--
:api: authenticate
:response: AuthenticateResponse
--
[role="xpack"]
[id="{upid}-{api}"]
=== Authenticate API

[id="{upid}-{api}-sync"]
==== Execution

Authenticating and retrieving information about a user can be performed
using the `security().authenticate()` method:

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This method does not require a request object. The client waits for the
+{response}+ to be returned before continuing with code execution.

[id="{upid}-{api}-response"]
==== Response

The returned +{response}+ contains four fields. The `user` field
, accessed with `getUser`, contains all the information about this
authenticated user. The field `enabled`, tells if this user is actually
usable or has been temporarily deactivated. The field `authentication_realm`,
accessed with `getAuthenticationRealm` contains the name and type of the
Realm that has authenticated the user and the field `lookup_realm`,
accessed with `getLookupRealm` contains the name and type of the Realm where
the user information were retrieved from.

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<1> `getUser` retrieves the `User` instance containing the information,
see {javadoc-client}/security/user/User.html.
<2> `enabled` tells if this user is usable or is deactivated.
<3> `getAuthenticationRealm().getName()` retrieves the name of the realm that authenticated the user.
<4> `getAuthenticationRealm().getType()` retrieves the type of the realm that authenticated the user.
<5> `getLookupRealm().getName()` retrieves the name of the realm from where the user information is looked up.
<6> `getLookupRealm().getType()` retrieves the type of the realm from where the user information is looked up.

[id="{upid}-{api}-async"]
==== Asynchronous Execution

This request can also be executed asynchronously:

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<1> The `ActionListener` to use when the execution completes. This method does
not require a request object.

The asynchronous method does not block and returns immediately. Once the request
has completed the `ActionListener` is called back using the `onResponse` method
if the execution completed successfully or using the `onFailure` method if
it failed.

A typical listener for a +{response}+ looks like:

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<1> Called when the execution completed successfully. The response is
provided as an argument.
<2> Called in case of a failure. The exception is provided as an argument.