Polish spring-security-oauth2-jose main code

Manually polish `spring-security-oauth-jose` following the
formatting and checkstyle fixes.

Issue gh-8945

oauth2/oauth2-jose/src/main/java/org/springframework/security/oauth2/jose/jws/MacAlgorithm.java

@@ -55,6 +55,15 @@ public enum MacAlgorithm implements JwsAlgorithm {
 		this.name = name;
 	}
 
+	/**
+	 * Returns the algorithm name.
+	 * @return the algorithm name
+	 */
+	@Override
+	public String getName() {
+		return this.name;
+	}
+
 	/**
 	 * Attempt to resolve the provided algorithm name to a {@code MacAlgorithm}.
 	 * @param name the algorithm name
@@ -69,13 +78,4 @@ public enum MacAlgorithm implements JwsAlgorithm {
 		return null;
 	}
 
-	/**
-	 * Returns the algorithm name.
-	 * @return the algorithm name
-	 */
-	@Override
-	public String getName() {
-		return this.name;
-	}
-
 }

oauth2/oauth2-jose/src/main/java/org/springframework/security/oauth2/jose/jws/SignatureAlgorithm.java

@@ -85,6 +85,15 @@ public enum SignatureAlgorithm implements JwsAlgorithm {
 		this.name = name;
 	}
 
+	/**
+	 * Returns the algorithm name.
+	 * @return the algorithm name
+	 */
+	@Override
+	public String getName() {
+		return this.name;
+	}
+
 	/**
 	 * Attempt to resolve the provided algorithm name to a {@code SignatureAlgorithm}.
 	 * @param name the algorithm name
@@ -99,13 +108,4 @@ public enum SignatureAlgorithm implements JwsAlgorithm {
 		return null;
 	}
 
-	/**
-	 * Returns the algorithm name.
-	 * @return the algorithm name
-	 */
-	@Override
-	public String getName() {
-		return this.name;
-	}
-
 }

oauth2/oauth2-jose/src/main/java/org/springframework/security/oauth2/jwt/JwtClaimValidator.java

@@ -58,9 +58,6 @@ public final class JwtClaimValidator<T> implements OAuth2TokenValidator<Jwt> {
 				"https://tools.ietf.org/html/rfc6750#section-3.1");
 	}
 
-	/**
-	 * {@inheritDoc}
-	 */
 	@Override
 	public OAuth2TokenValidatorResult validate(Jwt token) {
 		Assert.notNull(token, "token cannot be null");
@@ -68,10 +65,8 @@ public final class JwtClaimValidator<T> implements OAuth2TokenValidator<Jwt> {
 		if (this.test.test(claimValue)) {
 			return OAuth2TokenValidatorResult.success();
 		}
-		else {
 		this.logger.debug(this.error.getDescription());
 		return OAuth2TokenValidatorResult.failure(this.error);
 	}
-	}
 
 }

oauth2/oauth2-jose/src/main/java/org/springframework/security/oauth2/jwt/JwtDecoderProviderConfigurationUtils.java

@@ -23,6 +23,7 @@ import java.util.Map;
 import org.springframework.core.ParameterizedTypeReference;
 import org.springframework.http.RequestEntity;
 import org.springframework.http.ResponseEntity;
+import org.springframework.util.Assert;
 import org.springframework.web.client.HttpClientErrorException;
 import org.springframework.web.client.RestTemplate;
 import org.springframework.web.util.UriComponentsBuilder;
@@ -46,7 +47,7 @@ final class JwtDecoderProviderConfigurationUtils {
 
 	private static final RestTemplate rest = new RestTemplate();
 
-	private static final ParameterizedTypeReference<Map<String, Object>> typeReference = new ParameterizedTypeReference<Map<String, Object>>() {
+	private static final ParameterizedTypeReference<Map<String, Object>> STRING_OBJECT_MAP = new ParameterizedTypeReference<Map<String, Object>>() {
 	};
 
 	private JwtDecoderProviderConfigurationUtils() {
@@ -62,14 +63,16 @@ final class JwtDecoderProviderConfigurationUtils {
 	}
 
