Setting "Host" header for Spring RestTemplate doesn't work

Question

I want to send an HTTP request using Spring RestTemplate, via the exchange method.

The third parameter is an instance of HttpEntity, which allows setting the headers/body of the request. I tried the following code snippet:

import org.springframework.http.*;
import org.springframework.web.client.RestTemplate;

public class Connector {
    public static void main(String[] args) {

        HttpHeaders headers = new HttpHeaders();
        headers.set("Host", "www.example.com");
        headers.set("User-Agent", "whatever");


        RestTemplate restTemplate = new RestTemplate();

        ResponseEntity<String> responseEntity = restTemplate.exchange(
                "http://httpbin.org/headers", HttpMethod.GET,
                new HttpEntity<String>(null, headers), String.class);

        System.out.println(responseEntity.getBody());
    }
}

Notice that http://httpbin.org/headers is a simple HTTP Request & Response Service, which (in this case) returns HTTP headers.

The result of running the Java code is as follows:

{
  "headers": {
    "Accept": "text/plain, */*", 
    "Connection": "close", 
    "Host": "httpbin.org", 
    "User-Agent": "whatever"
  }
}

As you can see, the User-Agent is set to what I wanted, but the Host is not.

How can I set Host to the value I desire?

I'm not sure you can--it doesn't usually make sense to set the Host header to something different from the URI. — chrylis -cautiouslyoptimistic-
– chrylis -cautiouslyoptimistic-, Commented Apr 5, 2017 at 6:30
@chrylis: Thanks for the comment. In my use case, I'm writing a reverse proxy for some host H. The proxy is to be hosted at host H, and will contact the actual host H by IP. However, as the actual host H uses virtual hosting, I have to specify the host name H in my request (i.e., the request from the reverse proxy to the IP address). — Sadeq Dousti
– Sadeq Dousti, Commented Apr 5, 2017 at 6:42

Community · Accepted Answer · 2017-05-23 12:25:49Z

4

Perhaps this helps. I don't know if the underlying http call is made through HttpUrlConnection, but setting sun.net.http.allowRestrictedHeaders to true might be worth trying.

See:

edited May 23, 2017 at 12:25

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answered Apr 5, 2017 at 7:13

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3 Comments

Sadeq Dousti Over a year ago

Thank you very much; you saved my day! Setting System.setProperty("sun.net.http.allowRestrictedHeaders", "true"); seems to work perfectly.

slim Over a year ago

Beware! You've asked a question about Spring RestTemplate, but this fix is about Sun HttpURLConnection. If you configure RestTemplate with an Apache ConnectionFactory (which is a very good idea), this fix becomes irrelevant.

NewestUser Over a year ago

I followed this example to reconfigure RestTemplate and use Appache http client which can override the host header without any issues. springframework.guru/using-resttemplate-with-apaches-httpclient

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