wkhtmltopdf called from java getting hanged

Question

We are the using the following code to generate PDFs using wkhtmltopdf

    public class SystemUtils{   
    public String executeCommand(String... command) {
        Process process = null;
        try {
            // Using redirectErrorStream as true. Otherwise we have to read both process.getInputStream() and
            // process.getErrorStream() in order to not exhaust the stream buffer.
            process = new ProcessBuilder(command).redirectErrorStream(true).start();
            process.waitFor();

            StringBuilder outputBuilder = new StringBuilder();
            try(BufferedReader stdError = new BufferedReader(new InputStreamReader(process.getInputStream()))) {
                String line;
                while ((line = stdError.readLine()) != null) {
                    outputBuilder.append(line).append(StringConstants.CARRIAGE_RETURN);
                }
            }
            return outputBuilder.toString();
        } catch (IOException | InterruptedException e) {
            String exceptionMsg = "Error while executing command '"+command+"' : ";
            LOGGER.error(exceptionMsg, e);
            throw new AppException(exceptionMsg, e);
        } finally {
            if(process != null){
                process.destroy();
            }
        }
    }

       public static void main(String[] args){
        SystemUtils systemUtils = new SystemUtils();
        String[] array = {"wkhtmltopdf", "/home/pgullapalli/Desktop/testsimilar1.html", "/home/pgullapalli/Desktop/test.pdf"};
        systemUtils.executeCommand(array);
    }
}

This works absolutely fine for smaller size files. But when we try to process a larger file, it is indefinitely waiting without any response. I am not sure what is going wrong? Can someone please suggest?

Answer 1

I moved process.waitFor() before the return statement and it started working. This probably could be happening as the output buffer has filled and we are not reading from it. After moving the process.waitFor after the stream reading, things are working fine.