[#3346] Allow for omitting the JDBC driver property in the code generator

jOOQ-codegen/src/main/java/org/jooq/util/GenerationTool.java

@@ -191,7 +191,7 @@ public class GenerationTool {
             // ---------------------
             if (connection == null) {
                 errorIfNull(j, "The <jdbc/> tag is mandatory.");
-                loadClass(j.getDriver());
+                loadClass(driverClass(j));
 
                 Properties properties = new Properties();
                 for (Property p : j.getProperties()) {
@@ -384,6 +384,17 @@ public class GenerationTool {
         }
     }
 
+    private String driverClass(Jdbc j) {
+        String result = j.getDriver();
+
+        if (result == null) {
+            result = JDBCUtils.driver(j.getUrl());
+            log.info("Database", "Inferring driver " + result + " from URL " + j.getUrl());
+        }
+
+        return result;
+    }
+
     private Class<? extends Database> databaseClass(Jdbc j) {
         SQLDialect dialect = JDBCUtils.dialect(j.getUrl());
         Class<? extends Database> result = JDBCDatabase.class;

jOOQ-test/src/test/java/org/jooq/test/all/testcases/JDBCTests.java

@@ -101,4 +101,8 @@ extends BaseTest<A, AP, B, S, B2S, BS, L, X, DATE, BOOL, D, T, U, UU, I, IPK, T7
             cp.release(c);
         }
     }
+
+    public void testDriverGuessing() throws Exception {
+        Class.forName(JDBCUtils.driver(getConnection().getMetaData().getURL()));
+    }
 }

jOOQ-test/src/test/java/org/jooq/test/jOOQAbstractTest.java

@@ -2967,6 +2967,11 @@ public abstract class jOOQAbstractTest<
         new JDBCTests(this).testDialectGuessing();
     }
 
+    @Test
+    public void testDriverGuessing() throws Exception {
+        new JDBCTests(this).testDriverGuessing();
+    }
+
     @Test
     public void testTransactionsWithJDBCSimple() throws Exception {
         new TransactionTests(this).testTransactionsWithJDBCSimple();

jOOQ/src/main/java/org/jooq/tools/jdbc/JDBCUtils.java

@@ -179,6 +179,51 @@ public class JDBCUtils {
         return SQLDialect.SQL99;
     }
 
+    /**
+     * "Guess" the JDBC driver from a connection URL.
+     */
+    public static final String driver(String url) {
+        switch (dialect(url).family()) {
+            case CUBRID:
+                return "cubrid.jdbc.driver.CUBRIDDriver";
+            case DERBY:
+                return "org.apache.derby.jdbc.ClientDriver";
+            case FIREBIRD:
+                return "org.firebirdsql.jdbc.FBDriver";
+            case H2:
+                return "org.h2.Driver";
+            case HSQLDB:
+                return "org.hsqldb.jdbcDriver";
+            case MARIADB:
+                return "org.mariadb.jdbc.Driver";
+            case MYSQL:
+                return "com.mysql.jdbc.Driver";
+            case POSTGRES:
+                return "org.postgresql.Driver";
+            case SQLITE:
+                return "org.sqlite.JDBC";
+
+            /* [pro] xx
+            xxxx xxxxxxx
+                xxxxxx xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
+            xxxx xxxx
+                xxxxxx xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
+            xxxx xxxx
+                xxxxxx xxxxxxxxxxxxxxxxxxxxxxxxxxxx
+            xxxx xxxxxxx
+                xxxxxx xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
+            xxxx xxxxxxx
+                xxxxxx xxxxxxxxxxxxxxxxxxxxxxxxxxx
+            xxxx xxxxxxxxxx
+                xxxxxx xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
+            xxxx xxxxxxx
+                xxxxxx xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
+            xx [/pro] */
+        }
+
+        return "java.sql.Driver";
+    }
+
     /**
      * Safely close a connection.
      * <p>