java JDBC-演示事务出错回滚操做

public class Demo6 {
    public static void main(String[] args)  {
        Connection conn=null;
        PreparedStatement ps=null;
        PreparedStatement ps2=null;
        ResultSet rs=null;
        try {
            Class.forName("com.mysql.jdbc.Driver");
                conn=DriverManager.getConnection("jdbc:mysql://localhost:3306/test","root","dyl123");

        conn.setAutoCommit(false);

        ps=conn.prepareStatement("insert into t_user (username,pwd) values(?,?)");
        ps.setString(1, "前端");
        ps.setObject(2,"123456");
        ps.execute();
        System.out.println("插入一个用户1");

        try {
            Thread.sleep(6000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }

        ps2=conn.prepareStatement("insert into t_user (username,pwd) values(?,?,?)"); //现出错误
        ps2.setString(1, "html");
        ps2.setObject(2,"2222");
        ps2.execute();
        System.out.println("插入一个用户2");
        conn.commit();

    } catch (ClassNotFoundException e) {
        e.printStackTrace();
        try {
            conn.rollback();  //事务回滚，使得事务出错都不执行
        } catch (SQLException e1) {
            e1.printStackTrace();
        }

    } catch (SQLException e) {
        e.printStackTrace();
    }finally {
        try {
            if(null!=rs)
            {
                rs.close();
            }
        }catch (SQLException e) {
            e.printStackTrace();
        }
            try {
                if(null!=ps)
                {
                    ps.close();
                }
            }catch (SQLException e) {
                e.printStackTrace();
            }
            try{
                if(null!=conn)
                {
                    conn.close();
                }

            }catch (SQLException e) {
                e.printStackTrace();
            }

    }
}
}