MySQL & JDCB Αλέξανδρος Καρακασίδης Δεκέμβριος 2004

// Main Class. It also inherits from JFrame to open a window public class Example1 extends JFrame{ // Connect to the database test, at server localhost static String url="jdbc:mysql://localhost/test"; // The connection object. This holds all connection information static Connection con; … }

Main Function Example1(login,pass); // Constructor – Connection Initialization app.createTable(); // Creation of the Table in the Database app.insertData(); // Data Insertion app.getData(); // Data Selection and Display in a Window app.dropTable(); // Creation of the Table in the Database

Connection Initialization public void myinit(String login, String pass){ //Driver to be added at: $JAVA_HOME/jre/lib/ext/ //Driver refers to a.jar file, e.g., mysql-connector-java stable-bin.jar // Load the Driver by adding the proper path inside the jar try { Class.forName("com.mysql.jdbc.Driver"); //Class.forName("org.gjt.mm.mysql.Driver"); } catch (java.lang.ClassNotFoundException e) {...} // Connect to the Database try { con = DriverManager.getConnection (url, login, pass); } catch(SQLException ex) {...} }

public void createTable() Statement stmt; // Used to send the SQL Query through the connection to the DBMS // Query to create the table String query="CREATE TABLE `partsupp` ( PS_PARTKEY` int(11) NOT NULL default '0',"+ "`PS_SUPPKEY` int(11) NOT NULL default '0', `PS_AVAILQTY` int(11) NOT NULL default '0',"+ "`PS_SUPPLYCOST` decimal(10,0) NOT NULL default '0',`PS_COMMENT` varchar(199) NOT NULL default '') COMMENT='TPC-H partsup table'"; try // Connect to the DBMS and send the query { stmt = con.createStatement(); // Create the statement stmt.executeUpdate(query); // Execute UPDATE. CAUTION! It is an update! stmt.close(); // Close the statement } catch(SQLException ex){ System.err.println("SQLException: "+ex.getMessage()); }

public void insertData() (1/2) public void insertData() { Statement stmt; // Used to send the SQL Query through the connection to the DBMS String data= // Data to insert "2|3|8895|378.49|furiously_even_asymptotes_are_furiously_regular_plate |\n“ +…. + "2|939|3025|306.39|deposits_according_to_the_final,_special_foxes_dete c|\n"; // Separate the rows StringTokenizer rowt = new StringTokenizer(data,"\n"); …

public void insertData() (2/2) int num_rows = rowt.countTokens(); // Count rows try{ for(int j=0; j<num_rows; j++){ row = rowt.nextToken(); // Take each row StringTokenizer st = new StringTokenizer(row,"|"); // Separate Fields for(int i=0; i<5; i++) {mytoken[i] = st.nextToken();} // we have 5 fields query ="INSERT INTO `partsupp` VALUES ('"+ // Query to insert data mytoken[0]+"','"+mytoken[1]+"','"+mytoken[2]+"','"+mytoken[3]+"','"+mytoken [4]+"')"; stmt.executeUpdate(query); // Execute UPDATE. CAUTION! It is an update! } stmt.close(); } catch(SQLException ex) {…}}

public void getData() ResultSet res; // The cursor that holds the result String query="SELECT PS_AVAILQTY,PS_SUPPLYCOST FROM `partsupp`"; try {stmt = con.createStatement(); // Execute QUERY. CAUTION! It is a query returning results! res = stmt.executeQuery(query); while( res.next() ) { // Extract each result row and print it on screen qty = res.getInt("PS_AVAILQTY"); cost = res.getInt("PS_SUPPLYCOST"); System.out.println(qty+":"+cost); } // End while stmt.close(); } catch(SQLException ex) {..}

public void dropTable() // Can You Explain it? Statement stmt; String query="DROP TABLE `partsupp`"; try{ stmt = con.createStatement(); stmt.executeUpdate(query); stmt.close(); } catch(SQLException ex) { System.err.println("SQLException: "+ex.getMessage()); }