Autodetect Kotlin nullability for optional injection points (analogous to java.util.Optional)

Built-in support in MethodParameter and DependencyDescriptor supersedes our separate KotlinUtils helper.

Issue: SPR-14951

spring-beans/src/test/kotlin/org/springframework/beans/factory/annotation/KotlinAutowiredTests.kt

@@ -0,0 +1,87 @@
+/*
+ * Copyright 2002-2016 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.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.beans.factory.annotation
+
+import java.lang.reflect.Method
+
+import org.junit.Before
+import org.junit.Test
+
+import org.springframework.beans.factory.annotation.Autowired
+import org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor
+import org.springframework.beans.factory.support.DefaultListableBeanFactory
+import org.springframework.beans.factory.support.RootBeanDefinition
+import org.springframework.tests.sample.beans.TestBean
+
+import org.junit.Assert.*
+
+/**
+ * Tests for Kotlin support with [@Autowired].
+ *
+ * @author Juergen Hoeller
+ */
+class KotlinAutowiredTests {
+
+	@Test
+	fun autowiringWithTarget() {
+		var bf = DefaultListableBeanFactory()
+		var bpp = AutowiredAnnotationBeanPostProcessor()
+		bpp.setBeanFactory(bf)
+		bf.addBeanPostProcessor(bpp)
+		var bd = RootBeanDefinition(KotlinBean::class.java)
+		bd.setScope(RootBeanDefinition.SCOPE_PROTOTYPE)
+		bf.registerBeanDefinition("annotatedBean", bd)
+		var tb = TestBean()
+		bf.registerSingleton("testBean", tb)
+
+		var kb = bf.getBean("annotatedBean", KotlinBean::class.java)
+		assertSame(tb, kb.injectedFromConstructor)
+		assertSame(tb, kb.injectedFromMethod)
+		assertSame(tb, kb.injectedField)
+	}
+
+	@Test
+	fun autowiringWithoutTarget() {
+		var bf = DefaultListableBeanFactory()
+		var bpp = AutowiredAnnotationBeanPostProcessor()
+		bpp.setBeanFactory(bf)
+		bf.addBeanPostProcessor(bpp)
+		var bd = RootBeanDefinition(KotlinBean::class.java)
+		bd.setScope(RootBeanDefinition.SCOPE_PROTOTYPE)
+		bf.registerBeanDefinition("annotatedBean", bd)
+
+		var kb = bf.getBean("annotatedBean", KotlinBean::class.java)
+		assertNull(kb.injectedFromConstructor)
+		assertNull(kb.injectedFromMethod)
+		assertNull(kb.injectedField)
+	}
+
+
+	class KotlinBean(val injectedFromConstructor: TestBean?) {
+
+		var injectedFromMethod: TestBean? = null
+
+		@Autowired
+		var injectedField: TestBean? = null
+
+		@Autowired
+		fun injectedMethod(p1: TestBean?) {
+			injectedFromMethod = p1
+		}
+	}
+
+}