Fix JdbcOperations Kotlin extensions

This commit updates JdbcOperationsExtensions.kt to:
 - Properly use the spread operator for invoking Java methods with
   a varargs parameter
 - Align JdbcOperationsExtensions return values nullability
   with the Java API (breaking change)
 - Use varargs where Java counterpart does (breaking change, undo some
   changes from gh-34668)
 - Use nullable args instead of non-nullable ones

 Closes gh-35846

spring-jdbc/src/main/kotlin/org/springframework/jdbc/core/JdbcOperationsExtensions.kt

@@ -24,8 +24,8 @@ import java.sql.ResultSet
  * @author Mario Arias
  * @since 5.0
  */
-inline fun <reified T> JdbcOperations.queryForObject(sql: String): T =
-		queryForObject(sql, T::class.java as Class<*>) as T
+inline fun <reified T : Any> JdbcOperations.queryForObject(sql: String): T? =
+		queryForObject(sql, T::class.java)
 
 /**
  * Extensions for [JdbcOperations.queryForObject] providing a RowMapper-like function
@@ -34,7 +34,7 @@ inline fun <reified T> JdbcOperations.queryForObject(sql: String): T =
  * @author Mario Arias
  * @since 5.0
  */
-inline fun <reified T> JdbcOperations.queryForObject(sql: String, vararg args: Any, crossinline function: (ResultSet, Int) -> T): T =
+inline fun <reified T> JdbcOperations.queryForObject(sql: String, vararg args: Any?, crossinline function: (ResultSet, Int) -> T): T =
 		queryForObject(sql, { resultSet, i -> function(resultSet, i) }, *args)
 
 /**
@@ -44,18 +44,18 @@ inline fun <reified T> JdbcOperations.queryForObject(sql: String, vararg args: A
  * @author Mario Arias
  * @since 5.0
  */
-inline fun <reified T> JdbcOperations.queryForObject(sql: String, args: Array<out Any>, argTypes: IntArray): T =
-		queryForObject(sql, args, argTypes, T::class.java as Class<*>) as T
+inline fun <reified T : Any> JdbcOperations.queryForObject(sql: String, args: Array<out Any?>, argTypes: IntArray): T? =
+		queryForObject(sql, args, argTypes, T::class.java)
 
 /**
  * Extension for [JdbcOperations.queryForObject] providing a
- * `queryForObject<Foo>("...", arrayOf(arg1, argN))` variant.
+ * `queryForObject<Foo>("...", arg1, argN)` variant.
  *
- * @author Mario Arias
- * @since 5.0
+ * @author Sébastien Deleuze
+ * @since 7.0
  */
-inline fun <reified T> JdbcOperations.queryForObject(sql: String, args: Array<out Any>): T =
-		queryForObject(sql, T::class.java as Class<*>, args) as T
+inline fun <reified T : Any> JdbcOperations.queryForObject(sql: String, vararg args: Any?): T? =
+		queryForObject(sql, T::class.java, *args)
 
 /**
  * Extension for [JdbcOperations.queryForList] providing a `queryForList<Foo>("...")` variant.
@@ -63,9 +63,8 @@ inline fun <reified T> JdbcOperations.queryForObject(sql: String, args: Array<ou
  * @author Mario Arias
  * @since 5.0
  */
-@Suppress("UNCHECKED_CAST")
-inline fun <reified T> JdbcOperations.queryForList(sql: String): List<T> =
-		queryForList(sql, T::class.java) as List<T>
+inline fun <reified T : Any> JdbcOperations.queryForList(sql: String): List<T?> =
+		queryForList(sql, T::class.java)
 
 /**
  * Extension for [JdbcOperations.queryForList] providing a
@@ -74,21 +73,19 @@ inline fun <reified T> JdbcOperations.queryForList(sql: String): List<T> =
  * @author Mario Arias
  * @since 5.0
  */
-@Suppress("UNCHECKED_CAST")
-inline fun <reified T> JdbcOperations.queryForList(sql: String, args: Array<out Any>,
-												   argTypes: IntArray): List<T> =
-		queryForList(sql, args, argTypes, T::class.java) as List<T>
+inline fun <reified T : Any> JdbcOperations.queryForList(sql: String, args: Array<out Any?>,
+												   argTypes: IntArray): List<T?> =
+		queryForList(sql, args, argTypes, T::class.java)
 
 /**
  * Extension for [JdbcOperations.queryForList] providing a
- * `queryForList<Foo>("...", arrayOf(arg1, argN))` variant.
+ * `queryForList<Foo>("...", arg1, argN)` variant.
  *
- * @author Mario Arias
- * @since 5.0
+ * @author Sebastien Deleuze
+ * @since 7.0
  */
-@Suppress("UNCHECKED_CAST")
-inline fun <reified T> JdbcOperations.queryForList(sql: String, args: Array<out Any>): List<T> =
-		queryForList(sql, T::class.java, args) as List<T>
+inline fun <reified T : Any> JdbcOperations.queryForList(sql: String, vararg args: Any?): List<T?> =
+		queryForList(sql, T::class.java, *args)
 