 	static void validateIssuer(Map<String, Object> configuration, String issuer) {
-		String metadataIssuer = "(unavailable)";
+		String metadataIssuer = getMetadataIssuer(configuration);
-		if (configuration.containsKey("issuer")) {
+		Assert.state(issuer.equals(metadataIssuer), () -> "The Issuer \"" + metadataIssuer
-			metadataIssuer = configuration.get("issuer").toString();
-		}
-		if (!issuer.equals(metadataIssuer)) {
-			throw new IllegalStateException("The Issuer \"" + metadataIssuer
 				+ "\" provided in the configuration did not " + "match the requested issuer \"" + issuer + "\"");
 	}
+
+	private static String getMetadataIssuer(Map<String, Object> configuration) {
+		if (configuration.containsKey("issuer")) {
+			return configuration.get("issuer").toString();
+		}
+		return "(unavailable)";
 	}
 
 	private static Map<String, Object> getConfiguration(String issuer, URI... uris) {
@@ -77,13 +80,9 @@ final class JwtDecoderProviderConfigurationUtils {
 		for (URI uri : uris) {
 			try {
 				RequestEntity<Void> request = RequestEntity.get(uri).build();
-				ResponseEntity<Map<String, Object>> response = rest.exchange(request, typeReference);
+				ResponseEntity<Map<String, Object>> response = rest.exchange(request, STRING_OBJECT_MAP);
 				Map<String, Object> configuration = response.getBody();
-
+				Assert.isTrue(configuration.get("jwks_uri") != null, "The public JWK set URI must not be null");
-				if (configuration.get("jwks_uri") == null) {
-					throw new IllegalArgumentException("The public JWK set URI must not be null");
-				}
-
 				return configuration;
 			}
 			catch (IllegalArgumentException ex) {

oauth2/oauth2-jose/src/main/java/org/springframework/security/oauth2/jwt/JwtDecoders.java

@@ -34,6 +34,9 @@ import org.springframework.util.Assert;
  */
 public final class JwtDecoders {
 
+	private JwtDecoders() {
+	}
+
 	/**
 	 * Creates a {@link JwtDecoder} using the provided <a href=
 	 * "https://openid.net/specs/openid-connect-core-1_0.html#IssuerIdentifier">Issuer</a>
@@ -105,11 +108,7 @@ public final class JwtDecoders {
 		OAuth2TokenValidator<Jwt> jwtValidator = JwtValidators.createDefaultWithIssuer(issuer);
 		NimbusJwtDecoder jwtDecoder = NimbusJwtDecoder.withJwkSetUri(configuration.get("jwks_uri").toString()).build();
 		jwtDecoder.setJwtValidator(jwtValidator);
-
 		return jwtDecoder;
 	}
 
-	private JwtDecoders() {
-	}
-
 }

oauth2/oauth2-jose/src/main/java/org/springframework/security/oauth2/jwt/JwtIssuerValidator.java

@@ -39,9 +39,6 @@ public final class JwtIssuerValidator implements OAuth2TokenValidator<Jwt> {
 		this.validator = new JwtClaimValidator(JwtClaimNames.ISS, issuer::equals);
 	}
 
-	/**
-	 * {@inheritDoc}
-	 */
 	@Override
 	public OAuth2TokenValidatorResult validate(Jwt token) {
 		Assert.notNull(token, "token cannot be null");

oauth2/oauth2-jose/src/main/java/org/springframework/security/oauth2/jwt/JwtTimestampValidator.java

@@ -68,31 +68,23 @@ public final class JwtTimestampValidator implements OAuth2TokenValidator<Jwt> {
 		this.clockSkew = clockSkew;
 	}
 
-	/**
-	 * {@inheritDoc}
-	 */
 	@Override
 	public OAuth2TokenValidatorResult validate(Jwt jwt) {
 		Assert.notNull(jwt, "jwt cannot be null");
-
 		Instant expiry = jwt.getExpiresAt();
-
 		if (expiry != null) {
 			if (Instant.now(this.clock).minus(this.clockSkew).isAfter(expiry)) {
 				OAuth2Error oAuth2Error = createOAuth2Error(String.format("Jwt expired at %s", jwt.getExpiresAt()));
 				return OAuth2TokenValidatorResult.failure(oAuth2Error);
 			}
 		}
-
 		Instant notBefore = jwt.getNotBefore();
-
 		if (notBefore != null) {
 			if (Instant.now(this.clock).plus(this.clockSkew).isBefore(notBefore)) {
 				OAuth2Error oAuth2Error = createOAuth2Error(String.format("Jwt used before %s", jwt.getNotBefore()));
 				return OAuth2TokenValidatorResult.failure(oAuth2Error);
 			}
 		}
-
 		return OAuth2TokenValidatorResult.success();
 	}
 
