spring-security/docs/modules/ROOT/pages/servlet/oauth2/client/authorization-grants.adoc

[[oauth2Client-auth-grant-support]]
= Authorization Grant Support

This section describes Spring Security's support for authorization grants.

[[oauth2Client-auth-code-grant]]
== Authorization Code

[NOTE]
====
See the OAuth 2.0 Authorization Framework for further details on the https://tools.ietf.org/html/rfc6749#section-1.3.1[Authorization Code] grant.
====

=== Obtaining Authorization

[NOTE]
====
See the https://tools.ietf.org/html/rfc6749#section-4.1.1[Authorization Request/Response] protocol flow for the Authorization Code grant.
====



=== Initiating the Authorization Request

The `OAuth2AuthorizationRequestRedirectFilter` uses an `OAuth2AuthorizationRequestResolver` to resolve an `OAuth2AuthorizationRequest` and initiate the Authorization Code grant flow by redirecting the end-user's user-agent to the Authorization Server's Authorization Endpoint.

The primary role of the `OAuth2AuthorizationRequestResolver` is to resolve an `OAuth2AuthorizationRequest` from the provided web request.
The default implementation `DefaultOAuth2AuthorizationRequestResolver` matches on the (default) path `+/oauth2/authorization/{registrationId}+`, extracting the `registrationId`, and using it to build the `OAuth2AuthorizationRequest` for the associated `ClientRegistration`.

Consider the following Spring Boot 2.x properties for an OAuth 2.0 Client registration:

[source,yaml,attrs="-attributes"]
----
spring:
  security:
    oauth2:
      client:
        registration:
          okta:
            client-id: okta-client-id
            client-secret: okta-client-secret
            authorization-grant-type: authorization_code
            redirect-uri: "{baseUrl}/authorized/okta"
            scope: read, write
        provider:
          okta:
            authorization-uri: https://dev-1234.oktapreview.com/oauth2/v1/authorize
            token-uri: https://dev-1234.oktapreview.com/oauth2/v1/token
----

Given the preceding properties, a request with the base path `/oauth2/authorization/okta` initiates the Authorization Request redirect by the `OAuth2AuthorizationRequestRedirectFilter` and ultimately starts the Authorization Code grant flow.

[NOTE]
====
The `AuthorizationCodeOAuth2AuthorizedClientProvider` is an implementation of `OAuth2AuthorizedClientProvider` for the Authorization Code grant,
which also initiates the Authorization Request redirect by the `OAuth2AuthorizationRequestRedirectFilter`.
====

If the OAuth 2.0 Client is a https://tools.ietf.org/html/rfc6749#section-2.1[Public Client], configure the OAuth 2.0 Client registration as follows:

[source,yaml,attrs="-attributes"]
----
spring:
  security:
    oauth2:
      client:
        registration:
          okta:
            client-id: okta-client-id
            client-authentication-method: none
            authorization-grant-type: authorization_code
            redirect-uri: "{baseUrl}/authorized/okta"
            ...
----

Public Clients are supported by using https://tools.ietf.org/html/rfc7636[Proof Key for Code Exchange] (PKCE).
If the client is running in an untrusted environment (such as a native application or web browser-based application) and is therefore incapable of maintaining the confidentiality of its credentials, PKCE is automatically used when the following conditions are true:

. `client-secret` is omitted (or empty)
. `client-authentication-method` is set to `none` (`ClientAuthenticationMethod.NONE`)

[TIP]
If the OAuth 2.0 Provider supports PKCE for https://tools.ietf.org/html/rfc6749#section-2.1[Confidential Clients], you may (optionally) configure it using `DefaultOAuth2AuthorizationRequestResolver.setAuthorizationRequestCustomizer(OAuth2AuthorizationRequestCustomizers.withPkce())`.

[[oauth2Client-auth-code-redirect-uri]]
The `DefaultOAuth2AuthorizationRequestResolver` also supports `URI` template variables for the `redirect-uri` by using `UriComponentsBuilder`.

The following configuration uses all the supported `URI` template variables:

[source,yaml,attrs="-attributes"]
----
spring:
  security:
    oauth2:
      client:
        registration:
          okta:
            ...
            redirect-uri: "{baseScheme}://{baseHost}{basePort}{basePath}/authorized/{registrationId}"
            ...
----

[NOTE]
====
`+{baseUrl}+` resolves to `+{baseScheme}://{baseHost}{basePort}{basePath}+`
====

Configuring the `redirect-uri` with `URI` template variables is especially useful when the OAuth 2.0 Client is running behind a xref:features/exploits/http.adoc#http-proxy-server[Proxy Server].
Doing so ensures that the `X-Forwarded-*` headers are used when expanding the `redirect-uri`.

=== Customizing the Authorization Request

One of the primary use cases an `OAuth2AuthorizationRequestResolver` can realize is the ability to customize the Authorization Request with additional parameters above the standard parameters defined in the OAuth 2.0 Authorization Framework.

For example, OpenID Connect defines additional OAuth 2.0 request parameters for the https://openid.net/specs/openid-connect-core-1_0.html#AuthRequest[Authorization Code Flow] extending from the standard parameters defined in the https://tools.ietf.org/html/rfc6749#section-4.1.1[OAuth 2.0 Authorization Framework].
One of those extended parameters is the `prompt` parameter.

[NOTE]
====
The `prompt` parameter is optional. Space delimited, case sensitive list of ASCII string values that specifies whether the Authorization Server prompts the End-User for re-authentication and consent. The defined values are: `none`, `login`, `consent`, and `select_account`.
====

The following example shows how to configure the `DefaultOAuth2AuthorizationRequestResolver` with a `Consumer<OAuth2AuthorizationRequest.Builder>` that customizes the Authorization Request for `oauth2Login()`, by including the request parameter `prompt=consent`.

[tabs]
======
Java::
+
[source,java,role="primary"]
----
@Configuration
@EnableWebSecurity
public class OAuth2LoginSecurityConfig {

	@Autowired
	private ClientRegistrationRepository clientRegistrationRepository;

	@Bean
	public SecurityFilterChain filterChain(HttpSecurity http) throws Exception {
		http
			.authorizeHttpRequests(authorize -> authorize
				.anyRequest().authenticated()
			)
			.oauth2Login(oauth2 -> oauth2
				.authorizationEndpoint(authorization -> authorization
					.authorizationRequestResolver(
						authorizationRequestResolver(this.clientRegistrationRepository)
					)
				)
			);
		return http.build();
	}

	private OAuth2AuthorizationRequestResolver authorizationRequestResolver(
			ClientRegistrationRepository clientRegistrationRepository) {

		DefaultOAuth2AuthorizationRequestResolver authorizationRequestResolver =
				new DefaultOAuth2AuthorizationRequestResolver(
						clientRegistrationRepository, "/oauth2/authorization");
		authorizationRequestResolver.setAuthorizationRequestCustomizer(
				authorizationRequestCustomizer());

		return  authorizationRequestResolver;
	}

	private Consumer<OAuth2AuthorizationRequest.Builder> authorizationRequestCustomizer() {
		return customizer -> customizer
					.additionalParameters(params -> params.put("prompt", "consent"));
	}
}
----

Kotlin::
+
[source,kotlin,role="secondary"]
----
@Configuration
@EnableWebSecurity
class SecurityConfig {

    @Autowired
    private lateinit var customClientRegistrationRepository: ClientRegistrationRepository

    @Bean
    open fun filterChain(http: HttpSecurity): SecurityFilterChain {
        http {
            authorizeRequests {
                authorize(anyRequest, authenticated)
            }
            oauth2Login {
                authorizationEndpoint {
                    authorizationRequestResolver = authorizationRequestResolver(customClientRegistrationRepository)
                }
            }
        }
        return http.build()
    }

    private fun authorizationRequestResolver(
            clientRegistrationRepository: ClientRegistrationRepository?): OAuth2AuthorizationRequestResolver? {
        val authorizationRequestResolver = DefaultOAuth2AuthorizationRequestResolver(
                clientRegistrationRepository, "/oauth2/authorization")
        authorizationRequestResolver.setAuthorizationRequestCustomizer(
                authorizationRequestCustomizer())
        return authorizationRequestResolver
    }

    private fun authorizationRequestCustomizer(): Consumer<OAuth2AuthorizationRequest.Builder> {
        return Consumer { customizer ->
            customizer
                    .additionalParameters { params -> params["prompt"] = "consent" }
        }
    }
}
----
======

For the simple use case where the additional request parameter is always the same for a specific provider, you can add it directly in the `authorization-uri` property.

