To access a database directly from a Java™ Platform, Enterprise Edition (Java EE)
application client, you retrieve a javax.sql.DataSource object from
a resource reference configured in the client deployment descriptor. This
resource reference is configured as part of the deployment descriptor for
the client application, and provides a reference to a pre-configured data
source object.
About this task
Note that data access from an application client uses the JDBC
driver connection functionality directly from the client side. It does not
take advantage of the additional pooling support available in the application
server run time. For this reason, your client application should utilize an
enterprise bean running on the server side to perform data access. This enterprise
bean can then take advantage of the connection reuse and additional added
functionality provided by the product run time.
Procedure
- Import the appropriate JDBC API and naming packages:
import java.sql.*;
import javax.sql.*;
import javax.naming.*;
- Create the initial naming context:
InitialContext ctx = new InitialContext();
- Use the InitialContext object to look up a data source object
from a resource reference.
javax.sql.DataSource ds = (DataSource)ctx.lookup("java:comp/env/jdbc/myDS");
//where jdbc/myDS is the name of the resource reference
- Get a java.sql.Connection from the data source.
- If no user ID and password are required for the connection, or if you
are going to use the defaultUser and defaultPassword that are
specified when the data source is created in the Application Client Resource
Configuration tool (ACRCT) in a future step, use this approach:
java.sql.Connection conn = ds.getConnection();
- Otherwise, you should make the connection with a specific user ID and
password:
java.sql.Connection conn = ds.getConnection("user", "password");
//where user and password are the user id and password for the connection
- Run a database query using the java.sql.Statement, java.sql.PreparedStatement,
or java.sql.CallableStatement interfaces as appropriate.
Statement stmt = conn.createStatement();
String query = "Select FirstNme from " + owner.toUpperCase() + ".Employee where LASTNAME = '" + searchName + "'";
ResultSet rs = stmt.executeQuery(query);
while (rs.next()) { firstNameList.addElement(rs.getString(1));
}
- Close the database objects used in the previous step, including
any ResultSet, Statement, PreparedStatement, or CallableStatement objects.
- Close the connection. Ideally, you should close the
connection in a finally block of the try...catch statement wrapped
around the database operation. This action ensures that the connection gets
closed, even in the case of an exception.
conn.close();