Fix RestOperations extensions parameters nullability

Issue: SPR-16328

spring-web/src/main/kotlin/org/springframework/web/client/RestOperationsExtensions.kt

@@ -115,7 +115,8 @@ inline fun <reified T: Any> RestOperations.getForEntity(url: String, uriVariable
  * @since 5.0.2
  */
 @Throws(RestClientException::class)
-inline fun <reified T: Any> RestOperations.patchForObject(url: String, request: Any, vararg uriVariables: Any): T? =
+inline fun <reified T: Any> RestOperations.patchForObject(url: String, request: Any? = null,
+														  vararg uriVariables: Any): T? =
 		patchForObject(url, request, T::class.java, *uriVariables)
 
 /**
@@ -128,7 +129,8 @@ inline fun <reified T: Any> RestOperations.patchForObject(url: String, request:
  * @since 5.0.2
  */
 @Throws(RestClientException::class)
-inline fun <reified T: Any> RestOperations.patchForObject(url: String, request: Any, uriVariables: Map<String, *>): T? =
+inline fun <reified T: Any> RestOperations.patchForObject(url: String, request: Any? = null,
+														  uriVariables: Map<String, *>): T? =
 		patchForObject(url, request, T::class.java, uriVariables)
 
 /**
@@ -141,7 +143,7 @@ inline fun <reified T: Any> RestOperations.patchForObject(url: String, request:
  * @since 5.0.2
  */
 @Throws(RestClientException::class)
-inline fun <reified T: Any> RestOperations.patchForObject(url: URI, request: Any): T? =
+inline fun <reified T: Any> RestOperations.patchForObject(url: URI, request: Any? = null): T? =
 		patchForObject(url, request, T::class.java)
 
 /**
@@ -155,7 +157,8 @@ inline fun <reified T: Any> RestOperations.patchForObject(url: URI, request: Any
  * @since 5.0
  */
 @Throws(RestClientException::class)
-inline fun <reified T: Any> RestOperations.postForObject(url: String, request: Any, vararg uriVariables: Any): T? =
+inline fun <reified T: Any> RestOperations.postForObject(url: String, request: Any? = null,
+														 vararg uriVariables: Any): T? =
 		postForObject(url, request, T::class.java, *uriVariables)
 
 /**
@@ -169,7 +172,8 @@ inline fun <reified T: Any> RestOperations.postForObject(url: String, request: A
  * @since 5.0
  */
 @Throws(RestClientException::class)
-inline fun <reified T: Any> RestOperations.postForObject(url: String, request: Any, uriVariables: Map<String, *>): T? =
+inline fun <reified T: Any> RestOperations.postForObject(url: String, request: Any? = null,
+														 uriVariables: Map<String, *>): T? =
 		postForObject(url, request, T::class.java, uriVariables)
 
 /**
@@ -183,7 +187,7 @@ inline fun <reified T: Any> RestOperations.postForObject(url: String, request: A
  * @since 5.0
  */
 @Throws(RestClientException::class)
-inline fun <reified T: Any> RestOperations.postForObject(url: URI, request: Any): T? =
+inline fun <reified T: Any> RestOperations.postForObject(url: URI, request: Any? = null): T? =
 		postForObject(url, request, T::class.java)
 
 /**
@@ -197,7 +201,7 @@ inline fun <reified T: Any> RestOperations.postForObject(url: URI, request: Any)
  * @since 5.0
  */
 @Throws(RestClientException::class)
-inline fun <reified T: Any> RestOperations.postForEntity(url: String, request: Any,
+inline fun <reified T: Any> RestOperations.postForEntity(url: String, request: Any? = null,
 		vararg uriVariables: Any): ResponseEntity<T> =
 		postForEntity(url, request, T::class.java, *uriVariables)
 
@@ -212,7 +216,7 @@ inline fun <reified T: Any> RestOperations.postForEntity(url: String, request: A
  * @since 5.0
  */
 @Throws(RestClientException::class)
-inline fun <reified T: Any> RestOperations.postForEntity(url: String, request: Any,
+inline fun <reified T: Any> RestOperations.postForEntity(url: String, request: Any? = null,
 		uriVariables: Map<String, *>): ResponseEntity<T> =
 		postForEntity(url, request, T::class.java, uriVariables)
 
@@ -227,7 +231,7 @@ inline fun <reified T: Any> RestOperations.postForEntity(url: String, request: A
  * @since 5.0
  */
 @Throws(RestClientException::class)
-inline fun <reified T: Any> RestOperations.postForEntity(url: URI, request: Any): ResponseEntity<T> =
+inline fun <reified T: Any> RestOperations.postForEntity(url: URI, request: Any? = null): ResponseEntity<T> =
 		postForEntity(url, request, T::class.java)
 
 /**
@@ -241,7 +245,7 @@ inline fun <reified T: Any> RestOperations.postForEntity(url: URI, request: Any)
  */
 @Throws(RestClientException::class)
 inline fun <reified T: Any> RestOperations.exchange(url: String, method: HttpMethod,
-		requestEntity: HttpEntity<*>, vararg uriVariables: Any): ResponseEntity<T> =
+		requestEntity: HttpEntity<*>? = null, vararg uriVariables: Any): ResponseEntity<T> =
 		exchange(url, method, requestEntity, object : ParameterizedTypeReference<T>() {}, *uriVariables)
 
