Remove use of `@PostConstruct` from main code

When running on Java 11 (where `@PostConstruct` is no longer part of
the JRE) and without a dependency on jakarta-annotation-api,
`@PostContruct` annotions are silently dropped. This leads to obscure and
hard-to-track down changes in the behaviour of our auto-configuration
as the `@PostConstruct`-annotated methods are not invoked.

To allow users to run on Java 11 without having jakarta-annotation-api
on the classpath, this commit removes use of `@PostConstruct` from main
code. A Checkstyle rule has also been added to prevent its usage in
main code from being reintroduced.

Closes gh-23723

spring-boot-project/spring-boot-actuator-autoconfigure/src/main/java/org/springframework/boot/actuate/autoconfigure/endpoint/web/jersey/JerseyWebEndpointManagementContextConfiguration.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2019 the original author or authors.
+ * Copyright 2012-2020 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.
@@ -21,8 +21,6 @@ import java.util.Collection;
 import java.util.HashSet;
 import java.util.List;
 
-import javax.annotation.PostConstruct;
-
 import org.glassfish.jersey.server.ResourceConfig;
 import org.glassfish.jersey.server.model.Resource;
 
@@ -112,10 +110,10 @@ class JerseyWebEndpointManagementContextConfiguration {
 			this.mediaTypes = endpointMediaTypes;
 			this.basePath = basePath;
 			this.shouldRegisterLinks = shouldRegisterLinks;
+			register();
 		}
 
-		@PostConstruct
+		private void register() {
-		void register() {
 			// We can't easily use @ConditionalOnBean because @AutoConfigureBefore is
 			// not an option for management contexts. Instead we manually check if
 			// the resource config bean exists

spring-boot-project/spring-boot-actuator-autoconfigure/src/main/java/org/springframework/boot/actuate/autoconfigure/metrics/cache/CacheMetricsRegistrarConfiguration.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2019 the original author or authors.
+ * Copyright 2012-2020 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.
@@ -19,8 +19,6 @@ package org.springframework.boot.actuate.autoconfigure.metrics.cache;
 import java.util.Collection;
 import java.util.Map;
 
-import javax.annotation.PostConstruct;
-
 import io.micrometer.core.instrument.MeterRegistry;
 import io.micrometer.core.instrument.Tag;
 
@@ -56,6 +54,7 @@ class CacheMetricsRegistrarConfiguration {
 		this.registry = registry;
 		this.cacheManagers = cacheManagers;
 		this.cacheMetricsRegistrar = new CacheMetricsRegistrar(this.registry, binderProviders);
+		bindCachesToRegistry();
 	}
 
 	@Bean
@@ -63,8 +62,7 @@ class CacheMetricsRegistrarConfiguration {
 		return this.cacheMetricsRegistrar;
 	}
 
-	@PostConstruct
+	private void bindCachesToRegistry() {
-	void bindCachesToRegistry() {
 		this.cacheManagers.forEach(this::bindCacheManagerToRegistry);
 	}
 

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/batch/BasicBatchConfigurer.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2019 the original author or authors.
+ * Copyright 2012-2020 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.
@@ -16,7 +16,6 @@
 
 package org.springframework.boot.autoconfigure.batch;
 
-import javax.annotation.PostConstruct;
 import javax.sql.DataSource;
 
 import org.springframework.batch.core.configuration.annotation.BatchConfigurer;
@@ -26,6 +25,7 @@ import org.springframework.batch.core.launch.JobLauncher;
 import org.springframework.batch.core.launch.support.SimpleJobLauncher;
 import org.springframework.batch.core.repository.JobRepository;
 import org.springframework.batch.core.repository.support.JobRepositoryFactoryBean;
+import org.springframework.beans.factory.InitializingBean;
 import org.springframework.boot.autoconfigure.transaction.TransactionManagerCustomizers;
 import org.springframework.boot.context.properties.PropertyMapper;
 import org.springframework.jdbc.datasource.DataSourceTransactionManager;
@@ -40,7 +40,7 @@ import org.springframework.transaction.PlatformTransactionManager;
  * @author Stephane Nicoll
  * @since 1.0.0
  */
-public class BasicBatchConfigurer implements BatchConfigurer {
+public class BasicBatchConfigurer implements BatchConfigurer, InitializingBean {
 
 	private final BatchProperties properties;
 