@@ -103,8 +95,7 @@ public final class JwtTimestampValidator implements OAuth2TokenValidator<Jwt> {
 	}
 
 	/**
-	 * ' Use this {@link Clock} with {@link Instant#now()} for assessing timestamp
+	 * Use this {@link Clock} with {@link Instant#now()} for assessing timestamp validity
-	 * validity
 	 * @param clock
 	 */
 	public void setClock(Clock clock) {

oauth2/oauth2-jose/src/main/java/org/springframework/security/oauth2/jwt/JwtValidationException.java

@@ -54,7 +54,6 @@ public class JwtValidationException extends BadJwtException {
 	 */
 	public JwtValidationException(String message, Collection<OAuth2Error> errors) {
 		super(message);
-
 		Assert.notEmpty(errors, "errors cannot be empty");
 		this.errors = new ArrayList<>(errors);
 	}

oauth2/oauth2-jose/src/main/java/org/springframework/security/oauth2/jwt/JwtValidators.java

@@ -32,6 +32,9 @@ import org.springframework.security.oauth2.core.OAuth2TokenValidator;
  */
 public final class JwtValidators {
 
+	private JwtValidators() {
+	}
+
 	/**
 	 * <p>
 	 * Create a {@link Jwt} Validator that contains all standard validators when an issuer
@@ -69,7 +72,4 @@ public final class JwtValidators {
 		return new DelegatingOAuth2TokenValidator<>(Arrays.asList(new JwtTimestampValidator()));
 	}
 
-	private JwtValidators() {
-	}
-
 }

oauth2/oauth2-jose/src/main/java/org/springframework/security/oauth2/jwt/MappedJwtClaimSetConverter.java

@@ -93,11 +93,9 @@ public final class MappedJwtClaimSetConverter implements Converter<Map<String, O
 	 */
 	public static MappedJwtClaimSetConverter withDefaults(Map<String, Converter<Object, ?>> claimTypeConverters) {
 		Assert.notNull(claimTypeConverters, "claimTypeConverters cannot be null");
-
 		Converter<Object, ?> stringConverter = getConverter(STRING_TYPE_DESCRIPTOR);
 		Converter<Object, ?> collectionStringConverter = getConverter(
 				TypeDescriptor.collection(Collection.class, STRING_TYPE_DESCRIPTOR));
-
 		Map<String, Converter<Object, ?>> claimNameToConverter = new HashMap<>();
 		claimNameToConverter.put(JwtClaimNames.AUD, collectionStringConverter);
 		claimNameToConverter.put(JwtClaimNames.EXP, MappedJwtClaimSetConverter::convertInstant);
@@ -107,7 +105,6 @@ public final class MappedJwtClaimSetConverter implements Converter<Map<String, O
 		claimNameToConverter.put(JwtClaimNames.NBF, MappedJwtClaimSetConverter::convertInstant);
 		claimNameToConverter.put(JwtClaimNames.SUB, stringConverter);
 		claimNameToConverter.putAll(claimTypeConverters);
-
 		return new MappedJwtClaimSetConverter(claimNameToConverter);
 	}
 
@@ -120,9 +117,7 @@ public final class MappedJwtClaimSetConverter implements Converter<Map<String, O
 			return null;
 		}
 		Instant result = (Instant) CONVERSION_SERVICE.convert(source, OBJECT_TYPE_DESCRIPTOR, INSTANT_TYPE_DESCRIPTOR);
-		if (result == null) {
+		Assert.state(result != null, () -> "Could not coerce " + source + " into an Instant");
-			throw new IllegalStateException("Could not coerce " + source + " into an Instant");
-		}
 		return result;
 	}
 
@@ -145,24 +140,17 @@ public final class MappedJwtClaimSetConverter implements Converter<Map<String, O
 		return (String) CONVERSION_SERVICE.convert(source, OBJECT_TYPE_DESCRIPTOR, STRING_TYPE_DESCRIPTOR);
 	}
 
