headerValue

Description

Traverses the list of request headers with the specified function and extracts the first value the function returns a non empty Optional<T>.

The headerValue-java directive is a mixture of map and find on the list of request headers. The specified function is called once for each header until the function returns a non empty Optional<T>. The value of this Optional is extracted and presented to the inner route. If the function throws an exception the request is rejected with a MalformedHeaderRejection. If the function returns Optional.empty() for every header the request is rejected as “NotFound”.

This directive is the basis for building other request header related directives.

See also headerValuePF for a nicer syntactic alternative.

Example

final Function<HttpHeader, Optional<Host>> extractHostPort = header -> {
  if (header instanceof Host) {
    return Optional.of((Host) header);
  } else {
    return Optional.empty();
  }
};

final Route route = headerValue(extractHostPort, host ->
  complete("The port was " + host.port())
);

// tests:
testRoute(route).run(HttpRequest.GET("/").addHeader(Host.create("example.com", 5043)))
  .assertEntity("The port was 5043");

testRoute(route).run(HttpRequest.GET("/"))
  .assertStatusCode(StatusCodes.NOT_FOUND)
  .assertEntity("The requested resource could not be found.");

Get headerValue or return a default value

Using provide and composing directives one can build a pattern where a headerValue is extracted if available or a default is returned.

final Function<HttpHeader, Optional<String>> extractExampleHeader = header -> {
  if (header.is("x-example-header")) {
    return Optional.of(header.value());
  } else {
    return Optional.empty();
  }
};

final Route route = anyOf(
  bindParameter(this::headerValue, extractExampleHeader),
  bindParameter(this::provide, "newValue"),
  (String value) -> complete("header is " + value));

// tests:
final RawHeader exampleHeader = RawHeader.create("X-Example-Header", "theHeaderValue");
testRoute(route).run(HttpRequest.GET("/").addHeader(exampleHeader))
  .assertEntity("header is theHeaderValue");

testRoute(route).run(HttpRequest.GET("/"))
  .assertEntity("header is newValue");