@@ -90,7 +90,11 @@ public class BasicBatchConfigurer implements BatchConfigurer {
 		return this.jobExplorer;
 	}
 
-	@PostConstruct
+	@Override
+	public void afterPropertiesSet() {
+		initialize();
+	}
+
 	public void initialize() {
 		try {
 			this.transactionManager = buildTransactionManager();

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/freemarker/FreeMarkerAutoConfiguration.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2019 the original author or authors.
+ * Copyright 2012-2020 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.
@@ -19,8 +19,6 @@ package org.springframework.boot.autoconfigure.freemarker;
 import java.util.ArrayList;
 import java.util.List;
 
-import javax.annotation.PostConstruct;
-
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
 
@@ -57,9 +55,9 @@ public class FreeMarkerAutoConfiguration {
 	public FreeMarkerAutoConfiguration(ApplicationContext applicationContext, FreeMarkerProperties properties) {
 		this.applicationContext = applicationContext;
 		this.properties = properties;
+		checkTemplateLocationExists();
 	}
 
-	@PostConstruct
 	public void checkTemplateLocationExists() {
 		if (logger.isWarnEnabled() && this.properties.isCheckTemplateLocation()) {
 			List<TemplateLocation> locations = getLocations();

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/groovy/template/GroovyTemplateAutoConfiguration.java

@@ -19,7 +19,6 @@ package org.springframework.boot.autoconfigure.groovy.template;
 import java.security.CodeSource;
 import java.security.ProtectionDomain;
 
-import javax.annotation.PostConstruct;
 import javax.servlet.Servlet;
 
 import groovy.text.markup.MarkupTemplateEngine;
@@ -77,9 +76,9 @@ public class GroovyTemplateAutoConfiguration {
 		public GroovyMarkupConfiguration(ApplicationContext applicationContext, GroovyTemplateProperties properties) {
 			this.applicationContext = applicationContext;
 			this.properties = properties;
+			checkTemplateLocationExists();
 		}
 
-		@PostConstruct
 		public void checkTemplateLocationExists() {
 			if (this.properties.isCheckTemplateLocation() && !isUsingGroovyAllJar()) {
 				TemplateLocation location = new TemplateLocation(this.properties.getResourceLoaderPath());

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/hateoas/HypermediaHttpMessageConverterConfiguration.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2019 the original author or authors.
+ * Copyright 2012-2020 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.
@@ -20,11 +20,10 @@ import java.util.ArrayList;
 import java.util.Collection;
 import java.util.List;
 
-import javax.annotation.PostConstruct;
-
 import org.springframework.beans.BeansException;
 import org.springframework.beans.factory.BeanFactory;
 import org.springframework.beans.factory.BeanFactoryAware;
+import org.springframework.beans.factory.InitializingBean;
 import org.springframework.beans.factory.ListableBeanFactory;
 import org.springframework.beans.factory.config.BeanPostProcessor;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnProperty;
@@ -60,12 +59,13 @@ public class HypermediaHttpMessageConverterConfiguration {
 	 * {@code Jackson2ModuleRegisteringBeanPostProcessor} has registered the converter and
 	 * it is unordered.
 	 */
-	private static class HalMessageConverterSupportedMediaTypesCustomizer implements BeanFactoryAware {
+	private static class HalMessageConverterSupportedMediaTypesCustomizer
+			implements BeanFactoryAware, InitializingBean {
 
 		private volatile BeanFactory beanFactory;
 
-		@PostConstruct
+		@Override
-		void configureHttpMessageConverters() {
+		public void afterPropertiesSet() {
 			if (this.beanFactory instanceof ListableBeanFactory) {
 				configureHttpMessageConverters(((ListableBeanFactory) this.beanFactory)
 						.getBeansOfType(RequestMappingHandlerAdapter.class).values());

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/jdbc/DataSourceJmxConfiguration.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2019 the original author or authors.
+ * Copyright 2012-2020 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.
@@ -18,7 +18,6 @@ package org.springframework.boot.autoconfigure.jdbc;
 
 import java.sql.SQLException;
 
