如何使用 spring RestTemplate 发送 multipartFile？

Question

我正在尝试将文件从一个 SpringBoot 应用程序发布到另一个 SpringBoot 应用程序。 我试图到达的终点看起来像

@PostMapping(
        value = "/upload",
        consumes = MULTIPART_FORM_DATA_VALUE)
public ResponseEntity<ArmResponse<JobData>> uploadInvoices(@RequestParam("file") MultipartFile interestingStuff) {

    String incomingFilename = interestingStuff.getName();
    String originalFilename = interestingStuff.getOriginalFilename();
    String contentType = interestingStuff.getContentType();

    // do interesting stuff here

    return ok(successfulResponse(new JobData()));
}

应用程序中向 thios 端点执行 POST 请求的代码如下所示

public void loadInvoices(MultipartFile invoices) throws IOException {

    File invoicesFile = new File(invoices.getOriginalFilename());
    invoices.transferTo(invoicesFile);

    LinkedMultiValueMap<String, Object> parts = new LinkedMultiValueMap<>();
    parts.add("file", invoicesFile);


    HttpHeaders httpHeaders = new HttpHeaders();
    httpHeaders.setContentType(MediaType.MULTIPART_FORM_DATA);

    HttpEntity<LinkedMultiValueMap<String, Object>> httpEntity = new HttpEntity<>(parts, httpHeaders);

    String url = String.format("%s/rest/inbound/invoices/upload", baseUrl);

    final List<HttpMessageConverter<?>> messageConverters = new ArrayList<>();
    messageConverters.add(new ByteArrayHttpMessageConverter());
    messageConverters.add(new ResourceHttpMessageConverter());
    messageConverters.add(new AllEncompassingFormHttpMessageConverter());
    messageConverters.add(new FormHttpMessageConverter());
    messageConverters.add(new SourceHttpMessageConverter<Source>());

    RestTemplate template = new RestTemplate(messageConverters);

    template.exchange(
            url,
            HttpMethod.POST,
            httpEntity,
            new ParameterizedTypeReference<ArmResponse<JobData>>() {

            });
}

如果我使用邮递员在表单中发布文件 - 它可以工作邮递员请求的内容类型标头看起来像

content-type:"multipart/form-data; boundary=--------------------------286899320410555838190774"

当 RestTemplate 执行 POST 时，我收到以下错误。

com.fasterxml.jackson.databind.exc.MismatchedInputException：由于[来源：（字符串）“”的输入结束，没有要映射的内容； 行：1，列：0]

我怀疑请求中发送的内容类型标头是错误的。 有谁知道如何正确设置 MULTIPART_FORM_DATA 的内容类型标头？

Answer 1

与往常一样，解决方案非常简单。 只需在 multipartFile 上调用 getResource()。

public void loadInvoices(MultipartFile invoices) throws IOException {

    Resource invoicesResource = invoices.getResource();

    LinkedMultiValueMap<String, Object> parts = new LinkedMultiValueMap<>();
    parts.add("file", invoicesResource);

    HttpHeaders httpHeaders = new HttpHeaders();
    httpHeaders.setContentType(MediaType.MULTIPART_FORM_DATA);

    HttpEntity<LinkedMultiValueMap<String, Object>> httpEntity = new HttpEntity<>(parts, httpHeaders);

    restTemplate.postForEntity("my/url", httpEntity, SommeClass.class);
}

Answer 2

为什么需要 messageConverters？ 只需简单地使用本教程中的代码： https : //www.baeldung.com/spring-rest-template-multipart-upload

RestTemplate restTemplate = new RestTemplate();
ResponseEntity<String> response = restTemplate
  .postForEntity(url , httpEntity, String.class);

Answer 3

Kotlin 中稍微漂亮的解决方案：

    @Test
    fun testMultipartUpload() {
        val bytes = ByteArray(10240) // Get your bytes however you like.
        val resource = object : ByteArrayResource(bytes) {
            override fun getFilename() = "xyzzy.jpg"
        }
        val request = RequestEntity.post("/foobar")
            .contentType(MediaType.MULTIPART_FORM_DATA)
            .body(LinkedMultiValueMap<String, Any>().apply { add("data", resource) })
        val result = testRestTemplate.exchange(request, FooBar::class.java)
        Assertions.assertTrue(result.statusCode.is2xxSuccessful)
    }