操作方法：实现扩展授权授权类型

import java.util.HashMap;
import java.util.Map;

import jakarta.servlet.http.HttpServletRequest;

import org.springframework.lang.Nullable;
import org.springframework.security.core.Authentication;
import org.springframework.security.core.context.SecurityContextHolder;
import org.springframework.security.oauth2.core.OAuth2AuthenticationException;
import org.springframework.security.oauth2.core.OAuth2ErrorCodes;
import org.springframework.security.oauth2.core.endpoint.OAuth2ParameterNames;
import org.springframework.security.web.authentication.AuthenticationConverter;
import org.springframework.util.LinkedMultiValueMap;
import org.springframework.util.MultiValueMap;
import org.springframework.util.StringUtils;

public class CustomCodeGrantAuthenticationConverter implements AuthenticationConverter {

	@Nullable
	@Override
	public Authentication convert(HttpServletRequest request) {
		// grant_type (REQUIRED)
		String grantType = request.getParameter(OAuth2ParameterNames.GRANT_TYPE);
		if (!"urn:ietf:params:oauth:grant-type:custom_code".equals(grantType)) { (1)
			return null;
		}

		Authentication clientPrincipal = SecurityContextHolder.getContext().getAuthentication();

		MultiValueMap<String, String> parameters = getParameters(request);

		// code (REQUIRED)
		String code = parameters.getFirst(OAuth2ParameterNames.CODE); (2)
		if (!StringUtils.hasText(code) ||
				parameters.get(OAuth2ParameterNames.CODE).size() != 1) {
			throw new OAuth2AuthenticationException(OAuth2ErrorCodes.INVALID_REQUEST);
		}

		Map<String, Object> additionalParameters = new HashMap<>();
		parameters.forEach((key, value) -> {
			if (!key.equals(OAuth2ParameterNames.GRANT_TYPE) &&
					!key.equals(OAuth2ParameterNames.CLIENT_ID) &&
					!key.equals(OAuth2ParameterNames.CODE)) {
				additionalParameters.put(key, value.get(0));
			}
		});

		return new CustomCodeGrantAuthenticationToken(code, clientPrincipal, additionalParameters); (3)
	}

	private static MultiValueMap<String, String> getParameters(HttpServletRequest request) {
		Map<String, String[]> parameterMap = request.getParameterMap();
		MultiValueMap<String, String> parameters = new LinkedMultiValueMap<>(parameterMap.size());
		parameterMap.forEach((key, values) -> {
			if (values.length > 0) {
				for (String value : values) {
					parameters.add(key, value);
				}
			}
		});
		return parameters;
	}

}

import org.springframework.security.authentication.AuthenticationProvider;
import org.springframework.security.core.Authentication;
import org.springframework.security.core.AuthenticationException;
import org.springframework.security.oauth2.core.ClaimAccessor;
import org.springframework.security.oauth2.core.OAuth2AccessToken;
import org.springframework.security.oauth2.core.OAuth2AuthenticationException;
import org.springframework.security.oauth2.core.OAuth2Error;
import org.springframework.security.oauth2.core.OAuth2ErrorCodes;
import org.springframework.security.oauth2.core.OAuth2Token;
import org.springframework.security.oauth2.server.authorization.OAuth2Authorization;
import org.springframework.security.oauth2.server.authorization.OAuth2AuthorizationService;
import org.springframework.security.oauth2.server.authorization.OAuth2TokenType;
import org.springframework.security.oauth2.server.authorization.authentication.OAuth2AccessTokenAuthenticationToken;
import org.springframework.security.oauth2.server.authorization.authentication.OAuth2ClientAuthenticationToken;
import org.springframework.security.oauth2.server.authorization.client.RegisteredClient;
import org.springframework.security.oauth2.server.authorization.context.AuthorizationServerContextHolder;
import org.springframework.security.oauth2.server.authorization.token.DefaultOAuth2TokenContext;
import org.springframework.security.oauth2.server.authorization.token.OAuth2TokenContext;
import org.springframework.security.oauth2.server.authorization.token.OAuth2TokenGenerator;
import org.springframework.util.Assert;

public class CustomCodeGrantAuthenticationProvider implements AuthenticationProvider {
	private final OAuth2AuthorizationService authorizationService;
	private final OAuth2TokenGenerator<? extends OAuth2Token> tokenGenerator;

	public CustomCodeGrantAuthenticationProvider(OAuth2AuthorizationService authorizationService,
			OAuth2TokenGenerator<? extends OAuth2Token> tokenGenerator) {
		Assert.notNull(authorizationService, "authorizationService cannot be null");
		Assert.notNull(tokenGenerator, "tokenGenerator cannot be null");
		this.authorizationService = authorizationService;
		this.tokenGenerator = tokenGenerator;
	}

