XML Schema Validation Example

/****************************************************************************
**
** Copyright (C) 2017 The Qt Company Ltd.
** Contact: https://www.qt.io/licensing/
**
** This file is part of the examples of the Qt Toolkit.
**
** $QT_BEGIN_LICENSE:BSD$
** Commercial License Usage
** Licensees holding valid commercial Qt licenses may use this file in
** accordance with the commercial license agreement provided with the
** Software or, alternatively, in accordance with the terms contained in
** a written agreement between you and The Qt Company. For licensing terms
** and conditions see https://www.qt.io/terms-conditions. For further
** information use the contact form at https://www.qt.io/contact-us.
**
** BSD License Usage
** Alternatively, you may use this file under the terms of the BSD license
** as follows:
**
** "Redistribution and use in source and binary forms, with or without
** modification, are permitted provided that the following conditions are
** met:
**   * Redistributions of source code must retain the above copyright
**     notice, this list of conditions and the following disclaimer.
**   * Redistributions in binary form must reproduce the above copyright
**     notice, this list of conditions and the following disclaimer in
**     the documentation and/or other materials provided with the
**     distribution.
**   * Neither the name of The Qt Company Ltd nor the names of its
**     contributors may be used to endorse or promote products derived
**     from this software without specific prior written permission.
**
**
** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
** A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
** OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
** SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
** LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
** DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
** THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
** OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE."
**
** $QT_END_LICENSE$
**
****************************************************************************/

#include <QtGui>
#include <QtXmlPatterns>

#include "mainwindow.h"
#include "xmlsyntaxhighlighter.h"

class MessageHandler : public QAbstractMessageHandler
{
public:
    MessageHandler()
        : QAbstractMessageHandler(0)
    {
    }

    QString statusMessage() const
    {
        return m_description;
    }

    int line() const
    {
        return m_sourceLocation.line();
    }

    int column() const
    {
        return m_sourceLocation.column();
    }

protected:
    virtual void handleMessage(QtMsgType type, const QString &description,
                               const QUrl &identifier, const QSourceLocation &sourceLocation)
    {
        Q_UNUSED(type);
        Q_UNUSED(identifier);

        m_description = description;
        m_sourceLocation = sourceLocation;
    }

private:
    QString m_description;
    QSourceLocation m_sourceLocation;
};

MainWindow::MainWindow()
{
    setupUi(this);

    new XmlSyntaxHighlighter(schemaView->document());
    new XmlSyntaxHighlighter(instanceEdit->document());

    schemaSelection->addItem(tr("Contact Schema"));
    schemaSelection->addItem(tr("Recipe Schema"));
    schemaSelection->addItem(tr("Order Schema"));

    instanceSelection->addItem(tr("Valid Contact Instance"));
    instanceSelection->addItem(tr("Invalid Contact Instance"));

    connect(schemaSelection, SIGNAL(currentIndexChanged(int)), SLOT(schemaSelected(int)));
    connect(instanceSelection, SIGNAL(currentIndexChanged(int)), SLOT(instanceSelected(int)));
    connect(validateButton, SIGNAL(clicked()), SLOT(validate()));
    connect(instanceEdit, SIGNAL(textChanged()), SLOT(textChanged()));

    validationStatus->setAlignment(Qt::AlignCenter | Qt::AlignVCenter);

    schemaSelected(0);
    instanceSelected(0);
}

void MainWindow::schemaSelected(int index)
{
    instanceSelection->clear();
    if (index == 0) {
        instanceSelection->addItem(tr("Valid Contact Instance"));
        instanceSelection->addItem(tr("Invalid Contact Instance"));
    } else if (index == 1) {
        instanceSelection->addItem(tr("Valid Recipe Instance"));
        instanceSelection->addItem(tr("Invalid Recipe Instance"));
    } else if (index == 2) {
        instanceSelection->addItem(tr("Valid Order Instance"));
        instanceSelection->addItem(tr("Invalid Order Instance"));
    }
    textChanged();

    const QString fileName = QStringLiteral(":/schema_")
        + QString::number(index) + QStringLiteral(".xsd");
    QFile schemaFile(fileName);
    if (!schemaFile.open(QIODevice::ReadOnly)) {
        qWarning() << "Cannot open" << QDir::toNativeSeparators(fileName)
            << ':' << schemaFile.errorString();
        return;
    }

    const QString schemaText(QString::fromUtf8(schemaFile.readAll()));
    schemaView->setPlainText(schemaText);

    validate();
}

void MainWindow::instanceSelected(int index)
{
    if (index < 0) {
        instanceEdit->setPlainText(QString());
        return;
    }
    const QString fileName = QStringLiteral(":/instance_")
        + QString::number(2 * schemaSelection->currentIndex() + index)
        + QStringLiteral(".xml");
    QFile instanceFile(fileName);
    if (!instanceFile.open(QIODevice::ReadOnly)) {
        qWarning() << "Cannot open" << QDir::toNativeSeparators(fileName)
            << ':' << instanceFile.errorString();
        return;
    }
    const QString instanceText(QString::fromUtf8(instanceFile.readAll()));
    instanceEdit->setPlainText(instanceText);

    validate();
}

void MainWindow::validate()
{
    const QByteArray schemaData = schemaView->toPlainText().toUtf8();
    const QByteArray instanceData = instanceEdit->toPlainText().toUtf8();

    MessageHandler messageHandler;

    QXmlSchema schema;
    schema.setMessageHandler(&messageHandler);

    schema.load(schemaData);

    bool errorOccurred = false;
    if (!schema.isValid()) {
        errorOccurred = true;
    } else {
        QXmlSchemaValidator validator(schema);
        if (!validator.validate(instanceData))
            errorOccurred = true;
    }

    if (errorOccurred) {
        validationStatus->setText(messageHandler.statusMessage());
        moveCursor(messageHandler.line(), messageHandler.column());
    } else {
        validationStatus->setText(tr("validation successful"));
    }

    const QString styleSheet = QString("QLabel {background: %1; padding: 3px}")
                                      .arg(errorOccurred ? QColor(Qt::red).lighter(160).name() :
                                                           QColor(Qt::green).lighter(160).name());
    validationStatus->setStyleSheet(styleSheet);
}

void MainWindow::textChanged()
{
    instanceEdit->setExtraSelections(QList<QTextEdit::ExtraSelection>());
}

void MainWindow::moveCursor(int line, int column)
{
    instanceEdit->moveCursor(QTextCursor::Start);
    for (int i = 1; i < line; ++i)
        instanceEdit->moveCursor(QTextCursor::Down);

    for (int i = 1; i < column; ++i)
        instanceEdit->moveCursor(QTextCursor::Right);

    QList<QTextEdit::ExtraSelection> extraSelections;
    QTextEdit::ExtraSelection selection;

    const QColor lineColor = QColor(Qt::red).lighter(160);
    selection.format.setBackground(lineColor);
    selection.format.setProperty(QTextFormat::FullWidthSelection, true);
    selection.cursor = instanceEdit->textCursor();
    selection.cursor.clearSelection();
    extraSelections.append(selection);

    instanceEdit->setExtraSelections(extraSelections);

    instanceEdit->setFocus();
}