For example, if the value for the request parameter `prompt` is always `consent` for the provider `okta`, you can configure it as follows:

[source,yaml]
----
spring:
  security:
    oauth2:
      client:
        provider:
          okta:
            authorization-uri: https://dev-1234.oktapreview.com/oauth2/v1/authorize?prompt=consent
----

The preceding example shows the common use case of adding a custom parameter on top of the standard parameters.
Alternatively, if your requirements are more advanced, you can take full control in building the Authorization Request URI by overriding the `OAuth2AuthorizationRequest.authorizationRequestUri` property.

[TIP]
====
`OAuth2AuthorizationRequest.Builder.build()` constructs the `OAuth2AuthorizationRequest.authorizationRequestUri`, which represents the Authorization Request URI including all query parameters using the `application/x-www-form-urlencoded` format.
====

The following example shows a variation of `authorizationRequestCustomizer()` from the preceding example and instead overrides the `OAuth2AuthorizationRequest.authorizationRequestUri` property:

[tabs]
======
Java::
+
[source,java,role="primary"]
----
private Consumer<OAuth2AuthorizationRequest.Builder> authorizationRequestCustomizer() {
	return customizer -> customizer
				.authorizationRequestUri(uriBuilder -> uriBuilder
					.queryParam("prompt", "consent").build());
}
----

Kotlin::
+
[source,kotlin,role="secondary"]
----
private fun authorizationRequestCustomizer(): Consumer<OAuth2AuthorizationRequest.Builder> {
    return Consumer { customizer: OAuth2AuthorizationRequest.Builder ->
        customizer
                .authorizationRequestUri { uriBuilder: UriBuilder ->
                    uriBuilder
                            .queryParam("prompt", "consent").build()
                }
    }
}
----
======


=== Storing the Authorization Request

The `AuthorizationRequestRepository` is responsible for the persistence of the `OAuth2AuthorizationRequest` from the time the Authorization Request is initiated to the time the Authorization Response is received (the callback).

[TIP]
====
The `OAuth2AuthorizationRequest` is used to correlate and validate the Authorization Response.
====

The default implementation of `AuthorizationRequestRepository` is `HttpSessionOAuth2AuthorizationRequestRepository`, which stores the `OAuth2AuthorizationRequest` in the `HttpSession`.

If you have a custom implementation of `AuthorizationRequestRepository`, you can configure it as follows:

.AuthorizationRequestRepository Configuration
[tabs]
======
Java::
+
[source,java,role="primary"]
----
@Configuration
@EnableWebSecurity
public class OAuth2ClientSecurityConfig {

	@Bean
	public SecurityFilterChain filterChain(HttpSecurity http) throws Exception {
		http
			.oauth2Client(oauth2 -> oauth2
				.authorizationCodeGrant(codeGrant -> codeGrant
					.authorizationRequestRepository(this.authorizationRequestRepository())
					...
				)
            .oauth2Login(oauth2 -> oauth2
                .authorizationEndpoint(endpoint -> endpoint
                    .authorizationRequestRepository(this.authorizationRequestRepository())
                    ...
                )
            ).build();
	}

    @Bean
    public AuthorizationRequestRepository<OAuth2AuthorizationRequest> authorizationRequestRepository() {
        return new CustomOAuth2AuthorizationRequestRepository();
    }
}
----

Kotlin::
+
[source,kotlin,role="secondary"]
----
@Configuration
@EnableWebSecurity
class OAuth2ClientSecurityConfig {

    @Bean
    open fun filterChain(http: HttpSecurity): SecurityFilterChain {
        http {
            oauth2Client {
                authorizationCodeGrant {
                    authorizationRequestRepository = authorizationRequestRepository()
                }
            }
        }
        return http.build()
    }
}
----

Xml::
+
[source,xml,role="secondary"]
----
<http>
	<oauth2-client>
		<authorization-code-grant authorization-request-repository-ref="authorizationRequestRepository"/>
	</oauth2-client>
</http>
----
======

=== Requesting an Access Token

[NOTE]
====
See the https://tools.ietf.org/html/rfc6749#section-4.1.3[Access Token Request/Response] protocol flow for the Authorization Code grant.
====

The default implementation of `OAuth2AccessTokenResponseClient` for the Authorization Code grant is `DefaultAuthorizationCodeTokenResponseClient`, which uses a `RestOperations` instance to exchange an authorization code for an access token at the Authorization Server’s Token Endpoint.

The `DefaultAuthorizationCodeTokenResponseClient` is flexible, as it lets you customize the pre-processing of the Token Request and/or post-handling of the Token Response.


=== Customizing the Access Token Request

If you need to customize the pre-processing of the Token Request, you can provide `DefaultAuthorizationCodeTokenResponseClient.setRequestEntityConverter()` with a custom `Converter<OAuth2AuthorizationCodeGrantRequest, RequestEntity<?>>`.
The default implementation (`OAuth2AuthorizationCodeGrantRequestEntityConverter`) builds a `RequestEntity` representation of a standard https://tools.ietf.org/html/rfc6749#section-4.1.3[OAuth 2.0 Access Token Request].
However, providing a custom `Converter` would let you extend the standard Token Request and add custom parameter(s).

To customize only the parameters of the request, you can provide `OAuth2AuthorizationCodeGrantRequestEntityConverter.setParametersConverter()` with a custom `Converter<OAuth2AuthorizationCodeGrantRequest, MultiValueMap<String, String>>` to completely override the parameters sent with the request. This is often simpler than constructing a `RequestEntity` directly.

[TIP]
====
If you prefer to only add additional parameters, you can provide `OAuth2AuthorizationCodeGrantRequestEntityConverter.addParametersConverter()` with a custom `Converter<OAuth2AuthorizationCodeGrantRequest, MultiValueMap<String, String>>` which constructs an aggregate `Converter`.
====

[IMPORTANT]
====
The custom `Converter` must return a valid `RequestEntity` representation of an OAuth 2.0 Access Token Request that is understood by the intended OAuth 2.0 Provider.
====

=== Customizing the Access Token Response

On the other end, if you need to customize the post-handling of the Token Response, you need to provide `DefaultAuthorizationCodeTokenResponseClient.setRestOperations()` with a custom configured `RestOperations`.
The default `RestOperations` is configured as follows:

[tabs]
======
Java::
+
[source,java,role="primary"]
----
RestTemplate restTemplate = new RestTemplate(Arrays.asList(
		new FormHttpMessageConverter(),
		new OAuth2AccessTokenResponseHttpMessageConverter()));

restTemplate.setErrorHandler(new OAuth2ErrorResponseErrorHandler());
----

Kotlin::
+
[source,kotlin,role="secondary"]
----
val restTemplate = RestTemplate(listOf(
        FormHttpMessageConverter(),
        OAuth2AccessTokenResponseHttpMessageConverter()))

restTemplate.errorHandler = OAuth2ErrorResponseErrorHandler()
----
======

[TIP]
====
Spring MVC `FormHttpMessageConverter` is required, as it is used when sending the OAuth 2.0 Access Token Request.
====

`OAuth2AccessTokenResponseHttpMessageConverter` is an `HttpMessageConverter` for an OAuth 2.0 Access Token Response.
You can provide `OAuth2AccessTokenResponseHttpMessageConverter.setAccessTokenResponseConverter()` with a custom `Converter<Map<String, Object>, OAuth2AccessTokenResponse>` that is used for converting the OAuth 2.0 Access Token Response parameters to an `OAuth2AccessTokenResponse`.

`OAuth2ErrorResponseErrorHandler` is a `ResponseErrorHandler` that can handle an OAuth 2.0 Error, such as `400 Bad Request`.
It uses an `OAuth2ErrorHttpMessageConverter` for converting the OAuth 2.0 Error parameters to an `OAuth2Error`.

