An Introduction to JDBC
renamed and included in the exjava directory. Another directory,
exgwe, contains the source and classes for the Gwe Mysql JDBC driver.
These classes make use of the classes in the exjava directory. Add the
directory in which the tar file was unpacked to the CLASSPATH
environment variable. This completes the installation of the JDBC
driver.
A Sample JDBC Program:
This example below assumes you have some familiarity with Java. The
Java code below loads the JDBC driver class, establishes a connection
with a database, builds an SQL statement, submits the statement, and
retrieves the results. We assume there is an existing database and a
table populated with some data.
import java.net.URL;
import exjava.sql.*;
import exgwe.sql.*;
public class jdbc_test {
public static void main (String argv[] )
{
try {
// Load the gweMysqlDriver JDBC Driver
Class.forName("exgwe.sql.gweMysqlDriver");
// Create the url of the database we wish to connect to
String url = "jdbc:mysql://localhost:3306/test";
// Set up a connection
Connection con = DriverManager.getConnection(url, "userid","pass");
// Create statement
Statement stmt = con.createStatement();
// Execute query
String query = "select name, phone from test_table";
// Obtain the result set
ResultSet rs = stmt.executeQuery(query);
// Loop through each result row
while (rs.next() )
{ System.out.println( rs.getString(0), rs.getInt(1) ); }
// Close result set
rs.close();
// Close statement
stmt.close();
// Close connection
con.close();
}
catch( Exception e ) { e.printStackTrace(); }
}
}
In the first line, the class object for the JDBC driver is loaded by
passing its fully qualified name to the Class.forname() method. This
method loads the class, if it is not already loaded and returns a
Class object for it. In the next line, the database URL string is
constructed. It is in the form "jdbc:subprotocol name: hostname:
port/database name/other parameters". The subprotocol name is mysql
since we are using the Mysql database. The hostname is localhost in
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