import java.sql.Connection;
import javax.naming.Context;
import javax.naming.InitialContext;
import javax.sql.Datasource;
...
System.setProperty(Context.INITIAL_CONTEXT_FACTORY,
"com.sun.jndi.fscontext.RefFSContextFactory");
System.setProperty(Context.PROVIDER_URL, "file:///tmp");
Context initalContext = new InitialContext();
Context envContext = (Context) initialContext.lookup("java:comp/env");
DataSource ds = (DataSource)envContext.lookup( "jdbc/Mammals" );
Connection conn = ds.getConnection();
stmt = conn.createStatement();
...
conn.close();