Testing DB2 behavior regarding https://github.com/mybatis/mybatis-3/issues/1288

Db2GenKeys.java

/**
 *    Copyright 2009-2018 the original author or authors.
 *
 *    Licensed under the Apache License, Version 2.0 (the "License");
 *    you may not use this file except in compliance with the License.
 *    You may obtain a copy of the License at
 *
 *       http://www.apache.org/licenses/LICENSE-2.0
 *
 *    Unless required by applicable law or agreed to in writing, software
 *    distributed under the License is distributed on an "AS IS" BASIS,
 *    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *    See the License for the specific language governing permissions and
 *    limitations under the License.
 */
import java.sql.*;
import java.util.*;
import java.nio.file.*;

public class Db2GenKeys {
  public static void main(String[] args) throws Exception {
    try {
      Class.forName("com.ibm.db2.jcc.DB2Driver");
      String url = "jdbc:db2://192.168.62.100:50000/mybatis:enableExtendedDescribe=1;";
      String username = "db2inst1";
      String password = "db2inst1";
      Connection con = DriverManager.getConnection(url, username, password);

      {
        Statement stmt = con.createStatement();
        try {
          stmt.execute("drop table gh1288");
        } catch (SQLException e) {
          //
        }
        stmt.execute("create table gh1288 (id int primary key generated always as identity, name varchar(16))");
        stmt.close();
      }

      try {

        {
          System.out.println("INSERT without batch");
          PreparedStatement stmt = con.prepareStatement("insert into gh1288 (name) values (?)", Statement.RETURN_GENERATED_KEYS);
          stmt.setString(1, "aaa" + 1);
          int result = stmt.executeUpdate();
          System.out.println(result);
          ResultSet rs = stmt.getGeneratedKeys();
          ResultSetMetaData rsmd = rs.getMetaData();
          System.out.println(rsmd);
          stmt.close();
          con.commit();
        }

        {
          System.out.println("INSERT with batch");
          PreparedStatement stmt = con.prepareStatement("insert into gh1288 (name) values (?)", Statement.RETURN_GENERATED_KEYS);
          for (int i = 0; i < 3; i++) {
            stmt.setString(1, "aaa" + i);
            stmt.addBatch();
          }
          int[] result = stmt.executeBatch();
          System.out.println(Arrays.toString(result));
          ResultSet rs = stmt.getGeneratedKeys();
          ResultSetMetaData rsmd = rs.getMetaData();
          System.out.println(rsmd);
          stmt.close();
          con.commit();
        }

      } finally {
        con.close();
      }
    } catch (Exception e) {
      e.printStackTrace();
    }
  }
}

Result:

INSERT without batch
1
com.ibm.db2.jcc.am.an@1810399e
INSERT with batch
[1, 1, 1]
null

• DB2 Express-C 11.1
• db2jcc4-4.24.92.jar
• enableExtendedDescribe=1 in the URL didn't change the result.