	@Override
	public Authentication authenticate(Authentication authentication) throws AuthenticationException {
		CustomCodeGrantAuthenticationToken customCodeGrantAuthentication =
				(CustomCodeGrantAuthenticationToken) authentication;

		// Ensure the client is authenticated
		OAuth2ClientAuthenticationToken clientPrincipal =
				getAuthenticatedClientElseThrowInvalidClient(customCodeGrantAuthentication);
		RegisteredClient registeredClient = clientPrincipal.getRegisteredClient();

		// Ensure the client is configured to use this authorization grant type
		if (!registeredClient.getAuthorizationGrantTypes().contains(customCodeGrantAuthentication.getGrantType())) {
			throw new OAuth2AuthenticationException(OAuth2ErrorCodes.UNAUTHORIZED_CLIENT);
		}

		// TODO Validate the code parameter

		// Generate the access token
		OAuth2TokenContext tokenContext = DefaultOAuth2TokenContext.builder()
				.registeredClient(registeredClient)
				.principal(clientPrincipal)
				.authorizationServerContext(AuthorizationServerContextHolder.getContext())
				.tokenType(OAuth2TokenType.ACCESS_TOKEN)
				.authorizationGrantType(customCodeGrantAuthentication.getGrantType())
				.authorizationGrant(customCodeGrantAuthentication)
				.build();

		OAuth2Token generatedAccessToken = this.tokenGenerator.generate(tokenContext);
		if (generatedAccessToken == null) {
			OAuth2Error error = new OAuth2Error(OAuth2ErrorCodes.SERVER_ERROR,
					"The token generator failed to generate the access token.", null);
			throw new OAuth2AuthenticationException(error);
		}
		OAuth2AccessToken accessToken = new OAuth2AccessToken(OAuth2AccessToken.TokenType.BEARER,
				generatedAccessToken.getTokenValue(), generatedAccessToken.getIssuedAt(),
				generatedAccessToken.getExpiresAt(), null);

		// Initialize the OAuth2Authorization
		OAuth2Authorization.Builder authorizationBuilder = OAuth2Authorization.withRegisteredClient(registeredClient)
				.principalName(clientPrincipal.getName())
				.authorizationGrantType(customCodeGrantAuthentication.getGrantType());
		if (generatedAccessToken instanceof ClaimAccessor) {
			authorizationBuilder.token(accessToken, (metadata) ->
				metadata.put(
					OAuth2Authorization.Token.CLAIMS_METADATA_NAME,
					((ClaimAccessor) generatedAccessToken).getClaims())
			);
		} else {
			authorizationBuilder.accessToken(accessToken);
		}
		OAuth2Authorization authorization = authorizationBuilder.build();

		// Save the OAuth2Authorization
		this.authorizationService.save(authorization);

		return new OAuth2AccessTokenAuthenticationToken(registeredClient, clientPrincipal, accessToken);
	}

	@Override
	public boolean supports(Class<?> authentication) {
		return CustomCodeGrantAuthenticationToken.class.isAssignableFrom(authentication);
	}

	private static OAuth2ClientAuthenticationToken getAuthenticatedClientElseThrowInvalidClient(Authentication authentication) {
		OAuth2ClientAuthenticationToken clientPrincipal = null;
		if (OAuth2ClientAuthenticationToken.class.isAssignableFrom(authentication.getPrincipal().getClass())) {
			clientPrincipal = (OAuth2ClientAuthenticationToken) authentication.getPrincipal();
		}
		if (clientPrincipal != null && clientPrincipal.isAuthenticated()) {
			return clientPrincipal;
		}
		throw new OAuth2AuthenticationException(OAuth2ErrorCodes.INVALID_CLIENT);
	}

}

import java.util.UUID;

import com.nimbusds.jose.jwk.source.JWKSource;
import com.nimbusds.jose.proc.SecurityContext;

