在显示之前检查PDF是否已创建？

Question

I am creating a PDF, from a template, using JasperPHP.

I then immediately try to display it.

How can I ensure that it is completely created, before displaying?

I am checking that the file exists but the PDF is corrupt, at this point, so I am assuming it is still being created.

I have also tried using flock, to open it with an exclusive lock, but this seems to work, even when the PDF is not completely rendered.

This is what I am doing (the dd is just for testing, it never gets here):

/**
     * Check that we can lock a file
     * this ensures that it has been completely created.
     *
     * @param $filename
     * @return bool
     */
    function stillWriting($filename)
    {
        $stillWriting = true;

        if($fp = fopen($filename, "r+"))
        {
            if (flock($fp, LOCK_EX)) // Try to get an exclusive lock on the file
            {
                flock($fp, LOCK_UN); // Unlock - we're just checking
                $stillWriting = false;
            }else{
                dd('failed');
            }
            fclose($fp);
        }
        return $stillWriting;
    }

Mick

Edit - added more detail

This is where the PDF gets created:

exec($this->the_command, $output, $return_var);

I am using https://github.com/cossou/JasperPHP

It executes JasperStart [https://sourceforge.net/projects/

This is where the PDF is displayed:

return Response::make(file_get_contents($this->outputFilename .'.pdf'), 200, [ 'Content-Type' => 'application/pdf', 'Content-Disposition' => 'inline; filename="' . $this->outputFilename .'.pdf' .'"' ]);

The actual problem that I am getting is that Chrome says "Failed to load PDF document", I am guessing from this, that it is a timing problem. The file opens correctly If I then go to Windows and double click.

Answer 1

JasperPHP has a flag $background = true.

If I set this to false it looks like it waits for the compile to finish before continuing.

Mick