public class UserDao {
    public void get(String username){
        Connection conn=null;
        try {
            conn=OracleConnectionUtil.getConnection();
            conn.setAutoCommit(false);
            conn.setTransactionIsolation(Connection.TRANSACTION_SERIALIZABLE);
            PreparedStatement pstat = conn.prepareStatement("select * from user2 where username=?");
            pstat.setString(1,username);
            ResultSet rs = pstat.executeQuery();
            if(rs.next()){
                System.out.println(rs.getString(2));
            }
            rs.close();
            pstat.close();
            update(username,"2dddddddd");//更新上面查询的字段
            conn.commit();
        } catch (SQLException e) {
            e.printStackTrace();
        }finally{
            if(conn!=null){
                try {
                    conn.close();
                } catch (SQLException e) {
                    e.printStackTrace();
                }
            }
        }
    }
    public void insert(String username, String password){
        Connection conn=null;
        try {
            conn=OracleConnectionUtil.getConnection();
            conn.setAutoCommit(false);
            PreparedStatement pstat = conn.prepareStatement("insert into user2 values(?,?)");
            pstat.setString(1, username);
            pstat.setString(2, password);
            pstat.execute();
            pstat.close();
            conn.commit();
        } catch (SQLException e) {
            
            e.printStackTrace();
        }finally{
            if(conn!=null){
                try {
                    conn.close();
                } catch (SQLException e) {
                    e.printStackTrace();
                }
            }
        }
    }
    public void update(String username, String password){
        Connection conn=null;
        try {
            conn=OracleConnectionUtil.getConnection();
            conn.setAutoCommit(false);
            PreparedStatement pstat = conn.prepareStatement("update user2 set password=? where username=?");
            pstat.setString(2, username);
            pstat.setString(1, password);
            pstat.execute();
            pstat.close();
            conn.commit();
        } catch (SQLException e) {
            
            e.printStackTrace();
        }finally{
            if(conn!=null){
                try {
                    conn.close();
                } catch (SQLException e) {
                    e.printStackTrace();
                }
            }
        }
    }
    public static void main(String[] args) {
        UserDao dao = new UserDao();
        dao.get("u1");
    }
}