Whether you customize `DefaultAuthorizationCodeTokenResponseClient` or provide your own implementation of `OAuth2AccessTokenResponseClient`, you need to configure it as follows:

.Access Token Response Configuration
[tabs]
======
Java::
+
[source,java,role="primary"]
----
@Configuration
@EnableWebSecurity
public class OAuth2ClientSecurityConfig {

	@Bean
	public SecurityFilterChain filterChain(HttpSecurity http) throws Exception {
		http
			.oauth2Client(oauth2 -> oauth2
				.authorizationCodeGrant(codeGrant -> codeGrant
					.accessTokenResponseClient(this.accessTokenResponseClient())
					...
				)
			);
		return http.build();
	}
}
----

Kotlin::
+
[source,kotlin,role="secondary"]
----
@Configuration
@EnableWebSecurity
class OAuth2ClientSecurityConfig {

    @Bean
    open fun filterChain(http: HttpSecurity): SecurityFilterChain {
        http {
            oauth2Client {
                authorizationCodeGrant {
                    accessTokenResponseClient = accessTokenResponseClient()
                }
            }
        }
        return http.build()
    }
}
----

Xml::
+
[source,xml,role="secondary"]
----
<http>
	<oauth2-client>
		<authorization-code-grant access-token-response-client-ref="accessTokenResponseClient"/>
	</oauth2-client>
</http>
----
======


[[oauth2Client-refresh-token-grant]]
== Refresh Token

[NOTE]
====
See the OAuth 2.0 Authorization Framework for further details on the https://tools.ietf.org/html/rfc6749#section-1.5[Refresh Token].
====


=== Refreshing an Access Token

[NOTE]
====
See the https://tools.ietf.org/html/rfc6749#section-6[Access Token Request/Response] protocol flow for the Refresh Token grant.
====

The default implementation of `OAuth2AccessTokenResponseClient` for the Refresh Token grant is `DefaultRefreshTokenTokenResponseClient`, which uses a `RestOperations` when refreshing an access token at the Authorization Server’s Token Endpoint.

The `DefaultRefreshTokenTokenResponseClient` is flexible, as it lets you customize the pre-processing of the Token Request or post-handling of the Token Response.


=== Customizing the Access Token Request

If you need to customize the pre-processing of the Token Request, you can provide `DefaultRefreshTokenTokenResponseClient.setRequestEntityConverter()` with a custom `Converter<OAuth2RefreshTokenGrantRequest, RequestEntity<?>>`.
The default implementation (`OAuth2RefreshTokenGrantRequestEntityConverter`) builds a `RequestEntity` representation of a standard https://tools.ietf.org/html/rfc6749#section-6[OAuth 2.0 Access Token Request].
However, providing a custom `Converter` would let you extend the standard Token Request and add custom parameter(s).

To customize only the parameters of the request, you can provide `OAuth2RefreshTokenGrantRequestEntityConverter.setParametersConverter()` with a custom `Converter<OAuth2RefreshTokenGrantRequest, MultiValueMap<String, String>>` to completely override the parameters sent with the request. This is often simpler than constructing a `RequestEntity` directly.

[TIP]
====
If you prefer to only add additional parameters, you can provide `OAuth2RefreshTokenGrantRequestEntityConverter.addParametersConverter()` with a custom `Converter<OAuth2RefreshTokenGrantRequest, MultiValueMap<String, String>>` which constructs an aggregate `Converter`.
====

[IMPORTANT]
====
The custom `Converter` must return a valid `RequestEntity` representation of an OAuth 2.0 Access Token Request that is understood by the intended OAuth 2.0 Provider.
====


=== Customizing the Access Token Response

On the other end, if you need to customize the post-handling of the Token Response, you need to provide `DefaultRefreshTokenTokenResponseClient.setRestOperations()` with a custom configured `RestOperations`.
The default `RestOperations` is configured as follows:

[tabs]
======
Java::
+
[source,java,role="primary"]
----
RestTemplate restTemplate = new RestTemplate(Arrays.asList(
		new FormHttpMessageConverter(),
		new OAuth2AccessTokenResponseHttpMessageConverter()));

restTemplate.setErrorHandler(new OAuth2ErrorResponseErrorHandler());
----

Kotlin::
+
[source,kotlin,role="secondary"]
----
val restTemplate = RestTemplate(listOf(
        FormHttpMessageConverter(),
        OAuth2AccessTokenResponseHttpMessageConverter()))

restTemplate.errorHandler = OAuth2ErrorResponseErrorHandler()
----
======

[TIP]
====
Spring MVC `FormHttpMessageConverter` is required, as it is used when sending the OAuth 2.0 Access Token Request.
====

`OAuth2AccessTokenResponseHttpMessageConverter` is a `HttpMessageConverter` for an OAuth 2.0 Access Token Response.
You can provide `OAuth2AccessTokenResponseHttpMessageConverter.setAccessTokenResponseConverter()` with a custom `Converter<Map<String, Object>, OAuth2AccessTokenResponse>` that is used for converting the OAuth 2.0 Access Token Response parameters to an `OAuth2AccessTokenResponse`.

`OAuth2ErrorResponseErrorHandler` is a `ResponseErrorHandler` that can handle an OAuth 2.0 Error, such as `400 Bad Request`.
It uses an `OAuth2ErrorHttpMessageConverter` for converting the OAuth 2.0 Error parameters to an `OAuth2Error`.

Whether you customize `DefaultRefreshTokenTokenResponseClient` or provide your own implementation of `OAuth2AccessTokenResponseClient`, you need to configure it as follows:

[tabs]
======
Java::
+
[source,java,role="primary"]
----
// Customize
OAuth2AccessTokenResponseClient<OAuth2RefreshTokenGrantRequest> refreshTokenTokenResponseClient = ...

OAuth2AuthorizedClientProvider authorizedClientProvider =
		OAuth2AuthorizedClientProviderBuilder.builder()
				.authorizationCode()
				.refreshToken(configurer -> configurer.accessTokenResponseClient(refreshTokenTokenResponseClient))
				.build();

...

authorizedClientManager.setAuthorizedClientProvider(authorizedClientProvider);
----

Kotlin::
+
[source,kotlin,role="secondary"]
----
// Customize
val refreshTokenTokenResponseClient: OAuth2AccessTokenResponseClient<OAuth2RefreshTokenGrantRequest> = ...

val authorizedClientProvider = OAuth2AuthorizedClientProviderBuilder.builder()
        .authorizationCode()
        .refreshToken { it.accessTokenResponseClient(refreshTokenTokenResponseClient) }
        .build()

...

authorizedClientManager.setAuthorizedClientProvider(authorizedClientProvider)
----
======

[NOTE]
====
`OAuth2AuthorizedClientProviderBuilder.builder().refreshToken()` configures a `RefreshTokenOAuth2AuthorizedClientProvider`,
which is an implementation of an `OAuth2AuthorizedClientProvider` for the Refresh Token grant.
====

The `OAuth2RefreshToken` can optionally be returned in the Access Token Response for the `authorization_code` and `password` grant types.
If the `OAuth2AuthorizedClient.getRefreshToken()` is available and the `OAuth2AuthorizedClient.getAccessToken()` is expired, it is automatically refreshed by the `RefreshTokenOAuth2AuthorizedClientProvider`.


[[oauth2Client-client-creds-grant]]
== Client Credentials

[NOTE]
Please refer to the OAuth 2.0 Authorization Framework for further details on the https://tools.ietf.org/html/rfc6749#section-1.3.4[Client Credentials] grant.


=== Requesting an Access Token

[NOTE]
====
See the OAuth 2.0 Authorization Framework for further details on the https://tools.ietf.org/html/rfc6749#section-1.3.4[Client Credentials] grant.
====

The default implementation of `OAuth2AccessTokenResponseClient` for the Client Credentials grant is `DefaultClientCredentialsTokenResponseClient`, which uses a `RestOperations` when requesting an access token at the Authorization Server’s Token Endpoint.

The `DefaultClientCredentialsTokenResponseClient` is flexible, as it lets you customize the pre-processing of the Token Request or post-handling of the Token Response.


