From 04e441f468ae41e54e8f8a0c3ecc2483a4cdcb72 Mon Sep 17 00:00:00 2001
From: Andy Wilkinson <wilkinsona@vmware.com>
Date: Tue, 13 Apr 2021 12:48:46 +0100
Subject: [PATCH] Add a config prop for the embedded database connection

Previously, the embedded database connection that would be used
could only be controlled via the classpath. If multiple embedded
database dependencies were present, it wasn't possible to control
the one that the auto-configured would use. It also wasn't possible
to disable auto-configuration of an embedded database.

This commit introduces a new configuration property,
spring.datasource.embedded-database-connection. It can be set to
one of the values of the EmbeddedDatabaseConnection enum to control
the auto-configuration of an embedded database. Setting it to none
will disable the auto-configuration and ensure that an external
database is used instead.

Closes gh-23412
---
 .../jdbc/DataSourceProperties.java             | 18 ++++++++++++++++--
 .../jdbc/DataSourcePropertiesTests.java        | 18 ++++++++++++++++++
 .../docs/asciidoc/spring-boot-features.adoc    |  2 ++
 3 files changed, 36 insertions(+), 2 deletions(-)

diff --git a/spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/jdbc/DataSourceProperties.java b/spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/jdbc/DataSourceProperties.java
index 3c86b3830b3..956e605d61a 100644
--- a/spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/jdbc/DataSourceProperties.java
+++ b/spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/jdbc/DataSourceProperties.java
@@ -162,7 +162,11 @@ public class DataSourceProperties implements BeanClassLoaderAware, InitializingB
 	@Deprecated
 	private Charset sqlScriptEncoding;
 
-	private EmbeddedDatabaseConnection embeddedDatabaseConnection = EmbeddedDatabaseConnection.NONE;
+	/**
+	 * Connection details for an embedded database. Defaults to the most suitable embedded
+	 * database that is available on the classpath.
+	 */
+	private EmbeddedDatabaseConnection embeddedDatabaseConnection;
 
 	private Xa xa = new Xa();
 
@@ -175,7 +179,9 @@ public class DataSourceProperties implements BeanClassLoaderAware, InitializingB
 
 	@Override
 	public void afterPropertiesSet() throws Exception {
-		this.embeddedDatabaseConnection = EmbeddedDatabaseConnection.get(this.classLoader);
+		if (this.embeddedDatabaseConnection == null) {
+			this.embeddedDatabaseConnection = EmbeddedDatabaseConnection.get(this.classLoader);
+		}
 	}
 
 	/**
@@ -506,6 +512,14 @@ public class DataSourceProperties implements BeanClassLoaderAware, InitializingB
 		this.sqlScriptEncoding = sqlScriptEncoding;
 	}
 
+	public EmbeddedDatabaseConnection getEmbeddedDatabaseConnection() {
+		return this.embeddedDatabaseConnection;
+	}
+
+	public void setEmbeddedDatabaseConnection(EmbeddedDatabaseConnection embeddedDatabaseConnection) {
+		this.embeddedDatabaseConnection = embeddedDatabaseConnection;
+	}
+
 	public ClassLoader getClassLoader() {
 		return this.classLoader;
 	}
diff --git a/spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/jdbc/DataSourcePropertiesTests.java b/spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/jdbc/DataSourcePropertiesTests.java
index 623891402c5..b82438dde9f 100644
--- a/spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/jdbc/DataSourcePropertiesTests.java
+++ b/spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/jdbc/DataSourcePropertiesTests.java
@@ -69,6 +69,24 @@ class DataSourcePropertiesTests {
 				.isThrownBy(properties::determineUrl).withMessageContaining("Failed to determine suitable jdbc url");
 	}
 
+	@Test
+	void determineUrlWithSpecificEmbeddedConnection() throws Exception {
+		DataSourceProperties properties = new DataSourceProperties();
+		properties.setGenerateUniqueName(false);
+		properties.setEmbeddedDatabaseConnection(EmbeddedDatabaseConnection.HSQLDB);
+		properties.afterPropertiesSet();
+		assertThat(properties.determineUrl()).isEqualTo(EmbeddedDatabaseConnection.HSQLDB.getUrl("testdb"));
+	}
+
+	@Test
+	void whenEmbeddedConnectionIsNoneAndNoUrlIsConfiguredThenDetermineUrlThrows() throws Exception {
+		DataSourceProperties properties = new DataSourceProperties();
+		properties.setGenerateUniqueName(false);
+		properties.setEmbeddedDatabaseConnection(EmbeddedDatabaseConnection.NONE);
+		assertThatExceptionOfType(DataSourceProperties.DataSourceBeanCreationException.class)
+				.isThrownBy(properties::determineUrl).withMessageContaining("Failed to determine suitable jdbc url");
+	}
+
 	@Test
 	void determineUrlWithExplicitConfig() throws Exception {
 		DataSourceProperties properties = new DataSourceProperties();
diff --git a/spring-boot-project/spring-boot-docs/src/docs/asciidoc/spring-boot-features.adoc b/spring-boot-project/spring-boot-docs/src/docs/asciidoc/spring-boot-features.adoc
index 6a9a8959f06..e01d927024c 100644
--- a/spring-boot-project/spring-boot-docs/src/docs/asciidoc/spring-boot-features.adoc
+++ b/spring-boot-project/spring-boot-docs/src/docs/asciidoc/spring-boot-features.adoc
@@ -3565,6 +3565,8 @@ TIP: The "`How-to`" section includes a <<howto.adoc#howto-database-initializatio
 Spring Boot can auto-configure embedded https://www.h2database.com[H2], http://hsqldb.org/[HSQL], and https://db.apache.org/derby/[Derby] databases.
 You need not provide any connection URLs.
 You need only include a build dependency to the embedded database that you want to use.
+If there are multiple embedded databases on the classpath, set the configprop:spring.datasource.embedded-database-connection[] configuration property to control which one is used.
+Setting the property to `none` disables auto-configuration of an embedded database.
 
 [NOTE]
 ====