Support for "request parameters"

ServerWebExchange now provides access to "requestParams" as a
MulitValueMap with query parameters and form data combined.

The combined map is then used for the params condition of
@RequestMapping purposes () and also for @RequestParam arguments.

Issue: SPR-15000

spring-web/src/main/java/org/springframework/web/server/ServerWebExchange.java

@@ -76,11 +76,18 @@ public interface ServerWebExchange {
 	<T extends Principal> Mono<T> getPrincipal();
 
 	/**
-	 * Return the form data from the body of the request or an empty {@code Mono}
-	 * if the Content-Type is not "application/x-www-form-urlencoded".
+	 * Return the form data from the body of the request if the Content-Type is
+	 * {@code "application/x-www-form-urlencoded"} or an empty map.
 	 */
 	Mono<MultiValueMap<String, String>> getFormData();
 
+	/**
+	 * Return a combined map that represents both
+	 * {@link ServerHttpRequest#getQueryParams()} and {@link #getFormData()}
+	 * or an empty map.
+	 */
+	Mono<MultiValueMap<String, String>> getRequestParams();
+
 	/**
 	 * Returns {@code true} if the one of the {@code checkNotModified} methods
 	 * in this contract were used and they returned true.

spring-web/src/main/java/org/springframework/web/server/ServerWebExchangeDecorator.java

@@ -93,6 +93,11 @@ public class ServerWebExchangeDecorator implements ServerWebExchange {
 		return getDelegate().getFormData();
 	}
 
+	@Override
+	public Mono<MultiValueMap<String, String>> getRequestParams() {
+		return getDelegate().getRequestParams();
+	}
+
 	@Override
 	public boolean isNotModified() {
 		return getDelegate().isNotModified();

spring-web/src/main/java/org/springframework/web/server/adapter/DefaultServerWebExchange.java

@@ -38,6 +38,8 @@ import org.springframework.http.codec.FormHttpMessageReader;
 import org.springframework.http.server.reactive.ServerHttpRequest;
 import org.springframework.http.server.reactive.ServerHttpResponse;
 import org.springframework.util.Assert;
+import org.springframework.util.CollectionUtils;
+import org.springframework.util.LinkedMultiValueMap;
 import org.springframework.util.MultiValueMap;
 import org.springframework.util.StringUtils;
 import org.springframework.web.server.ServerWebExchange;
@@ -56,9 +58,13 @@ public class DefaultServerWebExchange implements ServerWebExchange {
 
 	private static final FormHttpMessageReader FORM_READER = new FormHttpMessageReader();
 
-	private static final ResolvableType MULTIVALUE_TYPE =
+	private static final ResolvableType FORM_DATA_VALUE_TYPE =
 			ResolvableType.forClassWithGenerics(MultiValueMap.class, String.class, String.class);
 
+	private static final Mono<MultiValueMap<String, String>> EMPTY_FORM_DATA =
+			Mono.just(CollectionUtils.unmodifiableMultiValueMap(new LinkedMultiValueMap<String, String>(0)))
+					.cache();
+
 
 	private final ServerHttpRequest request;
 
@@ -70,6 +76,8 @@ public class DefaultServerWebExchange implements ServerWebExchange {
 
 	private final Mono<MultiValueMap<String, String>> formDataMono;
 
+	private final Mono<MultiValueMap<String, String>> requestParamsMono;
+
 	private volatile boolean notModified;
 
 
@@ -80,10 +88,12 @@ public class DefaultServerWebExchange implements ServerWebExchange {
 		Assert.notNull(response, "'response' is required");
 		Assert.notNull(response, "'sessionManager' is required");
 		Assert.notNull(response, "'formReader' is required");
+
 		this.request = request;
 		this.response = response;
 		this.sessionMono = sessionManager.getSession(this).cache();
 		this.formDataMono = initFormData(request);
+		this.requestParamsMono = initRequestParams(request, this.formDataMono);
 	}
 
 	private static Mono<MultiValueMap<String, String>> initFormData(ServerHttpRequest request) {
@@ -91,13 +101,28 @@ public class DefaultServerWebExchange implements ServerWebExchange {
 		try {
 			contentType = request.getHeaders().getContentType();
 			if (MediaType.APPLICATION_FORM_URLENCODED.isCompatibleWith(contentType)) {
-				return FORM_READER.readMono(MULTIVALUE_TYPE, request, Collections.emptyMap()).cache();
+				Map<String, Object> hints = Collections.emptyMap();
+				return FORM_READER.readMono(FORM_DATA_VALUE_TYPE, request, hints).cache();
 			}
 		}
 		catch (InvalidMediaTypeException ex) {
 			// Ignore
 		}
-		return Mono.empty();
+		return EMPTY_FORM_DATA;
+	}
+
+	private static Mono<MultiValueMap<String, String>> initRequestParams(
+			ServerHttpRequest request, Mono<MultiValueMap<String, String>> formDataMono) {
+
+		return formDataMono
+				.map(formData -> {
+					MultiValueMap<String, String> result = new LinkedMultiValueMap<>();
+					result.putAll(request.getQueryParams());
+					result.putAll(formData);
+					return CollectionUtils.unmodifiableMultiValueMap(result);
+				})
+				.defaultIfEmpty(request.getQueryParams())
+				.cache();
 	}
 
 
@@ -144,6 +169,11 @@ public class DefaultServerWebExchange implements ServerWebExchange {
 		return this.formDataMono;
 	}
 
+	@Override
+	public Mono<MultiValueMap<String, String>> getRequestParams() {
+		return this.requestParamsMono;
+	}
+
 	@Override
 	public boolean isNotModified() {
 		return this.notModified;