Prevent H2 console from causing early DataSource initialization

Update `H2ConsoleAutoConfiguration` so that DataSource connection
logging occurs outside of the `ServletRegistrationBean`.

Fixes gh-43337

Author: philwebb

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/h2/H2ConsoleAutoConfiguration.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2022 the original author or authors.
+ * Copyright 2012-2024 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.
@@ -46,6 +46,7 @@
  * @author Andy Wilkinson
  * @author Marten Deinum
  * @author Stephane Nicoll
+ * @author Phillip Webb
  * @since 1.3.0
  */
 @AutoConfiguration(after = DataSourceAutoConfiguration.class)
@@ -57,46 +58,25 @@ public class H2ConsoleAutoConfiguration {
 
 	private static final Log logger = LogFactory.getLog(H2ConsoleAutoConfiguration.class);
 
+	private final H2ConsoleProperties properties;
+
+	H2ConsoleAutoConfiguration(H2ConsoleProperties properties) {
+		this.properties = properties;
+	}
+
 	@Bean
-	public ServletRegistrationBean<JakartaWebServlet> h2Console(H2ConsoleProperties properties,
-			ObjectProvider<DataSource> dataSource) {
-		String path = properties.getPath();
+	public ServletRegistrationBean<JakartaWebServlet> h2Console() {
+		String path = this.properties.getPath();
 		String urlMapping = path + (path.endsWith("/") ? "*" : "/*");
 		ServletRegistrationBean<JakartaWebServlet> registration = new ServletRegistrationBean<>(new JakartaWebServlet(),
 				urlMapping);
-		configureH2ConsoleSettings(registration, properties.getSettings());
-		if (logger.isInfoEnabled()) {
-			withThreadContextClassLoader(getClass().getClassLoader(), () -> logDataSources(dataSource, path));
-		}
+		configureH2ConsoleSettings(registration, this.properties.getSettings());
 		return registration;
 	}
 
-	private void withThreadContextClassLoader(ClassLoader classLoader, Runnable action) {
-		ClassLoader previous = Thread.currentThread().getContextClassLoader();
-		try {
-			Thread.currentThread().setContextClassLoader(classLoader);
-			action.run();
-		}
-		finally {
-			Thread.currentThread().setContextClassLoader(previous);
-		}
-	}
-
-	private void logDataSources(ObjectProvider<DataSource> dataSource, String path) {
-		List<String> urls = dataSource.orderedStream().map(this::getConnectionUrl).filter(Objects::nonNull).toList();
-		if (!urls.isEmpty()) {
-			logger.info(LogMessage.format("H2 console available at '%s'. %s available at %s", path,
-					(urls.size() > 1) ? "Databases" : "Database", String.join(", ", urls)));
-		}
-	}
-
-	private String getConnectionUrl(DataSource dataSource) {
-		try (Connection connection = dataSource.getConnection()) {
-			return "'" + connection.getMetaData().getURL() + "'";
-		}
-		catch (Exception ex) {
-			return null;
-		}
+	@Bean
+	H2ConsoleLogger h2ConsoleLogger(ObjectProvider<DataSource> dataSource) {
+		return new H2ConsoleLogger(dataSource, this.properties.getPath());
 	}
 
 	private void configureH2ConsoleSettings(ServletRegistrationBean<JakartaWebServlet> registration,
@@ -112,4 +92,46 @@ private void configureH2ConsoleSettings(ServletRegistrationBean<JakartaWebServle
 		}
 	}
 
