Provide orNull extensions for WebFlux ServerRequest

Closes gh-23761

spring-webflux/src/main/kotlin/org/springframework/web/reactive/function/server/ServerRequestExtensions.kt

@@ -21,11 +21,14 @@ import kotlinx.coroutines.reactive.awaitFirstOrNull
 import kotlinx.coroutines.reactive.awaitSingle
 import kotlinx.coroutines.reactive.asFlow
 import org.springframework.core.ParameterizedTypeReference
+import org.springframework.http.MediaType
 import org.springframework.http.codec.multipart.Part
+import org.springframework.util.CollectionUtils
 import org.springframework.util.MultiValueMap
 import org.springframework.web.server.WebSession
 import reactor.core.publisher.Flux
 import reactor.core.publisher.Mono
+import java.net.InetSocketAddress
 import java.security.Principal
 
 /**
@@ -112,3 +115,56 @@ suspend fun ServerRequest.awaitPrincipal(): Principal? =
  */
 suspend fun ServerRequest.awaitSession(): WebSession =
 		session().awaitSingle()
+
+/**
+ * Nullable variant of [ServerRequest.remoteAddress]
+ *
+ * @author Sebastien Deleuze
+ * @since 5.2.2
+ */
+fun ServerRequest.remoteAddressOrNull(): InetSocketAddress? = remoteAddress().orElse(null)
+
+/**
+ * Nullable variant of [ServerRequest.attribute]
+ *
+ * @author Sebastien Deleuze
+ * @since 5.2.2
+ */
+fun ServerRequest.attributeOrNull(name: String): Any? = attributes()[name]
+
+/**
+ * Nullable variant of [ServerRequest.queryParam]
+ *
+ * @author Sebastien Deleuze
+ * @since 5.2.2
+ */
+fun ServerRequest.queryParamOrNull(name: String): String? {
+	val queryParamValues = queryParams()[name]
+	return if (CollectionUtils.isEmpty(queryParamValues)) {
+		null
+	} else {
+		var value: String? = queryParamValues!![0]
+		if (value == null) {
+			value = ""
+		}
+		value
+	}
+}
+
+/**
+ * Nullable variant of [ServerRequest.Headers.contentLength]
+ *
+ * @author Sebastien Deleuze
+ * @since 5.2.2
+ */
+fun ServerRequest.Headers.contentLengthOrNull(): Long? =
+		contentLength().run { if (isPresent) asLong else null }
+
+/**
+ * Nullable variant of [ServerRequest.Headers.contentType]
+ *
+ * @author Sebastien Deleuze
+ * @since 5.2.2
+ */
+fun ServerRequest.Headers.contentTypeOrNull(): MediaType? =
+		contentType().orElse(null)