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JDBC Drivers
DB2 UDB provides for JDBC connectivity through a number of Java classes and interfaces that implement the JDBC specification. The implementation is known as a JDBC driver. DB2 currently offers JDBC drivers known as legacy/CLI drivers and the universal JDBC driver.
Using the JDBC Type 2 Driver
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JDBC 2 Type 2 drivers use an OS-specific library to facilitate communication with DB2. DB2 ships with two different type 2 drivers: the legacy/CLI JDBC driver and the universal JDBC driver. This interaction is illustrated in Figure 1.
Figure 1 JDBC Type 2 driver implementation: the legacy/CLI JDBC driver.
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The legacy/CLI JDBC driver is provided in the file db2java.zip which is in the default DB2 installation directory, "c:\Program Files\IBM\SQLLIB\java".
If you are trying to interact with a remote database using the legacy/CLI JDBC driver, you need to use the DB2 Configuration Assistant. Under the covers, this driver performs a native connect through a local DB2 client. If you have installed a DB2 UDB v8 server, you will have the Configuration Assistant and the rest of the DB2 product. If you are connecting to a remote DB2 server, you should install the DB2 Application Development Client or the DB2 Runtime Client. These clients are downloadable for free at http://www-306.ibm.com/software/data/db2/udb/support.html.
For Java development, the only required DB2 software is the runtime client, and it is a much smaller download image (around 68MB for Windows and 200MB for Linux). If you decide that the Universal JDBC driver in type 4 mode is all you really need, you can simply copy the db2jcc.jar file and its corresponding license jar file from an existing installation. These two files would result in less than 1MB of disk space.
If you are just getting started with DB2 locally on your own machine we would recommend that you download the DB2 Personal Developer's Edition product.
Figure 2 shows the DB2 Configuration Assistant (db2ca), it can be used to catalog the DB2 database and the node directory information that will be used by the JDBC driver to locate the DB2 database on a remote server.
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Figure
2 DB2 Configuration Assistant.
Before you start your endeavors of hooking up to DB2 via Java, it is a good idea to ensure connectivity to your remote database. This can be done using the Configuration Assistant, as shown in Figure 3.
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Figure
3 Test the DB2 connection.
The code of Listing 1 shows the programmatic access of the database we created earlier. Note that the implementation package name is com.ibm.db2.jdbc.app.DB2Driver. Listing 1, 2, and 3 all do the same thing. They simply retrieve data from the database we created using a simple SQL query.
Listing 1 Use of the legacy/CLI JDBC driver (db2java.zip), a JDBC-type driver to interact with DB2
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
public class Type2ExampleLegacy {
public static void main(String[] args)
{
try
{
// load the DB2 Driver
Class.forName("COM.ibm.db2.jdbc.app.DB2Driver");
// establish a connection to DB2
Connection db2Conn =
DriverManager.getConnection
("jdbc:db2:phoneDB","db2admin","db2admin");
// use a statement to gather data from the database
Statement st = db2Conn.createStatement();
String myQuery = "SELECT * FROM PHONENUMBERS";
// execute the query
ResultSet resultSet = st.executeQuery(myQuery);
// cycle through the resulSet and display what was grabbed
while (resultSet.next())
{
String name = resultSet.getString("name");
String phoneNumber = resultSet.getString("phonenumber");
System.out.println("Name: " + name);
System.out.println("Phone Number: " + phoneNumber);
System.out.println("-------------------------------");
}
// clean up resources
resultSet.close();
st.close();
db2Conn.close();
}
catch (ClassNotFoundException cnfe)
{
cnfe.printStackTrace();
}
catch (SQLException sqle)
{
sqle.printStackTrace();
}
}
}
We are assuming that you have a background in JDBC. (If not, it might be a good idea to take a look at articles on this topic on the InformIT site.) The only difference is that they use the different drivers, driver architectures, and syntax to achieve their connectivity. Figure 4 shows the successful execution of the code.
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Figure
4 Successful execution of our sample code.
The Universal JDBC driver
With the advent of DB2 8.1 came the new Universal JDBC driver, which can be used either in a Type 2 architecture or a Type 4 architecture (see below). In a Type 2 mode, the Universal JDBC driver provides local application performance gains (because it avoids using TCP/IP protocol to communicate to the DB2 server). In Type 2 mode, there is also full support for distributed transactions. Therefore, if the application and the DB2 server are on the same machine, we recommend that you use the Universal JDBC driver in Type 2 mode. The driver is located in the file db2jcc.jar. Note from the code of Listing 2 that the implementation package is com.ibm.db2.jcc.DB2Driver. Also, at runtime, in type 2 mode and attempt will be made to load a file named db2jcct2.dll. This file is installed when the Runtime Client or Application Development client of the product are installed.