-import javax.annotation.PostConstruct;
 import javax.sql.DataSource;
 
 import com.zaxxer.hikari.HikariDataSource;
@@ -59,10 +58,10 @@ class DataSourceJmxConfiguration {
 		Hikari(DataSource dataSource, ObjectProvider<MBeanExporter> mBeanExporter) {
 			this.dataSource = dataSource;
 			this.mBeanExporter = mBeanExporter;
+			validateMBeans();
 		}
 
-		@PostConstruct
+		private void validateMBeans() {
-		void validateMBeans() {
 			HikariDataSource hikariDataSource = DataSourceUnwrapper.unwrap(this.dataSource, HikariDataSource.class);
 			if (hikariDataSource != null && hikariDataSource.isRegisterMbeans()) {
 				this.mBeanExporter.ifUnique((exporter) -> exporter.addExcludedBean("dataSource"));

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/jersey/JerseyAutoConfiguration.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2019 the original author or authors.
+ * Copyright 2012-2020 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.
@@ -19,7 +19,6 @@ package org.springframework.boot.autoconfigure.jersey;
 import java.util.Collections;
 import java.util.EnumSet;
 
-import javax.annotation.PostConstruct;
 import javax.servlet.DispatcherType;
 import javax.servlet.ServletContext;
 import javax.servlet.ServletException;
@@ -95,22 +94,11 @@ public class JerseyAutoConfiguration implements ServletContextAware {
 
 	private final ResourceConfig config;
 
-	private final ObjectProvider<ResourceConfigCustomizer> customizers;
-
 	public JerseyAutoConfiguration(JerseyProperties jersey, ResourceConfig config,
 			ObjectProvider<ResourceConfigCustomizer> customizers) {
 		this.jersey = jersey;
 		this.config = config;
-		this.customizers = customizers;
+		customizers.orderedStream().forEach((customizer) -> customizer.customize(this.config));
-	}
-
-	@PostConstruct
-	public void path() {
-		customize();
-	}
-
-	private void customize() {
-		this.customizers.orderedStream().forEach((customizer) -> customizer.customize(this.config));
 	}
 
 	@Bean

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/mail/MailSenderValidatorAutoConfiguration.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2019 the original author or authors.
+ * Copyright 2012-2020 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.
@@ -16,7 +16,6 @@
 
 package org.springframework.boot.autoconfigure.mail;
 
-import javax.annotation.PostConstruct;
 import javax.mail.MessagingException;
 
 import org.springframework.boot.autoconfigure.AutoConfigureAfter;
@@ -44,9 +43,9 @@ public class MailSenderValidatorAutoConfiguration {
 
 	public MailSenderValidatorAutoConfiguration(JavaMailSenderImpl mailSender) {
 		this.mailSender = mailSender;
+		validateConnection();
 	}
 
-	@PostConstruct
 	public void validateConnection() {
 		try {
 			this.mailSender.testConnection();

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/mustache/MustacheAutoConfiguration.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2019 the original author or authors.
+ * Copyright 2012-2020 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.
@@ -16,8 +16,6 @@
 
 package org.springframework.boot.autoconfigure.mustache;
 
-import javax.annotation.PostConstruct;
-
 import com.samskivert.mustache.Mustache;
 import com.samskivert.mustache.Mustache.Collector;
 import com.samskivert.mustache.Mustache.TemplateLoader;
@@ -57,9 +55,9 @@ public class MustacheAutoConfiguration {
 	public MustacheAutoConfiguration(MustacheProperties mustache, ApplicationContext applicationContext) {
 		this.mustache = mustache;
 		this.applicationContext = applicationContext;
+		checkTemplateLocationExists();
 	}
 
-	@PostConstruct
 	public void checkTemplateLocationExists() {
 		if (this.mustache.isCheckTemplateLocation()) {
 			TemplateLocation location = new TemplateLocation(this.mustache.getPrefix());

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/security/oauth2/client/OAuth2ClientProperties.java

@@ -20,8 +20,7 @@ import java.util.HashMap;
 import java.util.Map;
 import java.util.Set;
 
-import javax.annotation.PostConstruct;
+import org.springframework.beans.factory.InitializingBean;
-
 import org.springframework.boot.context.properties.ConfigurationProperties;
 import org.springframework.util.StringUtils;
 
