Merge branch '2.4.x'

Closes gh-25342

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

 /*
- * Copyright 2012-2020 the original author or authors.
+ * Copyright 2012-2021 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.
@@ -196,6 +196,8 @@ public final class DataSourceBuilder<T extends DataSource> {
 									(aliases) -> aliases.addAliases("driver-class-name", "driver-class"))));
 			addIfAvailable(this.allDataSourceSettings,
 					create(classLoader, "oracle.jdbc.datasource.OracleDataSource", OracleDataSourceSettings::new));
+			addIfAvailable(this.allDataSourceSettings, create(classLoader, "org.h2.jdbcx.JdbcDataSource",
+					(type) -> new DataSourceSettings(type, (aliases) -> aliases.addAliases("username", "user"))));
 		}
 
 		private static List<DataSourceSettings> resolveAvailableDataSourceSettings(ClassLoader classLoader) {

spring-boot-project/spring-boot/src/test/java/org/springframework/boot/jdbc/DataSourceBuilderTests.java

 /*
- * Copyright 2012-2020 the original author or authors.
+ * Copyright 2012-2021 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.
@@ -30,6 +30,7 @@ import oracle.jdbc.pool.OracleDataSource;
 import oracle.ucp.jdbc.PoolDataSourceImpl;
 import org.apache.commons.dbcp2.BasicDataSource;
 import org.h2.Driver;
+import org.h2.jdbcx.JdbcDataSource;
 import org.junit.jupiter.api.AfterEach;
 import org.junit.jupiter.api.Test;
 
@@ -119,6 +120,15 @@ class DataSourceBuilderTests {
 		assertThat(upcDataSource.getUser()).isEqualTo("test");
 	}
 
+	@Test
+	void dataSourceCanBeCreatedWithH2JdbcDataSource() {
+		this.dataSource = DataSourceBuilder.create().url("jdbc:h2:test").type(JdbcDataSource.class).username("test")
+				.build();
+		assertThat(this.dataSource).isInstanceOf(JdbcDataSource.class);
+		JdbcDataSource h2DataSource = (JdbcDataSource) this.dataSource;
+		assertThat(h2DataSource.getUser()).isEqualTo("test");
+	}
+
 	@Test
 	void dataSourceAliasesAreOnlyAppliedToRelevantDataSource() {
 		this.dataSource = DataSourceBuilder.create().url("jdbc:h2:test").type(TestDataSource.class).username("test")