Support autowiring by constructor in Kotlin bean DSL

Issue: SPR-16014

Author: sdeleuze

spring-context/src/main/kotlin/org/springframework/context/support/BeanDefinitionDsl.kt

@@ -17,6 +17,7 @@
 package org.springframework.context.support
 
 import org.springframework.beans.factory.config.BeanDefinitionCustomizer
+import org.springframework.beans.factory.support.AbstractBeanDefinition
 import org.springframework.context.ApplicationContextInitializer
 import org.springframework.core.env.ConfigurableEnvironment
 import java.util.function.Supplier
@@ -29,9 +30,7 @@ import java.util.function.Supplier
  * ```
  * beans {
  * 	bean<UserHandler>()
- * 	bean {
- * 		Routes(ref(), ref())
- * 	}
+ * 	bean<Routes>()
  * 	bean<WebHandler>("webHandler") {
  * 	RouterFunctions.toWebHandler(
  * 		ref<Routes>().router(),
@@ -100,6 +99,35 @@ open class BeanDefinitionDsl(private val condition: (ConfigurableEnvironment) ->
 		PROTOTYPE
 	}
 
+	/**
+	 * Autowire enum constants.
+	 */
+	enum class Autowire {
+
+		/**
+		 * Autowire constant that indicates no externally defined autowiring
+		 * @see org.springframework.beans.factory.config.AutowireCapableBeanFactory.AUTOWIRE_NO
+		 */
+		NO,
+		/**
+		 * Autowire constant that indicates autowiring bean properties by name
+		 * @see org.springframework.beans.factory.config.AutowireCapableBeanFactory.AUTOWIRE_BY_NAME
+		 */
+		BY_NAME,
+		/**
+		 * Autowire constant that indicates autowiring bean properties by type
+		 * @see org.springframework.beans.factory.config.AutowireCapableBeanFactory.AUTOWIRE_BY_TYPE
+		 */
+		BY_TYPE,
+
+		/**
+		 * Autowire constant that indicates autowiring the greediest constructor that can be satisfied
+		 * @see org.springframework.beans.factory.config.AutowireCapableBeanFactory.AUTOWIRE_CONSTRUCTOR
+		 */
+		CONSTRUCTOR
+
+	}
+
 	/**
 	 * Provide read access to some application context facilities.
 	 * @constructor Create a new bean definition context.
@@ -134,6 +162,7 @@ open class BeanDefinitionDsl(private val condition: (ConfigurableEnvironment) ->
 	 * @param scope Override the target scope of this bean, specifying a new scope name.
 	 * @param isLazyInit Set whether this bean should be lazily initialized.
 	 * @param isPrimary Set whether this bean is a primary autowire candidate.
+	 * @param autowireMode Set the autowire mode, `Autowire.CONSTRUCTOR` by default
 	 * @param isAutowireCandidate Set whether this bean is a candidate for getting autowired into some other bean.
 	 * @see GenericApplicationContext.registerBean
 	 * @see org.springframework.beans.factory.config.BeanDefinition
@@ -142,6 +171,7 @@ open class BeanDefinitionDsl(private val condition: (ConfigurableEnvironment) ->
 									  scope: Scope? = null,
 									  isLazyInit: Boolean? = null,
 									  isPrimary: Boolean? = null,
+									  autowireMode: Autowire = Autowire.CONSTRUCTOR,
 									  isAutowireCandidate: Boolean? = null) {
 
 		registrations.add {
@@ -150,6 +180,9 @@ open class BeanDefinitionDsl(private val condition: (ConfigurableEnvironment) ->
 				isLazyInit?.let { bd.isLazyInit = isLazyInit }
 				isPrimary?.let { bd.isPrimary = isPrimary }
 				isAutowireCandidate?.let { bd.isAutowireCandidate = isAutowireCandidate }
+				if (bd is AbstractBeanDefinition) {
+					bd.autowireMode = autowireMode.ordinal
+				}
 			}
 
 			when (name) {
@@ -162,12 +195,21 @@ open class BeanDefinitionDsl(private val condition: (ConfigurableEnvironment) ->
 	/**
 	 * Declare a bean definition using the given supplier for obtaining a new instance.
 	 *
+	 * @param name the name of the bean
+	 * @param scope Override the target scope of this bean, specifying a new scope name.
+	 * @param isLazyInit Set whether this bean should be lazily initialized.
+	 * @param isPrimary Set whether this bean is a primary autowire candidate.
+	 * @param autowireMode Set the autowire mode, `Autowire.NO` by default
+	 * @param isAutowireCandidate Set whether this bean is a candidate for getting autowired into some other bean.
+	 * @param function the bean supplier function
 	 * @see GenericApplicationContext.registerBean
+	 * @see org.springframework.beans.factory.config.BeanDefinition
 	 */
 	inline fun <reified T : Any> bean(name: String? = null,
 									  scope: Scope? = null,
 									  isLazyInit: Boolean? = null,
 									  isPrimary: Boolean? = null,
+									  autowireMode: Autowire = Autowire.NO,
 									  isAutowireCandidate: Boolean? = null,
 									  crossinline function: BeanDefinitionContext.() -> T) {
 
@@ -176,6 +218,9 @@ open class BeanDefinitionDsl(private val condition: (ConfigurableEnvironment) ->
 			isLazyInit?.let { bd.isLazyInit = isLazyInit }
 			isPrimary?.let { bd.isPrimary = isPrimary }
 			isAutowireCandidate?.let { bd.isAutowireCandidate = isAutowireCandidate }
+			if (bd is AbstractBeanDefinition) {
+				bd.autowireMode = autowireMode.ordinal
+			}
 		}
 
 		registrations.add {

src/docs/asciidoc/kotlin.adoc

@@ -192,9 +192,7 @@ how beans are registered.
 ----
 fun beans() = beans {
   bean<UserHandler>()
-  bean {
-    Routes(ref(), ref())
-  }
+  bean<Routes>()
   bean<WebHandler>("webHandler") {
     RouterFunctions.toWebHandler(
       ref<Routes>().router(),
@@ -222,9 +220,7 @@ fun beans() = beans {
 }
 ----
 
-In this example, `Routes(ref(), ref())` is the equivalent of `Routes(ref<UserHandler>(), ref<MessageSource>())`
-(types are not required thanks to Kotlin type inference) where `ref<UserHandler>()`
-is a shortcut for `applicationContext.getBean(UserHandler::class.java)`.
+In this example, `ref<Routes>()` is a shortcut for `applicationContext.getBean(Routes::class.java)`.
 
 This `beans()` function can then be used to register beans on the application context.
 
@@ -242,7 +238,7 @@ This DSL is programmatic, thus it allows custom registration logic of beans
 via an `if` expression, a `for` loop or any other Kotlin constructs.
 ====
 
-See https://github.com/sdeleuze/spring-kotlin-functional/blob/3d12ab102c28f4761bd6a0736e2f585713eb2243/src/main/kotlin/functional/Beans.kt[spring-kotlin-functional beans declaration]
+See https://github.com/sdeleuze/spring-kotlin-functional/blob/master/src/main/kotlin/functional/Beans.kt[spring-kotlin-functional beans declaration]
 for a concrete example.
 
 [NOTE]