java - Resttemplate 表单/多部分 : image + JSON in POST

Question

我正在尝试调用接受图像和一些 JSON 的 rest ws(使用 resttemplate)。但是，我似乎无法让它运行。

相关代码如下:

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

    MultiValueMap<String, Object> map = new LinkedMultiValueMap<>();
    ByteArrayResource bytes = new ByteArrayResource(pictureData) {
        @Override
        public String getFilename() {
            return pictureName;
        }
    };
    map.add("x", x);
    map.add("file", bytes);

    HttpEntity<MultiValueMap<String, Object>> requestEntity = new HttpEntity(map, header);
    String response =  restTemplate.postForObject(UPLOAD_URL, requestEntity, String.class);

其中 x 是一些带有所有必需的 JSON 注释的 POJO(我从另一个 Web 服务接收到它，那部分工作正常)。

但是，这件事告诉我:HttpMessageNotWritableException:无法写入请求:找不到适合 x 的 HttpMessageConverter。

如果我将 ByteArrayResource 更改为 byte[]，则会收到 400 Bad Request。如果我将内容类型更改为 JSON，则 ByteArrayResource 无法序列化为 JSON:

Caused by: org.springframework.http.converter.HttpMessageNotWritableException: Could not write JSON: No serializer found for class java.io.ByteArrayInputStream and no properties discovered to create BeanSerializer (to avoid exception, disable SerializationFeature.FAIL_ON_EMPTY_BEANS) ) (through reference chain: org.springframework.util.LinkedMultiValueMap["file"]->java.util.LinkedList[0]->a.b.c.["inputStream"]); nested exception is com.fasterxml.jackson.databind.JsonMappingException: No serializer found for class java.io.ByteArrayInputStream and no properties discovered to create BeanSerializer (to avoid exception, disable SerializationFeature.FAIL_ON_EMPTY_BEANS) ) (through reference chain: org.springframework.util.LinkedMultiValueMap["file"]->java.util.LinkedList[0]->a.b.c.["inputStream"])

我配置了以下转换器:

StringHttpMessageConverter,
MappingJackson2HttpMessageConverter
FormHttpMessageConverter

有什么想法吗？提前致谢。

更新

所以这就是我目前在说明之后所拥有的:我这样注册转换器:

    RestTemplate restTemplate = new RestTemplate();
    restTemplate.getMessageConverters().add(new StringHttpMessageConverter());
    restTemplate.getMessageConverters().add(new MappingJackson2HttpMessageConverter());

    FormHttpMessageConverter formHttpMessageConverter = new FormHttpMessageConverter();
        formHttpMessageConverter.addPartConverter(new MappingJackson2HttpMessageConverter());
        formHttpMessageConverter.addPartConverter(new ResourceHttpMessageConverter()); // This is hope driven programming

    restTemplate.getMessageConverters().add(new ResourceHttpMessageConverter());
    restTemplate.getMessageConverters().add(formHttpMessageConverter);

然后在 ws 调用中我有:

    HttpHeaders header = new HttpHeaders();
    header.setContentType(MediaType.APPLICATION_JSON); //Also tried with multipart...

    MultiValueMap<String, Object> multipartRequest = new LinkedMultiValueMap<>();

    ByteArrayResource bytes = new ByteArrayResource(pictureData) {
        @Override
        public String getFilename() {
            return pictureName;
        }
    };

    HttpHeaders xHeader = new HttpHeaders();
    xHeader.setContentType(MediaType.APPLICATION_JSON);
    HttpEntity<X> xPart = new HttpEntity<>(x, xHeader);
    multipartRequest.add("x", xPart);

    HttpHeaders pictureHeader = new HttpHeaders();
    pictureHeader.setContentType(MediaType.IMAGE_PNG);
    HttpEntity<ByteArrayResource> picturePart = new HttpEntity<>(bytes, pictureHeader);
    multipartRequest.add("file", picturePart);

    HttpEntity<MultiValueMap<String, Object>> requestEntity = new HttpEntity(multipartRequest, header);
    return restTemplate.postForObject(UPLOAD_URL, requestEntity, String.class);

Answer 1

如果你想使用ByteArrayResource，只需注册一个ResourceHttpMessageConverter。

如果您想使用byte[]，只需注册一个ByteArrayHttpMessageConverter。

图片部分的内容类型应该是图片类型，比如image/png，而不是application/json。

您可以使用

设置每个单独部分的数据类型

HttpHeaders partHeaders = new HttpHeaders();
partHeaders.setContentType(MediaType.IMAGE_PNG);
HttpEntity<ByteArrayResource> bytesPart = new HttpEntity<ByteArrayResource>(bytes, partHeaders);

map.add("file", bytesPart);

---

通过提供您的 HttpMessageConverter 集合来创建您的 RestTemplate

HttpMessageConverter<Object> jackson = new MappingJackson2HttpMessageConverter();
HttpMessageConverter<Resource> resource = new ResourceHttpMessageConverter();
FormHttpMessageConverter formHttpMessageConverter = new FormHttpMessageConverter();
formHttpMessageConverter.addPartConverter(jackson);
formHttpMessageConverter.addPartConverter(resource); // This is hope driven programming

RestTemplate restTemplate = new RestTemplate(Arrays.asList(jackson, resource, formHttpMessageConverter));

最外层的 HttpEntity 应该有一个多部分内容类型

header.setContentType(MediaType.MULTIPART_FORM_DATA);