Do not fallback to embedded configuration if a datasource url is set

This commit makes sure that a fallback embedded datasource is not
created if no suitable connection pool is found and an url has been
explicitly registered.

This is consistent with EmbeddedDataSourceConfiguration as it is using
EmbeddedDatabaseBuilder behind the scenes and the latter does not
honour the configured URL anyway.

Closes gh-19192

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

 /*
- * 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.
@@ -38,6 +38,7 @@ import org.springframework.context.annotation.Configuration;
 import org.springframework.context.annotation.Import;
 import org.springframework.core.type.AnnotatedTypeMetadata;
 import org.springframework.jdbc.datasource.embedded.EmbeddedDatabaseType;
+import org.springframework.util.StringUtils;
 
 /**
  * {@link EnableAutoConfiguration Auto-configuration} for {@link DataSource}.
@@ -133,6 +134,10 @@ public class DataSourceAutoConfiguration {
 		@Override
 		public ConditionOutcome getMatchOutcome(ConditionContext context, AnnotatedTypeMetadata metadata) {
 			ConditionMessage.Builder message = ConditionMessage.forCondition("EmbeddedDataSource");
+			String url = context.getEnvironment().getProperty("spring.datasource.url");
+			if (StringUtils.hasText(url)) {
+				return ConditionOutcome.noMatch(message.found("explicit url").items(url));
+			}
 			if (anyMatches(context, metadata, this.pooledCondition)) {
 				return ConditionOutcome.noMatch(message.foundExactly("supported pooled data source"));
 			}

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

 /*
- * 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.
@@ -27,6 +27,7 @@ import java.util.List;
 import java.util.Properties;
 import java.util.Random;
 import java.util.function.Consumer;
+import java.util.function.Function;
 import java.util.logging.Logger;
 
 import javax.sql.DataSource;
@@ -143,15 +144,19 @@ public class DataSourceAutoConfigurationTests {
 				});
 	}
 
+	@Test
+	public void dataSourceWhenNoConnectionPoolsAreAvailableWithUrlDoesNotCreateDataSource() {
+		this.contextRunner.with(hideConnectionPools())
+				.run((context) -> assertThat(context).doesNotHaveBean(DataSource.class));
+	}
+
 	/**
 	 * This test makes sure that if no supported data source is present, a datasource is
 	 * still created if "spring.datasource.type" is present.
 	 */
 	@Test
-	public void explicitTypeNoSupportedDataSource() {
-		this.contextRunner
-				.withClassLoader(new FilteredClassLoader("org.apache.tomcat", "com.zaxxer.hikari",
-						"org.apache.commons.dbcp", "org.apache.commons.dbcp2"))
+	public void dataSourceWhenNoConnectionPoolsAreAvailableWithUrlAndTypeCreatesDataSource() {
+		this.contextRunner.with(hideConnectionPools())
 				.withPropertyValues("spring.datasource.driverClassName:org.hsqldb.jdbcDriver",
 						"spring.datasource.url:jdbc:hsqldb:mem:testdb",
 						"spring.datasource.type:" + SimpleDriverDataSource.class.getName())
@@ -197,6 +202,11 @@ public class DataSourceAutoConfigurationTests {
 						.isTrue());
 	}
 
+	private static Function<ApplicationContextRunner, ApplicationContextRunner> hideConnectionPools() {
+		return (runner) -> runner.withClassLoader(new FilteredClassLoader("org.apache.tomcat", "com.zaxxer.hikari",
+				"org.apache.commons.dbcp", "org.apache.commons.dbcp2"));
+	}
+
 	private <T extends DataSource> void assertDataSource(Class<T> expectedType, List<String> hiddenPackages,
 			Consumer<T> consumer) {
 		FilteredClassLoader classLoader = new FilteredClassLoader(StringUtils.toStringArray(hiddenPackages));