Upload pdf file in the MySQL database

[sujan.dasmahapatra]

Dear Friends

I am working with MySQL database using Qt. I want to store a pdf file in the database. and show the contents of the pdf when user wants. How can I upload a pdf file in the database and open the file when needed from the database. Please give me some idea.

I know only two types INT and VARCHAR to store int and some string. But how can i upload the pdf file. Please help me if you know anyone. Thanks a lot. sujan

[boudie]

You can store it in the database as a BLOB (Binary Large Object).
To show the pdf you can use the poppler library.

[ChrisW67]

You can store it in the database as a BLOB (Binary Large Object).

This is handled as a QByteArray inside your Qt code. Reading a PDF file into a QByteArray is trivial. You will need to use a QSqlQuery::prepare()-ed query and QSqlQuery::bindValue() to insert it into the database.

To show the pdf you can use the poppler library.

Qt does not have any built-in PDF viewing capability: Poppler is an external library that could be use to add a in-program viewer. You could also extract the BLOB to a temporary file and use QDesktopServices::openUrl() to launch the user's PDF viewer of choice.

[sujan.dasmahapatra]

where can i find the poppler library do i need to install it.

[boudie]

Forget poppler (for now...)

As ChrisW67 suggests:

...You could also extract the BLOB to a temporary file and use QDesktopServices:penUrl() to launch the user's PDF viewer of choice.

It's much simpler to implement.

[sujan.dasmahapatra]

Please check this code snippet ui.lineEdit_APPLICATION is the control fetching the filename..........With this my table is not getting updated with the value resume........My table is blank........Whats wrong please tell me .

if(!ui.lineEdit_APPLICATION->text().isEmpty()) {
    QByteArray inside;
    QString filename = ui.lineEdit_APPLICATION->text();
    QStringList list = filename.split(QRegExp("/"), QString::SkipEmptyParts);
    QFile file(filename);
    if (file.exists()) {
      if (file.open(QFile::ReadOnly)) {
      inside = file.readAll();
      file.close();
            }
        }
    query4.bindValue(":applicationpdf",list.last());
    query4.bindValue(":resume",inside);
    list.clear();
    }
    else {
    query4.bindValue(":applicationpdf", "");
    query4.bindValue(":resume", "");
}

if(!ui.lineEdit_APPLICATION->text().isEmpty()) {
    QByteArray inside;
    QString filename = ui.lineEdit_APPLICATION->text();
    QStringList list = filename.split(QRegExp("/"), QString::SkipEmptyParts);
    QFile file(filename);
    if (file.exists()) {
      if (file.open(QFile::ReadOnly)) {
      inside = file.readAll();
      file.close();
            }
        }
    query4.bindValue(":applicationpdf",list.last());
    query4.bindValue(":resume",inside);
    list.clear();
    }
    else {
    query4.bindValue(":applicationpdf", "");
    query4.bindValue(":resume", "");
}

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[wysota]

It pays off to execute the query once it is prepared (if at all).

[sujan.dasmahapatra]

If I load a pdf or .doc file my table is not updated. But if I load a jpeg file then its uploading in the database. Please tell me why its happening. why pdf or doc file data is not uploading as QByteArray. Thanks Sujan

---

Added after 24 minutes:

If I give LONGBLOB instead of BLOB then its storing something. Can u tell me how can I fetch the data from database check if this is correct

void CDisplayEntry::openPDF()
{
 
    QSqlQuery  query(console->mainwindow->db);
    QString queryString = "SELECT * FROM Tbl_StudentLink";
    query.exec(queryString);
 
    int field1 = query.record().indexOf("resume");
    if(query.seek(index,false))
    {
        QUrl url = QUrl::fromEncoded(query.value(field1).toByteArray());
        QTextEdit *viewPDF = new QTextEdit(url.toString());
        viewPDF->show();
    }
 
}

void CDisplayEntry::openPDF()
{

    QSqlQuery  query(console->mainwindow->db);
    QString queryString = "SELECT * FROM Tbl_StudentLink";
    query.exec(queryString);

    int field1 = query.record().indexOf("resume");
    if(query.seek(index,false))
    {
        QUrl url = QUrl::fromEncoded(query.value(field1).toByteArray());
        QTextEdit *viewPDF = new QTextEdit(url.toString());
        viewPDF->show();
    }

}

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[ChrisW67]

Here's what you are doing:

• You store the actual bytes of the PDF file into the database
• You retrieve the actual bytes of the PDF file and try to interpret those bytes as a URL
• You use a QTextEdit to display a string made from the URL and expect to see the PDF file.

