--- a/java/sql-dk/src/info/globalcode/sql/dk/InfoLister.java	Sun May 17 15:43:20 2015 +0200
+++ b/java/sql-dk/src/info/globalcode/sql/dk/InfoLister.java	Mon May 18 00:33:10 2015 +0200
@@ -35,6 +35,7 @@
 import java.io.PrintStream;
 import java.sql.Array;
 import java.sql.Driver;
+import java.sql.DriverManager;
 import java.sql.DriverPropertyInfo;
 import java.sql.SQLException;
 import java.util.ArrayList;
@@ -47,6 +48,7 @@
 import java.util.concurrent.Executors;
 import java.util.concurrent.TimeUnit;
 import java.util.logging.Level;
+import java.util.logging.LogRecord;
 import java.util.logging.Logger;
 import javax.sql.rowset.RowSetMetaDataImpl;
 
@@ -306,6 +308,10 @@
 		printHeader(currentFormatter, header, "-- database configuration and connectivity test", null);
 
 		for (final String dbName : options.getDatabaseNamesToTest()) {
+			preloadDriver(dbName);
+		}
+
+		for (final String dbName : options.getDatabaseNamesToTest()) {
 			es.submit(new Runnable() {
 				// TODO: Java 8 – lambda
 				@Override
@@ -335,6 +341,29 @@
 		printFooter(currentFormatter);
 	}
 
+	/**
+	 * JDBC driver classes should be preloaded in single thread to avoid deadlocks while doing
+	 * {@linkplain DriverManager#registerDriver(java.sql.Driver)} during parallel connections.
+	 *
+	 * @param dbName
+	 */
+	private void preloadDriver(String dbName) {
+		try {
+			DatabaseDefinition dd = configurationProvider.getConfiguration().getDatabase(dbName);
+			Driver driver = findDriver(dd);
+			if (driver == null) {
+				log.log(Level.WARNING, "No Driver found for DB: {0}", dbName);
+			} else {
+				log.log(Level.FINEST, "Driver preloading for DB: {0} was successfull", dbName);
+			}
+		} catch (Exception e) {
+			LogRecord r = new LogRecord(Level.WARNING, "Failed to preload the Driver for DB: {0}");
+			r.setParameters(new Object[]{dbName});
+			r.setThrown(e);
+			log.log(r);
+		}
+	}
+
 	public Object[] testConnection(String dbName) {
 		log.log(Level.FINE, "Testing connection to database: {0}", dbName);
 
@@ -349,7 +378,7 @@
 				succesfullyConnected = dc.test();
 			}
 			log.log(Level.FINE, "Database connection test was successful");
-		} catch (ConfigurationException | SQLException e) {
+		} catch (ConfigurationException | SQLException | RuntimeException e) {
 			log.log(Level.SEVERE, "Error during testing connection " + dbName, e);
 		}
 

--- a/java/sql-dk/src/info/globalcode/sql/dk/configuration/Loader.java	Sun May 17 15:43:20 2015 +0200
+++ b/java/sql-dk/src/info/globalcode/sql/dk/configuration/Loader.java	Mon May 18 00:33:10 2015 +0200
@@ -78,7 +78,13 @@
 			try {
 				Class<Driver> driverClass = (Class<Driver>) Class.forName(driverClassName);
 				Driver driver = driverClass.newInstance();
-				return driver.connect(url, javaProperties);
+				Connection connection = driver.connect(url, javaProperties);
+				if (connection == null) {
+					log.log(Level.SEVERE, "Driver „{0}“ returend null → it does not accept the URL: „{1}“", new Object[]{driverClassName, url});
+					throw new SQLException("Unable to connect: driver returned null.");
+				} else {
+					return connection;
+				}
 			} catch (ClassNotFoundException | InstantiationException | IllegalAccessException | SQLException e) {
 				throw new SQLException("Unable to connect usig specific driver: " + driverClassName, e);
 			}