创建多部分表单/数据客户端的 Spring Rest 模板像邮递员一样工作，抛出不可转换的异常

Question

我想将这个带有 multipart/form-data 标头请求的邮递员客户端转换为 spring 模板客户端。

现在，我有一个基本的休息控制器，效果很好。

@RestController
@RequestMapping("/api")
public class MainConroller {

    private static final Logger log = LoggerFactory.getLogger(MainConroller.class);
    @Autowired
    private MainService mainService;

    public MainConroller(MainService mainService) {
        this.mainService = mainService;
    }

    @PostMapping("/mails/send")
    public void send(
            @RequestParam("usertoken") String usertoken,
            @RequestParam("sendTo") String sendTo,
            @RequestParam("subject") String subject,
            @RequestParam("content") String content,
            @RequestParam(required = false, name = "files") List<MultipartFile> multipartFiles) {
        log.debug("{}, {}, {}, {}", usertoken, sendTo, subject, content);

        mainService.processMessage(usertoken, sendTo, subject, content, multipartFiles);

    }

}

但是，我需要创建一个休息客户端，所以我使用了一个休息模板，它现在看起来像这样：

ArrayList<HttpMessageConverter<?>> converters = new ArrayList<>(
            Arrays.asList(new MappingJackson2HttpMessageConverter(), new ResourceHttpMessageConverter(), new FormHttpMessageConverter()));
    @Bean
    public RestTemplate restTemplate() {
        return new RestTemplate(converters);
    }
    File file = new File("*********");

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

            MultiValueMap<String, Object> fileValueMap = new LinkedMultiValueMap<>();
            fileValueMap.add(file.getName(), file);
            fileValueMap.add(file.getName(), file);
            fileValueMap.add(file.getName(), file);

            HttpEntity<MultiValueMap<String, Object>> filesPart = new HttpEntity<>(fileValueMap, httpHeaders);

    //        String key values part

            MultiValueMap<String, String> stringPart = new LinkedMultiValueMap<>();
            stringPart.add("usertoken", "test");
            stringPart.add("sendTo", "test");
            stringPart.add("subject", "test");
            stringPart.add("content", "test");

            HttpEntity<MultiValueMap<String, String>> objectPart = new HttpEntity<>(stringPart, httpHeaders);


            MultiValueMap<String, Object> multiPartRequest = new LinkedMultiValueMap<>();
            multiPartRequest.add("ObjectPart", objectPart);
            multiPartRequest.add("FilesPart", filesPart);


            HttpEntity<MultiValueMap<String, Object>> requestEntity = new HttpEntity<>(multiPartRequest, httpHeaders);

            String serverUrl = "****";

            restTemplate().postForEntity(serverUrl, requestEntity, String.class);

问题是当我尝试发送发布请求时，它抛出

Exception in thread "main" org.springframework.web.client.RestClientException: Could not write request: no suitable HttpMessageConverter found for request type [org.springframework.util.LinkedMultiValueMap] and content type [multipart/form-data]

更新

客户端的解决方案非常简单，您只需在对象值中发送字符串值，这些值将通过泛型自动转换为字符串。

此外，文件不能作为文件发送，而是必须创建 FileSystemResource，这是客户端的完整代码：

@Service
public class RestTemplatePost {

    @Bean
    public RestTemplate restTemplate() {
        return new RestTemplate();
    }

    public void prepareMessage() throws Exception {


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

        MultiValueMap<String, Object> form = new LinkedMultiValueMap<>();
        form.add("usertoken", "test");
        form.add("sendTo", "test");
        form.add("subject", "test");
        form.add("content", "test");
        form.add("files", getTestFile());
        form.add("files", getTestFile());

        HttpEntity<MultiValueMap<String, Object>> requestEntity = new HttpEntity<>(form, httpHeaders);

        String serverUrl = "******";

        restTemplate().postForEntity(serverUrl, requestEntity, String.class);


    }

    public static Resource getTestFile() throws IOException {
    Path testFile = Paths.get("C****");
    System.out.println("Creating and Uploading Test File: " + testFile);
    Files.write(testFile, "Hello World !!, This is a test file.".getBytes());
    return new FileSystemResource(testFile.toFile());
}

}

Answer 1

默认的 RestTemplate 构造函数不包含任何消息转换器，您需要添加它。例如，您可以这样做：

HttpEntity<MultiValueMap<String, Object>> requestEntity = new 
HttpEntity<MultiValueMap<String, Object>>(parts, requestHeaders);

RestTemplate restTemplate = getRestTemplate();
restTemplate.getMessageConverters().add(new FormHttpMessageConverter());
restTemplate.getMessageConverters().add(new MappingJackson2HttpMessageConverter());

return restTemplate.postForObject(apiURI, requestEntity, String.class);

Answer 2

你把事情搞得太复杂了。您应该使用单个地图来保存表单值，而不是地图的地图。在 Spring Boot 旁边已经提供了一个，RestTemplate所以你不需要再次配置你自己的。

File file = new File("*********");

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

MultiValueMap<String, Object> form = new LinkedMultiValueMap<>();
form.add("files", file);
form.add("files", file);
form.add("files", file);

form.add("usertoken", "test");
form.add("sendTo", "test");
form.add("subject", "test");
form.add("content", "test");

HttpEntity<MultiValueMap<String, Object>> requestEntity = new HttpEntity<>(form, httpHeaders);

String serverUrl = "****";

restTemplate().postForEntity(serverUrl, requestEntity, String.class);

在RestTemplate（或实际上的FormHttpMessageConverter），将其转化为一个正确的请求。