Does this sound correct to you?

Go back and read the earlier responses about your options.

[sujan.dasmahapatra]

PDF is not working only txt files are working. Poppler library is linux based I need windows. Give me some suggestion how can i view pdf document.

check my snippet.

// To read the document and store in the database

QByteArray inside="";
QFile file(filename);
        if (file.exists()) {
          if (file.open(QFile::ReadOnly)) {
           inside = file.readAll();
          file.close();
                }
query4.bindValue(":resume",inside);

QByteArray inside="";
QFile file(filename);
        if (file.exists()) {
          if (file.open(QFile::ReadOnly)) {
           inside = file.readAll();
          file.close();
                }
query4.bindValue(":resume",inside);

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Retrieving from the database and viewing in TextEdit

QSqlQuery  query(console->mainwindow->db);
    QString queryString = "SELECT * FROM Tbl_StudentLink";
    query.exec(queryString);
 
    int field1 = query.record().indexOf("resume");
    if(query.seek(index,false))
    {
 //       QUrl url = QUrl::fromEncoded(query.value(field1).toByteArray());
        QByteArray pdf = query.value(field1).toByteArray();
        QTextEdit *viewPDF = new QTextEdit(QString(pdf));
        viewPDF->show();
    }

QSqlQuery  query(console->mainwindow->db);
    QString queryString = "SELECT * FROM Tbl_StudentLink";
    query.exec(queryString);

    int field1 = query.record().indexOf("resume");
    if(query.seek(index,false))
    {
 //       QUrl url = QUrl::fromEncoded(query.value(field1).toByteArray());
        QByteArray pdf = query.value(field1).toByteArray();
        QTextEdit *viewPDF = new QTextEdit(QString(pdf));
        viewPDF->show();
    }

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[stampede]

QByteArray pdf = query.value(field1).toByteArray();
        QTextEdit *viewPDF = new QTextEdit(QString(pdf));

QByteArray pdf = query.value(field1).toByteArray();
        QTextEdit *viewPDF = new QTextEdit(QString(pdf));

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What do you expect to see in text edit when you convert the bytes of the file to a string ? A rendered pdf document ?

Anyway, why don't you just write the "pdf" byte array to a file and open it with the system default pdf viewer ?

[ChrisW67]

PDF is not working only txt files are working.

Surprising given the mangling you put the content rhough in your code snippets.

Poppler library is linux based I need windows.

Poppler can be built in Windows but it is an effort. From the discussion to date I suspect that you do not have the requisite understanding to build it. For example: Compiling Poppler on Windows. MuPDF is another option under GPL3.

Give me some suggestion how can i view pdf document.

We already have, several times. Here for example.

check my snippet.

Retrieving from the database and viewing in TextEdit

QSqlQuery  query(console->mainwindow->db);
    QString queryString = "SELECT * FROM Tbl_StudentLink";
    query.exec(queryString);
 
    int field1 = query.record().indexOf("resume");
    if(query.seek(index,false))
    {
 //       QUrl url = QUrl::fromEncoded(query.value(field1).toByteArray());
        QByteArray pdf = query.value(field1).toByteArray();
        QTextEdit *viewPDF = new QTextEdit(QString(pdf));
        viewPDF->show();
    }

QSqlQuery  query(console->mainwindow->db);
    QString queryString = "SELECT * FROM Tbl_StudentLink";
    query.exec(queryString);

    int field1 = query.record().indexOf("resume");
    if(query.seek(index,false))
    {
 //       QUrl url = QUrl::fromEncoded(query.value(field1).toByteArray());
        QByteArray pdf = query.value(field1).toByteArray();
        QTextEdit *viewPDF = new QTextEdit(QString(pdf));
        viewPDF->show();
    }

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Uh huh! You have tweaked this since the last time but you still have not grasped that a PDF in a binary data stream and that displaying the raw bytes in a text edit is wasting your time. On the upside you are no longer trying to mangle the binary data by treating it as a URL.

Write the data to a temporary file (use QDesktopServices to find where this should go), build a URL pointing at the temporary file, and use openUrl() to launch the user's PDF reader. This is about as simple as it gets.