-	/**
-	 * {@inheritDoc}
-	 */
 	@Override
 	public Map<String, Object> convert(Map<String, Object> claims) {
 		Assert.notNull(claims, "claims cannot be null");
-
 		Map<String, Object> mappedClaims = this.delegate.convert(claims);
-
 		mappedClaims = removeClaims(mappedClaims);
 		mappedClaims = addClaims(mappedClaims);
-
 		Instant issuedAt = (Instant) mappedClaims.get(JwtClaimNames.IAT);
 		Instant expiresAt = (Instant) mappedClaims.get(JwtClaimNames.EXP);
 		if (issuedAt == null && expiresAt != null) {
 			mappedClaims.put(JwtClaimNames.IAT, expiresAt.minusSeconds(1));
 		}
-
 		return mappedClaims;
 	}
 

oauth2/oauth2-jose/src/main/java/org/springframework/security/oauth2/jwt/NimbusJwtDecoder.java

@@ -145,20 +145,16 @@ public final class NimbusJwtDecoder implements JwtDecoder {
 		try {
 			// Verify the signature
 			JWTClaimsSet jwtClaimsSet = this.jwtProcessor.process(parsedJwt, null);
-
 			Map<String, Object> headers = new LinkedHashMap<>(parsedJwt.getHeader().toJSONObject());
 			Map<String, Object> claims = this.claimSetConverter.convert(jwtClaimsSet.getClaims());
-
 			return Jwt.withTokenValue(token).headers((h) -> h.putAll(headers)).claims((c) -> c.putAll(claims)).build();
 		}
 		catch (RemoteKeySourceException ex) {
 			if (ex.getCause() instanceof ParseException) {
 				throw new JwtException(String.format(DECODING_ERROR_MESSAGE_TEMPLATE, "Malformed Jwk set"));
 			}
-			else {
 			throw new JwtException(String.format(DECODING_ERROR_MESSAGE_TEMPLATE, ex.getMessage()), ex);
 		}
-		}
 		catch (JOSEException ex) {
 			throw new JwtException(String.format(DECODING_ERROR_MESSAGE_TEMPLATE, ex.getMessage()), ex);
 		}
@@ -166,28 +162,27 @@ public final class NimbusJwtDecoder implements JwtDecoder {
 			if (ex.getCause() instanceof ParseException) {
 				throw new BadJwtException(String.format(DECODING_ERROR_MESSAGE_TEMPLATE, "Malformed payload"));
 			}
-			else {
 			throw new BadJwtException(String.format(DECODING_ERROR_MESSAGE_TEMPLATE, ex.getMessage()), ex);
 		}
 	}
-	}
 
 	private Jwt validateJwt(Jwt jwt) {
 		OAuth2TokenValidatorResult result = this.jwtValidator.validate(jwt);
 		if (result.hasErrors()) {
 			Collection<OAuth2Error> errors = result.getErrors();
-			String validationErrorString = "Unable to validate Jwt";
+			String validationErrorString = getJwtValidationExceptionMessage(errors);
-			for (OAuth2Error oAuth2Error : errors) {
+			throw new JwtValidationException(validationErrorString, errors);
-				if (!StringUtils.isEmpty(oAuth2Error.getDescription())) {
-					validationErrorString = String.format(DECODING_ERROR_MESSAGE_TEMPLATE,
-							oAuth2Error.getDescription());
-					break;
 		}
-			}
+		return jwt;
-			throw new JwtValidationException(validationErrorString, result.getErrors());
 	}
 
-		return jwt;
+	private String getJwtValidationExceptionMessage(Collection<OAuth2Error> errors) {
+		for (OAuth2Error oAuth2Error : errors) {
+			if (!StringUtils.isEmpty(oAuth2Error.getDescription())) {
+				return String.format(DECODING_ERROR_MESSAGE_TEMPLATE, oAuth2Error.getDescription());
+			}
+		}
+		return "Unable to validate Jwt";
 	}
 