=== Customizing the Access Token Request

If you need to customize the pre-processing of the Token Request, you can provide `DefaultClientCredentialsTokenResponseClient.setRequestEntityConverter()` with a custom `Converter<OAuth2ClientCredentialsGrantRequest, RequestEntity<?>>`.
The default implementation (`OAuth2ClientCredentialsGrantRequestEntityConverter`) builds a `RequestEntity` representation of a standard https://tools.ietf.org/html/rfc6749#section-4.4.2[OAuth 2.0 Access Token Request].
However, providing a custom `Converter` would let you extend the standard Token Request and add custom parameter(s).

To customize only the parameters of the request, you can provide `OAuth2ClientCredentialsGrantRequestEntityConverter.setParametersConverter()` with a custom `Converter<OAuth2ClientCredentialsGrantRequest, MultiValueMap<String, String>>` to completely override the parameters sent with the request. This is often simpler than constructing a `RequestEntity` directly.

[TIP]
====
If you prefer to only add additional parameters, you can provide `OAuth2ClientCredentialsGrantRequestEntityConverter.addParametersConverter()` with a custom `Converter<OAuth2ClientCredentialsGrantRequest, MultiValueMap<String, String>>` which constructs an aggregate `Converter`.
====

[IMPORTANT]
====
The custom `Converter` must return a valid `RequestEntity` representation of an OAuth 2.0 Access Token Request that is understood by the intended OAuth 2.0 Provider.
====


=== Customizing the Access Token Response

On the other end, if you need to customize the post-handling of the Token Response, you need to provide `DefaultClientCredentialsTokenResponseClient.setRestOperations()` with a custom configured `RestOperations`.
The default `RestOperations` is configured as follows:

[tabs]
======
Java::
+
[source,java,role="primary"]
----
RestTemplate restTemplate = new RestTemplate(Arrays.asList(
		new FormHttpMessageConverter(),
		new OAuth2AccessTokenResponseHttpMessageConverter()));

restTemplate.setErrorHandler(new OAuth2ErrorResponseErrorHandler());
----

Kotlin::
+
[source,kotlin,role="secondary"]
----
val restTemplate = RestTemplate(listOf(
        FormHttpMessageConverter(),
        OAuth2AccessTokenResponseHttpMessageConverter()))

restTemplate.errorHandler = OAuth2ErrorResponseErrorHandler()
----
======

[TIP]
====
Spring MVC `FormHttpMessageConverter` is required, as it is used when sending the OAuth 2.0 Access Token Request.
====

`OAuth2AccessTokenResponseHttpMessageConverter` is a `HttpMessageConverter` for an OAuth 2.0 Access Token Response.
You can provide `OAuth2AccessTokenResponseHttpMessageConverter.setAccessTokenResponseConverter()` with a custom `Converter<Map<String, Object>, OAuth2AccessTokenResponse>` that is used for converting the OAuth 2.0 Access Token Response parameters to an `OAuth2AccessTokenResponse`.

`OAuth2ErrorResponseErrorHandler` is a `ResponseErrorHandler` that can handle an OAuth 2.0 Error, such as `400 Bad Request`.
It uses an `OAuth2ErrorHttpMessageConverter` to convert the OAuth 2.0 Error parameters to an `OAuth2Error`.

Whether you customize `DefaultClientCredentialsTokenResponseClient` or provide your own implementation of `OAuth2AccessTokenResponseClient`, you need to configure it as follows:

[tabs]
======
Java::
+
[source,java,role="primary"]
----
// Customize
OAuth2AccessTokenResponseClient<OAuth2ClientCredentialsGrantRequest> clientCredentialsTokenResponseClient = ...

OAuth2AuthorizedClientProvider authorizedClientProvider =
		OAuth2AuthorizedClientProviderBuilder.builder()
				.clientCredentials(configurer -> configurer.accessTokenResponseClient(clientCredentialsTokenResponseClient))
				.build();

...

authorizedClientManager.setAuthorizedClientProvider(authorizedClientProvider);
----

Kotlin::
+
[source,kotlin,role="secondary"]
----
// Customize
val clientCredentialsTokenResponseClient: OAuth2AccessTokenResponseClient<OAuth2ClientCredentialsGrantRequest> = ...

val authorizedClientProvider = OAuth2AuthorizedClientProviderBuilder.builder()
        .clientCredentials { it.accessTokenResponseClient(clientCredentialsTokenResponseClient) }
        .build()

...

authorizedClientManager.setAuthorizedClientProvider(authorizedClientProvider)
----
======

[NOTE]
====
`OAuth2AuthorizedClientProviderBuilder.builder().clientCredentials()` configures a `ClientCredentialsOAuth2AuthorizedClientProvider`,
which is an implementation of an `OAuth2AuthorizedClientProvider` for the Client Credentials grant.
====

=== Using the Access Token

Consider the following Spring Boot 2.x properties for an OAuth 2.0 Client registration:

[source,yaml]
----
spring:
  security:
    oauth2:
      client:
        registration:
          okta:
            client-id: okta-client-id
            client-secret: okta-client-secret
            authorization-grant-type: client_credentials
            scope: read, write
        provider:
          okta:
            token-uri: https://dev-1234.oktapreview.com/oauth2/v1/token
----

Further consider the following `OAuth2AuthorizedClientManager` `@Bean`:

[tabs]
======
Java::
+
[source,java,role="primary"]
----
@Bean
public OAuth2AuthorizedClientManager authorizedClientManager(
		ClientRegistrationRepository clientRegistrationRepository,
		OAuth2AuthorizedClientRepository authorizedClientRepository) {

	OAuth2AuthorizedClientProvider authorizedClientProvider =
			OAuth2AuthorizedClientProviderBuilder.builder()
					.clientCredentials()
					.build();

	DefaultOAuth2AuthorizedClientManager authorizedClientManager =
			new DefaultOAuth2AuthorizedClientManager(
					clientRegistrationRepository, authorizedClientRepository);
	authorizedClientManager.setAuthorizedClientProvider(authorizedClientProvider);

	return authorizedClientManager;
}
----

Kotlin::
+
[source,kotlin,role="secondary"]
----
@Bean
fun authorizedClientManager(
        clientRegistrationRepository: ClientRegistrationRepository,
        authorizedClientRepository: OAuth2AuthorizedClientRepository): OAuth2AuthorizedClientManager {
    val authorizedClientProvider = OAuth2AuthorizedClientProviderBuilder.builder()
            .clientCredentials()
            .build()
    val authorizedClientManager = DefaultOAuth2AuthorizedClientManager(
            clientRegistrationRepository, authorizedClientRepository)
    authorizedClientManager.setAuthorizedClientProvider(authorizedClientProvider)
    return authorizedClientManager
}
----
======

Given the preceding properties and bean, you can obtain the `OAuth2AccessToken` as follows:

[tabs]
======
Java::
+
[source,java,role="primary"]
----
@Controller
public class OAuth2ClientController {

	@Autowired
	private OAuth2AuthorizedClientManager authorizedClientManager;

	@GetMapping("/")
	public String index(Authentication authentication,
						HttpServletRequest servletRequest,
						HttpServletResponse servletResponse) {

		OAuth2AuthorizeRequest authorizeRequest = OAuth2AuthorizeRequest.withClientRegistrationId("okta")
				.principal(authentication)
				.attributes(attrs -> {
					attrs.put(HttpServletRequest.class.getName(), servletRequest);
					attrs.put(HttpServletResponse.class.getName(), servletResponse);
				})
				.build();
		OAuth2AuthorizedClient authorizedClient = this.authorizedClientManager.authorize(authorizeRequest);

		OAuth2AccessToken accessToken = authorizedClient.getAccessToken();

		...

		return "index";
	}
}
----

Kotlin::
+
[source,kotlin,role="secondary"]
----
class OAuth2ClientController {

    @Autowired
    private lateinit var authorizedClientManager: OAuth2AuthorizedClientManager

