KMUTNB - Internet Programming 6/7

KMUTNB - Internet Programming 6/7

• 1.
  JSP&DB Programming By: Mr. PHUPHA PUNYAPOTASAKUL ( ภูผา ปัญญาโพธาสกุล )
• 2.
  Architecture
• 3.
  JDBC Connect toa data source, like a database Send queries and update statements to the database Retrieve and process the results received from the database in answer to your query
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  Establish connection Initializedriver Class . forName ( driver ) ; Create Connection Connection conn = DriverManager . getConnection ( url,user,password ) ; Each JDBC Vendor may use different driver class name and url
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  Driver class nameand URL example Oracle 10i driver = oracle . jdbc . driver . OracleDriver url = jdbc : oracle : thin : @ // {DBSERVER} : 1521 / {DBNAME} MySQL 4 . x, 5 . x driver = com . mysql . jdbc . Driver url = jdbc : mysql :// {DBSERVER} / {DBNAME} MS SQLServer 2000, 2005 driver = com . microsoft . sqlserver . jdbc . SQLServerDriver url = jdbc : sqlserver :// {DBSERVER} : 1433;databaseName = {DBNAME};integratedSecurity = false;
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  Create statement andexecute SQL command Create statement Statement stmt = con.createStatement( ResultSet.TYPE_SCROLL_INSENSITIVE,ResultSet.CONCUR_READ_ONLY ) ; Execute Update stmt.execut eUpdate ( sql ); Execute Query ResultSet rs = stmt . executeQuery ( sql ) ;
• 7.
  ResultSet type TYPE_FORWARD_ONLY — The result set is not scrollable; its cursor moves forward only, from before the first row to after the last row. The rows contained in the result set depend on how the underlying database materializes the results. That is, it contains the rows that satisfy the query at either the time the query is executed or as the rows are retrieved. TYPE_SCROLL_INSENSITIVE — The result set is scrollable; its cursor can move both forward and backward relative to the current position, and it can move to an absolute position . TYPE_SCROLL_SENSITIVE — The result set is scrollable; its cursor can move both forward and backward relative to the current position, and it can move to an absolute position.
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  Concurent Type CONCUR_READ_ONLYCONCUR_UPDATABLE
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  ResultSet movement next() - moves the cursor forward one row. Returns true if the cursor is now positioned on a row and false if the cursor is positioned after the last row. previous () - moves the cursor backwards one row. Returns true if the cursor is now positioned on a row and false if the cursor is positioned before the first row. first () - moves the cursor to the first row in the ResultSet object. Returns true if the cursor is now positioned on the first row and false if the ResultSet object does not contain any rows. last() - moves the cursor to the last row in the ResultSet object . Returns true if the cursor is now positioned on the last row and false if the ResultSet object does not contain any rows .
• 10.
  ResultSet movement beforeFirst() - positions the cursor at the start of the ResultSet object, before the first row . If the ResultSet object does not contain any rows, this method has no effect . afterLast() - positions the cursor at the end of the ResultSet object, after the last row . If the ResultSet object does not contain any rows, this method has no effect . relative(int rows) - moves the cursor relative to its current position . absolute(int row) - positions the cursor on the row - th row of the ResultSet object .
• 11.
  Retrieving data Datatype conversion getString() getInt() getFloat() getDate() etc. 2 ways to retrieve data e.g. select product_name from product By column name getString("product_name"); By column index (start from 1) getString(1);
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  Updating data Onlyif using CONCUR_UPDATABLE Not all JDBC Driver support this mode Data type conversion upateString() updateInt() updateFloat() updateDate() etc. Be able to use both column name and index
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  Updating data Toinsert a new record rs.moveToInsertRow() rs.updateString(1,"XXX"); rs.insertRow(); To update a record //move to expected record rs.updateString(1,"XXX"); rs.updateRow(); To delete a record //move to expected record rs.deleteRow();
• 14.
  Exception handling Connectionconn = null; Statement stmt = null; ResultSet rs = null; try{ ... }catch ( SQLException ex ) { String sqlErr ="" ; while ( ex != null ) { sqlErr = sqlErr + " \nMessage : " + ex . getMessage () ; sqlErr = sqlErr + " \nSQLState : " + ex . getSQLState () ; sqlErr = sqlErr + " \nErrorCode : " + ex . getErrorCode () ; sqlErr = sqlErr + " \n -----------------------------------------------------------" ; ex = ex . getNextException () ; } System . out . println ( sqlErr ) ; }catch ( Exception ex ) { ex . printStackTrace () ; }finally{ try{ if ( rs != null ) rs . close () ; }catch ( Exception e ) {} try{ if ( stmt != null ) stmt . close () ; }catch ( Exception e ) {} try{ if ( conn != null ) conn . close () ; }catch ( Exception e ) {} }
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  Prepared Statement CreateStatement PreparedStatement pstmt = conn . prepareStatement ( sql,rtype,concur ) ; SQL with parameter using "?" E.g. select * from product where product_id=? and is_enable=? Set parameter value setString() setFloat() setInt() setDate()
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  Prepared Statement Useparameter index only - can't use column name (start from 1) pstmt.setString(1,"XXX"); Execute query or update normally ResultSet rs=pstmt.executeQuery(); pstmt.executeUpdate(); Re-usable
• 17.
  Question & Answer