Listing 2 Use of the Universal driver (db2jcc.jar)in a JDBC Type 2 setup to interact with DB2.
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
public class Type2ExampleUniversal {
public static void main(String[] args)
{
try
{
// load the DB2 Driver
Class.forName("com.ibm.db2.jcc.DB2Driver");
// establish a connection to DB2
Connection db2Conn =
DriverManager.getConnection
("jdbc:db2:phoneDB","db2admin","db2admin");
// use a statement to gather data from the database
Statement st = db2Conn.createStatement();
String myQuery = "SELECT * FROM PHONENUMBERS";
// execute the query
ResultSet resultSet = st.executeQuery(myQuery);
// cycle through the resulSet and display what was grabbed
while (resultSet.next())
{
String name = resultSet.getString("name");
String phoneNumber = resultSet.getString("phonenumber");
System.out.println("Name: " + name);
System.out.println("Phone Number: " + phoneNumber);
System.out.println("-------------------------------");
}
// clean up resources
resultSet.close();
st.close();
db2Conn.close();
}
catch (ClassNotFoundException cnfe)
{
cnfe.printStackTrace();
}
catch (SQLException sqle)
{
sqle.printStackTrace();
}
}
}
Using the JDBC Type 4 Driver
A Type 4 JDBC driver connects directly to the database server using Java. (Refer to Figure 1 for an illustration of this interaction.)
In a Type 4 setup, no client Configuration Assistant is needed to catalog remote databases as with the Type 2 driver. The same db2jcc.jar file is used for the Universal driver regardless of communication mode (Type 2 or Type 4). We demonstrate how to connect to our DB2 server in Listing 3. (Note that our implementation package name is again: com.ibm.db2.jcc.DB2Driver.)
At a quick glance, it is a bit difficult to see the difference between the syntax of Listing 2 (showing the use of the Universal driver as JDBC Type 2 driver) and Listing 3 (showing the use of the Universal driver as a JDBC Type 4 driver).
Listing 3 Use of the Universal driver (db2jcc.jar) in a JDBC Type 4 setup to interact with DB2.
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
public class Type4ExampleUniversal {
public static void main(String[] args)
{
try
{
// load the DB2 Driver
Class.forName("com.ibm.db2.jcc.DB2Driver");
// establish a connection to DB2
Connection db2Conn =
DriverManager.getConnection
("jdbc:db2://localhost:50000/phonedb","db2admin","db2admin");
// use a statement to gather data from the database
Statement st = db2Conn.createStatement();
String myQuery = "SELECT * FROM PHONENUMBERS";
// execute the query
ResultSet resultSet = st.executeQuery(myQuery);
// cycle through the resulSet and display what was grabbed
while (resultSet.next())
{
String name = resultSet.getString("name");
String phoneNumber = resultSet.getString("phonenumber");
System.out.println("Name: " + name);
System.out.println("Phone Number: " + phoneNumber);
System.out.println("-------------------------------");
}
// clean up resources
resultSet.close();
st.close();
db2Conn.close();
}
catch (ClassNotFoundException cnfe)
{
cnfe.printStackTrace();
}
catch (SQLException sqle)
{
sqle.printStackTrace();
}
}
}
Let's go over some key differences. In the Type 4 driver, our connection URL takes the form jdbc:db2://server1:50000/phonedb (as opposed to the form jdbc:sample). The DB2 server in this case is listening for client connections on port 50000. This is the default port that DB2 listens to upon installation unless you specify otherwise.
Also, note that the hostname (server1) and the port number is included in the database connection URL. These (with the port number) provide the driver with information to connect directly to the database server without having to reference the database and node catalog entries, as was required for the legacy/CLI JDBC driver discussed earlier.
Note that if you are using DB2 UDB V8.1.2 or later versions of the Universal JDBC driver, then you have to include a license JAR file in your CLASSPATH in addition to the db2jcc.jar file. Refer to the DB2 documentation to determine which JAR file to include (this file is used to determine which DB2 server platforms you will be able to access).