    @GetMapping("/")
    fun index(authentication: Authentication?,
              servletRequest: HttpServletRequest,
              servletResponse: HttpServletResponse): String {
        val authorizeRequest: OAuth2AuthorizeRequest = OAuth2AuthorizeRequest.withClientRegistrationId("okta")
                .principal(authentication)
                .attributes(Consumer { attrs: MutableMap<String, Any> ->
                    attrs[HttpServletRequest::class.java.name] = servletRequest
                    attrs[HttpServletResponse::class.java.name] = servletResponse
                })
                .build()
        val authorizedClient = authorizedClientManager.authorize(authorizeRequest)
        val accessToken: OAuth2AccessToken = authorizedClient.accessToken

        ...

        return "index"
    }
}
----
======

[NOTE]
====
`HttpServletRequest` and `HttpServletResponse` are both OPTIONAL attributes.
If not provided, they default to `ServletRequestAttributes` by using `RequestContextHolder.getRequestAttributes()`.
====

[[oauth2Client-password-grant]]
== Resource Owner Password Credentials

[NOTE]
====
See the OAuth 2.0 Authorization Framework for further details on the https://tools.ietf.org/html/rfc6749#section-1.3.3[Resource Owner Password Credentials] grant.
====

=== Requesting an Access Token

[NOTE]
====
See the https://tools.ietf.org/html/rfc6749#section-4.3.2[Access Token Request/Response] protocol flow for the Resource Owner Password Credentials grant.
====

The default implementation of `OAuth2AccessTokenResponseClient` for the Resource Owner Password Credentials grant is `DefaultPasswordTokenResponseClient`, which uses a `RestOperations` when requesting an access token at the Authorization Server’s Token Endpoint.

The `DefaultPasswordTokenResponseClient` is flexible, as it lets you customize the pre-processing of the Token Request or post-handling of the Token Response.

=== Customizing the Access Token Request

If you need to customize the pre-processing of the Token Request, you can provide `DefaultPasswordTokenResponseClient.setRequestEntityConverter()` with a custom `Converter<OAuth2PasswordGrantRequest, RequestEntity<?>>`.
The default implementation (`OAuth2PasswordGrantRequestEntityConverter`) builds a `RequestEntity` representation of a standard https://tools.ietf.org/html/rfc6749#section-4.3.2[OAuth 2.0 Access Token Request].
However, providing a custom `Converter` would let you extend the standard Token Request and add custom parameter(s).

To customize only the parameters of the request, you can provide `OAuth2PasswordGrantRequestEntityConverter.setParametersConverter()` with a custom `Converter<OAuth2PasswordGrantRequest, MultiValueMap<String, String>>` to completely override the parameters sent with the request. This is often simpler than constructing a `RequestEntity` directly.

[TIP]
====
If you prefer to only add additional parameters, you can provide `OAuth2PasswordGrantRequestEntityConverter.addParametersConverter()` with a custom `Converter<OAuth2PasswordGrantRequest, MultiValueMap<String, String>>` which constructs an aggregate `Converter`.
====

[IMPORTANT]
====
The custom `Converter` must return a valid `RequestEntity` representation of an OAuth 2.0 Access Token Request that is understood by the intended OAuth 2.0 Provider.
====


=== Customizing the Access Token Response

On the other end, if you need to customize the post-handling of the Token Response, you need to provide `DefaultPasswordTokenResponseClient.setRestOperations()` with a custom configured `RestOperations`.
The default `RestOperations` is configured as follows:

[tabs]
======
Java::
+
[source,java,role="primary"]
----
RestTemplate restTemplate = new RestTemplate(Arrays.asList(
		new FormHttpMessageConverter(),
		new OAuth2AccessTokenResponseHttpMessageConverter()));

restTemplate.setErrorHandler(new OAuth2ErrorResponseErrorHandler());
----

Kotlin::
+
[source,kotlin,role="secondary"]
----
val restTemplate = RestTemplate(listOf(
        FormHttpMessageConverter(),
        OAuth2AccessTokenResponseHttpMessageConverter()))

restTemplate.errorHandler = OAuth2ErrorResponseErrorHandler()
----
======

[TIP]
====
Spring MVC `FormHttpMessageConverter` is required, as it is used when sending the OAuth 2.0 Access Token Request.
====

`OAuth2AccessTokenResponseHttpMessageConverter` is a `HttpMessageConverter` for an OAuth 2.0 Access Token Response.
You can provide `OAuth2AccessTokenResponseHttpMessageConverter.setTokenResponseConverter()` with a custom `Converter<Map<String, String>, OAuth2AccessTokenResponse>` that is used to convert the OAuth 2.0 Access Token Response parameters to an `OAuth2AccessTokenResponse`.

`OAuth2ErrorResponseErrorHandler` is a `ResponseErrorHandler` that can handle an OAuth 2.0 Error, such as `400 Bad Request`.
It uses an `OAuth2ErrorHttpMessageConverter` to convert the OAuth 2.0 Error parameters to an `OAuth2Error`.

Whether you customize `DefaultPasswordTokenResponseClient` or provide your own implementation of `OAuth2AccessTokenResponseClient`, you need to configure it as follows:

[tabs]
======
Java::
+
[source,java,role="primary"]
----
// Customize
OAuth2AccessTokenResponseClient<OAuth2PasswordGrantRequest> passwordTokenResponseClient = ...

OAuth2AuthorizedClientProvider authorizedClientProvider =
		OAuth2AuthorizedClientProviderBuilder.builder()
				.password(configurer -> configurer.accessTokenResponseClient(passwordTokenResponseClient))
				.refreshToken()
				.build();

...

authorizedClientManager.setAuthorizedClientProvider(authorizedClientProvider);
----

Kotlin::
+
[source,kotlin,role="secondary"]
----
val passwordTokenResponseClient: OAuth2AccessTokenResponseClient<OAuth2PasswordGrantRequest> = ...

val authorizedClientProvider = OAuth2AuthorizedClientProviderBuilder.builder()
        .password { it.accessTokenResponseClient(passwordTokenResponseClient) }
        .refreshToken()
        .build()

...

authorizedClientManager.setAuthorizedClientProvider(authorizedClientProvider)
----
======

[NOTE]
====
`OAuth2AuthorizedClientProviderBuilder.builder().password()` configures a `PasswordOAuth2AuthorizedClientProvider`,
which is an implementation of an `OAuth2AuthorizedClientProvider` for the Resource Owner Password Credentials grant.
====

=== Using the Access Token

Consider the following Spring Boot 2.x properties for an OAuth 2.0 Client registration:

[source,yaml]
----
spring:
  security:
    oauth2:
      client:
        registration:
          okta:
            client-id: okta-client-id
            client-secret: okta-client-secret
            authorization-grant-type: password
            scope: read, write
        provider:
          okta:
            token-uri: https://dev-1234.oktapreview.com/oauth2/v1/token
----

Further consider the `OAuth2AuthorizedClientManager` `@Bean`:

[tabs]
======
Java::
+
[source,java,role="primary"]
----
@Bean
public OAuth2AuthorizedClientManager authorizedClientManager(
		ClientRegistrationRepository clientRegistrationRepository,
		OAuth2AuthorizedClientRepository authorizedClientRepository) {

	OAuth2AuthorizedClientProvider authorizedClientProvider =
			OAuth2AuthorizedClientProviderBuilder.builder()
					.password()
					.refreshToken()
					.build();

	DefaultOAuth2AuthorizedClientManager authorizedClientManager =
			new DefaultOAuth2AuthorizedClientManager(
					clientRegistrationRepository, authorizedClientRepository);
	authorizedClientManager.setAuthorizedClientProvider(authorizedClientProvider);

	// Assuming the `username` and `password` are supplied as `HttpServletRequest` parameters,
	// map the `HttpServletRequest` parameters to `OAuth2AuthorizationContext.getAttributes()`
	authorizedClientManager.setContextAttributesMapper(contextAttributesMapper());

	return authorizedClientManager;
}

private Function<OAuth2AuthorizeRequest, Map<String, Object>> contextAttributesMapper() {
	return authorizeRequest -> {
		Map<String, Object> contextAttributes = Collections.emptyMap();
		HttpServletRequest servletRequest = authorizeRequest.getAttribute(HttpServletRequest.class.getName());
		String username = servletRequest.getParameter(OAuth2ParameterNames.USERNAME);
		String password = servletRequest.getParameter(OAuth2ParameterNames.PASSWORD);
		if (StringUtils.hasText(username) && StringUtils.hasText(password)) {
			contextAttributes = new HashMap<>();

