转发具有完全相同的json正文的请求

Question

I have a SpringBoot application which simply acts as a middleman. It receives an API request in JSON and forwards this to another server S by calling S's API with the exact same body.

I was exploring the solutions and came across a solution which involved the usage of RestTemplate and MultiValueMap . However, since the json body contains objects rather than simple String, I believe I have to create a DTO with corresponding POJO for the solution to work.

May I ask is the above the only solution, or there is a simple way to forward the request over and get back the response?

Answer 1

The middleman server can expose a endpoint that accepts a @RequestBody of Object and HttpServletRequest then use RestTemplate to forward it to the remote server.

The middleman

@RestController
@RequestMapping("/middleman")
public class MiddleManRestController {

    private RestTemplate restTemplate;

    @PostConstruct
    public void init() {
        this.restTemplate = new RestTemplate();
        this.restTemplate.setRequestFactory(new BufferingClientHttpRequestFactory(this.restTemplate.getRequestFactory()));
    }

    @RequestMapping(value = "/forward", method = RequestMethod.POST)
    public ResponseEntity<Object> forward(@RequestBody Object object, HttpServletRequest request) throws RestClientException {

        //setup the url and path
        final UriComponentsBuilder builder = UriComponentsBuilder.fromHttpUrl("Remote server URL").path("EnpointPath");

        //add query params from previous request
        addQueryParams(request, builder);

        //specify the method
        final RequestEntity.BodyBuilder requestBuilder = RequestEntity.method(HttpMethod.POST, builder.build().toUri());

        //add headers from previous request
        addHeaders(request, requestBuilder);

        RequestEntity<Object> requestEntity = requestBuilder.body(object);
        ParameterizedTypeReference<Object> returnType = new ParameterizedTypeReference<Object>() {};

        //forward to the remote server
        return this.restTemplate.exchange(requestEntity, returnType);
    }

    private void addHeaders(HttpServletRequest request, RequestEntity.BodyBuilder requestBuilder) {
        Enumeration<String> headerNames = request.getHeaderNames();
        while(headerNames.hasMoreElements()) {
            String headerName = headerNames.nextElement();
            String headerValue = request.getHeader(headerName);
            requestBuilder.header(headerName, headerValue);
        }
    }

    private void addQueryParams(HttpServletRequest request, UriComponentsBuilder builder) {
        final MultiValueMap<String, String> queryParams = new LinkedMultiValueMap<String, String>();
        Map<String, String[]> parameterMap = request.getParameterMap();
        if (parameterMap != null) {
            parameterMap.forEach((key, value) -> queryParams.addAll(key, Arrays.asList(value)));
        }
        builder.queryParams(queryParams);
    }
}

Answer 2

Even complex and nested JSON objects can be taken into a Map with key as String and value as Object. I believe you should just use such a map as your request body and transfer the same to another api.