 /**
@@ -255,7 +259,7 @@ inline fun <reified T: Any> RestOperations.exchange(url: String, method: HttpMet
  */
 @Throws(RestClientException::class)
 inline fun <reified T: Any> RestOperations.exchange(url: String, method: HttpMethod,
-		requestEntity: HttpEntity<*>, uriVariables: Map<String, *>): ResponseEntity<T> =
+		requestEntity: HttpEntity<*>? = null, uriVariables: Map<String, *>): ResponseEntity<T> =
 		exchange(url, method, requestEntity, object : ParameterizedTypeReference<T>() {}, uriVariables)
 
 /**
@@ -269,7 +273,7 @@ inline fun <reified T: Any> RestOperations.exchange(url: String, method: HttpMet
  */
 @Throws(RestClientException::class)
 inline fun <reified T: Any> RestOperations.exchange(url: URI, method: HttpMethod,
-		requestEntity: HttpEntity<*>): ResponseEntity<T> =
+		requestEntity: HttpEntity<*>? = null): ResponseEntity<T> =
 		exchange(url, method, requestEntity, object : ParameterizedTypeReference<T>() {})
 
 /**

spring-web/src/test/kotlin/org/springframework/web/client/RestOperationsExtensionsTests.kt

@@ -112,13 +112,20 @@ class RestOperationsExtensionsTests {
 	}
 
 	@Test
-	fun `patchForObject with reified type parameters`() {
+	fun `patchForObject with reified type parameters and String`() {
 		val url = "https://spring.io"
 		val body: Any = "body"
 		template.patchForObject<Foo>(url, body)
 		verify(template, times(1)).patchForObject(url, body, Foo::class.java)
 	}
 
+	@Test
+	fun `patchForObject with reified type parameters`() {
+		val url = "https://spring.io"
+		template.patchForObject<Foo>(url)
+		verify(template, times(1)).patchForObject(url, null, Foo::class.java)
+	}
+
 	@Test
 	fun `postForObject with reified type parameters, String and varargs`() {
 		val url = "https://spring.io"
@@ -139,13 +146,20 @@ class RestOperationsExtensionsTests {
 	}
 
 	@Test
-	fun `postForObject with reified type parameters`() {
+	fun `postForObject with reified type parameters and String`() {
 		val url = "https://spring.io"
 		val body: Any = "body"
 		template.postForObject<Foo>(url, body)
 		verify(template, times(1)).postForObject(url, body, Foo::class.java)
 	}
 
+	@Test
+	fun `postForObject with reified type parameters`() {
+		val url = "https://spring.io"
+		template.postForObject<Foo>(url)
+		verify(template, times(1)).postForObject(url, null, Foo::class.java)
+	}
+
 	@Test
 	fun `postForEntity with reified type parameters, String and varargs`() {
 		val url = "https://spring.io"
@@ -166,13 +180,20 @@ class RestOperationsExtensionsTests {
 	}
 
 	@Test
-	fun `postForEntity with reified type parameters`() {
+	fun `postForEntity with reified type parameters and String`() {
 		val url = "https://spring.io"
 		val body: Any = "body"
 		template.postForEntity<Foo>(url, body)
 		verify(template, times(1)).postForEntity(url, body, Foo::class.java)
 	}
 
+	@Test
+	fun `postForEntity with reified type parameters`() {
+		val url = "https://spring.io"
+		template.postForEntity<Foo>(url)
+		verify(template, times(1)).postForEntity(url, null, Foo::class.java)
+	}
+
 	@Test
 	fun `exchange with reified type parameters, String, HttpMethod, HttpEntity and varargs`() {
 		val url = "https://spring.io"
@@ -197,7 +218,7 @@ class RestOperationsExtensionsTests {
 	}
 
 	@Test
-	fun `exchange with reified type parameters, String, HttpMethod, HttpEntity`() {
+	fun `exchange with reified type parameters, String, HttpMethod and HttpEntity`() {
 		val url = "https://spring.io"
 		val method = HttpMethod.GET
 		val entity = mock<HttpEntity<Foo>>()
@@ -207,7 +228,16 @@ class RestOperationsExtensionsTests {
 	}
 
 	@Test
-	fun `exchange with reified type parameters, String, HttpEntity`() {
+	fun `exchange with reified type parameters, String and HttpMethod`() {
+		val url = "https://spring.io"
+		val method = HttpMethod.GET
+		template.exchange<List<Foo>>(url, method)
+		verify(template, times(1)).exchange(url, method, null,
+				object : ParameterizedTypeReference<List<Foo>>() {})
+	}
+
+	@Test
+	fun `exchange with reified type parameters, String and HttpEntity`() {
 		val entity = mock<RequestEntity<Foo>>()
 		template.exchange<List<Foo>>(entity)
 		verify(template, times(1)).exchange(entity,