com.qindesign.servlet.example
Class FastOneWireServlet

java.lang.Object
  javax.servlet.GenericServlet
      javax.servlet.http.HttpServlet
          com.qindesign.servlet.example.FastOneWireServlet

All Implemented Interfaces:

Servlet, ServletConfig

public class FastOneWireServlet
extends HttpServlet

Simple 1-Wire servlet that can list adapters and devices, and can also read a device. The output is XML.

The output is generated according to the following rules:

• If the adapter is not specified, then all adapters are listed.
• If the adapter, but no port, is specified, then all ports available to that adapter are listed.
• If the adapter and port, but no device, is specified, then all devices on that adapter are listed.
• If the adapter and device are specified, then printDevice is called to output something appropriate.
• If there is an error anywhere along the process, then an error message will be given, and the status code set to something other than "200 OK".

Version:

1.0.4

Author:

Shawn Silverman

Constructor Summary

FastOneWireServlet()

Method Summary

void	destroy() Destroys the servlet.
protected void	doGet(HttpServletRequest req, HttpServletResponse resp) Process a GET request.
void	init() Initializes the servlet.
protected void	printDevice(HttpServletRequest req, HttpServletResponse resp, DSPortAdapter a, OneWireContainer c) Retrieves a value from the given container.
protected void	printErrorMessage(HttpServletResponse resp, String msg) Prints an error message.

Methods inherited from class javax.servlet.http.HttpServlet

doDelete, doOptions, doPost, doPut, doTrace, getLastModified, service, service

Methods inherited from class javax.servlet.GenericServlet

getInitParameter, getInitParameterNames, getServletConfig, getServletContext, getServletInfo, getServletName, init, log, log

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

FastOneWireServlet

public FastOneWireServlet()

Method Detail

init

public void init()
          throws ServletException

Initializes the servlet.

Overrides:

init in class GenericServlet

Throws:

ServletException

destroy

public void destroy()

Destroys the servlet.

Specified by:

destroy in interface Servlet

Overrides:

destroy in class GenericServlet

doGet

protected void doGet(HttpServletRequest req,
                     HttpServletResponse resp)
              throws ServletException,
                     IOException

Process a GET request.

Overrides:

doGet in class HttpServlet

Throws:

ServletException

IOException

printErrorMessage

protected void printErrorMessage(HttpServletResponse resp,
                                 String msg)
                          throws IOException

Prints an error message. This assumes the response has not already been committed.

Parameters:

resp - the HTTP response object

msg - the error message, a string

Throws:

IOException

printDevice

protected void printDevice(HttpServletRequest req,
                           HttpServletResponse resp,
                           DSPortAdapter a,
                           OneWireContainer c)
                    throws OneWireIOException,
                           OneWireException,
                           IOException

Retrieves a value from the given container. This simple implementation only reads values from temperature containers.

Remember to use begin/endExclusive calls on the adapter, and also try to perform output as late as possible to allow for an error status to be generated in the calling code. If the response has already been committed (eg. obtaining the output stream), then any 1-Wire exeption cannot be properly reported to the user.

Parameters:

req - the HTTP request object, for extracting request parameters, etc.

resp - the HTTP response object, for setting the status and getting the output stream, etc.

a - the port adapter, for exclusive calls, etc.

c - the 1-Wire container object, assumed to be present

Throws:

OneWireIOException

OneWireException

IOException