diff --git a/jOOQ-codegen/src/main/java/org/jooq/util/GenerationTool.java b/jOOQ-codegen/src/main/java/org/jooq/util/GenerationTool.java
index 9092caee90..f732efc395 100644
--- a/jOOQ-codegen/src/main/java/org/jooq/util/GenerationTool.java
+++ b/jOOQ-codegen/src/main/java/org/jooq/util/GenerationTool.java
@@ -55,6 +55,7 @@
 import java.io.StringReader;
 import java.sql.Connection;
 import java.sql.Driver;
+import java.sql.SQLException;
 import java.util.List;
 import java.util.Properties;
 
@@ -237,9 +238,11 @@ public void run(Configuration configuration) throws Exception {
 
             org.jooq.util.jaxb.Database d = defaultIfNull(g.getDatabase(), new org.jooq.util.jaxb.Database());
             String databaseName = trim(d.getName());
-            Class<? extends Database> databaseClass = isBlank(databaseName)
-                ? databaseClass(j)
-                : (Class<? extends Database>) loadClass(databaseName);
+            Class<? extends Database> databaseClass = !isBlank(databaseName)
+                ? (Class<? extends Database>) loadClass(databaseName)
+                : connection != null
+                ? databaseClass(connection)
+                : databaseClass(j);
             Database database = databaseClass.newInstance();
             database.setProperties(properties(d.getProperties()));
 
@@ -442,8 +445,24 @@ private String driverClass(Jdbc j) {
     }
 
     private Class<? extends Database> databaseClass(Jdbc j) {
-        Class<? extends Database> result = Databases.databaseClass(JDBCUtils.dialect(j.getUrl()));
-        log.info("Database", "Inferring database " + result.getName() + " from URL " + j.getUrl());
+        return databaseClass(j.getUrl());
+    }
+
+    private Class<? extends Database> databaseClass(Connection c) {
+        try {
+            return databaseClass(c.getMetaData().getURL());
+        }
+        catch (SQLException e) {
+            throw new RuntimeException(e);
+        }
+    }
+
+    private Class<? extends Database> databaseClass(String url) {
+        if (isBlank(url))
+            throw new RuntimeException("No JDBC URL configured.");
+
+        Class<? extends Database> result = Databases.databaseClass(JDBCUtils.dialect(url));
+        log.info("Database", "Inferring database " + result.getName() + " from URL " + url);
         return result;
     }
 
diff --git a/jOOQ/src/main/java/org/jooq/tools/jdbc/JDBCUtils.java b/jOOQ/src/main/java/org/jooq/tools/jdbc/JDBCUtils.java
index 7c151de90e..073ad031b2 100644
--- a/jOOQ/src/main/java/org/jooq/tools/jdbc/JDBCUtils.java
+++ b/jOOQ/src/main/java/org/jooq/tools/jdbc/JDBCUtils.java
@@ -43,6 +43,7 @@
 // ...
 import static org.jooq.SQLDialect.CUBRID;
 // ...
+import static org.jooq.SQLDialect.DEFAULT;
 import static org.jooq.SQLDialect.DERBY;
 import static org.jooq.SQLDialect.FIREBIRD;
 import static org.jooq.SQLDialect.H2;
@@ -94,20 +95,22 @@ public class JDBCUtils {
     public static final SQLDialect dialect(Connection connection) {
         SQLDialect result = SQLDialect.DEFAULT;
 
-        try {
-            DatabaseMetaData m = connection.getMetaData();
+        if (connection != null) {
+            try {
+                DatabaseMetaData m = connection.getMetaData();
 
-            /* [pro] xx
-            xxxxxx xxxxxxx x xxxxxxxxxxxxxxxxxxxxxxxxxxx
-            xx xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx x
-                xxxxxx xxxxxxxxxxxxxxxxxx
-            x
-            xx [/pro] */
+                /* [pro] xx
+                xxxxxx xxxxxxx x xxxxxxxxxxxxxxxxxxxxxxxxxxx
+                xx xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx x
+                    xxxxxx xxxxxxxxxxxxxxxxxx
+                x
+                xx [/pro] */
 
-            String url = m.getURL();
-            result = dialect(url);
+                String url = m.getURL();
+                result = dialect(url);
+            }
+            catch (SQLException ignore) {}
         }
-        catch (SQLException ignore) {}
 
         if (result == SQLDialect.DEFAULT) {
             // If the dialect cannot be guessed from the URL, take some other
@@ -121,6 +124,8 @@ public static final SQLDialect dialect(Connection connection) {
      * "Guess" the {@link SQLDialect} from a connection URL.
      */
     public static final SQLDialect dialect(String url) {
+        if (url == null)
+            return DEFAULT;
 
         // The below list might not be accurate or complete. Feel free to
         // contribute fixes related to new / different JDBC driver configuraitons
@@ -185,7 +190,7 @@ else if (url.startsWith("jdbc:sqlite:")) {
         x
         xx [/pro] */
 
-        return SQLDialect.DEFAULT;
+        return DEFAULT;
     }
 
     /**