 	/**
@@ -316,7 +311,6 @@ public final class NimbusJwtDecoder implements JwtDecoder {
 			if (this.signatureAlgorithms.isEmpty()) {
 				return new JWSVerificationKeySelector<>(JWSAlgorithm.RS256, jwkSource);
 			}
-			else {
 			Set<JWSAlgorithm> jwsAlgorithms = new HashSet<>();
 			for (SignatureAlgorithm signatureAlgorithm : this.signatureAlgorithms) {
 				JWSAlgorithm jwsAlgorithm = JWSAlgorithm.parse(signatureAlgorithm.getName());
@@ -324,7 +318,6 @@ public final class NimbusJwtDecoder implements JwtDecoder {
 			}
 			return new JWSVerificationKeySelector<>(jwsAlgorithms, jwkSource);
 		}
-		}
 
 		JWKSource<SecurityContext> jwkSource(ResourceRetriever jwkSetRetriever) {
 			if (this.cache == null) {
@@ -339,13 +332,10 @@ public final class NimbusJwtDecoder implements JwtDecoder {
 			JWKSource<SecurityContext> jwkSource = jwkSource(jwkSetRetriever);
 			ConfigurableJWTProcessor<SecurityContext> jwtProcessor = new DefaultJWTProcessor<>();
 			jwtProcessor.setJWSKeySelector(jwsKeySelector(jwkSource));
-
 			// Spring Security validates the claim set independent from Nimbus
 			jwtProcessor.setJWTClaimsSetVerifier((claims, context) -> {
 			});
-
 			this.jwtProcessorCustomizer.accept(jwtProcessor);
-
 			return jwtProcessor;
 		}
 
@@ -397,10 +387,10 @@ public final class NimbusJwtDecoder implements JwtDecoder {
 
 			@Override
 			public Resource retrieveResource(URL url) throws IOException {
-				String jwkSet;
 				try {
-					jwkSet = this.cache.get(url.toString(),
+					String jwkSet = this.cache.get(url.toString(),
 							() -> this.resourceRetriever.retrieveResource(url).getContent());
+					return new Resource(jwkSet, "UTF-8");
 				}
 				catch (Cache.ValueRetrievalException ex) {
 					Throwable thrownByValueLoader = ex.getCause();
@@ -412,8 +402,6 @@ public final class NimbusJwtDecoder implements JwtDecoder {
 				catch (Exception ex) {
 					throw new IOException(ex);
 				}
-
-				return new Resource(jwkSet, "UTF-8");
 			}
 
 		}
@@ -433,21 +421,21 @@ public final class NimbusJwtDecoder implements JwtDecoder {
 			public Resource retrieveResource(URL url) throws IOException {
 				HttpHeaders headers = new HttpHeaders();
 				headers.setAccept(Arrays.asList(MediaType.APPLICATION_JSON, APPLICATION_JWK_SET_JSON));
+				ResponseEntity<String> response = getResponse(url, headers);
+				if (response.getStatusCodeValue() != 200) {
+					throw new IOException(response.toString());
+				}
+				return new Resource(response.getBody(), "UTF-8");
+			}
 
-				ResponseEntity<String> response;
+			private ResponseEntity<String> getResponse(URL url, HttpHeaders headers) throws IOException {
 				try {
 					RequestEntity<Void> request = new RequestEntity<>(headers, HttpMethod.GET, url.toURI());
-					response = this.restOperations.exchange(request, String.class);
+					return this.restOperations.exchange(request, String.class);
 				}
 				catch (Exception ex) {
 					throw new IOException(ex);
 				}
-
-				if (response.getStatusCodeValue() != 200) {
-					throw new IOException(response.toString());
-				}
-
-				return new Resource(response.getBody(), "UTF-8");
 			}
 
 		}
@@ -506,22 +494,16 @@ public final class NimbusJwtDecoder implements JwtDecoder {
 		}
 
 		JWTProcessor<SecurityContext> processor() {
-			if (!JWSAlgorithm.Family.RSA.contains(this.jwsAlgorithm)) {
+			Assert.state(JWSAlgorithm.Family.RSA.contains(this.jwsAlgorithm),
-				throw new IllegalStateException(
+					() -> "The provided key is of type RSA; however the signature algorithm is of some other type: "
-						"The provided key is of type RSA; " + "however the signature algorithm is of some other type: "
 							+ this.jwsAlgorithm + ". Please indicate one of RS256, RS384, or RS512.");
-			}
-
 			JWSKeySelector<SecurityContext> jwsKeySelector = new SingleKeyJWSKeySelector<>(this.jwsAlgorithm, this.key);
 			DefaultJWTProcessor<SecurityContext> jwtProcessor = new DefaultJWTProcessor<>();
 			jwtProcessor.setJWSKeySelector(jwsKeySelector);
-
 			// Spring Security validates the claim set independent from Nimbus
 			jwtProcessor.setJWTClaimsSetVerifier((claims, context) -> {
 			});
-
 			this.jwtProcessorCustomizer.accept(jwtProcessor);
-
 			return jwtProcessor;
 		}
 
