Oracle: Lightweight Connection Validation (#1451)

* Oracle: Lightweight Connection Validation

See #1450

Signed-off-by: Thomas Segismont <tsegismont@gmail.com>

* Use NONE Connection validation.

This setting does not make the driver block and is implemented as a simple lifecycle check.

This is exactly what we do with other clients (Pg, MySQL, ...etc).

Signed-off-by: Thomas Segismont <tsegismont@gmail.com>

---------

Signed-off-by: Thomas Segismont <tsegismont@gmail.com>

vertx-oracle-client/src/main/java/io/vertx/oracleclient/impl/OracleJdbcConnection.java

@@ -34,6 +34,8 @@
 
 public class OracleJdbcConnection implements Connection {
 
+  private static final Logger log = LoggerFactory.getLogger(OracleJdbcConnection.class);
+
   private final ClientMetrics metrics;
   private final OracleConnection connection;
   private final OracleMetadata metadata;
@@ -104,7 +106,12 @@ public boolean isSsl() {
 
   @Override
   public boolean isValid() {
-    return true;
+    try {
+      return connection.isValid(OracleConnection.ConnectionValidation.NONE, 0);
+    } catch (SQLException e) {
+      log.trace("Failed to validate connection", e);
+      return false;
+    }
   }
 
   @Override