java - 防止Spring的RestTemplate为multipart/form-data中的每个参数添加 header

Question

我必须使用 Spring 的 RestTemplate 来调用外部 API，该 API 接受带有 Content-Type: multipart/form-data 的 POST 请求。输入数据只是键值，没有附件，但服务器强制我使用multipart/form-data。

以下是运行良好的原始请求。

POST http://the-api:8080 HTTP/1.1
Content-Type: multipart/form-data; boundary=--Eh0oKOHPOSEIJTzFevDxHhPNKhQl7AP6kQL
Accept: */*
Host: the-api:8080
accept-encoding: gzip, deflate
content-length: 680
Connection: keep-alive

--Eh0oKOHPOSEIJTzFevDxHhPNKhQl7AP6kQL
Content-Disposition: form-data; name="param1"

value1
--Eh0oKOHPOSEIJTzFevDxHhPNKhQl7AP6kQL
Content-Disposition: form-data; name="param2"

value2
--Eh0oKOHPOSEIJTzFevDxHhPNKhQl7AP6kQL--

以下是我从 RestTemplate 日志中提取并重新排列的原始请求，它不起作用，因为服务器将 header 误认为是值。

POST http://the-api:8080 HTTP/1.1
Content-Type: multipart/form-data; boundary=--Eh0oKOHPOSEIJTzFevDxHhPNKhQl7AP6kQL
Accept: */*
Host: the-api:8080
accept-encoding: gzip, deflate
content-length: 680
Connection: keep-alive

--Eh0oKOHPOSEIJTzFevDxHhPNKhQl7AP6kQL
Content-Disposition: form-data; name="param1"
Content-Type: text/plain;charset=UTF-8
Content-Length: 29

value1
--Eh0oKOHPOSEIJTzFevDxHhPNKhQl7AP6kQL
Content-Disposition: form-data; name="param2"
Content-Type: text/plain;charset=UTF-8
Content-Length: 14

value2
--Eh0oKOHPOSEIJTzFevDxHhPNKhQl7AP6kQL--

下面是代码

HttpHeaders headers = new HttpHeaders();
headers.setContentType(MediaType.MULTIPART_FORM_DATA);
MultiValueMap<String, String> params = new LinkedMultiValueMap<>();
params.add("param1", "value1);
params.add("param2", "value2);
HttpEntity<MultiValueMap<String, String>> request = new HttpEntity<>(params, headers);

URI uri = UriComponentsBuilder.fromHttpUrl("http://the-api:8080")
        .build().encode(Charset.forName("UTF-8")).toUri();

return restTemplate.postForObject(uri, request, KKPMailResponse.class);

问题

如何防止 Spring 的 RestTemplate 自动为每个参数添加 header Content-Type: text/plain;charset=UTF-8 和 Content-Length: xx

Answer 1

我没有找到阻止 Spring 生成条目的方法，但您可以使用拦截器在发送请求之前删除它们。为此，您必须按如下方式操作拦截器中的请求正文:

public class MultiPartFormDataCleaningInterceptor implements ClientHttpRequestInterceptor {

    @Override
    public ClientHttpResponse intercept(HttpRequest request, byte[] body, ClientHttpRequestExecution execution) throws IOException {
        final MediaType contentType = request.getHeaders().getContentType();
        if (contentType != null
                && MediaType.MULTIPART_FORM_DATA.getType().equals(contentType.getType())
                && MediaType.MULTIPART_FORM_DATA.getSubtype().equals(contentType.getSubtype())) {
            return execution.execute(request, stripContentTypeAndLength(body));
        }
        return execution.execute(request, body);
    }

    private byte[] stripContentTypeAndLength(byte[] body) {
        final String bodyStr = new String(body);
        final StringBuilder builder = new StringBuilder();
        try (final Scanner scanner = new Scanner(bodyStr)) {
            while (scanner.hasNextLine()) {
                final String line = scanner.nextLine();
                if (!line.startsWith("Content-Type:")
                        && !line.startsWith("Content-Length:")) {
                    builder.append(line).append("\r\n");
                }
            }
        }
        final String newBodyStr = builder.toString();
        return newBodyStr.getBytes();
    }
}