This document discusses JDBC (Java Database Connectivity), which defines how Java programs can access databases. It describes the four types of JDBC drivers that convert Java requests into protocols understood by different database systems. It also explains how to load JDBC drivers at runtime, make database connections using the DriverManager, execute SQL queries with Statement objects to retrieve ResultSets, and move between rows in a ResultSet using a cursor.

1. By Rajan Shrivastava
Wipro 1

2. •API for Java which defines how program can
access a DB.
•JDBC(TM) - developed by Sun Microsystems
• Exploited an existing interface library (ODBC)
• ODBC - Open Database Connectivity (C library)—
standard Application Programming Interface for
connecting to db; independent of programming
languages, db systems, OS
• ODBC - C programmers DB interface, early 1990's

3. JDBC Drivers
 Client-side adaptors that convert Java program
requests into a protocol that DBMS understands
 4 types:
1. Type 1—JDBC-ODBC bridge
2. Type 2—Native API driver (converts JDBC calls to
DBMS API)
3. Type 3—Network protocol driver—can connect JDBC
to middleware-net server
4. Type 4—Driver-native protocol driver (converts
JDBC calls directly to DBMS protocol)

4. Loading a DriverManager
 DriverManager provides DB interface methods & defines objects
which can connect Java app to driver; it manages set of drivers
program can use to connect to db; finds driver & runs it to connect to
db
 Most Java programs use import to load a class
 With JDBC, usually load driver class at runtime:
import java.lang.*;
public static void main (String args[]) {
try { // this loads & initialises the driver
Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
// now connect to DB ...
} catch (ClassNotFoundException e) {
System.err.println(e.getMessage());
e.printStackTrace();
System.exit(1);
}
}

5. Making a JDBC-ODBC
Database Connection
import java.sql.*;
Connection con;
String URL = "jdbc:odbc:DataSource";
String Username = "";
String Password = "";
con = DriverManager.getConnection(URL,Username, Password);
// make more calls to JDBC methods here...
con.close();
 ‘DataSource’ is a ‘logical name’ (not a real filename)
 Need to set DataSource = MyDatabase.mdb elsewhere
 Use ODBC Data Source Administrator for this...

6. Statement and ResultSet Objects
Statement stmt = con.createStatement();
String sql = "SELECT * FROM Staff;";
ResultSet rs = stmt.executeQuery(sql);
print_rs(rs); // shown later
rs.close(); // free memory
stmt.close();
 Statement objects let you execute SQL queries: 3 types:
Statement (simple, no parameters), Prepared Statement
(precompiled queries), Callable Statement (execute call to
db stored sql procedure)
 Can pass any legal SQL query to executeQuery()
 Here, rs holds the entire results table (Staff)...

7. ResultSets and Cursors
The ResultSet object is a ‘container’ for the results of a
query (table):
 Each ResultSet contains:
 Numbered Fields (columns)
 Field names & types
(metadata)
 A Cursor (current row)
•First cursor position is BEFORE FIRST ROW
• Rows and columns COUNT FROM ONE
•Move cursor via: rs.next(), previous(), first(), last(),
relative(), absolute(), beforeFirst(), afterLast()

8. Type I Drivers
 Use bridging technology
 Requires installation/configuration on client
machines
 Not good for Web
 e.g. ODBC Bridge
Copyright © 1997 Alex Chaffee

9. Type II Drivers
 Native API drivers
 Requires installation/configuration on client
machines
 Used to leverage existing CLI libraries
 Usually not thread-safe
 Mostly obsolete now
 e.g. Intersolv Oracle Driver, WebLogic drivers
Copyright © 1997 Alex Chaffee

10. Type III Drivers
 Calls middleware server, usually on database host
 Very flexible -- allows access to multiple databases
using one driver
 Only need to download one driver
 But it’s another server application to install and
maintain
 e.g. Symantec DBAnywhere

11. Type IV Drivers
 100% Pure Java -- the Holy Grail
 Use Java networking libraries to talk directly to
database engines
 Only disadvantage: need to download a new driver
for each database engine
 e.g. Oracle, mSQL