`@RequestHeader`

You can use the @RequestHeader annotation to bind a request header to a method argument in a controller.

Consider the following request, with headers:

Host                    localhost:8080
Accept                  text/html,application/xhtml+xml,application/xml;q=0.9
Accept-Language         fr,en-gb;q=0.7,en;q=0.3
Accept-Encoding         gzip,deflate
Accept-Charset          ISO-8859-1,utf-8;q=0.7,*;q=0.7
Keep-Alive              300

The following example gets the value of the Accept-Encoding and Keep-Alive headers:

Java
Kotlin

@GetMapping("/demo")
public void handle(
		@RequestHeader("Accept-Encoding") String encoding, (1)
		@RequestHeader("Keep-Alive") long keepAlive) { (2)
	//...
}

1	Get the value of the `Accept-Encoding` header.
2	Get the value of the `Keep-Alive` header.

@GetMapping("/demo")
fun handle(
		@RequestHeader("Accept-Encoding") encoding: String, (1)
		@RequestHeader("Keep-Alive") keepAlive: Long) { (2)
	//...
}

1	Get the value of the `Accept-Encoding` header.
2	Get the value of the `Keep-Alive` header.

If the target method parameter type is not String, type conversion is automatically applied. See Type Conversion.

When an @RequestHeader annotation is used on a Map<String, String>, MultiValueMap<String, String>, or HttpHeaders argument, the map is populated with all header values.

Built-in support is available for converting a comma-separated string into an array or collection of strings or other types known to the type conversion system. For example, a method parameter annotated with @RequestHeader("Accept") can be of type String but also String[] or List<String>.