Java JDBC Only Inserts Nulls into MySQL Table

Question

I am trying to insert data into a MySQL table via a JDBC connection in Java. I can establish a connection. However, my code only inserts null values for all my columns. I am using dummy data in my prepared statement and expect to see non-null values.

Any thoughts or guidance as to what may be going on? I am new to JBDC and Java.

Here is how I create my table:

    drop table market_data.abc;
create table market_data.abc(
`v` int,
`w` int
)
;

Here is how I create a connection:

    public static Connection ConnectToDB() throws Exception {

        // register driver
        DriverManager.registerDriver(new com.mysql.jdbc.Driver());

        // create database url
        mysqlUrl = "jdbc:mysql://localhost:3306/" + databaseName + "?characterEncoding=" + encoding
                + "&&useUnicode=" + unicode; 

        // create connection
        Connection con = DriverManager.getConnection(mysqlUrl, userName, password);

        // print connection status message
        System.out.println("Connection established......");

        // return database connection
        return con;
    }

Here is where I insert data:

void insertRecords() {
        try {

            // Establish Connection
            Connection con = cc.ConnectToDB();

            // Set the query structure
            String insertString = "INSERT INTO abc values (" + "v=?,w=?)";

            // Set prepared statement
            PreparedStatement statement = con.prepareStatement(insertString);

            // set values to variables
            int v1 = 2;
            int w1 = 3;

            // set values to statement
            statement.setInt(1, v1);
            statement.setInt(2, w1);

            // execute the insert operation; 
            statement.executeUpdate();

            // print status message for record insertion
            System.out.println("New Records inserted.....");

        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } catch (ParseException e) {
            e.printStackTrace();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

Here is what I see when I do a Select * from the CLI:

 v    | w    |
+------+------+
| NULL | NULL |
| NULL | NULL |
+------+------+

Here are my MySQL character set variables:

show variables like 'char%';
+--------------------------+-----------------------------------------------------------+
| Variable_name            | Value                                                     |
+--------------------------+-----------------------------------------------------------+
| character_set_client     | utf8mb4                                                   |
| character_set_connection | utf8mb4                                                   |
| character_set_database   | utf8mb4                                                   |
| character_set_filesystem | binary                                                    |
| character_set_results    | utf8mb4                                                   |
| character_set_server     | utf8mb4                                                   |
| character_set_system     | utf8                                                      |
| character_sets_dir       | /usr/local/mysql-8.0.20-macos10.15-x86_64/share/charsets/ |
+--------------------------+-----------------------------------------------------------+

Answer 1

try to replace insertString value with this one value

String insertString = "INSERT INTO abc values (v=?,w=?)";

and take care that INSERT statement has tow writing types.

first type is:

INSERT INTO table_name (column1, column2, column3, ...)
VALUES (value1, value2, value3, ...); 

second one is:

INSERT INTO table_name
VALUES (value1, value2, value3, ...);