spring mvc http proxy - spring-mvc

Question

I would like to write a spring MVC Controller class that just take any http request in input, add basic authentication headers to it and forward this request to another server.
I try something like this without success.
#Controller
#RequestMapping("/proxyws")
public class ProxyController {
#RequestMapping("/**")
#ResponseBody
public String mirrorRest( #RequestBody String body, HttpMethod method, HttpServletRequest request, HttpServletResponse response) throws URISyntaxException
{
String server = "localhost";
int port = 8080;
URI uri = new URI("http", null, server, port, request.getRequestURI(), request.getQueryString(), null);
RestTemplate restTemplate=new RestTemplate();
HttpEntity entity = new HttpEntity<String>(body);
String plainCreds = "APP_CLIENT:APP_PASSWORD";
byte[] plainCredsBytes = plainCreds.getBytes();
byte[] base64CredsBytes = Base64.encodeBase64(plainCredsBytes);
String base64Creds = new String(base64CredsBytes);
entity.getHeaders().add("Authorization", "Basic " + base64Creds);
ResponseEntity<String> responseEntity = restTemplate.exchange(uri, method, entity, String.class);
return responseEntity.getBody();
}
For a GET method in input, I get the following exception :
org.springframework.http.converter.HttpMessageNotReadableException: Required request body content is missing:
org.springframework.web.method.HandlerMethod$HandlerMethodParameter#8051792a
at org.springframework.web.servlet.mvc.method.annotation.RequestResponseBodyMethodProcessor.handleEmptyBody(RequestResponseBodyMethodProcessor.java:189)
at org.springframework.web.servlet.mvc.method.annotation.RequestResponseBodyMethodProcessor.readWithMessageConverters(RequestResponseBodyMethodProcessor.java:170)
at org.springframework.web.servlet.mvc.method.annotation.RequestResponseBodyMethodProcessor.resolveArgument(RequestResponseBodyMethodProcessor.java:105)
For a POST request, I get other trouble with le basic auth headers:
java.lang.UnsupportedOperationException
at java.util.Collections$UnmodifiableMap.put(Collections.java:1342)
at org.springframework.http.HttpHeaders.add(HttpHeaders.java:831)
Thanx for your help!

Answer 1

You cannot modify the headers of the HttpEntity object once it's instantiated. You need to pass your headers in through a different HttpEntity constructor, e.g.
public HttpEntity(T body, MultiValueMap<String, String> headers) {
this.body = body;
HttpHeaders tempHeaders = new HttpHeaders();
if (headers != null) {
tempHeaders.putAll(headers);
}
this.headers = HttpHeaders.readOnlyHttpHeaders(tempHeaders);
}
Note the initialization of this.headers: that's where the read-only copy is created.