 
 /**
@@ -98,7 +95,7 @@ inline fun <reified T> JdbcOperations.queryForList(sql: String, args: Array<out
  * @author Mario Arias
  * @since 5.0
  */
-fun <T> JdbcOperations.query(sql: String, vararg args: Any,
+fun <T> JdbcOperations.query(sql: String, vararg args: Any?,
 		function: (ResultSet) -> T): T =
 		query(sql, ResultSetExtractor { function(it) }, *args)
 
@@ -109,7 +106,7 @@ fun <T> JdbcOperations.query(sql: String, vararg args: Any,
  * @author Mario Arias
  * @since 5.0
  */
-fun JdbcOperations.query(sql: String, vararg args: Any, function: (ResultSet) -> Unit): Unit =
+fun JdbcOperations.query(sql: String, vararg args: Any?, function: (ResultSet) -> Unit): Unit =
 		query(sql, { function(it) }, *args)
 
 /**
@@ -119,5 +116,5 @@ fun JdbcOperations.query(sql: String, vararg args: Any, function: (ResultSet) ->
  * @author Mario Arias
  * @since 5.0
  */
-fun <T> JdbcOperations.query(sql: String, vararg args: Any, function: (ResultSet, Int) -> T): List<T> =
+fun <T> JdbcOperations.query(sql: String, vararg args: Any?, function: (ResultSet, Int) -> T): List<T> =
 		query(sql, { rs, i -> function(rs, i) }, *args)

spring-jdbc/src/test/kotlin/org/springframework/jdbc/core/JdbcOperationsExtensionsTests.kt

@@ -46,7 +46,7 @@ class JdbcOperationsExtensionsTests {
 	@Test
 	fun `queryForObject with nullable reified type parameters`() {
 		every { template.queryForObject(sql, any<Class<Int>>()) } returns null
-		assertThat(template.queryForObject<Int?>(sql)).isNull()
+		assertThat(template.queryForObject<Int>(sql)).isNull()
 		verify { template.queryForObject(sql, any<Class<Int>>()) }
 	}
 
@@ -65,8 +65,17 @@ class JdbcOperationsExtensionsTests {
 	}
 
 	@Test
-	fun `queryForObject with reified type parameters and argTypes`() {
-		val args = arrayOf(3)
+	fun `queryForObject with reified type parameters, non-null args array and argTypes`() {
+		val args = arrayOf(3, 4)
+		val argTypes = intArrayOf(JDBCType.INTEGER.vendorTypeNumber)
+		every { template.queryForObject(sql, args, argTypes, any<Class<Int>>()) } returns 2
+		assertThat(template.queryForObject<Int>(sql, args, argTypes)).isEqualTo(2)
+		verify { template.queryForObject(sql, args, argTypes, any<Class<Int>>()) }
+	}
+
+	@Test
+	fun `queryForObject with reified type parameters, nullable args array and argTypes`() {
+		val args = arrayOf(3, null)
 		val argTypes = intArrayOf(JDBCType.INTEGER.vendorTypeNumber)
 		every { template.queryForObject(sql, args, argTypes, any<Class<Int>>()) } returns 2
 		assertThat(template.queryForObject<Int>(sql, args, argTypes)).isEqualTo(2)
@@ -78,24 +87,22 @@ class JdbcOperationsExtensionsTests {
 		val args = arrayOf(3)
 		val argTypes = intArrayOf(JDBCType.INTEGER.vendorTypeNumber)
 		every { template.queryForObject(sql, args, argTypes, any<Class<Int>>()) } returns null
-		assertThat(template.queryForObject<Int?>(sql, args, argTypes)).isNull()
+		assertThat(template.queryForObject<Int>(sql, args, argTypes)).isNull()
 		verify { template.queryForObject(sql, args, argTypes, any<Class<Int>>()) }
 	}
 
 	@Test
 	fun `queryForObject with reified type parameters and args`() {
-		val args = arrayOf(3, 4)
-		every { template.queryForObject(sql, any<Class<Int>>(), args) } returns 2
-		assertThat(template.queryForObject<Int>(sql, args)).isEqualTo(2)
-		verify { template.queryForObject(sql, any<Class<Int>>(), args) }
+		every { template.queryForObject(sql, any<Class<Int>>(), 3, null) } returns 2
+		assertThat(template.queryForObject<Int>(sql, 3, null)).isEqualTo(2)
+		verify { template.queryForObject(sql, any<Class<Int>>(), 3, null) }
 	}
 