@@ -599,13 +581,10 @@ public final class NimbusJwtDecoder implements JwtDecoder {
 					this.secretKey);
 			DefaultJWTProcessor<SecurityContext> jwtProcessor = new DefaultJWTProcessor<>();
 			jwtProcessor.setJWSKeySelector(jwsKeySelector);
-
 			// Spring Security validates the claim set independent from Nimbus
 			jwtProcessor.setJWTClaimsSetVerifier((claims, context) -> {
 			});
-
 			this.jwtProcessorCustomizer.accept(jwtProcessor);
-
 			return jwtProcessor;
 		}
 

oauth2/oauth2-jose/src/main/java/org/springframework/security/oauth2/jwt/NimbusJwtDecoderJwkSupport.java

@@ -79,7 +79,6 @@ public final class NimbusJwtDecoderJwkSupport implements JwtDecoder {
 	public NimbusJwtDecoderJwkSupport(String jwkSetUrl, String jwsAlgorithm) {
 		Assert.hasText(jwkSetUrl, "jwkSetUrl cannot be empty");
 		Assert.hasText(jwsAlgorithm, "jwsAlgorithm cannot be empty");
-
 		this.jwtDecoderBuilder = NimbusJwtDecoder.withJwkSetUri(jwkSetUrl)
 				.jwsAlgorithm(SignatureAlgorithm.from(jwsAlgorithm));
 		this.delegate = makeDelegate();

oauth2/oauth2-jose/src/main/java/org/springframework/security/oauth2/jwt/NimbusReactiveJwtDecoder.java

@@ -161,8 +161,8 @@ public final class NimbusReactiveJwtDecoder implements ReactiveJwtDecoder {
 		try {
 			return this.jwtProcessor.convert(parsedToken).map((set) -> createJwt(parsedToken, set))
 					.map(this::validateJwt)
-					.onErrorMap((e) -> !(e instanceof IllegalStateException) && !(e instanceof JwtException),
+					.onErrorMap((ex) -> !(ex instanceof IllegalStateException) && !(ex instanceof JwtException),
-							(e) -> new JwtException("An error occurred while attempting to decode the Jwt: ", e));
+							(ex) -> new JwtException("An error occurred while attempting to decode the Jwt: ", ex));
 		}
 		catch (JwtException ex) {
 			throw ex;
@@ -176,7 +176,6 @@ public final class NimbusReactiveJwtDecoder implements ReactiveJwtDecoder {
 		try {
 			Map<String, Object> headers = new LinkedHashMap<>(parsedJwt.getHeader().toJSONObject());
 			Map<String, Object> claims = this.claimSetConverter.convert(jwtClaimsSet.getClaims());
-
 			return Jwt.withTokenValue(parsedJwt.getParsedString()).headers((h) -> h.putAll(headers))
 					.claims((c) -> c.putAll(claims)).build();
 		}
@@ -189,19 +188,21 @@ public final class NimbusReactiveJwtDecoder implements ReactiveJwtDecoder {
 		OAuth2TokenValidatorResult result = this.jwtValidator.validate(jwt);
 		if (result.hasErrors()) {
 			Collection<OAuth2Error> errors = result.getErrors();
-			String validationErrorString = "Unable to validate Jwt";
+			String validationErrorString = getJwtValidationExceptionMessage(errors);
-			for (OAuth2Error oAuth2Error : errors) {
-				if (!StringUtils.isEmpty(oAuth2Error.getDescription())) {
-					validationErrorString = oAuth2Error.getDescription();
-					break;
-				}
-			}
 			throw new JwtValidationException(validationErrorString, errors);
 		}
-
 		return jwt;
 	}
 
