Write a sql ResultSet to a csv file

ACupOfBreadTea :

I have a function that connects to a database, executes a sql query and tries to write the result into a file.

public class DBReader {

    public ResultSet executeSQL(SqlContainer sc) {
        String url = "url";
        String user = "user";
        String password = "pw";
        Connection con;
        Statement stmt;
        ResultSet rs;

        try {
            System.out.println("=== Started SQL ===");
            Class.forName("com.ibm.db2.jcc.DB2Driver");
            con = DriverManager.getConnection(url, user, password);
            con.setAutoCommit(false);
            stmt = con.createStatement();

            rs = stmt.executeQuery(sc.getSQL());


            CSVWriter writer = new CSVWriter(new FileWriter("result.csv"));
            writer.writeAll(rs, true);

            stmt.close();
            con.commit();
            con.close();

            System.out.println("    Finished SQL");
            return rs;
        } catch (SQLException | ClassNotFoundException | IOException e) {
            e.printStackTrace();
        }
        return null;
    }

}

Yet when I execute above function the file that comes out is empty. I've used following code to test if the result set is empty but if I execute:

while (rs.next()) {
                String value = rs.getString(4);
                System.out.println("Something = " + value);
            }

it returns some values.

I'd apreaciate any help or nods in the right direction, thanks in advance.

Kokogino :

You should close the writer as well:

writer.close();

Or better, you can use the try-with-resource statement which closes it automatically:

        try(CSVWriter writer = new CSVWriter(new FileWriter("result.csv"));) {
            System.out.println("=== Started SQL ===");
            Class.forName("com.ibm.db2.jcc.DB2Driver");
            con = DriverManager.getConnection(url, user, password);
            con.setAutoCommit(false);
            stmt = con.createStatement();

            rs = stmt.executeQuery(sc.getSQL());

            writer.writeAll(rs, true);

            stmt.close();
            con.commit();
            con.close();

            System.out.println("    Finished SQL");
            return rs;
        } catch (SQLException | ClassNotFoundException | IOException e) {
            e.printStackTrace();
        }