Add support for Kotlin BeanPostProcessor beans

This commit adds support for Kotlin BeanPostProcessor beans which should
be defined in a companion object and annotated with `@JvmStatic`.

Closes gh-32946

Author: sdeleuze

framework-docs/modules/ROOT/pages/core/validation/beanvalidation.adoc

@@ -287,32 +287,7 @@ As the preceding example shows, a `ConstraintValidator` implementation can have
 You can integrate the method validation feature of Bean Validation into a
 Spring context through a `MethodValidationPostProcessor` bean definition:
 
-[tabs]
-======
-Java::
-+
-[source,java,indent=0,subs="verbatim,quotes",role="primary"]
-----
-	import org.springframework.validation.beanvalidation.MethodValidationPostProcessor;
-
-	@Configuration
-	public class AppConfig {
-
-		@Bean
-		public static MethodValidationPostProcessor validationPostProcessor() {
-			return new MethodValidationPostProcessor();
-		}
-	}
-
-----
-
-XML::
-+
-[source,xml,indent=0,subs="verbatim,quotes",role="secondary"]
-----
-	<bean class="org.springframework.validation.beanvalidation.MethodValidationPostProcessor"/>
-----
-======
+include-code::./ApplicationConfiguration[tag=snippet,indent=0]
 
 To be eligible for Spring-driven method validation, target classes need to be annotated
 with Spring's `@Validated` annotation, which can optionally also declare the validation
@@ -345,36 +320,7 @@ By default, `jakarta.validation.ConstraintViolationException` is raised with the
 you can have `MethodValidationException` raised instead with ``ConstraintViolation``s
 adapted to `MessageSourceResolvable` errors. To enable set the following flag:
 
-[tabs]
-======
-Java::
-+
-[source,java,indent=0,subs="verbatim,quotes",role="primary"]
-----
-	import org.springframework.validation.beanvalidation.MethodValidationPostProcessor;
-
-	@Configuration
-	public class AppConfig {
-
-		@Bean
-		public static MethodValidationPostProcessor validationPostProcessor() {
-			MethodValidationPostProcessor processor = new MethodValidationPostProcessor();
-			processor.setAdaptConstraintViolations(true);
-			return processor;
-		}
-	}
-
-----
-
-XML::
-+
-[source,xml,indent=0,subs="verbatim,quotes",role="secondary"]
-----
-	<bean class="org.springframework.validation.beanvalidation.MethodValidationPostProcessor">
-		<property name="adaptConstraintViolations" value="true"/>
-	</bean>
-----
-======
+include-code::./ApplicationConfiguration[tag=snippet,indent=0]
 
 `MethodValidationException` contains a list of ``ParameterValidationResult``s which
 group errors by method parameter, and each exposes a `MethodParameter`, the argument

framework-docs/src/main/java/org/springframework/docs/core/validation/validationbeanvalidationspringmethod/ApplicationConfiguration.java

@@ -0,0 +1,32 @@
+/*
+ * Copyright 2002-2024 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
+ *
+ *      https://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.docs.core.validation.validationbeanvalidationspringmethod;
+
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.validation.beanvalidation.MethodValidationPostProcessor;
+
+// tag::snippet[]
+@Configuration
+public class ApplicationConfiguration {
+
+	@Bean
+	public static MethodValidationPostProcessor validationPostProcessor() {
+		return new MethodValidationPostProcessor();
+	}
+}
+// end::snippet[]

framework-docs/src/main/java/org/springframework/docs/core/validation/validationbeanvalidationspringmethodexceptions/ApplicationConfiguration.java

@@ -0,0 +1,34 @@
+/*
+ * Copyright 2002-2024 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
+ *
+ *      https://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.docs.core.validation.validationbeanvalidationspringmethodexceptions;
+
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.validation.beanvalidation.MethodValidationPostProcessor;
+
+// tag::snippet[]
+@Configuration
+public class ApplicationConfiguration {
+
+	@Bean
+	public static MethodValidationPostProcessor validationPostProcessor() {
+		MethodValidationPostProcessor processor = new MethodValidationPostProcessor();
+		processor.setAdaptConstraintViolations(true);
+		return processor;
+	}
+}
+// end::snippet[]

framework-docs/src/main/kotlin/org/springframework/docs/core/validation/validationbeanvalidationspringmethod/ApplicationConfiguration.kt

@@ -0,0 +1,34 @@
+/*
+ * Copyright 2002-2024 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
+ *
+ *      https://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.docs.core.validation.validationbeanvalidationspringmethod
+
+import org.springframework.context.annotation.Bean
+import org.springframework.context.annotation.Configuration
+import org.springframework.validation.beanvalidation.MethodValidationPostProcessor
+
+// tag::snippet[]
+@Configuration
+class ApplicationConfiguration {
+
+	companion object {
+
+		@Bean
+		@JvmStatic
+		fun validationPostProcessor() = MethodValidationPostProcessor()
+	}
+}
+// end::snippet[]

framework-docs/src/main/kotlin/org/springframework/docs/core/validation/validationbeanvalidationspringmethodexceptions/ApplicationConfiguration.kt

