Spring RestClient cannot use uri domain starting with a number

My request url is http://my-host.1domain:1234/path

if i use RestClient ResponseEntity<BackResponse> response = restClient.post().uri(url) .header("hs", config.getSecret()) .contentType(MediaType.APPLICATION_JSON) .body(request) .retrieve() .toEntity(BackResponse.class); will cause

` java.lang.IllegalArgumentException: unsupported URI http://my-host.1domain:1234/path

at java.net.http/jdk.internal.net.http.common.Utils.newIAE(Utils.java:326)
at java.net.http/jdk.internal.net.http.HttpRequestBuilderImpl.checkURI(HttpRequestBuilderImpl.java:85)
at java.net.http/jdk.internal.net.http.HttpRequestBuilderImpl.uri(HttpRequestBuilderImpl.java:71)
at java.net.http/jdk.internal.net.http.HttpRequestBuilderImpl.uri(HttpRequestBuilderImpl.java:43)

`

but RestTemplate will success

Comment From: bclozel

I don't think this is a Spring Framework issue. RestClient uses by default the new java.net.http.HttpClient, which shows this behavior. You can reproduce the same problem by instantiating the URI manually:

URI uri = new URI("http://my-host.1domain:1234/path");
assertThat(uri.getHost()).isNotNull();

If you think this behavior is incorrect, please raise a JDK issue.

You can choose a different request factory (like the org.springframework.http.client.SimpleClientHttpRequestFactory):

RestClient client = RestClient.builder().requestFactory(new SimpleClientHttpRequestFactory()).build();
String body = client.get().uri("http://myhost.1domain:" + port + "/test")
        .retrieve().body(String.class);
assertThat(body).isEqualTo("test");