+	static class H2ConsoleLogger {
+
+		H2ConsoleLogger(ObjectProvider<DataSource> dataSources, String path) {
+			if (logger.isInfoEnabled()) {
+				ClassLoader classLoader = getClass().getClassLoader();
+				withThreadContextClassLoader(classLoader, () -> log(getConnectionUrls(dataSources), path));
+			}
+		}
+
+		private void withThreadContextClassLoader(ClassLoader classLoader, Runnable action) {
+			ClassLoader previous = Thread.currentThread().getContextClassLoader();
+			try {
+				Thread.currentThread().setContextClassLoader(classLoader);
+				action.run();
+			}
+			finally {
+				Thread.currentThread().setContextClassLoader(previous);
+			}
+		}
+
+		private List<String> getConnectionUrls(ObjectProvider<DataSource> dataSources) {
+			return dataSources.orderedStream().map(this::getConnectionUrl).filter(Objects::nonNull).toList();
+		}
+
+		private String getConnectionUrl(DataSource dataSource) {
+			try (Connection connection = dataSource.getConnection()) {
+				return "'" + connection.getMetaData().getURL() + "'";
+			}
+			catch (Exception ex) {
+				return null;
+			}
+		}
+
+		private void log(List<String> urls, String path) {
+			if (!urls.isEmpty()) {
+				logger.info(LogMessage.format("H2 console available at '%s'. %s available at %s", path,
+						(urls.size() > 1) ? "Databases" : "Database", String.join(", ", urls)));
+			}
+		}
+
+	}
+
 }

spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/h2/H2ConsoleAutoConfigurationTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2023 the original author or authors.
+ * Copyright 2012-2024 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.
@@ -30,15 +30,20 @@
 import org.springframework.beans.factory.BeanCreationException;
 import org.springframework.boot.autoconfigure.AutoConfigurations;
 import org.springframework.boot.autoconfigure.jdbc.DataSourceAutoConfiguration;
+import org.springframework.boot.autoconfigure.web.servlet.ServletWebServerFactoryAutoConfiguration;
 import org.springframework.boot.context.properties.ConfigurationPropertiesBindException;
 import org.springframework.boot.context.properties.bind.BindException;
 import org.springframework.boot.test.context.runner.WebApplicationContextRunner;
 import org.springframework.boot.test.system.CapturedOutput;
 import org.springframework.boot.test.system.OutputCaptureExtension;
 import org.springframework.boot.web.servlet.ServletRegistrationBean;
+import org.springframework.boot.web.servlet.context.AnnotationConfigServletWebServerApplicationContext;
+import org.springframework.context.ConfigurableApplicationContext;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
 import org.springframework.core.annotation.Order;
+import org.springframework.jdbc.datasource.embedded.EmbeddedDatabaseBuilder;
+import org.springframework.jdbc.datasource.embedded.EmbeddedDatabaseType;
 
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.mockito.BDDMockito.given;
@@ -51,6 +56,7 @@
  * @author Marten Deinum
  * @author Stephane Nicoll
  * @author Shraddha Yeole
+ * @author Phillip Webb
  */
 class H2ConsoleAutoConfigurationTests {
 
@@ -163,6 +169,22 @@ void h2ConsoleShouldNotFailIfDatabaseConnectionFails() {
 			.run((context) -> assertThat(context.isRunning()).isTrue());
 	}
 
+	@Test
+	@ExtendWith(OutputCaptureExtension.class)
+	void dataSourceIsNotInitializedEarly(CapturedOutput output) {
+		new WebApplicationContextRunner(AnnotationConfigServletWebServerApplicationContext::new)
+			.withConfiguration(AutoConfigurations.of(H2ConsoleAutoConfiguration.class,
+					ServletWebServerFactoryAutoConfiguration.class))
+			.withUserConfiguration(EarlyInitializationConfiguration.class)
+			.withPropertyValues("spring.h2.console.enabled=true", "server.port=0")
+			.run((context) -> {
+				try (Connection connection = context.getBean(DataSource.class).getConnection()) {
+					assertThat(output).contains("H2 console available at '/h2-console'. Database available at '"
+							+ connection.getMetaData().getURL() + "'");
+				}
+			});
+	}
+
 	@Configuration(proxyBeanMethods = false)
 	static class FailingDataSourceConfiguration {
 
@@ -206,4 +228,15 @@ private DataSource mockDataSource(String url) throws SQLException {
 
 	}
 
+	@Configuration(proxyBeanMethods = false)
+	static class EarlyInitializationConfiguration {
+
+		@Bean
+		DataSource dataSource(ConfigurableApplicationContext applicationContext) {
+			assertThat(applicationContext.getBeanFactory().isConfigurationFrozen()).isTrue();
+			return new EmbeddedDatabaseBuilder().setType(EmbeddedDatabaseType.H2).build();
+		}
+
+	}
+
 }