Running Command Line in Java using Runtime.getRuntime()

Question

I'm creating web application using spring boot, in this web application i need to run a command line using Runtime.getRuntime(), but the problem is that: this command is executed after the web app and this is not what i want to do, the question is :

"how can i make sure that the Runtime.getRuntime() instruction start when it's called in spring boot application (not at the end of it)"

the controller:

@PostMapping("/toLinPDf")
public ResponseEntity<ByteArrayResource> convertion(@RequestParam(value = "input", required = false) String in,
        @RequestParam(value = "output", required = false) String out) throws IOException, InterruptedException, ExecutionException {

    // the methode LinearizePDF contain the command line

    linearizeService.LinearizePDf(in, out);
    logger.warn("call the method linearizeService.LinearizePDf ");
    FileSystemResource result = new FileSystemResource(out);
    return ResponseEntity
            .ok()
            .contentLength(result.contentLength())
            .contentType(
                    MediaType.parseMediaType("application/pdf"))
            .body(new ByteArrayResource(IOUtils.toByteArray(result.getInputStream())));

}

the linearizeService ( contain the method LinearizePDf(in, out)):

@Async
public void LinearizePDf(String Input , String Output) throws IOException, InterruptedException {
     Runtime rt = Runtime.getRuntime();

     // the command line 
     String command = "qpdf --linearize " + Input + "  " + Output;

     Process pr = rt.exec(command );
     logger.warn("run the command");
     pr.destroy();   
}

Please, If there's any suggestion, do not hesitate.

Thank You !

igorepst · Accepted Answer · 2019-04-11 09:41:26Z

1

Quoting the well known site

Simply put – annotating a method of a bean with @Async will make it execute in a separate thread i.e. the caller will not wait for the completion of the called method.

Remove the @Async from LinearizePDf

In addition, to wait for the completion of the external process you should use waitFor and not destroy, e.g. pr.waitFor()

edited Apr 11, 2019 at 9:41

answered Apr 11, 2019 at 9:01

igorepst

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5 Comments

youssef elhayani Over a year ago

Actually what i want to do is: " to run the command line and the java program in the same time " , in my case the command line is executed when the java app finish runnig

igorepst Over a year ago

Did you remove the Async? It will give you the possibility to return right ResponseEntity from the controller

youssef elhayani Over a year ago

indeed , i just remove the @Async and i get the same result, it's not working .

igorepst Over a year ago

Added waitFor - see the answer

youssef elhayani Over a year ago

Well i guess @Async is part of the problem you're right so i remove it and put it in the controller and also FileSystemResource somehow generate a problem : " file [D:\[Phenix-Monitor]1.pdf] cannot be resolved in the file system for checking its content length " so i remove it and it's working !

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