Enable Oracle integration tests.

Closes #560

pom.xml

@@ -320,6 +320,13 @@
 			<scope>test</scope>
 		</dependency>
 
+		<dependency>
+			<groupId>org.awaitility</groupId>
+			<artifactId>awaitility</artifactId>
+			<version>4.0.3</version>
+			<scope>test</scope>
+		</dependency>
+
 	</dependencies>
 
 	<build>
@@ -464,7 +471,6 @@
 		<profile>
 			<id>java11</id>
 
-			<!-- enable once oracle-r2db is available from Maven Central
 			<dependencies>
 				<dependency>
 					<groupId>com.oracle.database.r2dbc</groupId>
@@ -474,7 +480,6 @@
 				</dependency>
 			</dependencies>
 
-			-->
 		</profile>
 	</profiles>
 

src/test/java/org/springframework/data/r2dbc/testing/OracleTestSupport.java

@@ -24,7 +24,10 @@ import java.util.stream.Stream;
 
 import javax.sql.DataSource;
 
+import org.awaitility.Awaitility;
+
 import org.springframework.data.r2dbc.testing.ExternalDatabase.ProvidedDatabase;
+import org.springframework.jdbc.core.JdbcTemplate;
 import org.springframework.jdbc.datasource.DriverManagerDataSource;
 import org.springframework.util.ClassUtils;
 
@@ -119,6 +122,13 @@ public class OracleTestSupport {
 
 				testContainerDatabase = ProvidedDatabase.builder(container) //
 						.database("XEPDB1").build();
+
+				DataSource dataSource = createDataSource(testContainerDatabase);
+
+				Awaitility.await().ignoreExceptions().until(() -> {
+					new JdbcTemplate(dataSource).queryForList("SELECT 'Hello, Oracle' FROM sys.dual");
+					return true;
+				});
 			} catch (IllegalStateException ise) {
 				// docker not available.
 				testContainerDatabase = ExternalDatabase.unavailable();