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QDomDocument ClassThe QDomDocument class represents an XML document. More... #include <QDomDocument>Inherits: QDomNode. Note: All functions in this class are reentrant, except for setContent(), which is nonreentrant. Public Functions
Detailed DescriptionThe QDomDocument class represents an XML document. The QDomDocument class represents the entire XML document. Conceptually, it is the root of the document tree, and provides the primary access to the document's data. Since elements, text nodes, comments, processing instructions, etc., cannot exist outside the context of a document, the document class also contains the factory functions needed to create these objects. The node objects created have an ownerDocument() function which associates them with the document within whose context they were created. The DOM classes that will be used most often are QDomNode, QDomDocument, QDomElement and QDomText. The parsed XML is represented internally by a tree of objects that can be accessed using the various QDom classes. All QDom classes only reference objects in the internal tree. The internal objects in the DOM tree will get deleted once the last QDom object referencing them and the QDomDocument itself are deleted. Creation of elements, text nodes, etc. is done using the various factory functions provided in this class. Using the default constructors of the QDom classes will only result in empty objects that cannot be manipulated or inserted into the Document. The QDomDocument class has several functions for creating document data, for example, createElement(), createTextNode(), createComment(), createCDATASection(), createProcessingInstruction(), createAttribute() and createEntityReference(). Some of these functions have versions that support namespaces, i.e. createElementNS() and createAttributeNS(). The createDocumentFragment() function is used to hold parts of the document; this is useful for manipulating for complex documents. The entire content of the document is set with setContent(). This function parses the string it is passed as an XML document and creates the DOM tree that represents the document. The root element is available using documentElement(). The textual representation of the document can be obtained using toString(). Note: The DOM tree might end up reserving a lot of memory if the XML document is big. For such documents, the QXmlStreamReader or the QXmlQuery classes might be better solutions. It is possible to insert a node from another document into the document using importNode(). You can obtain a list of all the elements that have a particular tag with elementsByTagName() or with elementsByTagNameNS(). The QDom classes are typically used as follows: QDomDocument doc("mydocument"); QFile file("mydocument.xml"); if (!file.open(QIODevice::ReadOnly)) return; if (!doc.setContent(&file)) { file.close(); return; } file.close(); // print out the element names of all elements that are direct children // of the outermost element. QDomElement docElem = doc.documentElement(); QDomNode n = docElem.firstChild(); while(!n.isNull()) { QDomElement e = n.toElement(); // try to convert the node to an element. if(!e.isNull()) { cout << qPrintable(e.tagName()) << endl; // the node really is an element. } n = n.nextSibling(); } // Here we append a new element to the end of the document QDomElement elem = doc.createElement("img"); elem.setAttribute("src", "myimage.png"); docElem.appendChild(elem); Once doc and elem go out of scope, the whole internal tree representing the XML document is deleted. To create a document using DOM use code like this: QDomDocument doc("MyML"); QDomElement root = doc.createElement("MyML"); doc.appendChild(root); QDomElement tag = doc.createElement("Greeting"); root.appendChild(tag); QDomText t = doc.createTextNode("Hello World"); tag.appendChild(t); QString xml = doc.toString(); For further information about the Document Object Model see the Document Object Model (DOM) Level 1 and Level 2 Core Specifications. See also DOM Bookmarks Example and Simple DOM Model Example. Member Function Documentation
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| Node Type | Behavior |
|---|---|
| QDomAttr | The owner element is set to 0 and the specified flag is set to true in the generated attribute. The whole subtree of importedNode is always imported for attribute nodes: deep has no effect. |
| QDomDocument | Document nodes cannot be imported. |
| QDomDocumentFragment | If deep is true, this function imports the whole document fragment; otherwise it only generates an empty document fragment. |
| QDomDocumentType | Document type nodes cannot be imported. |
| QDomElement | Attributes for which QDomAttr::specified() is true are also imported, other attributes are not imported. If deep is true, this function also imports the subtree of importedNode; otherwise it imports only the element node (and some attributes, see above). |
| QDomEntity | Entity nodes can be imported, but at the moment there is no way to use them since the document type is read-only in DOM level 2. |
| QDomEntityReference | Descendants of entity reference nodes are never imported: deep has no effect. |
| QDomNotation | Notation nodes can be imported, but at the moment there is no way to use them since the document type is read-only in DOM level 2. |
| QDomProcessingInstruction | The target and value of the processing instruction is copied to the new node. |
| QDomText | The text is copied to the new node. |
| QDomCDATASection | The text is copied to the new node. |
| QDomComment | The text is copied to the new node. |
See also QDomElement::setAttribute(), QDomNode::insertBefore(), QDomNode::insertAfter(), QDomNode::replaceChild(), QDomNode::removeChild(), and QDomNode::appendChild().
QDomNode::NodeType QDomDocument::nodeType() const
Returns DocumentNode.
bool QDomDocument::setContent(const QByteArray & data, bool namespaceProcessing, QString * errorMsg = 0, int * errorLine = 0, int * errorColumn = 0)
This function parses the XML document from the byte array data and sets it as the content of the document. It tries to detect the encoding of the document as required by the XML specification.
