从Spring Controller下载文件

我有一个须要从网站下载PDF的要求。 PDF须要在代码中生成，我认为这将是freemarker和iText等PDF生成框架的结合。 还有更好的方法吗？

可是，个人主要问题是如何容许用户经过Spring Controller下载文件？

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#1楼

经过使用Spring的ResourceHttpMessageConverter中的内置支持，我可以简化这一过程。 若是能够肯定mime类型，则将设置content-length和content-type

@RequestMapping(value = "/files/{file_name}", method = RequestMethod.GET)
@ResponseBody
public FileSystemResource getFile(@PathVariable("file_name") String fileName) {
    return new FileSystemResource(myService.getFileFor(fileName)); 
}

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#2楼

在Spring 3.0中，您可使用HttpEntity返回对象。 若是使用此选项，则您的控制器不须要HttpServletResponse对象，所以测试起来更容易。 除此以外，这个答案相对于Infeligo之一 。

若是您的pdf框架的返回值是一个字节数组（请参阅个人答案的第二部分以获取其余返回值） ：

@RequestMapping(value = "/files/{fileName}", method = RequestMethod.GET)
public HttpEntity<byte[]> createPdf(
                 @PathVariable("fileName") String fileName) throws IOException {

    byte[] documentBody = this.pdfFramework.createPdf(filename);

    HttpHeaders header = new HttpHeaders();
    header.setContentType(MediaType.APPLICATION_PDF);
    header.set(HttpHeaders.CONTENT_DISPOSITION,
                   "attachment; filename=" + fileName.replace(" ", "_"));
    header.setContentLength(documentBody.length);

    return new HttpEntity<byte[]>(documentBody, header);
}

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若是您的PDF Framework的返回类型（ documentBbody ）还不是字节数组 （而且也没有ByteArrayInputStream ），那么明智的作法是不要首先使其成为字节数组。 相反，最好使用：

• InputStreamResource ，
• PathResource （从Spring 4.0开始）或
• FileSystemResource ，

FileSystemResource示例：

@RequestMapping(value = "/files/{fileName}", method = RequestMethod.GET)
public HttpEntity<byte[]> createPdf(
                 @PathVariable("fileName") String fileName) throws IOException {

    File document = this.pdfFramework.createPdf(filename);

    HttpHeaders header = new HttpHeaders();
    header.setContentType(MediaType.APPLICATION_PDF);
    header.set(HttpHeaders.CONTENT_DISPOSITION,
                   "attachment; filename=" + fileName.replace(" ", "_"));
    header.setContentLength(document.length());

    return new HttpEntity<byte[]>(new FileSystemResource(document),
                                  header);
}

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#3楼

在单击jsp上的连接时，该代码能够很好地从spring控制器自动下载文件。

@RequestMapping(value="/downloadLogFile")
public void getLogFile(HttpSession session,HttpServletResponse response) throws Exception {
    try {
        String filePathToBeServed = //complete file name with path;
        File fileToDownload = new File(filePathToBeServed);
        InputStream inputStream = new FileInputStream(fileToDownload);
        response.setContentType("application/force-download");
        response.setHeader("Content-Disposition", "attachment; filename="+fileName+".txt"); 
        IOUtils.copy(inputStream, response.getOutputStream());
        response.flushBuffer();
        inputStream.close();
    } catch (Exception e){
        LOGGER.debug("Request could not be completed at this moment. Please try again.");
        e.printStackTrace();
    }

}

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#4楼

若是你：

• 在发送到响应以前，不想将整个文件加载到byte[] ；
• 想要/须要经过InputStream发送/下载它；
• 但愿彻底控制发送的Mime类型和文件名；
• 让其余@ControllerAdvice为您拾取异常。

下面的代码是您须要的：

@RequestMapping(value = "/stuff/{stuffId}", method = RequestMethod.GET)
public ResponseEntity<InputStreamResource> downloadStuff(@PathVariable int stuffId)
                                                                  throws IOException {
    String fullPath = stuffService.figureOutFileNameFor(stuffId);
    File file = new File(fullPath);

    HttpHeaders respHeaders = new HttpHeaders();
    respHeaders.setContentType("application/pdf");
    respHeaders.setContentLength(12345678);
    respHeaders.setContentDispositionFormData("attachment", "fileNameIwant.pdf");

    InputStreamResource isr = new InputStreamResource(new FileInputStream(file));
    return new ResponseEntity<InputStreamResource>(isr, respHeaders, HttpStatus.OK);
}

还要注意，为避免读取整个文件只是为了计算其长度，最好事先存储它。 确保检查了InputStreamResource的文档。

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#5楼

下面的代码为我工做，以生成和下载文本文件。

@RequestMapping(value = "/download", method = RequestMethod.GET)
public ResponseEntity<byte[]> getDownloadData() throws Exception {

    String regData = "Lorem Ipsum is simply dummy text of the printing and typesetting industry. Lorem Ipsum has been the industry's standard dummy text ever since the 1500s, when an unknown printer took a galley of type and scrambled it to make a type specimen book. It has survived not only five centuries, but also the leap into electronic typesetting, remaining essentially unchanged. It was popularised in the 1960s with the release of Letraset sheets containing Lorem Ipsum passages, and more recently with desktop publishing software like Aldus PageMaker including versions of Lorem Ipsum.";
    byte[] output = regData.getBytes();

    HttpHeaders responseHeaders = new HttpHeaders();
    responseHeaders.set("charset", "utf-8");
    responseHeaders.setContentType(MediaType.valueOf("text/html"));
    responseHeaders.setContentLength(output.length);
    responseHeaders.set("Content-disposition", "attachment; filename=filename.txt");

    return new ResponseEntity<byte[]>(output, responseHeaders, HttpStatus.OK);
}