@@ -35,7 +34,7 @@ import org.springframework.util.StringUtils;
  * @since 2.0.0
  */
 @ConfigurationProperties(prefix = "spring.security.oauth2.client")
-public class OAuth2ClientProperties {
+public class OAuth2ClientProperties implements InitializingBean {
 
 	/**
 	 * OAuth provider details.
@@ -55,7 +54,11 @@ public class OAuth2ClientProperties {
 		return this.registration;
 	}
 
-	@PostConstruct
+	@Override
+	public void afterPropertiesSet() {
+		validate();
+	}
+
 	public void validate() {
 		this.getRegistration().values().forEach(this::validateRegistration);
 	}

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/security/oauth2/resource/OAuth2ResourceServerProperties.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2019 the original author or authors.
+ * Copyright 2012-2020 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.
@@ -19,8 +19,7 @@ import java.io.IOException;
 import java.io.InputStream;
 import java.nio.charset.StandardCharsets;
 
-import javax.annotation.PostConstruct;
+import org.springframework.beans.factory.InitializingBean;
-
 import org.springframework.boot.context.properties.ConfigurationProperties;
 import org.springframework.boot.context.properties.source.InvalidConfigurationPropertyValueException;
 import org.springframework.core.io.Resource;
@@ -35,7 +34,7 @@ import org.springframework.util.StreamUtils;
  * @since 2.1.0
  */
 @ConfigurationProperties(prefix = "spring.security.oauth2.resourceserver")
-public class OAuth2ResourceServerProperties {
+public class OAuth2ResourceServerProperties implements InitializingBean {
 
 	private final Jwt jwt = new Jwt();
 
@@ -49,7 +48,11 @@ public class OAuth2ResourceServerProperties {
 		return this.opaqueToken;
 	}
 
-	@PostConstruct
+	@Override
+	public void afterPropertiesSet() throws Exception {
+		validate();
+	}
+
 	public void validate() {
 		if (this.getOpaquetoken().getIntrospectionUri() != null) {
 			if (this.getJwt().getJwkSetUri() != null) {

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/session/SessionAutoConfiguration.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2019 the original author or authors.
+ * Copyright 2012-2020 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.
@@ -21,8 +21,7 @@ import java.util.Arrays;
 import java.util.List;
 import java.util.Locale;
 
-import javax.annotation.PostConstruct;
+import org.springframework.beans.factory.InitializingBean;
-
 import org.springframework.beans.factory.ObjectProvider;
 import org.springframework.boot.WebApplicationType;
 import org.springframework.boot.autoconfigure.AutoConfigureAfter;
@@ -226,10 +225,10 @@ public class SessionAutoConfiguration {
 			this.classLoader = applicationContext.getClassLoader();
 			this.sessionProperties = sessionProperties;
 			this.candidates = candidates;
+			checkAvailableImplementations();
 		}
 
-		@PostConstruct
+		private void checkAvailableImplementations() {
-		void checkAvailableImplementations() {
 			List<Class<?>> availableCandidates = new ArrayList<>();
 			for (String candidate : this.candidates) {
 				addCandidateIfAvailable(availableCandidates, candidate);
@@ -291,7 +290,7 @@ public class SessionAutoConfiguration {
 	/**
 	 * Base class for validating that a (reactive) session repository bean exists.
 	 */
-	abstract static class AbstractSessionRepositoryValidator {
+	abstract static class AbstractSessionRepositoryValidator implements InitializingBean {
 
 		private final SessionProperties sessionProperties;
 
@@ -303,8 +302,8 @@ public class SessionAutoConfiguration {
 			this.sessionRepositoryProvider = sessionRepositoryProvider;
 		}
 
-		@PostConstruct
+		@Override
-		void checkSessionRepository() {
+		public void afterPropertiesSet() {
 			StoreType storeType = this.sessionProperties.getStoreType();
 			if (storeType != StoreType.NONE && this.sessionRepositoryProvider.getIfAvailable() == null
 					&& storeType != null) {

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/thymeleaf/ThymeleafAutoConfiguration.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2019 the original author or authors.
+ * Copyright 2012-2020 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.
@@ -18,7 +18,6 @@ package org.springframework.boot.autoconfigure.thymeleaf;
 
 import java.util.LinkedHashMap;
 
