Prepare to support API versioning for fn

Add default method to resolve, parse, and validate version
Simplify tests

spring-web/src/main/java/org/springframework/web/accept/ApiVersionStrategy.java

@@ -62,6 +62,27 @@ public interface ApiVersionStrategy {
 	 */
 	@Nullable Comparable<?> getDefaultVersion();
 
+	/**
+	 * Convenience method to return the parsed and validated request version,
+	 * or the default version if configured.
+	 * @param request the current request
+	 * @return the parsed request version, or the default version
+	 */
+	default @Nullable Comparable<?> resolveParseAndValidateVersion(HttpServletRequest request) {
+		String value = resolveVersion(request);
+		if (value == null) {
+			return getDefaultVersion();
+		}
+		try {
+			Comparable<?> version = parseVersion(value);
+			validateVersion(version, request);
+			return version;
+		}
+		catch (Exception ex) {
+			throw new InvalidApiVersionException(value, null, ex);
+		}
+	}
+
 	/**
 	 * Check if the requested API version is deprecated, and if so handle it
 	 * accordingly, e.g. by setting response headers to signal the deprecation,

spring-webflux/src/main/java/org/springframework/web/reactive/accept/ApiVersionStrategy.java

@@ -64,6 +64,27 @@ public interface ApiVersionStrategy {
 	 */
 	@Nullable Comparable<?> getDefaultVersion();
 
+	/**
+	 * Convenience method to return the parsed and validated request version,
+	 * or the default version if configured.
+	 * @param exchange the current exchange
+	 * @return the parsed request version, or the default version
+	 */
+	default @Nullable Comparable<?> resolveParseAndValidateVersion(ServerWebExchange exchange) {
+		String value = resolveVersion(exchange);
+		if (value == null) {
+			return getDefaultVersion();
+		}
+		try {
+			Comparable<?> version = parseVersion(value);
+			validateVersion(version, exchange);
+			return version;
+		}
+		catch (Exception ex) {
+			throw new InvalidApiVersionException(value, null, ex);
+		}
+	}
+
 	/**
 	 * Check if the requested API version is deprecated, and if so handle it
 	 * accordingly, e.g. by setting response headers to signal the deprecation,

spring-webflux/src/main/java/org/springframework/web/reactive/accept/DefaultApiVersionStrategy.java

@@ -93,6 +93,16 @@ public class DefaultApiVersionStrategy implements ApiVersionStrategy {
 		return this.defaultVersion;
 	}
 
+	/**
+	 * Whether the strategy is configured to detect supported versions.
+	 * If this is set to {@code false} then {@link #addMappedVersion} is ignored
+	 * and the list of supported versions can be built explicitly through calls
+	 * to {@link #addSupportedVersion}.
+	 */
+	public boolean detectSupportedVersions() {
+		return this.detectSupportedVersions;
+	}
+
 	/**
 	 * Add to the list of supported versions to check against in
 	 * {@link ApiVersionStrategy#validateVersion} before raising

spring-webflux/src/main/java/org/springframework/web/reactive/result/method/annotation/RequestMappingHandlerMapping.java

@@ -42,7 +42,6 @@ import org.springframework.util.Assert;
 import org.springframework.util.CollectionUtils;
 import org.springframework.util.StringUtils;
 import org.springframework.util.StringValueResolver;
-import org.springframework.web.accept.InvalidApiVersionException;
 import org.springframework.web.bind.annotation.CrossOrigin;
 import org.springframework.web.bind.annotation.RequestBody;
 import org.springframework.web.bind.annotation.RequestMapping;
@@ -180,7 +179,7 @@ public class RequestMappingHandlerMapping extends RequestMappingInfoHandlerMappi
 		if (this.apiVersionStrategy != null) {
 			Comparable<?> version = exchange.getAttribute(API_VERSION_ATTRIBUTE);
 			if (version == null) {
-				version = getApiVersion(exchange, this.apiVersionStrategy);
+				version = this.apiVersionStrategy.resolveParseAndValidateVersion(exchange);
 				if (version != null) {
 					exchange.getAttributes().put(API_VERSION_ATTRIBUTE, version);
 				}
@@ -189,21 +188,6 @@ public class RequestMappingHandlerMapping extends RequestMappingInfoHandlerMappi
 		return super.getHandlerInternal(exchange);
 	}
 
-	private static @Nullable Comparable<?> getApiVersion(ServerWebExchange exchange, ApiVersionStrategy strategy) {
-		String value = strategy.resolveVersion(exchange);
-		if (value == null) {
-			return strategy.getDefaultVersion();
-		}
-		try {
-			Comparable<?> version = strategy.parseVersion(value);
-			strategy.validateVersion(version, exchange);
-			return version;
-		}
-		catch (Exception ex) {
-			throw new InvalidApiVersionException(value, null, ex);
-		}
-	}
-
 	/**
 	 * Uses type-level and method-level {@link RequestMapping @RequestMapping}
 	 * and {@link HttpExchange @HttpExchange} annotations to create the

spring-webflux/src/test/java/org/springframework/web/reactive/result/method/annotation/RequestMappingVersionIntegrationTests.java

