Dao层中的crud操作

JdbcTemplate jd = new JdbcTemplate(DBUtil.getDataSource());
@Override
public List queryAll() {

    List<Customer> list = null;
    String sql = "select * from customer";
    try {
        list = jd.query(sql, new BeanPropertyRowMapper<>(Customer.class));
    }catch (Exception e){
        e.printStackTrace();
    }
    return list;
}

@Override
public int add(Customer customer) {
    String sql = "insert into customer values(?,?,?,?,?,?)";
    int count = jd.update(sql,null,customer.getName(), customer.getAddress(), customer.getSource(), customer.getPhone(), customer.getLevel());
    return count;
}

@Override
public void delete(int id) {
    String sql = "delete  from customer where customer.id = ?";
    jd.update(sql,id);

}

@Override
public void update(int i, Customer customer) {
    String sql = "update customer set name = ?, address = ?,source = ?,phone = ?,level = ? where id = ?";
    jd.update(sql,customer.getName(),customer.getAddress(),customer.getSource(),customer.getPhone(),customer.getLevel(),i);
}

@Override
public Customer queryById(int i) {
    String sql = "select * from customer where customer.id = ?";
    return jd.queryForObject(sql, new BeanPropertyRowMapper<>(Customer.class),i);
}