- Qt 5.15
- Qt XML Patterns
- C++ Classes
- QXmlSchemaValidator
- Qt 5.15.11 Reference Documentation

# QXmlSchemaValidator Class

The QXmlSchemaValidator class validates XML instance documents against a W3C XML Schema. More...

Header: | #include <QXmlSchemaValidator>
qmake: | QT += xmlpatterns
Since: | Qt 4.6

This class was introduced in Qt 4.6.

- List of all members, including inherited members

Note: All functions in this class are reentrant.

## Public Functions

| QXmlSchemaValidator(const QXmlSchema &schema)
| QXmlSchemaValidator()
| ~QXmlSchemaValidator()
QAbstractMessageHandler * | messageHandler() const
QXmlNamePool | namePool() const
QNetworkAccessManager * | networkAccessManager() const
QXmlSchema | schema() const
void | setMessageHandler(QAbstractMessageHandler *handler)
void | setNetworkAccessManager(QNetworkAccessManager *manager)
void | setSchema(const QXmlSchema &schema)
void | setUriResolver(const QAbstractUriResolver *resolver)
const QAbstractUriResolver * | uriResolver() const
bool | validate(const QUrl &source) const
bool | validate(QIODevice *source, const QUrl &documentUri = QUrl()) const
bool | validate(const QByteArray &data, const QUrl &documentUri = QUrl()) const

## Detailed Description

The QXmlSchemaValidator class loads, parses an XML instance document and validates it against a W3C XML Schema that has been compiled with QXmlSchema.

The following example shows how to load a XML Schema from a local file, check whether it is a valid schema document and use it for validation of an XML instance document:

         QUrl schemaUrl("file:///home/user/schema.xsd");

         QXmlSchema schema;
         schema.load(schemaUrl);

         if (schema.isValid()) {
             QFile file("test.xml");
             file.open(QIODevice::ReadOnly);

             QXmlSchemaValidator validator(schema);
             if (validator.validate(&file, QUrl::fromLocalFile(file.fileName())))
                 qDebug() << "instance document is valid";
             else
                 qDebug() << "instance document is invalid";
         }

### XML Schema Version

This class implements schema validation according to the XML Schema 1.0 specification.

See also QXmlSchema and XML Schema Validation Example.

## Member Function Documentation

### QXmlSchemaValidator::QXmlSchemaValidator(const QXmlSchema &schema)

Constructs a schema validator that will use schema for validation. If an empty QXmlSchema schema is passed to the validator, the schema used for validation must be referenced in the XML instance document via the `xsi:schemaLocation` or `xsi:noNamespaceSchemaLocation` attribute.

### QXmlSchemaValidator::QXmlSchemaValidator()

Constructs a schema validator. The schema used for validation must be referenced in the XML instance document via the `xsi:schemaLocation` or `xsi:noNamespaceSchemaLocation` attribute.

### QXmlSchemaValidator::~QXmlSchemaValidator()

Destroys this QXmlSchemaValidator.

### QAbstractMessageHandler *QXmlSchemaValidator::messageHandler() const

Returns the message handler that handles parsing and validation messages for this QXmlSchemaValidator.

See also setMessageHandler().

### QXmlNamePool QXmlSchemaValidator::namePool() const

Returns the name pool used by this QXmlSchemaValidator for constructing names. There is no setter for the name pool, because mixing name pools causes errors due to name confusion.

### QNetworkAccessManager *QXmlSchemaValidator::networkAccessManager() const

Returns the network manager, or 0 if it has not been set.

See also setNetworkAccessManager().

### QXmlSchema QXmlSchemaValidator::schema() const

Returns the schema that is used for validation.

See also setSchema().

### void QXmlSchemaValidator::setMessageHandler(QAbstractMessageHandler *handler)

Changes the message handler for this QXmlSchemaValidator to handler. The schema validator sends all parsing and validation messages to this message handler. QXmlSchemaValidator does not take ownership of handler.

Normally, the default message handler is sufficient. It writes compile and validation messages to stderr. The default message handler includes color codes if stderr can render colors.

When QXmlSchemaValidator calls QAbstractMessageHandler::message(), the arguments are as follows:

message() argument | Semantics
--- | ---
QtMsgType type | Only QtWarningMsg and QtFatalMsg are used. The former identifies a warning, while the latter identifies an error.
const QString & description | An XHTML document which is the actual message. It is translated into the current language.
const QUrl &identifier | Identifies the error with a URI, where the fragment is the error code, and the rest of the URI is the error namespace.
const QSourceLocation & sourceLocation | Identifies where the error occurred.

See also messageHandler().

### void QXmlSchemaValidator::setNetworkAccessManager(QNetworkAccessManager *manager)

Sets the network manager to manager. QXmlSchemaValidator does not take ownership of manager.

See also networkAccessManager().

### void QXmlSchemaValidator::setSchema(const QXmlSchema &schema)

Sets the schema that shall be used for further validation. If the schema is empty, the schema used for validation must be referenced in the XML instance document via the `xsi:schemaLocation` or `xsi:noNamespaceSchemaLocation` attribute.

See also schema().

### void QXmlSchemaValidator::setUriResolver(const QAbstractUriResolver *resolver)

Sets the URI resolver to resolver. QXmlSchemaValidator does not take ownership of resolver.

See also uriResolver().

### const QAbstractUriResolver *QXmlSchemaValidator::uriResolver() const

Returns the schema's URI resolver. If no URI resolver has been set, Qt XML Patterns will use the URIs in instance documents as they are.

The URI resolver provides a level of abstraction, or polymorphic URIs. A resolver can rewrite logical URIs to physical ones, or it can translate obsolete or invalid URIs to valid ones.

When Qt XML Patterns calls QAbstractUriResolver::resolve() the absolute URI is the URI mandated by the schema specification, and the relative URI is the URI specified by the user.

See also setUriResolver().

### bool QXmlSchemaValidator::validate(const QUrl &source) const

Validates the XML instance document read from source against the schema.

Returns `true` if the XML instance document is valid according to the schema, `false` otherwise.

Example:

         const QXmlSchema schema = getSchema();

         const QUrl url("http://www.schema-example.org/test.xml");

         QXmlSchemaValidator validator(schema);
         if (validator.validate(url))
             qDebug() << "instance document is valid";
         else
             qDebug() << "instance document is invalid";

### bool QXmlSchemaValidator::validate(QIODevice *source, const QUrl &documentUri = QUrl()) const

Validates the XML instance document read from source with the given documentUri against the schema.

Returns `true` if the XML instance document is valid according to the schema, `false` otherwise.

Example:

         const QXmlSchema schema = getSchema();

         QFile file("test.xml");
         file.open(QIODevice::ReadOnly);

         QXmlSchemaValidator validator(schema);
         if (validator.validate(&file, QUrl::fromLocalFile(file.fileName())))
             qDebug() << "instance document is valid";
         else
             qDebug() << "instance document is invalid";

### bool QXmlSchemaValidator::validate(const QByteArray &data, const QUrl &documentUri = QUrl()) const

Validates the XML instance document read from data with the given documentUri against the schema.

Returns `true` if the XML instance document is valid according to the schema, `false` otherwise.

Example:

         const QXmlSchema schema = getSchema();

         QByteArray data("<?xml version=\"1.0\" encoding=\"UTF-8\"?>"
                         "<test></test>");

         QBuffer buffer(&data);
         buffer.open(QIODevice::ReadOnly);

         QXmlSchemaValidator validator(schema);
         if (validator.validate(&buffer))
             qDebug() << "instance document is valid";
         else
             qDebug() << "instance document is invalid";