			// `PasswordOAuth2AuthorizedClientProvider` requires both attributes
			contextAttributes.put(OAuth2AuthorizationContext.USERNAME_ATTRIBUTE_NAME, username);
			contextAttributes.put(OAuth2AuthorizationContext.PASSWORD_ATTRIBUTE_NAME, password);
		}
		return contextAttributes;
	};
}
----

Kotlin::
+
[source,kotlin,role="secondary"]
----
@Bean
fun authorizedClientManager(
        clientRegistrationRepository: ClientRegistrationRepository,
        authorizedClientRepository: OAuth2AuthorizedClientRepository): OAuth2AuthorizedClientManager {
    val authorizedClientProvider = OAuth2AuthorizedClientProviderBuilder.builder()
            .password()
            .refreshToken()
            .build()
    val authorizedClientManager = DefaultOAuth2AuthorizedClientManager(
            clientRegistrationRepository, authorizedClientRepository)
    authorizedClientManager.setAuthorizedClientProvider(authorizedClientProvider)

    // Assuming the `username` and `password` are supplied as `HttpServletRequest` parameters,
    // map the `HttpServletRequest` parameters to `OAuth2AuthorizationContext.getAttributes()`
    authorizedClientManager.setContextAttributesMapper(contextAttributesMapper())
    return authorizedClientManager
}

private fun contextAttributesMapper(): Function<OAuth2AuthorizeRequest, MutableMap<String, Any>> {
    return Function { authorizeRequest ->
        var contextAttributes: MutableMap<String, Any> = mutableMapOf()
        val servletRequest: HttpServletRequest = authorizeRequest.getAttribute(HttpServletRequest::class.java.name)
        val username = servletRequest.getParameter(OAuth2ParameterNames.USERNAME)
        val password = servletRequest.getParameter(OAuth2ParameterNames.PASSWORD)
        if (StringUtils.hasText(username) && StringUtils.hasText(password)) {
            contextAttributes = hashMapOf()

            // `PasswordOAuth2AuthorizedClientProvider` requires both attributes
            contextAttributes[OAuth2AuthorizationContext.USERNAME_ATTRIBUTE_NAME] = username
            contextAttributes[OAuth2AuthorizationContext.PASSWORD_ATTRIBUTE_NAME] = password
        }
        contextAttributes
    }
}
----
======

Given the preceding properties and bean, you can obtain the `OAuth2AccessToken` as follows:

[tabs]
======
Java::
+
[source,java,role="primary"]
----
@Controller
public class OAuth2ClientController {

	@Autowired
	private OAuth2AuthorizedClientManager authorizedClientManager;

	@GetMapping("/")
	public String index(Authentication authentication,
						HttpServletRequest servletRequest,
						HttpServletResponse servletResponse) {

		OAuth2AuthorizeRequest authorizeRequest = OAuth2AuthorizeRequest.withClientRegistrationId("okta")
				.principal(authentication)
				.attributes(attrs -> {
					attrs.put(HttpServletRequest.class.getName(), servletRequest);
					attrs.put(HttpServletResponse.class.getName(), servletResponse);
				})
				.build();
		OAuth2AuthorizedClient authorizedClient = this.authorizedClientManager.authorize(authorizeRequest);

		OAuth2AccessToken accessToken = authorizedClient.getAccessToken();

		...

		return "index";
	}
}
----

Kotlin::
+
[source,kotlin,role="secondary"]
----
@Controller
class OAuth2ClientController {
    @Autowired
    private lateinit var authorizedClientManager: OAuth2AuthorizedClientManager

    @GetMapping("/")
    fun index(authentication: Authentication?,
              servletRequest: HttpServletRequest,
              servletResponse: HttpServletResponse): String {
        val authorizeRequest: OAuth2AuthorizeRequest = OAuth2AuthorizeRequest.withClientRegistrationId("okta")
                .principal(authentication)
                .attributes(Consumer {
                    it[HttpServletRequest::class.java.name] = servletRequest
                    it[HttpServletResponse::class.java.name] = servletResponse
                })
                .build()
        val authorizedClient = authorizedClientManager.authorize(authorizeRequest)
        val accessToken: OAuth2AccessToken = authorizedClient.accessToken

        ...

        return "index"
    }
}
----
======

[NOTE]
====
`HttpServletRequest` and `HttpServletResponse` are both OPTIONAL attributes.
If not provided, they default to `ServletRequestAttributes` using `RequestContextHolder.getRequestAttributes()`.
====


[[oauth2Client-jwt-bearer-grant]]
== JWT Bearer

[NOTE]
====
Please refer to JSON Web Token (JWT) Profile for OAuth 2.0 Client Authentication and Authorization Grants for further details on the https://datatracker.ietf.org/doc/html/rfc7523[JWT Bearer] grant.
====


=== Requesting an Access Token

[NOTE]
====
Please refer to the https://datatracker.ietf.org/doc/html/rfc7523#section-2.1[Access Token Request/Response] protocol flow for the JWT Bearer grant.
====

The default implementation of `OAuth2AccessTokenResponseClient` for the JWT Bearer grant is `DefaultJwtBearerTokenResponseClient`, which uses a `RestOperations` when requesting an access token at the Authorization Server’s Token Endpoint.

The `DefaultJwtBearerTokenResponseClient` is quite flexible as it allows you to customize the pre-processing of the Token Request and/or post-handling of the Token Response.


=== Customizing the Access Token Request

If you need to customize the pre-processing of the Token Request, you can provide `DefaultJwtBearerTokenResponseClient.setRequestEntityConverter()` with a custom `Converter<JwtBearerGrantRequest, RequestEntity<?>>`.
The default implementation `JwtBearerGrantRequestEntityConverter` builds a `RequestEntity` representation of a https://datatracker.ietf.org/doc/html/rfc7523#section-2.1[OAuth 2.0 Access Token Request].
However, providing a custom `Converter`, would allow you to extend the Token Request and add custom parameter(s).

To customize only the parameters of the request, you can provide `JwtBearerGrantRequestEntityConverter.setParametersConverter()` with a custom `Converter<JwtBearerGrantRequest, MultiValueMap<String, String>>` to completely override the parameters sent with the request. This is often simpler than constructing a `RequestEntity` directly.

[TIP]
If you prefer to only add additional parameters, you can provide `JwtBearerGrantRequestEntityConverter.addParametersConverter()` with a custom `Converter<JwtBearerGrantRequest, MultiValueMap<String, String>>` which constructs an aggregate `Converter`.


=== Customizing the Access Token Response

On the other end, if you need to customize the post-handling of the Token Response, you will need to provide `DefaultJwtBearerTokenResponseClient.setRestOperations()` with a custom configured `RestOperations`.
The default `RestOperations` is configured as follows:

[tabs]
======
Java::
+
[source,java,role="primary"]
----
RestTemplate restTemplate = new RestTemplate(Arrays.asList(
		new FormHttpMessageConverter(),
		new OAuth2AccessTokenResponseHttpMessageConverter()));

restTemplate.setErrorHandler(new OAuth2ErrorResponseErrorHandler());
----

Kotlin::
+
[source,kotlin,role="secondary"]
----
val restTemplate = RestTemplate(listOf(
        FormHttpMessageConverter(),
        OAuth2AccessTokenResponseHttpMessageConverter()))

restTemplate.errorHandler = OAuth2ErrorResponseErrorHandler()
----
======

[TIP]
====
Spring MVC `FormHttpMessageConverter` is required as it's used when sending the OAuth 2.0 Access Token Request.
====

`OAuth2AccessTokenResponseHttpMessageConverter` is a `HttpMessageConverter` for an OAuth 2.0 Access Token Response.
You can provide `OAuth2AccessTokenResponseHttpMessageConverter.setAccessTokenResponseConverter()` with a custom `Converter<Map<String, Object>, OAuth2AccessTokenResponse>` that is used for converting the OAuth 2.0 Access Token Response parameters to an `OAuth2AccessTokenResponse`.

