Question

I have 3 columns in my MySQL table, 2 are INTs and one VARCHAR.

I am getting class cast exception: java.lang.ClassCastException: java.lang.Long cannot be cast to java.lang.Integer. Heres my code:

    List<Map<String, Object>> rows = getJdbcTemplate().queryForList(sql);
    for (Map row : rows) {
        Customer customer = new Customer();
            // throws ClassCastException
            // customer.setCustId((Integer)(row.get("CUST_ID")));

        customer.setCustId((Long)(row.get("CUST_ID")));  // had to change custId field in bean to long
        customer.setName((String)row.get("NAME"));

        // work around
        customer.setAge(((Long)row.get("AGE")).intValue());

        customers.add(customer);
    }

My question is why do i have to cast it to Long? Is it because the maximum allowed INT value in MySQL and the maximum allowed int value by java are not same?

Answer 1

MySQL primary key integers are unsigned, Java ints are signed. Same number of bits, but the unsigned has a full 4G positive range.