-import javax.annotation.PostConstruct;
 import javax.servlet.DispatcherType;
 
 import com.github.mxab.thymeleaf.extras.dataattribute.dialect.DataAttributeDialect;
@@ -95,10 +94,10 @@ public class ThymeleafAutoConfiguration {
 		DefaultTemplateResolverConfiguration(ThymeleafProperties properties, ApplicationContext applicationContext) {
 			this.properties = properties;
 			this.applicationContext = applicationContext;
+			checkTemplateLocationExists();
 		}
 
-		@PostConstruct
+		private void checkTemplateLocationExists() {
-		void checkTemplateLocationExists() {
 			boolean checkTemplateLocation = this.properties.isCheckTemplateLocation();
 			if (checkTemplateLocation) {
 				TemplateLocation location = new TemplateLocation(this.properties.getPrefix());

spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/session/SessionAutoConfigurationIntegrationTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2019 the original author or authors.
+ * Copyright 2012-2020 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.
@@ -48,7 +48,7 @@ class SessionAutoConfigurationIntegrationTests extends AbstractSessionAutoConfig
 	void severalCandidatesWithNoSessionStore() {
 		this.contextRunner.withUserConfiguration(HazelcastConfiguration.class).run((context) -> {
 			assertThat(context).hasFailed();
-			assertThat(context).getFailure().hasCauseInstanceOf(NonUniqueSessionRepositoryException.class);
+			assertThat(context).getFailure().hasRootCauseInstanceOf(NonUniqueSessionRepositoryException.class);
 			assertThat(context).getFailure()
 					.hasMessageContaining("Multiple session repository candidates are available");
 			assertThat(context).getFailure()

spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/session/SessionAutoConfigurationTests.java

@@ -62,7 +62,7 @@ class SessionAutoConfigurationTests extends AbstractSessionAutoConfigurationTest
 	void contextFailsIfMultipleStoresAreAvailable() {
 		this.contextRunner.run((context) -> {
 			assertThat(context).hasFailed();
-			assertThat(context).getFailure().hasCauseInstanceOf(NonUniqueSessionRepositoryException.class);
+			assertThat(context).getFailure().hasRootCauseInstanceOf(NonUniqueSessionRepositoryException.class);
 			assertThat(context).getFailure()
 					.hasMessageContaining("Multiple session repository candidates are available");
 		});

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/jackson/JsonComponentModule.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2019 the original author or authors.
+ * Copyright 2012-2020 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.
@@ -20,8 +20,6 @@ import java.lang.reflect.Modifier;
 import java.util.Map;
 import java.util.function.BiConsumer;
 
-import javax.annotation.PostConstruct;
-
 import com.fasterxml.jackson.databind.JsonDeserializer;
 import com.fasterxml.jackson.databind.JsonSerializer;
 import com.fasterxml.jackson.databind.KeyDeserializer;
@@ -33,6 +31,7 @@ import org.springframework.beans.BeansException;
 import org.springframework.beans.factory.BeanFactory;
 import org.springframework.beans.factory.BeanFactoryAware;
 import org.springframework.beans.factory.HierarchicalBeanFactory;
+import org.springframework.beans.factory.InitializingBean;
 import org.springframework.beans.factory.ListableBeanFactory;
 import org.springframework.boot.jackson.JsonComponent.Scope;
 import org.springframework.core.ResolvableType;
@@ -51,7 +50,7 @@ import org.springframework.util.ObjectUtils;
  * @since 1.4.0
  * @see JsonComponent
  */
-public class JsonComponentModule extends SimpleModule implements BeanFactoryAware {
+public class JsonComponentModule extends SimpleModule implements BeanFactoryAware, InitializingBean {
 
 	private BeanFactory beanFactory;
 
@@ -60,7 +59,11 @@ public class JsonComponentModule extends SimpleModule implements BeanFactoryAwar
 		this.beanFactory = beanFactory;
 	}
 
-	@PostConstruct
+	@Override
+	public void afterPropertiesSet() {
+		registerJsonComponents();
+	}
+
 	public void registerJsonComponents() {
 		BeanFactory beanFactory = this.beanFactory;
 		while (beanFactory != null) {

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/jdbc/AbstractDataSourceInitializer.java

@@ -18,9 +18,9 @@ package org.springframework.boot.jdbc;
 
 import java.sql.DatabaseMetaData;
 
