等到在 Java 中创建文件

Question

我正在开发一个Web API（使用弹簧启动），使用外部C++api转换pdf，该程序正在工作，但是当我想在正文响应中发送文件时，我收到此错误：

{

"timestamp": "2019-04-10T09:56:01.696+0000",

"status": 500,

"error": "Internal Server Error",

"message": "file [D:\\[Phenix-Monitor]1.pdf] cannot be resolved in the file system for checking its content length",

"path": "/convert/toLinPDf"}

控制器：

@PostMapping("/toLinPDf")

public ResponseEntity<ByteArrayResource> convertion(@RequestParam(value = "input", required = false) String in,

        @RequestParam(value = "output", required = false) String out) throws IOException, InterruptedException {

    linearizeService.LinearizePDf(in, out);

    FileSystemResource pdfFile = new FileSystemResource(out);

    return ResponseEntity

            .ok()

            .contentLength(pdfFile.contentLength())

            .contentType(

                    MediaType.parseMediaType("application/pdf"))

            .body(new ByteArrayResource(IOUtils.toByteArray(pdfFile.getInputStream())));

}

我想问题在于，因为在这种方法中我使用的是外部进程，所以发生的事情是，当我尝试打开文件时，linearizeService尚未完成处理，为什么我得到这个错误，我的问题是：我该如何处理这个问题，我的意思是如何等待文件被创建然后发送这个文件？linearizeService.LinearizePDf(in, out);FileSystemResource pdfFile = new FileSystemResource(out);

Answer 1

我建议你使用Java 8。Future API这是您的资源的更新。@PostMapping("/toLinPDf")public ResponseEntity<ByteArrayResource> convertion(&nbsp; &nbsp; @RequestParam(value = "input", required = false) String in,&nbsp; &nbsp; @RequestParam(value = "output", required = false) String out) throws IOException, InterruptedException {ExecutorService executorService = Executors.newSingleThreadExecutor();Callable<String> callable = () -> {&nbsp; &nbsp; &nbsp; &nbsp; linearizeService.LinearizePDf(in, out);&nbsp; &nbsp; &nbsp; &nbsp; return "Task ended";};Future<String> future = executorService.submit(callable);String result = future.get();executorService.shutdown();FileSystemResource pdfFile = new FileSystemResource(out);return ResponseEntity&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; .ok()&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; .contentLength(pdfFile.contentLength())&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; .contentType(&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; MediaType.parseMediaType("application/pdf"))&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; .body(new ByteArrayResource(IOUtils.toByteArray(pdfFile.getInputStream())));}