+	private String getJwtValidationExceptionMessage(Collection<OAuth2Error> errors) {
+		for (OAuth2Error oAuth2Error : errors) {
+			if (!StringUtils.isEmpty(oAuth2Error.getDescription())) {
+				return oAuth2Error.getDescription();
+			}
+		}
+		return "Unable to validate Jwt";
+	}
+
 	/**
 	 * Use the given <a href="https://tools.ietf.org/html/rfc7517#section-5">JWK Set</a>
 	 * uri to validate JWTs.
@@ -353,7 +354,6 @@ public final class NimbusReactiveJwtDecoder implements ReactiveJwtDecoder {
 			if (this.signatureAlgorithms.isEmpty()) {
 				return new JWSVerificationKeySelector<>(JWSAlgorithm.RS256, jwkSource);
 			}
-			else {
 			Set<JWSAlgorithm> jwsAlgorithms = new HashSet<>();
 			for (SignatureAlgorithm signatureAlgorithm : this.signatureAlgorithms) {
 				JWSAlgorithm jwsAlgorithm = JWSAlgorithm.parse(signatureAlgorithm.getName());
@@ -361,7 +361,6 @@ public final class NimbusReactiveJwtDecoder implements ReactiveJwtDecoder {
 			}
 			return new JWSVerificationKeySelector<>(jwsAlgorithms, jwkSource);
 		}
-		}
 
 		Converter<JWT, Mono<JWTClaimsSet>> processor() {
 			JWKSecurityContextJWKSet jwkSource = new JWKSecurityContextJWKSet();
@@ -370,16 +369,14 @@ public final class NimbusReactiveJwtDecoder implements ReactiveJwtDecoder {
 			jwtProcessor.setJWSKeySelector(jwsKeySelector);
 			jwtProcessor.setJWTClaimsSetVerifier((claims, context) -> {
 			});
-
 			this.jwtProcessorCustomizer.accept(jwtProcessor);
-
 			ReactiveRemoteJWKSource source = new ReactiveRemoteJWKSource(this.jwkSetUri);
 			source.setWebClient(this.webClient);
-
 			Function<JWSAlgorithm, Boolean> expectedJwsAlgorithms = getExpectedJwsAlgorithms(jwsKeySelector);
 			return (jwt) -> {
 				JWKSelector selector = createSelector(expectedJwsAlgorithms, jwt.getHeader());
-				return source.get(selector).onErrorMap((e) -> new IllegalStateException("Could not obtain the keys", e))
+				return source.get(selector)
+						.onErrorMap((ex) -> new IllegalStateException("Could not obtain the keys", ex))
 						.map((jwkList) -> createClaimsSet(jwtProcessor, jwt, new JWKSecurityContext(jwkList)));
 			};
 		}
@@ -396,7 +393,6 @@ public final class NimbusReactiveJwtDecoder implements ReactiveJwtDecoder {
 			if (!expectedJwsAlgorithms.apply(jwsHeader.getAlgorithm())) {
 				throw new BadJwtException("Unsupported algorithm of " + header.getAlgorithm());
 			}
-
 			return new JWKSelector(JWKMatcher.forJWSHeader(jwsHeader));
 		}
 
@@ -463,22 +459,16 @@ public final class NimbusReactiveJwtDecoder implements ReactiveJwtDecoder {
 		}
 
 		Converter<JWT, Mono<JWTClaimsSet>> processor() {
-			if (!JWSAlgorithm.Family.RSA.contains(this.jwsAlgorithm)) {
+			Assert.state(JWSAlgorithm.Family.RSA.contains(this.jwsAlgorithm),
-				throw new IllegalStateException(
+					() -> "The provided key is of type RSA; however the signature algorithm is of some other type: "
-						"The provided key is of type RSA; " + "however the signature algorithm is of some other type: "
 							+ this.jwsAlgorithm + ". Please indicate one of RS256, RS384, or RS512.");
-			}
-
 			JWSKeySelector<SecurityContext> jwsKeySelector = new SingleKeyJWSKeySelector<>(this.jwsAlgorithm, this.key);
 			DefaultJWTProcessor<SecurityContext> jwtProcessor = new DefaultJWTProcessor<>();
 			jwtProcessor.setJWSKeySelector(jwsKeySelector);
-
 			// Spring Security validates the claim set independent from Nimbus
 			jwtProcessor.setJWTClaimsSetVerifier((claims, context) -> {
 			});
-
 			this.jwtProcessorCustomizer.accept(jwtProcessor);
-
 			return (jwt) -> Mono.just(createClaimsSet(jwtProcessor, jwt, null));
 		}
 
