Ubiquitous email - Software Development Case Studies in Java - page 462

The sampling interval for the notifier is taken by the ContextListener class
from the application context.
public final class ContextListener
implements ServletContextListener {
public void contextInitialized(ServletContextEvent event) {
...
Long interval # (Long)initial.lookup
("java:comp/env/interval");
Manager mgr # new Manager(ds,interval.longValue());
...
}
}
The value of the interval attribute of the application context is set in the
application descriptor contained in the web.xml file.
<web-app>
...
<env-entry>
<env-entry-name>interval</env-entry-name>
<env-entry-value>10000</env-entry-value>
<env-entry-type>java.lang.Long</env-entry-type>
</env-entry>
</web-app>
The notification is based on the SMSSender class. It has a constructor that
tries to find a serial port connected to a GSM modem. To send a message we
need first to open the connection with the open() method, then to send one
or more messages using the send() method, and finally close the connection
with the close() method.
The communication with the modem is carried out by the method
sendCmdNoCR() . This method writes to the serial port and then blocks for a
given delay. In the meantime the modem sends a reply; the presence of data
coming from the modem is notified asynchronously via the serialEvent()
method, which reads the available data and puts it into the buffer answer .
When the serialEvent() method recognizes the end of a reply or the timeout
has expired the sendCmdNoCR() method is woken up and returns the content
of the answer buffer.
package sms;
import java.io.*;
import java.util.*;
import javax.comm.*;
// SMSSender is a class that can be used to send SMS messages
// through a mobile phone connected to a serial port.
public class SMSSender implements SerialPortEventListener {
InputStream inputStream;
OutputStream outputStream;
SerialPort serialPort;