`OAuth2ErrorResponseErrorHandler` is a `ResponseErrorHandler` that can handle an OAuth 2.0 Error, eg. 400 Bad Request.
It uses an `OAuth2ErrorHttpMessageConverter` for converting the OAuth 2.0 Error parameters to an `OAuth2Error`.

Whether you customize `DefaultJwtBearerTokenResponseClient` or provide your own implementation of `OAuth2AccessTokenResponseClient`, you'll need to configure it as shown in the following example:

[tabs]
======
Java::
+
[source,java,role="primary"]
----
// Customize
OAuth2AccessTokenResponseClient<JwtBearerGrantRequest> jwtBearerTokenResponseClient = ...

JwtBearerOAuth2AuthorizedClientProvider jwtBearerAuthorizedClientProvider = new JwtBearerOAuth2AuthorizedClientProvider();
jwtBearerAuthorizedClientProvider.setAccessTokenResponseClient(jwtBearerTokenResponseClient);

OAuth2AuthorizedClientProvider authorizedClientProvider =
		OAuth2AuthorizedClientProviderBuilder.builder()
				.provider(jwtBearerAuthorizedClientProvider)
				.build();

...

authorizedClientManager.setAuthorizedClientProvider(authorizedClientProvider);
----

Kotlin::
+
[source,kotlin,role="secondary"]
----
// Customize
val jwtBearerTokenResponseClient: OAuth2AccessTokenResponseClient<JwtBearerGrantRequest> = ...

val jwtBearerAuthorizedClientProvider = JwtBearerOAuth2AuthorizedClientProvider()
jwtBearerAuthorizedClientProvider.setAccessTokenResponseClient(jwtBearerTokenResponseClient);

val authorizedClientProvider = OAuth2AuthorizedClientProviderBuilder.builder()
        .provider(jwtBearerAuthorizedClientProvider)
        .build()

...

authorizedClientManager.setAuthorizedClientProvider(authorizedClientProvider)
----
======

=== Using the Access Token

Given the following Spring Boot 2.x properties for an OAuth 2.0 Client registration:

[source,yaml]
----
spring:
  security:
    oauth2:
      client:
        registration:
          okta:
            client-id: okta-client-id
            client-secret: okta-client-secret
            authorization-grant-type: urn:ietf:params:oauth:grant-type:jwt-bearer
            scope: read
        provider:
          okta:
            token-uri: https://dev-1234.oktapreview.com/oauth2/v1/token
----

...and the `OAuth2AuthorizedClientManager` `@Bean`:

[tabs]
======
Java::
+
[source,java,role="primary"]
----
@Bean
public OAuth2AuthorizedClientManager authorizedClientManager(
		ClientRegistrationRepository clientRegistrationRepository,
		OAuth2AuthorizedClientRepository authorizedClientRepository) {

	JwtBearerOAuth2AuthorizedClientProvider jwtBearerAuthorizedClientProvider =
			new JwtBearerOAuth2AuthorizedClientProvider();

	OAuth2AuthorizedClientProvider authorizedClientProvider =
			OAuth2AuthorizedClientProviderBuilder.builder()
					.provider(jwtBearerAuthorizedClientProvider)
					.build();

	DefaultOAuth2AuthorizedClientManager authorizedClientManager =
			new DefaultOAuth2AuthorizedClientManager(
					clientRegistrationRepository, authorizedClientRepository);
	authorizedClientManager.setAuthorizedClientProvider(authorizedClientProvider);

	return authorizedClientManager;
}
----

Kotlin::
+
[source,kotlin,role="secondary"]
----
@Bean
fun authorizedClientManager(
        clientRegistrationRepository: ClientRegistrationRepository,
        authorizedClientRepository: OAuth2AuthorizedClientRepository): OAuth2AuthorizedClientManager {
    val jwtBearerAuthorizedClientProvider = JwtBearerOAuth2AuthorizedClientProvider()
    val authorizedClientProvider = OAuth2AuthorizedClientProviderBuilder.builder()
            .provider(jwtBearerAuthorizedClientProvider)
            .build()
    val authorizedClientManager = DefaultOAuth2AuthorizedClientManager(
            clientRegistrationRepository, authorizedClientRepository)
    authorizedClientManager.setAuthorizedClientProvider(authorizedClientProvider)
    return authorizedClientManager
}
----
======

You may obtain the `OAuth2AccessToken` as follows:

[tabs]
======
Java::
+
[source,java,role="primary"]
----
@RestController
public class OAuth2ResourceServerController {

	@Autowired
	private OAuth2AuthorizedClientManager authorizedClientManager;

	@GetMapping("/resource")
	public String resource(JwtAuthenticationToken jwtAuthentication) {
		OAuth2AuthorizeRequest authorizeRequest = OAuth2AuthorizeRequest.withClientRegistrationId("okta")
				.principal(jwtAuthentication)
				.build();
		OAuth2AuthorizedClient authorizedClient = this.authorizedClientManager.authorize(authorizeRequest);
		OAuth2AccessToken accessToken = authorizedClient.getAccessToken();

		...

	}
}
----

Kotlin::
+
[source,kotlin,role="secondary"]
----
class OAuth2ResourceServerController {

    @Autowired
    private lateinit var authorizedClientManager: OAuth2AuthorizedClientManager

    @GetMapping("/resource")
    fun resource(jwtAuthentication: JwtAuthenticationToken?): String {
        val authorizeRequest: OAuth2AuthorizeRequest = OAuth2AuthorizeRequest.withClientRegistrationId("okta")
                .principal(jwtAuthentication)
                .build()
        val authorizedClient = authorizedClientManager.authorize(authorizeRequest)
        val accessToken: OAuth2AccessToken = authorizedClient.accessToken

        ...

    }
}
----
======

[NOTE]
`JwtBearerOAuth2AuthorizedClientProvider` resolves the `Jwt` assertion via `OAuth2AuthorizationContext.getPrincipal().getPrincipal()` by default, hence the use of `JwtAuthenticationToken` in the preceding example.

[TIP]
If you need to resolve the `Jwt` assertion from a different source, you can provide `JwtBearerOAuth2AuthorizedClientProvider.setJwtAssertionResolver()` with a custom `Function<OAuth2AuthorizationContext, Jwt>`.

[[oauth2Client-token-exchange-grant]]
== Token Exchange

[NOTE]
====
Please refer to OAuth 2.0 Token Exchange for further details on the https://datatracker.ietf.org/doc/html/rfc8693[Token Exchange] grant.
====


=== Requesting an Access Token

[NOTE]
====
Please refer to the https://datatracker.ietf.org/doc/html/rfc8693#section-2[Token Exchange Request and Response] protocol flow for the Token Exchange grant.
====

The default implementation of `OAuth2AccessTokenResponseClient` for the Token Exchange grant is `DefaultTokenExchangeTokenResponseClient`, which uses a `RestOperations` when requesting an access token at the Authorization Server’s Token Endpoint.

The `DefaultTokenExchangeTokenResponseClient` is quite flexible as it allows you to customize the pre-processing of the Token Request and/or post-handling of the Token Response.


=== Customizing the Access Token Request

If you need to customize the pre-processing of the Token Request, you can provide `DefaultTokenExchangeTokenResponseClient.setRequestEntityConverter()` with a custom `Converter<TokenExchangeGrantRequest, RequestEntity<?>>`.
The default implementation `TokenExchangeGrantRequestEntityConverter` builds a `RequestEntity` representation of a https://datatracker.ietf.org/doc/html/rfc8693#section-2.1[OAuth 2.0 Access Token Request].
However, providing a custom `Converter`, would allow you to extend the Token Request and add custom parameter(s).

To customize only the parameters of the request, you can provide `TokenExchangeGrantRequestEntityConverter.setParametersConverter()` with a custom `Converter<TokenExchangeGrantRequest, MultiValueMap<String, String>>` to completely override the parameters sent with the request. This is often simpler than constructing a `RequestEntity` directly.

[TIP]
If you prefer to only add additional parameters, you can provide `TokenExchangeGrantRequestEntityConverter.addParametersConverter()` with a custom `Converter<TokenExchangeGrantRequest, MultiValueMap<String, String>>` which constructs an aggregate `Converter`.