@@ -550,13 +540,10 @@ public final class NimbusReactiveJwtDecoder implements ReactiveJwtDecoder {
 					this.secretKey);
 			DefaultJWTProcessor<SecurityContext> jwtProcessor = new DefaultJWTProcessor<>();
 			jwtProcessor.setJWSKeySelector(jwsKeySelector);
-
 			// Spring Security validates the claim set independent from Nimbus
 			jwtProcessor.setJWTClaimsSetVerifier((claims, context) -> {
 			});
-
 			this.jwtProcessorCustomizer.accept(jwtProcessor);
-
 			return (jwt) -> Mono.just(createClaimsSet(jwtProcessor, jwt, null));
 		}
 
@@ -626,9 +613,7 @@ public final class NimbusReactiveJwtDecoder implements ReactiveJwtDecoder {
 			jwtProcessor.setJWSKeySelector(jwsKeySelector);
 			jwtProcessor.setJWTClaimsSetVerifier((claims, context) -> {
 			});
-
 			this.jwtProcessorCustomizer.accept(jwtProcessor);
-
 			return (jwt) -> {
 				if (jwt instanceof SignedJWT) {
 					return this.jwkSource.apply((SignedJWT) jwt)

oauth2/oauth2-jose/src/main/java/org/springframework/security/oauth2/jwt/ReactiveJwtDecoders.java

@@ -33,6 +33,9 @@ import org.springframework.util.Assert;
  */
 public final class ReactiveJwtDecoders {
 
+	private ReactiveJwtDecoders() {
+	}
+
 	/**
 	 * Creates a {@link ReactiveJwtDecoder} using the provided <a href=
 	 * "https://openid.net/specs/openid-connect-core-1_0.html#IssuerIdentifier">Issuer</a>
@@ -106,11 +109,7 @@ public final class ReactiveJwtDecoders {
 		NimbusReactiveJwtDecoder jwtDecoder = NimbusReactiveJwtDecoder
 				.withJwkSetUri(configuration.get("jwks_uri").toString()).build();
 		jwtDecoder.setJwtValidator(jwtValidator);
-
 		return jwtDecoder;
 	}
 
-	private ReactiveJwtDecoders() {
-	}
-
 }

oauth2/oauth2-jose/src/main/java/org/springframework/security/oauth2/jwt/ReactiveRemoteJWKSource.java

@@ -63,29 +63,23 @@ class ReactiveRemoteJWKSource implements ReactiveJWKSource {
 		return Mono.defer(() -> {
 			// Run the selector on the JWK set
 			List<JWK> matches = jwkSelector.select(jwkSet);
-
 			if (!matches.isEmpty()) {
 				// Success
 				return Mono.just(matches);
 			}
-
 			// Refresh the JWK set if the sought key ID is not in the cached JWK set
-
 			// Looking for JWK with specific ID?
 			String soughtKeyID = getFirstSpecifiedKeyID(jwkSelector.getMatcher());
 			if (soughtKeyID == null) {
 				// No key ID specified, return no matches
 				return Mono.just(Collections.emptyList());
 			}
-
 			if (jwkSet.getKeyByKeyId(soughtKeyID) != null) {
 				// The key ID exists in the cached JWK set, matching
 				// failed for some other reason, return no matches
 				return Mono.just(Collections.emptyList());
 			}
-
 			return Mono.empty();
-
 		});
 	}
 
@@ -114,13 +108,10 @@ class ReactiveRemoteJWKSource implements ReactiveJWKSource {
 	 * @return The first key ID, {@code null} if none.
 	 */
 	protected static String getFirstSpecifiedKeyID(final JWKMatcher jwkMatcher) {
-
 		Set<String> keyIDs = jwkMatcher.getKeyIDs();
-
 		if (keyIDs == null || keyIDs.isEmpty()) {
 			return null;
 		}
-
 		for (String id : keyIDs) {
 			if (id != null) {
 				return id;