pekko/akka-docs/rst/java/http/routing-dsl/directives/header-directives/optionalHeaderValue.rst

.. _-optionalHeaderValue-java-:

optionalHeaderValue
===================

Description
-----------
Traverses the list of request headers with the specified function and extracts the first value the function returns as
``Optional[value]``.

The ``optionalHeaderValue`` directive is similar to the :ref:`-headerValue-java-` directive but always extracts an ``Option``
value instead of rejecting the request if no matching header could be found.

Example
-------
TODO: Example snippets for JavaDSL are subject to community contributions! Help us complete the docs, read more about it here: `write example snippets for Akka HTTP Java DSL #20466 <https://github.com/akka/akka/issues/20466>`_.
!htp #18919 #19519 New JavaDSL for Akka HTTP (#20518) * !htt #18919 #19519 Align Java HTTP server DSL with Scala This commits replaces the Java HTTP server DSL with a Java-8 centric one which exposes all scala DSL concepts to be usable from Java, including custom directives, (un)marshallers, rejections, headers, and type safety for path and query parameters. * Add RequestContext and RouteResult to Java DSL fix websockets WIP bring java docs up to date. This applies some updates to the root-level documentation * [htp] Fix java documentation to correctly mention timeouts Timeouts are configured the same in Java and Scala. Hence, linking to the scala docs for timeouts from Java. * =htc fix optionalHeaderValueByType in Java * =htt #20200 fix java testkit always using NoLogging instead logger * +htt actually run new javadsl tests, allow overriding config * =htt improve javadsl test infra with more details when fails * =htt fix bug in wrong path matcher exposed * +htp add missing remaining path matcher * =htp Java DSL cookie tests fixed * =htt Java DSL ParameterDirectivesTest fixed Protect the tweets from scalariform Incorrect response expectations in cache condition directives spec fixed * =htt Path directives for Java DSL * +!htt PathMatchers rewritten, made uniform and tests passing * Bugfix in java reject and a little test-boyscouting * Revert "Incorrect response expectations in cache condition directives spec fixed" This reverts commit cd50e89d45db010309f8249b090ea654ebb11c7a. * +htc HttpAPIsTest is compile time only, not for running Also, moved from the client package since not strictly a client test. SecurityDirectives passing Two faulty tests and two actual bugs. Fix for cache condition spec not working * Not sending in Unit instad of the implicit magnet in the test * HeaderMagnet now works as expected * Java API added for - and + on DateTime PetStore example and test fixed * Annotations to make marshalling work without default constructor * Made model class immutable Incorrect tests fixed Some scaladoc boyscouting as bonus * =htt RequestValTest sprinkled out across multiple directive tests Client ip extraction test with incorrect header name fixed. * =htt Incorrect CodingDirectivesTest fixed. * =htt Bugfix for Java Unmarshaller.firstOf and fixes to JavaRouteTest * =htt MarshallerTest fixed * Missing seal signature added to JavaDSL * More consistent (with Scala) test kit setup for Java * missing Javadocs added * Thread.sleep in default exception handler removed * =htt copy directive docs, prepare for finishing it up * +htt SecurityDirectives.authorize variants and test coverage added * +htt Custom headers in Java DSL * =htt WIP on java docs * +htp add missing parameterOrDefault directive Fixed a lot of doc warnings * =htc intense progress on javadsl docs * =htc #20470 Link to issue about docs and fix compile error compile, migration guide don't mima check http-experimental * =htt Java DSL doc warnings fixed. Only `Could not lex literal_block` ones left now * =htc fix mima settings * =doc fix MethodDirectives doc test with custom method * =htc fix coding directives spec after bad merge * =htc fix concat being corresponding to route() in javadsl * =htt Disable consistency check for route/concat as it fails only on ci server * !htt Minor fixes to PathMatchers 2016-05-16 10:38:40 +02:00			`.. _-optionalHeaderValue-java-:`

			`optionalHeaderValue`
			`===================`

			`Description`
			`-----------`
			`Traverses the list of request headers with the specified function and extracts the first value the function returns as`
			``Optional[value]``.

			The ``optionalHeaderValue`` directive is similar to the :ref:`-headerValue-java-` directive but always extracts an ``Option``
			`value instead of rejecting the request if no matching header could be found.`

			`Example`
			`-------`
			TODO: Example snippets for JavaDSL are subject to community contributions! Help us complete the docs, read more about it here: `write example snippets for Akka HTTP Java DSL #20466 <https://github.com/akka/akka/issues/20466>`_.