The meaning of rollback---the research of JDBC transaction rollback

The common notation for JDBC manual transaction commit rollback has been that rollback is written after the commit catch:

Try　　{   conn.setautocommit (false);　　Ps.executeupdate (); Ps.executeupdate (); conn.commit ();} Catch (Exception e) {       }

However, there is no point in this rollback:

Once a commit error occurs, it is not committed and rollback is useless

Once commit, it's true, don't roll back.

Find an article with the same opinion as mine:

Rollback submission for <JDBC Transactions >

I thought there was no need to roll back, and even if I had to roll back, I would have to write the commit after the try...catch of the main business, and rollback when the main business went wrong.

Table: JDBC Transaction 3 notation Rollback comparison

ImportJava.sql.*; Public classTESTJDBC { Public Static FinalString URL = "Jdbc:mysql://127.0.0.1/test";  Public Static FinalString user_name = "root";  Public Static FinalString user_pwd = "root"; Private StaticConnection conn =NULL; Private StaticPreparedStatement PS; Private Static voidConnopen ()throwsSQLException {conn=drivermanager.getconnection (URL, user_name, user_pwd); }    Private Static voidConnclose ()throwsSQLException {if(PS! =NULL) {ps.close (); PS=NULL; }        if(Conn! =NULL) {conn.close (); Conn=NULL; }    }    Private Static voidTestrollback ()throwsSQLException {connopen (); Try{ conn.setautocommit ( false); String strSQL= "INSERT into customer (UNAME,PWD) VALUES (?, ' 1 ')"; PS=conn.preparestatement (strSQL); //Insert a piece of dataPs.setstring (1, "Goku");            Ps.executeupdate (); //out of the exception            if(true) {                Throw NewSQLException (); }            //Insert a second piece of dataPs.setstring (1, "Eight commandments");            Ps.executeupdate (); //conn.commit ();}Catch(Exception e) {System.out.println ("Exceptional!"); Try{ conn.rollback (); } Catch(SQLException E1) {e1.printstacktrace (); }        }        Try{ conn.commit (); } Catch(SQLException e) {e.printstacktrace ();    } connclose (); }    Private Static voidSelectAll ()throwsSQLException {connopen (); PS= Conn.preparestatement ("SELECT * FROM Customer"); ResultSet RS=Ps.executequery ();  while(Rs.next ()) {System.out.print (rs.getstring (2) + ":"); System.out.println (Rs.getstring (1));    } connclose (); }     Public Static voidMain (string[] args)throwsSQLException {testrollback ();    SelectAll (); }}

The meaning of rollback---the research of JDBC transaction rollback