如何在spring mvc rest controller中返回二进制数据而不是base64编码的byte []

Question

我想通过spring-mvc-rest控制器返回生成的pdf文件.这是我目前正在使用的代码的缩短版本:

@RestController
@RequestMapping("/x")
public class XController {
    @RequestMapping(value = "/", method = RequestMethod.GET)
    public ResponseEntity<byte[]> find() throws IOException {
        byte[] pdf = createPdf();

        HttpHeaders headers = new HttpHeaders();
        headers.setContentType(new MediaType("application", "pdf"));
        headers.setContentDispositionFormData("attachment", "x.pdf");
        headers.setContentLength(pdf.length);
        return new ResponseEntity<byte[]>(pdf, headers, HttpStatus.OK);
    }
}

这工作得很好,它只是返回实际的字节数组作为base64编码:(

curl -i 'http://127.0.0.1:8080/app/x'

Server: Apache-Coyote/1.1
Content-Disposition: form-data; name="attachment"; filename=x.pdf"
Content-Type: application/pdf
Content-Length: 138654
Date: Fri, 08 Jan 2016 11:25:38 GMT

"JVBERi0xLjYNJeLjz9MNCjMyNCAwIG9iag [...]

(顺便说一下,响应甚至不包含结束":)

任何提示赞赏!

Answer 1

我使用您的代码创建了示例，但一个非常相似的方法正在我的网络应用程序中完成他的工作：

@RequestMapping(value = "/", method = RequestMethod.GET)
public void downloadFile(HttpServletResponse response,
                         HttpServletRequest request) throws IOException
{
    byte[] pdf = createPdf();

    response.setContentType("application/x-download");
    response.setHeader("Content-Disposition", "attachment; filename=foo.pdf");
    response.setHeader("Pragma", "no-cache");
    response.setHeader("Cache-Control", "no-cache");
    response.getOutputStream().write(pdf);
}

否则，您可以尝试这个答案Open ResponseEntity PDF in new browser tab

Answer 2

该问题是由 Spring 尝试将响应编码为 Json 引起的。

您的请求可能指定Accepts = "*/*"并且由于 Spring 忽略了 ResponseEntity 的ContentType，因此发现最佳编码是application/json.

对此最简单的解决方法是将 a 添加produces到您的请求映射中，因此您的代码变为：

@RestController
@RequestMapping(value = "/x",
                produces = "application/pdf") // <-- Add this
public class XController {
    @RequestMapping(value = "/", method = RequestMethod.GET)
    public ResponseEntity<byte[]> find() throws IOException {
        byte[] pdf = createPdf();

        HttpHeaders headers = new HttpHeaders();
        headers.setContentType(new MediaType("application", "pdf"));
        headers.setContentDispositionFormData("attachment", "x.pdf");
        headers.setContentLength(pdf.length);
        return new ResponseEntity<byte[]>(pdf, headers, HttpStatus.OK);
    }
}