#29 - Polishing.

Add author tags. Add static factory method to create an unavailable database object instance. Simplify database selection. Javadoc.

Original pull request: #51.

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

@@ -32,11 +32,21 @@ import org.slf4j.LoggerFactory;
  * {@link org.testcontainers.containers.PostgreSQLContainer}.
  *
  * @author Mark Paluch
+ * @author Jens Schauder
  */
 public abstract class ExternalDatabase extends ExternalResource {
 
 	private static Logger LOG = LoggerFactory.getLogger(ExternalDatabase.class);
 
+	/**
+	 * Construct an absent database that is used as {@literal null} object if no database is available.
+	 *
+	 * @return an absent database.
+	 */
+	public static ExternalDatabase unavailable() {
+		return NoAvailableDatabase.INSTANCE;
+	}
+
 	/**
 	 * @return the post of the database service.
 	 */
@@ -70,7 +80,7 @@ public abstract class ExternalDatabase extends ExternalResource {
 	}
 
 	/**
-	 * performs a test if the database can actually be reached.
+	 * Performs a test if the database can actually be reached.
 	 *
 	 * @return true, if the database could be reached.
 	 */
@@ -79,7 +89,7 @@ public abstract class ExternalDatabase extends ExternalResource {
 		try (Socket socket = new Socket()) {
 
 			socket.connect(new InetSocketAddress(getHostname(), getPort()), Math.toIntExact(TimeUnit.SECONDS.toMillis(5)));
-			return  true;
+			return true;
 
 		} catch (IOException e) {
 			LOG.debug("external database not available.", e);
@@ -151,8 +161,13 @@ public abstract class ExternalDatabase extends ExternalResource {
 	 *
 	 * @author Jens Schauder
 	 */
-	static class NoSuchDatabase extends ExternalDatabase {
+	private static class NoAvailableDatabase extends ExternalDatabase {
 
+		private static final NoAvailableDatabase INSTANCE = new NoAvailableDatabase();
+
+		/* (non-Javadoc)
+		 * @see org.springframework.data.jdbc.core.function.ExternalDatabase#getPort()
+		 */
 		@Override
 		boolean checkValidity() {
 			return false;
@@ -160,27 +175,39 @@ public abstract class ExternalDatabase extends ExternalResource {
 
 		@Override
 		public int getPort() {
-			throw new UnsupportedOperationException();
+			throw new UnsupportedOperationException(getClass().getSimpleName());
 		}
 
+		/* (non-Javadoc)
+		 * @see org.springframework.data.jdbc.core.function.ExternalDatabase#getHostname()
+		 */
 		@Override
 		public String getHostname() {
-			throw new UnsupportedOperationException();
+			throw new UnsupportedOperationException(getClass().getSimpleName());
 		}
 
+		/* (non-Javadoc)
+		 * @see org.springframework.data.jdbc.core.function.ExternalDatabase#getDatabase()
+		 */
 		@Override
 		public String getDatabase() {
-			throw new UnsupportedOperationException();
+			throw new UnsupportedOperationException(getClass().getSimpleName());
 		}
 
+		/* (non-Javadoc)
+		 * @see org.springframework.data.jdbc.core.function.ExternalDatabase#getUsername()
+		 */
 		@Override
 		public String getUsername() {
-			throw new UnsupportedOperationException();
+			throw new UnsupportedOperationException(getClass().getSimpleName());
 		}
 
+		/* (non-Javadoc)
+		 * @see org.springframework.data.jdbc.core.function.ExternalDatabase#getPassword()
+		 */
 		@Override
 		public String getPassword() {
-			throw new UnsupportedOperationException();
+			throw new UnsupportedOperationException(getClass().getSimpleName());
 		}
 	}
 }

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

@@ -5,6 +5,7 @@ import io.r2dbc.postgresql.PostgresqlConnectionFactory;
 import io.r2dbc.spi.ConnectionFactory;
 
 import java.util.function.Supplier;
+import java.util.stream.Stream;
 
 import javax.sql.DataSource;
 
@@ -58,15 +59,13 @@ public class PostgresTestSupport {
 		}
 	}
 
-	private static ExternalDatabase getFirstWorkingDatabase(Supplier<ExternalDatabase> first,
-			Supplier<ExternalDatabase> second) {
+	@SafeVarargs
+	private static ExternalDatabase getFirstWorkingDatabase(Supplier<ExternalDatabase>... suppliers) {
 
-		ExternalDatabase database = first.get();
-		if (database.checkValidity()) {
-			return database;
-		} else {
-			return second.get();
-		}
+		return Stream.of(suppliers).map(Supplier::get) //
+				.filter(ExternalDatabase::checkValidity) //
+				.findFirst() //
+				.orElse(ExternalDatabase.unavailable());
 	}
 
 	/**
@@ -101,8 +100,8 @@ public class PostgresTestSupport {
 						.password(postgreSQLContainer.getPassword()).build();
 
 			} catch (IllegalStateException ise) {
-				// docker is not available.
-				testContainerDatabase = new ExternalDatabase.NoSuchDatabase();
+				// docker not available.
+				testContainerDatabase = ExternalDatabase.unavailable();
 			}
 
 		}