@@ -0,0 +1,36 @@
+/*
+ * Copyright 2002-2024 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
+ *
+ *      https://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.docs.core.validation.validationbeanvalidationspringmethodexceptions
+
+import org.springframework.context.annotation.Bean
+import org.springframework.context.annotation.Configuration
+import org.springframework.validation.beanvalidation.MethodValidationPostProcessor
+
+// tag::snippet[]
+@Configuration
+class ApplicationConfiguration {
+
+	companion object {
+
+		@Bean
+		@JvmStatic
+		fun validationPostProcessor() = MethodValidationPostProcessor().apply {
+			setAdaptConstraintViolations(true)
+		}
+	}
+}
+// end::snippet[]

framework-docs/src/main/resources/org/springframework/docs/core/validation/validationbeanvalidationspringmethod/ApplicationConfiguration.xml

@@ -0,0 +1,11 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<beans xmlns="http://www.springframework.org/schema/beans"
+	   xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+	   xsi:schemaLocation="
+			http://www.springframework.org/schema/beans
+			https://www.springframework.org/schema/beans/spring-beans.xsd">
+
+	<!-- tag::snippet[] -->
+	<bean class="org.springframework.validation.beanvalidation.MethodValidationPostProcessor"/>
+	<!-- end::snippet[] -->
+</beans>

framework-docs/src/main/resources/org/springframework/docs/core/validation/validationbeanvalidationspringmethodexceptions/ApplicationConfiguration.xml

@@ -0,0 +1,13 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<beans xmlns="http://www.springframework.org/schema/beans"
+	   xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+	   xsi:schemaLocation="
+			http://www.springframework.org/schema/beans
+			https://www.springframework.org/schema/beans/spring-beans.xsd">
+
+	<!-- tag::snippet[] -->
+	<bean class="org.springframework.validation.beanvalidation.MethodValidationPostProcessor">
+		<property name="adaptConstraintViolations" value="true"/>
+	</bean>
+	<!-- end::snippet[] -->
+</beans>

spring-context/src/main/java/org/springframework/context/annotation/ConfigurationClassParser.java

@@ -360,6 +360,9 @@ protected final SourceClass doProcessConfigurationClass(
 		// Process individual @Bean methods
 		Set<MethodMetadata> beanMethods = retrieveBeanMethodMetadata(sourceClass);
 		for (MethodMetadata methodMetadata : beanMethods) {
+			if (methodMetadata.isAnnotated("kotlin.jvm.JvmStatic") && !methodMetadata.isStatic()) {
+				continue;
+			}
 			configClass.addBeanMethod(new BeanMethod(methodMetadata, configClass));
 		}
 

spring-context/src/test/kotlin/org/springframework/context/annotation/ConfigurationClassKotlinTests.kt

@@ -19,8 +19,10 @@ package org.springframework.context.annotation
 import org.assertj.core.api.Assertions.assertThat
 import org.assertj.core.api.Assertions.assertThatExceptionOfType
 import org.junit.jupiter.api.Test
+import org.springframework.beans.factory.config.BeanPostProcessor
 import org.springframework.beans.factory.getBean
 import org.springframework.beans.factory.parsing.BeanDefinitionParsingException
+import org.springframework.beans.factory.support.DefaultListableBeanFactory
 
 /**
  * Integration tests for Kotlin configuration classes.
@@ -43,6 +45,16 @@ class ConfigurationClassKotlinTests {
 		assertThat(context.getBean<Bar>().foo).isEqualTo(foo)
 	}
 
+	@Test
+	fun `Configuration with @JvmStatic registers a single bean`() {
+		val beanFactory = DefaultListableBeanFactory().apply {
+			isAllowBeanDefinitionOverriding = false
+		}
+		val context = AnnotationConfigApplicationContext(beanFactory)
+		context.register(ProcessorConfiguration::class.java)
+		context.refresh()
+	}
+
 
 	@Configuration
 	class FinalConfigurationWithProxy {
@@ -64,6 +76,19 @@ class ConfigurationClassKotlinTests {
 		fun bar(foo: Foo) = Bar(foo)
 	}
 
+	@Configuration
+	open class ProcessorConfiguration {
+
+		companion object {
+
+			@Bean
+			@JvmStatic
+			fun processor(): BeanPostProcessor {
+				return object: BeanPostProcessor{}
+			}
+		}
+	}
+
 	class Foo
 
 	class Bar(val foo: Foo)