Do not fail if "spring.datasource.url" cannot be resolved

Previously, a condition checked the value of "spring.datasource.url" to
determine if an embedded database has to be created as a fallback. When
the value is set with an unresolved placeholder, this fails even if
the DataSource is going to created by another mean ultimately.

This commit makes a more conservative check by only checking the
presence of the property rather than its value.

Closes gh-20438

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

@@ -38,7 +38,6 @@
 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}.
@@ -129,14 +128,16 @@ private ClassLoader getDataSourceClassLoader(ConditionContext context) {
 	 */
 	static class EmbeddedDatabaseCondition extends SpringBootCondition {
 
+		private static final String DATASOURCE_URL_PROPERTY = "spring.datasource.url";
+
 		private final SpringBootCondition pooledCondition = new PooledDataSourceCondition();
 
 		@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));
+			boolean hasDatasourceUrl = context.getEnvironment().containsProperty(DATASOURCE_URL_PROPERTY);
+			if (hasDatasourceUrl) {
+				return ConditionOutcome.noMatch(message.because(DATASOURCE_URL_PROPERTY + " is set"));
 			}
 			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

@@ -194,6 +194,13 @@ public void testDefaultDataSourceCanBeOverridden() {
 				.run((context) -> assertThat(context).getBean(DataSource.class).isInstanceOf(BasicDataSource.class));
 	}
 
+	@Test
+	public void whenThereIsAUserProvidedDataSourceAnUnresolvablePlaceholderDoesNotCauseAProblem() {
+		this.contextRunner.withUserConfiguration(TestDataSourceConfiguration.class)
+				.withPropertyValues("spring.datasource.url:${UNRESOLVABLE_PLACEHOLDER}")
+				.run((context) -> assertThat(context).getBean(DataSource.class).isInstanceOf(BasicDataSource.class));
+	}
+
 	@Test
 	public void testDataSourceIsInitializedEarly() {
 		this.contextRunner.withUserConfiguration(TestInitializedDataSourceConfiguration.class)