Jdbc
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JDBC (Java Database Connectivity) is an API that provides Java programs with the ability to connect to and interact with databases. It allows database-independent access to different database management systems (DBMS) using Java programming language. JDBC drivers are used to connect to databases and come in four types depending on how they interface with the database. The basic steps to use JDBC include registering a driver, connecting to the database, executing SQL statements, handling results, and closing the connection. Scrollable result sets and prepared statements are also introduced as advanced JDBC features.
![Update
while(rs.next()){
System.out.println(rs.getString("Firstname"));
}
rs.previous();
rs.updateString("Firstname", args[0]);
rs.updateRow();](https://image.slidesharecdn.com/jdbc-120503010505-phpapp02/85/Jdbc-20-320.jpg)
Jdbc
- 1. JDBC Jussi Pohjolainen Tampere University of Applied Sciences
- 2. JDBC Intro • Java Database Connec@vity in Java since 1.1 • API in Java for accessing Databases • PlaDorm independent, Database independent
- 3. Drivers • To access a database, you need a driver • To code in Java is always the same, changing the driver changes the connec@on to different database. • Lot’s of drivers for different databases: MySQL, Text, MS SQL Server..
- 4. Driver Types • JDBC Drivers are divided into four categories – Type 1 that calls na@ve code of the locally available ODBC driver. – Type 2 that calls database vendor na.ve library on a client side. – Type 3, the pure-‐java driver that talks with the server-‐side middleware that then talks to database. – Type 4, the pure-‐java driver that uses database na@ve protocol. • In most cases you can access the same database with four different type of drivers • List of drivers: – hQp://developers.sun.com/product/jdbc/drivers
- 5. To use JDBC 1. Register driver 2. Access database 3. Do some SQL magic 4. Handle result 5. Close the connec@on
- 6. 1. Register the Driver try { // The driver string here is given you by the // driver documentation. Class.forName("sun.jdbc.odbc.JdbcOdbcDriver"); } catch(ClassNotFoundException e) { System.out.println(”Can’t find the driver!"); }
- 7. 2. Connect to Database try { Class.forName ("sun.jdbc.odbc.JdbcOdbcDriver"); Connection conn = DriverManager.getConnection( "jdbc:odbc:mydatabasename", ”userlogin", ”password"); } catch(SQLException e) { } catch(ClassNotFoundException e) { }
- 8. 3. Some SQL Magic try { Class.forName ("sun.jdbc.odbc.JdbcOdbcDriver"); Connection conn = DriverManager.getConnection( "jdbc:odbc:mydatabasename", ”userlogin", ”password"); Statement statement = conn.createStatement(); statement.executeUpdate("DELETE FROM employees WHERE id<20"); } catch(SQLException e) { } catch(ClassNotFoundException e) { }
- 9. 5. Close connec@on try { Class.forName ("sun.jdbc.odbc.JdbcOdbcDriver"); Connection conn = DriverManager.getConnection( "jdbc:odbc:mydatabasename", ”userlogin", ”password"); Statement statement = conn.createStatement(); statement.executeUpdate("DELETE FROM employees WHERE id<20"); statement.close(); conn.close(); } catch(SQLException e) { } catch(ClassNotFoundException e) { }
- 10. Handle Result? • In previous example, the result of the SQL was boolean value (we did not handle it). • If SQL is select, then you can retrieve the results • Use ResultSet object. ResultSet holds the result of your SQL query • You can navigate in result set
- 11. 4. Handling Results try { Class.forName ("sun.jdbc.odbc.JdbcOdbcDriver"); Connection conn = DriverManager.getConnection( "jdbc:odbc:mydatabasename", ”userlogin", ”password"); Statement statement = conn.createStatement(); ResultSet rs = statement.executeQuery("SELECT * FROM employees"); while(rs.next()) { System.out.println(rs.getString("someColumn")); } statement.close(); conn.close(); } catch(SQLException e) { } catch(ClassNotFoundException e) { }
- 12. ResultSet rs.next(); rs.next(); rs.next(); // Prints “Williams” System.out.println(rs.getString(“Last Name”));
- 13. ResultSetMetaData • Don’t know column names? Or amount? • You can check these using ResultSetMetaData • Example usage: ResultSetMetaData rsmd = rs.getMetaData(); int numCols = rsmd.getColumnCount (); while (rs.next()) { for (int i=1; i<=numCols; i++) { System.out.println(rs.getString(i)); } }
- 14. Transac@ons • If you want to commit several sql – commands into one: – conn.setAutoCommit(false); – // do some sql – conn.commit(); – conn.rollback();
- 15. Prepared Statements • Prepared statement or parameterized statement is a feature used to execute the same or similar database statements repeatedly with high efficiency. • Example Connection con = connect(); String sql = "UPDATE table1 set one = ?, two = ?"; PreparedStatement preStmt = con.prepareStatement(sql); preStmt.setInt(1, 123); preStmt.setString(2, "myNewValue2"); preStmt.executeUpdate();
- 16. Scrollable Resultset Statement stmt = con.createStatement(ResultSet.TYPE_SCROLL_INSENSITIVE, ResultSet.CONCUR_READ_ONLY); ResultSet srs = stmt.executeQuery(SQLQuery);
- 17. Values • TYPE_FORWARD_ONLY (default) • TYPE_SCROLL_INSENSITIVE • TYPE_SCROLL_SENSITIVE – all updates happens immediately • CONCUR_READONLY • CONCUR_UPDATABLE
- 18. Methods for Scrollable ResultSet • next() • previous() • beforeFirst() • aierLast() • absolute(int x)
- 19. Update Result • It’s possible to update the result using methods – updateString() – updateInt() – updateFloat().. • Once updated, call updateRow(), which will move the result to database
- 20. Update while(rs.next()){ System.out.println(rs.getString("Firstname")); } rs.previous(); rs.updateString("Firstname", args[0]); rs.updateRow();
- 21. Adding a Row rs.moveToInsertRow(); rs.updateString("firstname", "Jack"); rs.updateString("lastname", "Smith"); rs.updateInt("idnumber", 20); rs.insertRow();
- 22. Dele@ng a Row • rs.last(); • rs.deleteRow();