@@ -50,29 +50,24 @@ public class RequestMappingVersionIntegrationTests extends AbstractRequestMappin
 
 
 	@ParameterizedHttpServerTest
-	void initialVersion(HttpServer httpServer) throws Exception {
+	void mapVersion(HttpServer httpServer) throws Exception {
 		startServer(httpServer);
+
 		assertThat(exchangeWithVersion("1.0").getBody()).isEqualTo("none");
 		assertThat(exchangeWithVersion("1.1").getBody()).isEqualTo("none");
-	}
-
-	@ParameterizedHttpServerTest
-	void baselineVersion(HttpServer httpServer) throws Exception {
-		startServer(httpServer);
 		assertThat(exchangeWithVersion("1.2").getBody()).isEqualTo("1.2");
 		assertThat(exchangeWithVersion("1.3").getBody()).isEqualTo("1.2");
-	}
-
-	@ParameterizedHttpServerTest
-	void fixedVersion(HttpServer httpServer) throws Exception {
-		startServer(httpServer);
 		assertThat(exchangeWithVersion("1.5").getBody()).isEqualTo("1.5");
-		assertThatThrownBy(() -> exchangeWithVersion("1.6")).isInstanceOf(HttpClientErrorException.BadRequest.class);
+
+		assertThatThrownBy(() -> exchangeWithVersion("1.6"))
+				.as("Should reject if highest supported below request version is fixed")
+				.isInstanceOf(HttpClientErrorException.BadRequest.class);
 	}
 
 	@ParameterizedHttpServerTest
 	void deprecation(HttpServer httpServer) throws Exception {
 		startServer(httpServer);
+
 		assertThat(exchangeWithVersion("1").getHeaders().getFirst("Link"))
 				.isEqualTo("<https://example.org/deprecation>; rel=\"deprecation\"; type=\"text/html\"");
 	}

spring-webmvc/src/main/java/org/springframework/web/servlet/mvc/method/annotation/RequestMappingHandlerMapping.java

@@ -46,7 +46,6 @@ import org.springframework.util.StringValueResolver;
 import org.springframework.web.accept.ApiVersionStrategy;
 import org.springframework.web.accept.ContentNegotiationManager;
 import org.springframework.web.accept.DefaultApiVersionStrategy;
-import org.springframework.web.accept.InvalidApiVersionException;
 import org.springframework.web.bind.annotation.CrossOrigin;
 import org.springframework.web.bind.annotation.RequestBody;
 import org.springframework.web.bind.annotation.RequestMapping;
@@ -207,7 +206,7 @@ public class RequestMappingHandlerMapping extends RequestMappingInfoHandlerMappi
 		if (this.apiVersionStrategy != null) {
 			Comparable<?> version = (Comparable<?>) request.getAttribute(API_VERSION_ATTRIBUTE);
 			if (version == null) {
-				version = getApiVersion(request, this.apiVersionStrategy);
+				version = this.apiVersionStrategy.resolveParseAndValidateVersion(request);
 				if (version != null) {
 					request.setAttribute(API_VERSION_ATTRIBUTE, version);
 				}
@@ -216,21 +215,6 @@ public class RequestMappingHandlerMapping extends RequestMappingInfoHandlerMappi
 		return super.getHandlerInternal(request);
 	}
 
-	private static @Nullable Comparable<?> getApiVersion(HttpServletRequest request, ApiVersionStrategy strategy) {
-		String value = strategy.resolveVersion(request);
-		if (value == null) {
-			return strategy.getDefaultVersion();
-		}
-		try {
-			Comparable<?> version = strategy.parseVersion(value);
-			strategy.validateVersion(version, request);
-			return version;
-		}
-		catch (Exception ex) {
-			throw new InvalidApiVersionException(value, null, ex);
-		}
-	}
-
 	/**
 	 * Uses type-level and method-level {@link RequestMapping @RequestMapping}
 	 * and {@link HttpExchange @HttpExchange} annotations to create the

spring-webmvc/src/test/java/org/springframework/web/servlet/mvc/method/annotation/RequestMappingVersionHandlerMethodTests.java

@@ -59,23 +59,17 @@ public class RequestMappingVersionHandlerMethodTests {
 
 
 	@Test
-	void initialVersion() throws Exception {
+	void mapVersion() throws Exception {
 		assertThat(requestWithVersion("1.0").getContentAsString()).isEqualTo("none");
 		assertThat(requestWithVersion("1.1").getContentAsString()).isEqualTo("none");
-	}
-
-	@Test
-	void baselineVersion() throws Exception {
 		assertThat(requestWithVersion("1.2").getContentAsString()).isEqualTo("1.2");
 		assertThat(requestWithVersion("1.3").getContentAsString()).isEqualTo("1.2");
-	}
-
-	@Test
-	void fixedVersion() throws Exception {
 		assertThat(requestWithVersion("1.5").getContentAsString()).isEqualTo("1.5");
 
 		MockHttpServletResponse response = requestWithVersion("1.6");
-		assertThat(response.getStatus()).isEqualTo(400);
+		assertThat(response.getStatus())
+				.as("Should reject if highest supported below request version is fixed")
+				.isEqualTo(400);
 	}
 
 	@Test