[[_service_accounts]]
==== Using a Service Account
[role="_abstract"]
Each OIDC client has a built-in _service account_. Use this _service account_ to obtain an access token.

.Prerequisites

.Procedure
. Select your client in {project_name}.
. Click on the *Settings* tab.
. Set the <<_access-type, Access Type>> of your client is set to *confidential*.
. Toggle *Service Accounts Enabled* to ON.
. Click *Save*.
. Configure your <<_client-credentials, client credentials>>.
. Click on the *Scope* tab.
. Verify that you have roles or toggle *Full Scope Allowed* to ON.
. On the *Service Account Roles* tab, configure the roles available to this service account for your client.

Roles from access tokens are the intersection of:

* Role scope mappings of a client combined with the role scope mappings inherited from linked client scopes.
* Service account roles.

The REST URL to invoke is `/auth/realms/{realm-name}/protocol/openid-connect/token`. This URL must be invoked as a POST request and requires that you post the client credentials with the request. 

By default, client credentials are represented by the clientId and clientSecret of the client in the *Authorization: Basic* header but you can also authenticate the client with a signed JWT assertion or any other custom mechanism for client authentication.

You also need to set the *grant_type* parameter to "client_credentials" as per the OAuth2 specification.

For example, the POST invocation to retrieve a service account can look like this:

[source]
----

    POST /auth/realms/demo/protocol/openid-connect/token
    Authorization: Basic cHJvZHVjdC1zYS1jbGllbnQ6cGFzc3dvcmQ=
    Content-Type: application/x-www-form-urlencoded

    grant_type=client_credentials
----

The response would be similar to this https://tools.ietf.org/html/rfc6749#section-4.4.3[Access Token Response] from the OAuth 2.0 specification.

[source]
----

HTTP/1.1 200 OK
Content-Type: application/json;charset=UTF-8
Cache-Control: no-store
Pragma: no-cache

{
    "access_token":"2YotnFZFEjr1zCsicMWpAA",
    "token_type":"bearer",
    "expires_in":60,
    "refresh_token":"tGzv3JOkF0XG5Qx2TlKWIA",
    "refresh_expires_in":600,
    "id_token":"tGzv3JOkF0XG5Qx2TlKWIA",
    "not-before-policy":0,
    "session_state":"234234-234234-234234"
}
----

The retrieved access token can be refreshed or logged out by an out-of-bound request.