 	@Test
 	fun `queryForObject with nullable reified type parameters and args`() {
-		val args = arrayOf(3, 4)
-		every { template.queryForObject(sql, any<Class<Int>>(), args) } returns null
-		assertThat(template.queryForObject<Int?>(sql, args)).isNull()
-		verify { template.queryForObject(sql, any<Class<Int>>(), args) }
+		every { template.queryForObject(sql, any<Class<Int>>(), 3, 4) } returns null
+		assertThat(template.queryForObject<Int>(sql, 3, 4)).isNull()
+		verify { template.queryForObject(sql, any<Class<Int>>(), 3, 4) }
 	}
 
 	@Test
@@ -110,12 +117,12 @@ class JdbcOperationsExtensionsTests {
 	fun `queryForList with nullable reified type parameters`() {
 		val list = listOf(1, null, 3)
 		every { template.queryForList(sql, any<Class<Int>>()) } returns list
-		assertThat(template.queryForList<Int?>(sql)).isEqualTo(list)
+		assertThat(template.queryForList<Int>(sql)).isEqualTo(list)
 		verify { template.queryForList(sql, any<Class<Int>>()) }
 	}
 
 	@Test
-	fun `queryForList with reified type parameters and argTypes`() {
+	fun `queryForList with reified type parameters, non-null args and argTypes`() {
 		val list = listOf(1, 2, 3)
 		val args = arrayOf(3)
 		val argTypes = intArrayOf(JDBCType.INTEGER.vendorTypeNumber)
@@ -125,31 +132,49 @@ class JdbcOperationsExtensionsTests {
 	}
 
 	@Test
-	fun `queryForList with nullable reified type parameters and argTypes`() {
+	fun `queryForList with reified type parameters, nullable args and argTypes`() {
+		val list = listOf(1, 2, 3)
+		val args = arrayOf("foo", null)
+		val argTypes = intArrayOf(JDBCType.VARCHAR.vendorTypeNumber)
+		every { template.queryForList(sql, args, argTypes, any<Class<Int>>()) } returns list
+		assertThat(template.queryForList<Int>(sql, args, argTypes)).isEqualTo(list)
+		verify { template.queryForList(sql, args, argTypes, any<Class<Int>>()) }
+	}
+
+	@Test
+	fun `queryForList with nullable reified type parameters, non-null args and argTypes`() {
 		val list = listOf(1, null, 3)
 		val args = arrayOf(3)
 		val argTypes = intArrayOf(JDBCType.INTEGER.vendorTypeNumber)
 		every { template.queryForList(sql, args, argTypes, any<Class<Int>>()) } returns list
-		assertThat(template.queryForList<Int?>(sql, args, argTypes)).isEqualTo(list)
+		assertThat(template.queryForList<Int>(sql, args, argTypes)).isEqualTo(list)
+		verify { template.queryForList(sql, args, argTypes, any<Class<Int>>()) }
+	}
+
+	@Test
+	fun `queryForList with nullable reified type parameters, nullable args and argTypes`() {
+		val list = listOf(1, null, 3)
+		val args = arrayOf("foo", null)
+		val argTypes = intArrayOf(JDBCType.VARCHAR.vendorTypeNumber)
+		every { template.queryForList(sql, args, argTypes, any<Class<Int>>()) } returns list
+		assertThat(template.queryForList<Int>(sql, args, argTypes)).isEqualTo(list)
 		verify { template.queryForList(sql, args, argTypes, any<Class<Int>>()) }
 	}
 
 	@Test
 	fun `queryForList with reified type parameters and args`() {
 		val list = listOf(1, 2, 3)
-		val args = arrayOf(3, 4)
-		every { template.queryForList(sql, any<Class<Int>>(), args) } returns list
-		template.queryForList<Int>(sql, args)
-		verify { template.queryForList(sql, any<Class<Int>>(), args) }
+		every { template.queryForList(sql, any<Class<Int>>(), 3, null) } returns list
+		template.queryForList<Int>(sql, 3, null)
+		verify { template.queryForList(sql, any<Class<Int>>(), 3, null) }
 	}
 
 	@Test
 	fun `queryForList with nullable reified type parameters and args`() {
 		val list = listOf(1, null, 3)
-		val args = arrayOf(3, 4)
-		every { template.queryForList(sql, any<Class<Int>>(), args) } returns list
-		template.queryForList<Int?>(sql, args)
-		verify { template.queryForList(sql, any<Class<Int>>(), args) }
+		every { template.queryForList(sql, any<Class<Int>>(), 3, null) } returns list
+		template.queryForList<Int>(sql, 3, null)
+		verify { template.queryForList(sql, any<Class<Int>>(), 3, null) }
 	}
 
 	@Test