If namespaceProcessing is true, the parser recognizes namespaces in the XML file and sets the prefix name, local name and namespace URI to appropriate values. If namespaceProcessing is false, the parser does no namespace processing when it reads the XML file.
If a parse error occurs, this function returns false and the error message is placed in *errorMsg, the line number in *errorLine and the column number in *errorColumn (unless the associated pointer is set to 0); otherwise this function returns true. The various error messages are described in the QXmlParseException class documentation. Note that, if you want to display these error messages to your application's users, they will be displayed in English unless they are explicitly translated.
If namespaceProcessing is true, the function QDomNode::prefix() returns a string for all elements and attributes. It returns an empty string if the element or attribute has no prefix.
Text nodes consisting only of whitespace are stripped and won't appear in the QDomDocument. If this behavior is not desired, one can use the setContent() overload that allows a QXmlReader to be supplied.
If namespaceProcessing is false, the functions QDomNode::prefix(), QDomNode::localName() and QDomNode::namespaceURI() return an empty string.
Entity references are handled as follows:
- References to internal general entities and character entities occurring in the content are included. The result is a QDomText node with the references replaced by their corresponding entity values.
- References to parameter entities occurring in the internal subset are included. The result is a QDomDocumentType node which contains entity and notation declarations with the references replaced by their corresponding entity values.
- Any general parsed entity reference which is not defined in the internal subset and which occurs in the content is represented as a QDomEntityReference node.
- Any parsed entity reference which is not defined in the internal subset and which occurs outside of the content is replaced with an empty string.
- Any unparsed entity reference is replaced with an empty string.
Warning: This function is not reentrant.
See also QDomNode::namespaceURI(), QDomNode::localName(), QDomNode::prefix(), QString::isNull(), and QString::isEmpty().
bool QDomDocument::setContent(const QString & text, bool namespaceProcessing, QString * errorMsg = 0, int * errorLine = 0, int * errorColumn = 0)
This is an overloaded function.
This function reads the XML document from the string text, returning true if the content was successfully parsed; otherwise returns false. Since text is already a Unicode string, no encoding detection is done.
bool QDomDocument::setContent(QIODevice * dev, bool namespaceProcessing, QString * errorMsg = 0, int * errorLine = 0, int * errorColumn = 0)
This is an overloaded function.
This function reads the XML document from the IO device dev, returning true if the content was successfully parsed; otherwise returns false.
bool QDomDocument::setContent(QXmlInputSource * source, bool namespaceProcessing, QString * errorMsg = 0, int * errorLine = 0, int * errorColumn = 0)
This is an overloaded function.
This function reads the XML document from the QXmlInputSource source, returning true if the content was successfully parsed; otherwise returns false.
This function was introduced in Qt 4.5.
bool QDomDocument::setContent(const QString & text, QString * errorMsg = 0, int * errorLine = 0, int * errorColumn = 0)
This is an overloaded function.
This function reads the XML document from the string text, returning true if the content was successfully parsed; otherwise returns false. Since text is already a Unicode string, no encoding detection is performed.
No namespace processing is performed either.
bool QDomDocument::setContent(const QByteArray & buffer, QString * errorMsg = 0, int * errorLine = 0, int * errorColumn = 0)
This is an overloaded function.
This function reads the XML document from the byte array buffer, returning true if the content was successfully parsed; otherwise returns false.
No namespace processing is performed.
bool QDomDocument::setContent(QIODevice * dev, QString * errorMsg = 0, int * errorLine = 0, int * errorColumn = 0)
This is an overloaded function.
This function reads the XML document from the IO device dev, returning true if the content was successfully parsed; otherwise returns false.
No namespace processing is performed.
bool QDomDocument::setContent(QXmlInputSource * source, QXmlReader * reader, QString * errorMsg = 0, int * errorLine = 0, int * errorColumn = 0)
This is an overloaded function.
This function reads the XML document from the QXmlInputSource source and parses it with the QXmlReader reader, returning true if the content was successfully parsed; otherwise returns false.
This function doesn't change the features of the reader. If you want to use certain features for parsing you can use this function to set up the reader appropriately.
See also QXmlSimpleReader.
QByteArray QDomDocument::toByteArray(int indent = 1) const
Converts the parsed document back to its textual representation and returns a QByteArray containing the data encoded as UTF-8.
This function uses indent as the amount of space to indent subelements.
See also toString().
QString QDomDocument::toString(int indent = 1) const
Converts the parsed document back to its textual representation.
This function uses indent as the amount of space to indent subelements.
If indent is -1, no whitespace at all is added.
QDomDocument & QDomDocument::operator=(const QDomDocument & x)
Assigns x to this DOM document.
The data of the copy is shared (shallow copy): modifying one node will also change the other. If you want to make a deep copy, use cloneNode().