如果你:

不想在发送到响应之前将整个文件加载到字节[]中; 希望/需要通过InputStream发送/下载; 想要有Mime类型和文件名发送的完全控制; 让其他@ControllerAdvice为你(或不)拾取异常。

下面的代码是你需要的:

@RequestMapping(value = "/stuff/{stuffId}", method = RequestMethod.GET)
public ResponseEntity<FileSystemResource> downloadStuff(@PathVariable int stuffId)
                                                                      throws IOException {
    String fullPath = stuffService.figureOutFileNameFor(stuffId);
    File file = new File(fullPath);
    long fileLength = file.length(); // this is ok, but see note below

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

    return new ResponseEntity<FileSystemResource>(
        new FileSystemResource(file), respHeaders, HttpStatus.OK
    );
}

More on setContentLength(): First of all, the content-length header is optional per the HTTP 1.1 RFC. Still, if you can provide a value, it is better. To obtain such value, know that File#length() should be good enough in the general case, so it is a safe default choice. In very specific scenarios, though, it can be slow, in which case you should have it stored previously (e.g. in the DB), not calculated on the fly. Slow scenarios include: if the file is very large, specially if it is on a remote system or something more elaborated like that - a database, maybe.

InputStreamResource

如果你的资源不是一个文件，例如你从DB中获取数据，你应该使用InputStreamResource。例子:

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

我能够通过使用Spring的ResourceHttpMessageConverter中的内置支持来进行流处理。如果可以确定mime类型，这将设置内容长度和内容类型

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

如果你:

不想在发送到响应之前将整个文件加载到字节[]中; 希望/需要通过InputStream发送/下载; 想要有Mime类型和文件名发送的完全控制; 让其他@ControllerAdvice为你(或不)拾取异常。

下面的代码是你需要的:

@RequestMapping(value = "/stuff/{stuffId}", method = RequestMethod.GET)
public ResponseEntity<FileSystemResource> downloadStuff(@PathVariable int stuffId)
                                                                      throws IOException {
    String fullPath = stuffService.figureOutFileNameFor(stuffId);
    File file = new File(fullPath);
    long fileLength = file.length(); // this is ok, but see note below

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

    return new ResponseEntity<FileSystemResource>(
        new FileSystemResource(file), respHeaders, HttpStatus.OK
    );
}

More on setContentLength(): First of all, the content-length header is optional per the HTTP 1.1 RFC. Still, if you can provide a value, it is better. To obtain such value, know that File#length() should be good enough in the general case, so it is a safe default choice. In very specific scenarios, though, it can be slow, in which case you should have it stored previously (e.g. in the DB), not calculated on the fly. Slow scenarios include: if the file is very large, specially if it is on a remote system or something more elaborated like that - a database, maybe.

InputStreamResource

如果你的资源不是一个文件，例如你从DB中获取数据，你应该使用InputStreamResource。例子:

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

如下图所示

@RequestMapping(value = "/download", method = RequestMethod.GET)
public void getFile(HttpServletResponse response) {
    try {
        DefaultResourceLoader loader = new DefaultResourceLoader();
        InputStream is = loader.getResource("classpath:META-INF/resources/Accepted.pdf").getInputStream();
        IOUtils.copy(is, response.getOutputStream());
        response.setHeader("Content-Disposition", "attachment; filename=Accepted.pdf");
        response.flushBuffer();
    } catch (IOException ex) {
        throw new RuntimeException("IOError writing file to output stream");
    }
}

您可以在这里显示PDF或下载示例

如果这对谁有帮助的话。你可以按照Infeligo给出的答案去做，但只需要在强制下载的代码中添加额外的内容即可。

response.setContentType("application/force-download");

Do

从处理程序方法返回ResponseEntity<Resource> 指定内容类型 如果需要，设置Content-Disposition: 文件名 类型 内联以强制在浏览器中预览 附件强制下载

例子

@Controller
public class DownloadController {
    @GetMapping("/downloadPdf.pdf")
    // 1.
    public ResponseEntity<Resource> downloadPdf() {
        FileSystemResource resource = new FileSystemResource("/home/caco3/Downloads/JMC_Tutorial.pdf");
        // 2.
        MediaType mediaType = MediaTypeFactory
                .getMediaType(resource)
                .orElse(MediaType.APPLICATION_OCTET_STREAM);
        HttpHeaders headers = new HttpHeaders();
        headers.setContentType(mediaType);
        // 3
        ContentDisposition disposition = ContentDisposition
                // 3.2
                .inline() // or .attachment()
                // 3.1
                .filename(resource.getFilename())
                .build();
        headers.setContentDisposition(disposition);
        return new ResponseEntity<>(resource, headers, HttpStatus.OK);
    }
}

解释

返回ResponseEntity <资源>

当您返回ResponseEntity<Resource>时，ResourceHttpMessageConverter将写入文件内容

资源实现的例子:

基于字节的ByteArrayResource [] FileSystemResource—用于文件或路径 UrlResource -从java.net.URL检索 GridFsResource—存储在MongoDB中的blob ClassPathResource—用于类路径中的文件，例如资源目录中的文件。我对“从Spring Boot中的资源文件夹中读取文件”问题的回答详细解释了如何在类路径中定位资源

显式指定Content-Type:

原因:请参阅“FileSystemResource返回内容类型为json”问题

选项:

硬编码头文件 使用Spring中的MediaTypeFactory。MediaTypeFactory使用/org/springframework/http/mime将Resource映射到MediaType。类型文件 使用第三方库，如Apache Tika

如果需要，设置Content-Disposition:

关于Content-Disposition头:

HTTP上下文中的第一个参数要么是内联(默认值，表明它可以在Web页面中显示，也可以作为Web页面显示)，要么是附件(表明应该下载它;大多数浏览器会显示一个“另存为”对话框，如果存在的话，会预先填充文件名参数的值)。

在应用中使用ContentDisposition:

在浏览器中预览文件: 性格=性格 .inline () .filename (resource.getFilename ()) .build (); 强制下载: 性格=性格 .attachment () .filename (resource.getFilename ()) .build ();

小心使用InputStreamResource:

使用HttpHeaders#setContentLength方法指定Content-Length，如果:

长度是已知的 使用InputStreamResource

原因:Spring不会为InputStreamResource写Content-Length，因为Spring不能确定资源的长度。下面是来自ResourceHttpMessageConverter的一段代码:

@Override
protected Long getContentLength(Resource resource, @Nullable MediaType contentType) throws IOException {
    // Don't try to determine contentLength on InputStreamResource - cannot be read afterwards...
    // Note: custom InputStreamResource subclasses could provide a pre-calculated content length!
    if (InputStreamResource.class == resource.getClass()) {
        return null;
    }
    long contentLength = resource.contentLength();
    return (contentLength < 0 ? null : contentLength);
}

在其他情况下，Spring设置Content-Length:

~ $ curl -I localhost:8080/downloadPdf.pdf  | grep "Content-Length"
Content-Length: 7554270