How to make pdf file by reading content from database using beego?

I read a pdf file and then store its raw content into database. Now i want to read that content from database and create a pdf so that user can download it.

For this i read the content and write it to file with .pdf extension. But the result in an empty pdf file.

I am doing this because i want to avoid saving files in disk.

I am using beego framework.

Any suggestions/help?

Here what i am doing

Reading from pdf file and writing it to database

_,header,_:=c.GetFile("attachment[]")
attachment:=header.Filename
c.SaveToFile("attachment[]","/tmp/"+attachment)
content,_:= ioutil.ReadFile("/tmp/"+attachment)
s := string(content)

then write this 's' to database

reading from database and writing to pdf file

err := o.Raw("SELECT attachment FROM table_name WHERE id=?",id).QueryRow(&att)
if err == nil {
     fmt.Println(att)
}
var data []byte
data = []byte(att)
ioutil.WriteFile("/tmp/hello.pdf",data, 0666)

You're ignoring the multipart.File from the GetFile call. Use that directly. It's a waste of time to write it to disk and read it back again.

There's also no reason to save the file to disk between reading it from the DB and sending to the client.

(You may want to be sure that your DB is optimized to handle large blobs like this. It's not the usual use-case for most databases.)

I had the same issue of a pdf in a MongoDB document. It was stored as a string value Base64 encrypted. My steps were:

1. Find the record.

2. Decode the string:

3. Create a *Buffer from the pdfBytes

4. write it directly to the http.ResponseWritter:

   b := bytes.NewBuffer(pdfBytes) // Step 2
pdfBytes,err := b64.StdEncoding.DecodeString(doc.Image) // Step 3
if _, err := b.WriteTo(w); err != nil { // Step 4
fmt.Fprintf(w, "%s", err) // Handle the error
}

This works fine, I handle 40+ million documents using it. However, I am always interested in learning if there is a better way. As @JimB said, if you are required to read from a file his way is best. The problem is the question was very vague.

When is used github.com/jung-kurt/gofpdf library:

func (c *MyController) PrintPDF() {         
    pdf := gofpdf.New("", "", "", "")
    pdf.AddPage()
    pdf.Text(10, 20, "Circles")
    var b bytes.Buffer
    w := bufio.NewWriter(&b)
    pdf.Output(w)
    pdf.Close()
    w.Flush()
	c.Ctx.Output.ContentType("application/pdf")
	c.Ctx.Output.Body(b.bytes())
}