=== Customizing the Access Token Response

On the other end, if you need to customize the post-handling of the Token Response, you will need to provide `DefaultTokenExchangeTokenResponseClient.setRestOperations()` with a custom configured `RestOperations`.
The default `RestOperations` is configured as follows:

[tabs]
======
Java::
+
[source,java,role="primary"]
----
RestTemplate restTemplate = new RestTemplate(Arrays.asList(
		new FormHttpMessageConverter(),
		new OAuth2AccessTokenResponseHttpMessageConverter()));

restTemplate.setErrorHandler(new OAuth2ErrorResponseErrorHandler());
----

Kotlin::
+
[source,kotlin,role="secondary"]
----
val restTemplate = RestTemplate(listOf(
        FormHttpMessageConverter(),
        OAuth2AccessTokenResponseHttpMessageConverter()))

restTemplate.errorHandler = OAuth2ErrorResponseErrorHandler()
----
======

[TIP]
====
Spring MVC `FormHttpMessageConverter` is required as it's used when sending the OAuth 2.0 Access Token Request.
====

`OAuth2AccessTokenResponseHttpMessageConverter` is a `HttpMessageConverter` for an OAuth 2.0 Access Token Response.
You can provide `OAuth2AccessTokenResponseHttpMessageConverter.setAccessTokenResponseConverter()` with a custom `Converter<Map<String, Object>, OAuth2AccessTokenResponse>` that is used for converting the OAuth 2.0 Access Token Response parameters to an `OAuth2AccessTokenResponse`.

`OAuth2ErrorResponseErrorHandler` is a `ResponseErrorHandler` that can handle an OAuth 2.0 Error, eg. 400 Bad Request.
It uses an `OAuth2ErrorHttpMessageConverter` for converting the OAuth 2.0 Error parameters to an `OAuth2Error`.

Whether you customize `DefaultTokenExchangeTokenResponseClient` or provide your own implementation of `OAuth2AccessTokenResponseClient`, you'll need to configure it as shown in the following example:

[tabs]
======
Java::
+
[source,java,role="primary"]
----
// Customize
OAuth2AccessTokenResponseClient<TokenExchangeGrantRequest> tokenExchangeTokenResponseClient = ...

TokenExchangeOAuth2AuthorizedClientProvider tokenExchangeAuthorizedClientProvider = new TokenExchangeOAuth2AuthorizedClientProvider();
tokenExchangeAuthorizedClientProvider.setAccessTokenResponseClient(tokenExchangeTokenResponseClient);

OAuth2AuthorizedClientProvider authorizedClientProvider =
		OAuth2AuthorizedClientProviderBuilder.builder()
				.provider(tokenExchangeAuthorizedClientProvider)
				.build();

...

authorizedClientManager.setAuthorizedClientProvider(authorizedClientProvider);
----

Kotlin::
+
[source,kotlin,role="secondary"]
----
// Customize
val tokenExchangeTokenResponseClient: OAuth2AccessTokenResponseClient<TokenExchangeGrantRequest> = ...

val tokenExchangeAuthorizedClientProvider = TokenExchangeOAuth2AuthorizedClientProvider()
tokenExchangeAuthorizedClientProvider.setAccessTokenResponseClient(tokenExchangeTokenResponseClient)

val authorizedClientProvider = OAuth2AuthorizedClientProviderBuilder.builder()
        .provider(tokenExchangeAuthorizedClientProvider)
        .build()

...

authorizedClientManager.setAuthorizedClientProvider(authorizedClientProvider)
----
======

=== Using the Access Token

Given the following Spring Boot properties for an OAuth 2.0 Client registration:

[source,yaml]
----
spring:
  security:
    oauth2:
      client:
        registration:
          okta:
            client-id: okta-client-id
            client-secret: okta-client-secret
            authorization-grant-type: urn:ietf:params:oauth:grant-type:token-exchange
            scope: read
        provider:
          okta:
            token-uri: https://dev-1234.oktapreview.com/oauth2/v1/token
----

...and the `OAuth2AuthorizedClientManager` `@Bean`:

[tabs]
======
Java::
+
[source,java,role="primary"]
----
@Bean
public OAuth2AuthorizedClientManager authorizedClientManager(
		ClientRegistrationRepository clientRegistrationRepository,
		OAuth2AuthorizedClientRepository authorizedClientRepository) {

	TokenExchangeOAuth2AuthorizedClientProvider tokenExchangeAuthorizedClientProvider =
			new TokenExchangeOAuth2AuthorizedClientProvider();

	OAuth2AuthorizedClientProvider authorizedClientProvider =
			OAuth2AuthorizedClientProviderBuilder.builder()
					.provider(tokenExchangeAuthorizedClientProvider)
					.build();

	DefaultOAuth2AuthorizedClientManager authorizedClientManager =
			new DefaultOAuth2AuthorizedClientManager(
					clientRegistrationRepository, authorizedClientRepository);
	authorizedClientManager.setAuthorizedClientProvider(authorizedClientProvider);

	return authorizedClientManager;
}
----

Kotlin::
+
[source,kotlin,role="secondary"]
----
@Bean
fun authorizedClientManager(
        clientRegistrationRepository: ClientRegistrationRepository,
        authorizedClientRepository: OAuth2AuthorizedClientRepository): OAuth2AuthorizedClientManager {
    val tokenExchangeAuthorizedClientProvider = TokenExchangeOAuth2AuthorizedClientProvider()
    val authorizedClientProvider = OAuth2AuthorizedClientProviderBuilder.builder()
            .provider(tokenExchangeAuthorizedClientProvider)
            .build()
    val authorizedClientManager = DefaultOAuth2AuthorizedClientManager(
            clientRegistrationRepository, authorizedClientRepository)
    authorizedClientManager.setAuthorizedClientProvider(authorizedClientProvider)
    return authorizedClientManager
}
----
======

You may obtain the `OAuth2AccessToken` as follows:

[tabs]
======
Java::
+
[source,java,role="primary"]
----
@RestController
public class OAuth2ResourceServerController {

	@Autowired
	private OAuth2AuthorizedClientManager authorizedClientManager;

	@GetMapping("/resource")
	public String resource(JwtAuthenticationToken jwtAuthentication) {
		OAuth2AuthorizeRequest authorizeRequest = OAuth2AuthorizeRequest.withClientRegistrationId("okta")
				.principal(jwtAuthentication)
				.build();
		OAuth2AuthorizedClient authorizedClient = this.authorizedClientManager.authorize(authorizeRequest);
		OAuth2AccessToken accessToken = authorizedClient.getAccessToken();

		...

	}
}
----

Kotlin::
+
[source,kotlin,role="secondary"]
----
class OAuth2ResourceServerController {

    @Autowired
    private lateinit var authorizedClientManager: OAuth2AuthorizedClientManager

    @GetMapping("/resource")
    fun resource(jwtAuthentication: JwtAuthenticationToken?): String {
        val authorizeRequest: OAuth2AuthorizeRequest = OAuth2AuthorizeRequest.withClientRegistrationId("okta")
                .principal(jwtAuthentication)
                .build()
        val authorizedClient = authorizedClientManager.authorize(authorizeRequest)
        val accessToken: OAuth2AccessToken = authorizedClient.accessToken

        ...

    }
}
----
======

[NOTE]
`TokenExchangeOAuth2AuthorizedClientProvider` resolves the subject token (as an `OAuth2Token`) via `OAuth2AuthorizationContext.getPrincipal().getPrincipal()` by default, hence the use of `JwtAuthenticationToken` in the preceding example.
An actor token is not resolved by default.

[TIP]
If you need to resolve the subject token from a different source, you can provide `TokenExchangeOAuth2AuthorizedClientProvider.setSubjectTokenResolver()` with a custom `Function<OAuth2AuthorizationContext, OAuth2Token>`.

[TIP]
If you need to resolve an actor token, you can provide `TokenExchangeOAuth2AuthorizedClientProvider.setActorTokenResolver()` with a custom `Function<OAuth2AuthorizationContext, OAuth2Token>`.