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)

spring-webflux/src/test/kotlin/org/springframework/web/reactive/function/server/ServerRequestExtensionsTests.kt

@@ -23,11 +23,15 @@ import kotlinx.coroutines.runBlocking
 import org.assertj.core.api.Assertions.assertThat
 import org.junit.jupiter.api.Test
 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.Mono
+import java.net.InetSocketAddress
 import java.security.Principal
+import java.util.*
 
 /**
  * Mock object based tests for [ServerRequest] Kotlin extensions.
@@ -38,6 +42,8 @@ class ServerRequestExtensionsTests {
 
 	val request = mockk<ServerRequest>(relaxed = true)
 
+	val headers = mockk<ServerRequest.Headers>(relaxed = true)
+
 	@Test
 	fun `bodyToMono with reified type parameters`() {
 		request.bodyToMono<List<Foo>>()
@@ -108,6 +114,90 @@ class ServerRequestExtensionsTests {
 		}
 	}
 
+	@Test
+	fun `remoteAddressOrNull with value`() {
+		val remoteAddress = InetSocketAddress(1234)
+		every { request.remoteAddress() } returns Optional.of(remoteAddress)
+		assertThat(remoteAddress).isEqualTo(request.remoteAddressOrNull())
+		verify { request.remoteAddress() }
+	}
+
+	@Test
+	fun `remoteAddressOrNull with null`() {
+		every { request.remoteAddress() } returns Optional.empty()
+		assertThat(request.remoteAddressOrNull()).isNull()
+		verify { request.remoteAddress() }
+	}
+
+	@Test
+	fun `attributeOrNull with value`() {
+		every { request.attributes() } returns mapOf("foo" to "bar")
+		assertThat(request.attributeOrNull("foo")).isEqualTo("bar")
+		verify { request.attributes() }
+	}
+
+	@Test
+	fun `attributeOrNull with null`() {
+		every { request.attributes() } returns mapOf("foo" to "bar")
+		assertThat(request.attributeOrNull("baz")).isNull()
+		verify { request.attributes() }
+	}
+
+	@Test
+	fun `queryParamOrNull with value`() {
+		every { request.queryParams() } returns CollectionUtils.toMultiValueMap(mapOf("foo" to listOf("bar")))
+		assertThat(request.queryParamOrNull("foo")).isEqualTo("bar")
+		verify { request.queryParams() }
+	}
+
+	@Test
+	fun `queryParamOrNull with values`() {
+		every { request.queryParams() } returns CollectionUtils.toMultiValueMap(mapOf("foo" to listOf("bar", "bar")))
+		assertThat(request.queryParamOrNull("foo")).isEqualTo("bar")
+		verify { request.queryParams() }
+	}
+
+	@Test
+	fun `queryParamOrNull with null value`() {
+		every { request.queryParams() } returns CollectionUtils.toMultiValueMap(mapOf("foo" to listOf(null)))
+		assertThat(request.queryParamOrNull("foo")).isEqualTo("")
+		verify { request.queryParams() }
+	}
+
+	@Test
+	fun `queryParamOrNull with null`() {
+		every { request.queryParams() } returns CollectionUtils.toMultiValueMap(mapOf("foo" to listOf("bar")))
+		assertThat(request.queryParamOrNull("baz")).isNull()
+		verify { request.queryParams() }
+	}
+
+	@Test
+	fun `contentLengthOrNull with value`() {
+		every { headers.contentLength() } returns OptionalLong.of(123)
+		assertThat(headers.contentLengthOrNull()).isEqualTo(123)
+		verify { headers.contentLength() }
+	}
+
+	@Test
+	fun `contentLengthOrNull with null`() {
+		every { headers.contentLength() } returns OptionalLong.empty()
+		assertThat(headers.contentLengthOrNull()).isNull()
+		verify { headers.contentLength() }
+	}
+
+	@Test
+	fun `contentTypeOrNull with value`() {
+		every { headers.contentType() } returns Optional.of(MediaType.APPLICATION_JSON)
+		assertThat(headers.contentTypeOrNull()).isEqualTo(MediaType.APPLICATION_JSON)
+		verify { headers.contentType() }
+	}
+
+	@Test
+	fun `contentTypeOrNull with null`() {
+		every { headers.contentType() } returns Optional.empty()
+		assertThat(headers.contentTypeOrNull()).isNull()
+		verify { headers.contentType() }
+	}
 
 	class Foo
 }