Revisit PropertyResolver Kotlin extensions

Issue: SPR-16883

spring-context/src/test/kotlin/org/springframework/context/support/BeanDefinitionDslTests.kt

@@ -82,7 +82,7 @@ class BeanDefinitionDslTests {
 		val beans = beans {
 			bean<Foo>()
 			bean<Bar>("bar")
-			bean { FooFoo(env["name"]) }
+			bean { FooFoo(env["name"]!!) }
 			environment( { activeProfiles.contains("baz") } ) {
 				bean { Baz(ref()) }
 				bean { Baz(ref("bar")) }
@@ -109,7 +109,7 @@ class BeanDefinitionDslTests {
 	@Test  // SPR-16412
 	fun `Declare beans depending on environment properties`() {
 		val beans = beans {
-			val n = env["number-of-beans"].toInt()
+			val n = env["number-of-beans"]!!.toInt()
 			for (i in 1..n) {
 				bean("string$i") { Foo() }
 			}

spring-core/src/main/kotlin/org/springframework/core/env/PropertyResolverExtensions.kt

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2017 the original author or authors.
+ * Copyright 2002-2018 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -14,16 +14,40 @@
  * limitations under the License.
  */
 
+@file:Suppress("EXTENSION_SHADOWED_BY_MEMBER")
+
 package org.springframework.core.env
 
 /**
- * Extension for [PropertyResolver.getRequiredProperty] providing Array like getter.
+ * Extension for [PropertyResolver.getProperty] providing Array like getter returning a
+ * nullable [String].
  *
  * ```kotlin
- * env["name"] = "Seb"
+ * val name = env["name"] ?: "Seb"
  * ```
  *
  * @author Sebastien Deleuze
  * @since 5.0
  */
-operator fun PropertyResolver.get(key: String) : String = getRequiredProperty(key)
+operator fun PropertyResolver.get(key: String) : String? = getProperty(key)
+
+
+/**
+ * Extension for [PropertyResolver.getProperty] providing a `getProperty<Foo>(...)`
+ * variant returning a nullable [String].
+ *
+ * @author Sebastien Deleuze
+ * @since 5.1
+ */
+inline fun <reified T: Any?> PropertyResolver.getProperty(key: String) : T? =
+		getProperty(key, T::class.java)
+
+/**
+ * Extension for [PropertyResolver.getRequiredProperty] providing a
+ * `getRequiredProperty<Foo>(...)` variant.
+ *
+ * @author Sebastien Deleuze
+ * @since 5.1
+ */
+inline fun <reified T: Any> PropertyResolver.getRequiredProperty(key: String) : T =
+		getRequiredProperty(key, T::class.java)

spring-core/src/test/kotlin/org/springframework/core/env/PropertyResolverExtensionsTests.kt

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2017 the original author or authors.
+ * Copyright 2002-2018 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -16,9 +16,12 @@
 
 package org.springframework.core.env
 
+import com.nhaarman.mockito_kotlin.any
+import com.nhaarman.mockito_kotlin.whenever
 import org.junit.Test
 import org.junit.runner.RunWith
 import org.mockito.Answers
+import org.mockito.ArgumentMatchers.eq
 import org.mockito.Mock
 import org.mockito.Mockito
 import org.mockito.junit.MockitoJUnitRunner
@@ -29,16 +32,30 @@ import org.mockito.junit.MockitoJUnitRunner
  * @author Sebastien Deleuze
  */
 @RunWith(MockitoJUnitRunner::class)
+@Suppress("UNUSED_VARIABLE")
 class PropertyResolverExtensionsTests {
 
 	@Mock(answer = Answers.RETURNS_MOCKS)
 	lateinit var propertyResolver: PropertyResolver
 
-	@Suppress("UNUSED_VARIABLE")
 	@Test
 	fun `get operator`() {
-		val name = propertyResolver["name"]
+		val name = propertyResolver["name"] ?: "foo"
-		Mockito.verify(propertyResolver, Mockito.times(1)).getRequiredProperty("name")
+		Mockito.verify(propertyResolver, Mockito.times(1)).getProperty("name")
+	}
+
+	@Test
+	fun `getProperty extension`() {
+		whenever(propertyResolver.getProperty(any(), eq(String::class.java))).thenReturn("foo")
+		val name = propertyResolver.getProperty<String>("name") ?: "foo"
+		Mockito.verify(propertyResolver, Mockito.times(1)).getProperty("name", String::class.java)
+	}
+
+	@Test
+	fun `getRequiredProperty extension`() {
+		whenever(propertyResolver.getRequiredProperty(any(), eq(String::class.java))).thenReturn("foo")
+		val name = propertyResolver.getRequiredProperty<String>("name")
+		Mockito.verify(propertyResolver, Mockito.times(1)).getRequiredProperty("name", String::class.java)
 	}
 
 }