothing.

### `[virtual]` bool QXmlDefaultHandler::warning(const QXmlParseException &exception)

Reimplemented from QXmlErrorHandler::warning().

This reimplementation does nothing.