-import javax.annotation.PostConstruct;
 import javax.sql.DataSource;
 
+import org.springframework.beans.factory.InitializingBean;
 import org.springframework.core.io.ResourceLoader;
 import org.springframework.jdbc.datasource.init.DatabasePopulatorUtils;
 import org.springframework.jdbc.datasource.init.ResourceDatabasePopulator;
@@ -35,7 +35,7 @@ import org.springframework.util.Assert;
  * @author Stephane Nicoll
  * @since 1.5.0
  */
-public abstract class AbstractDataSourceInitializer {
+public abstract class AbstractDataSourceInitializer implements InitializingBean {
 
 	private static final String PLATFORM_PLACEHOLDER = "@@platform@@";
 
@@ -50,7 +50,11 @@ public abstract class AbstractDataSourceInitializer {
 		this.resourceLoader = resourceLoader;
 	}
 
-	@PostConstruct
+	@Override
+	public void afterPropertiesSet() {
+		initialize();
+	}
+
 	protected void initialize() {
 		if (!isEnabled()) {
 			return;

src/checkstyle/checkstyle-suppressions.xml

@@ -13,12 +13,14 @@
 	<suppress files="[\\/]src[\\/]main[\\/]java[\\/]sample[\\/]" checks="ImportControl" />
 	<suppress files="[\\/]src[\\/]test[\\/]java[\\/]sample[\\/]" checks="ImportControl" />
 	<suppress files="[\\/]src[\\/]test[\\/]java[\\/]" checks="Javadoc*" />
+	<suppress files="[\\/]src[\\/]test[\\/]java[\\/]" id="mainCodeIllegalImportCheck" />
 	<suppress files="[\\/]src[\\/]test[\\/]java[\\/]" checks="NonEmptyAtclauseDescription" />
 	<suppress files="[\\/]autoconfigure[\\/]" checks="JavadocType" />
 	<suppress files="[\\/]autoconfigure[\\/]" checks="JavadocVariable" />
 	<suppress files="[\\/]spring-boot-docs[\\/]" checks="JavadocType" />
 	<suppress files="[\\/]spring-boot-smoke-tests[\\/]" checks="JavadocType" />
 	<suppress files="[\\/]spring-boot-smoke-tests[\\/]" checks="ImportControl" />
+	<suppress files="[\\/]spring-boot-smoke-tests[\\/]" id="mainCodeIllegalImportCheck" />
 	<suppress files="[\\/]spring-boot-deployment-tests[\\/]" checks="JavadocType" />
 	<suppress files="[\\/]spring-boot-integration-tests[\\/]" checks="JavadocType" />
 	<suppress files="Ansi.*\.java" checks="JavadocVariable" />

src/checkstyle/checkstyle.xml

@@ -15,7 +15,14 @@
 			<property name="illegalPkgs"
 				value="^sun.*, ^org\.apache\.commons\.(?!compress|dbcp2|logging|pool2).*, ^com\.google\.common.*, ^io\.micrometer\.shaded.*, ^org\.flywaydb\.core\.internal.*, ^org\.testcontainers\.shaded.*" />
 			<property name="illegalClasses"
-				value="^com\.hazelcast\.util\.Base64, ^org\.junit\.rules\.ExpectedException, ^org\.mockito\.InjectMocks, ^org\.slf4j\.LoggerFactory, ^org.springframework.context.annotation.ScannedGenericBeanDefinition, ^reactor\.core\.support\.Assert" />
+				value="^com\.hazelcast\.util\.Base64, ^org\.junit\.rules\.ExpectedException, ^org\.mockito\.InjectMocks, ^org\.slf4j\.LoggerFactory, ^org.springframework.context.annotation.ScannedGenericBeanDefinition, ^reactor\.core\.support\.Assert"/>
+		</module>
+		<module
+			name="com.puppycrawl.tools.checkstyle.checks.imports.IllegalImportCheck">
+			<property name="id" value="mainCodeIllegalImportCheck"/>
+			<property name="regexp" value="true" />
+			<property name="illegalClasses"
+				value="^javax.annotation.PostConstruct"/>
 		</module>
 		<module
 			name="com.puppycrawl.tools.checkstyle.checks.imports.ImportControlCheck">