Spring - Read Http Request headers

In the previous article we saw how to use request parameters and request body of a request. In this article we will see how to use the request headers.

The request headers can be accessed using the @RequestHeader attribute.

@RequestMapping("/greeting")
public ResponseEntity<String> greeting(@RequestHeader("Accept-Language") String language,
        @RequestHeader("Content-Type") String contentType) {
    // do something with the headers
    return new ResponseEntity<String>(String.format("Language: %s, Content Type: %s", language, contentType), HttpStatus.OK);
}

Note that the name of the header field is case insensitive. So Content-Type and content-type are both same.

If in case the header value is not present in the request, then a 400 Bad Request error is sent as response.

Marking headers as optional

Headers can be marked as optional and 400 Bad Request will not be sent in case if the header is absent. This can be achieved using the required parameter.

@RequestHeader(name = 'Content-Type', required = false)

Make sure you check for null values or provide default values.

All headers as Map

We can get all the headers if we don’t provide the name of the header that we are extracting and use a Map instead.

@RequestMapping("/greeting")
public ResponseEntity<String> greeting(@RequestHeader Map<String, String> headers) {
    headers.entrySet().stream().map(it -> it.getKey() + ":" + it.getValue()).forEach(System.out::println);
    return new ResponseEntity<String>("ok", HttpStatus.OK);
}

Note that headers will have only one value if multi value headers are found. In that case we should use MultiValueMap.

Using the HttpHeader object

The HttpHeader objects is designed for the purpose of extracting headers from the request and should be preferred. HttpHeader is extends a MultiValueMap so it is exactly same as the above method of extracting headers but it provides method to extract common headers values.

For example these are some methods which are present:

headers.getContentType();
headers.getContentLength();
headers.getAccessControlAllowOrigin();
headers.getAccessControlAllowHeaders();
headers.getLocation();
headers.getOrigin();
// and lot more...

Conclusion

In this article we learned how to extract request headers in Sprint REST.

  • If we just want a single value, we can do that using @ReqeustHeader("name") method. Be sure to mark is optional is it’s not a required header.
  • We can get all headers using HttpHeaders object which is nothing but a MultiValueMap.

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