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.security.config.annotation.web.builders.HttpSecurity;
import org.springframework.security.config.annotation.web.configuration.EnableWebSecurity;
import org.springframework.security.oauth2.core.AuthorizationGrantType;
import org.springframework.security.oauth2.core.ClientAuthenticationMethod;
import org.springframework.security.oauth2.jwt.NimbusJwtEncoder;
import org.springframework.security.oauth2.server.authorization.InMemoryOAuth2AuthorizationService;
import org.springframework.security.oauth2.server.authorization.OAuth2AuthorizationService;
import org.springframework.security.oauth2.server.authorization.client.InMemoryRegisteredClientRepository;
import org.springframework.security.oauth2.server.authorization.client.RegisteredClient;
import org.springframework.security.oauth2.server.authorization.client.RegisteredClientRepository;
import org.springframework.security.oauth2.server.authorization.config.annotation.web.configurers.OAuth2AuthorizationServerConfigurer;
import org.springframework.security.oauth2.server.authorization.token.DelegatingOAuth2TokenGenerator;
import org.springframework.security.oauth2.server.authorization.token.JwtGenerator;
import org.springframework.security.oauth2.server.authorization.token.OAuth2AccessTokenGenerator;
import org.springframework.security.oauth2.server.authorization.token.OAuth2RefreshTokenGenerator;
import org.springframework.security.oauth2.server.authorization.token.OAuth2TokenGenerator;
import org.springframework.security.web.SecurityFilterChain;

@Configuration
@EnableWebSecurity
public class SecurityConfig {

	@Bean
	SecurityFilterChain authorizationServerSecurityFilterChain(
			HttpSecurity http,
			OAuth2AuthorizationService authorizationService,
			OAuth2TokenGenerator<?> tokenGenerator) throws Exception {

		OAuth2AuthorizationServerConfigurer authorizationServerConfigurer =
				OAuth2AuthorizationServerConfigurer.authorizationServer();

		http
			.securityMatcher(authorizationServerConfigurer.getEndpointsMatcher())
			.with(authorizationServerConfigurer, (authorizationServer) ->
				authorizationServer
					.tokenEndpoint(tokenEndpoint ->
						tokenEndpoint
							.accessTokenRequestConverter(	(1)
								new CustomCodeGrantAuthenticationConverter())
							.authenticationProvider(	(2)
								new CustomCodeGrantAuthenticationProvider(
									authorizationService, tokenGenerator)))
			)
			.authorizeHttpRequests(authorize ->
				authorize
					.anyRequest().authenticated()
			);

		return http.build();
	}

	@Bean
	RegisteredClientRepository registeredClientRepository() {
		RegisteredClient messagingClient = RegisteredClient.withId(UUID.randomUUID().toString())
				.clientId("messaging-client")
				.clientSecret("{noop}secret")
				.clientAuthenticationMethod(ClientAuthenticationMethod.CLIENT_SECRET_BASIC)
				.authorizationGrantType(new AuthorizationGrantType("urn:ietf:params:oauth:grant-type:custom_code"))
				.scope("message.read")
				.scope("message.write")
				.build();

		return new InMemoryRegisteredClientRepository(messagingClient);
	}

	@Bean
	OAuth2AuthorizationService authorizationService() {
		return new InMemoryOAuth2AuthorizationService();
	}

	@Bean
	OAuth2TokenGenerator<?> tokenGenerator(JWKSource<SecurityContext> jwkSource) {
		JwtGenerator jwtGenerator = new JwtGenerator(new NimbusJwtEncoder(jwkSource));
		OAuth2AccessTokenGenerator accessTokenGenerator = new OAuth2AccessTokenGenerator();
		OAuth2RefreshTokenGenerator refreshTokenGenerator = new OAuth2RefreshTokenGenerator();
		return new DelegatingOAuth2TokenGenerator(
				jwtGenerator, accessTokenGenerator, refreshTokenGenerator);
	}

}

POST /oauth2/token HTTP/1.1
Authorization: Basic bWVzc2FnaW5nLWNsaWVudDpzZWNyZXQ=
Content-Type: application/x-www-form-urlencoded

grant_type=urn:ietf:params:oauth:grant-type:custom_code&code=7QR49T1W3