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Posted to users@tomcat.apache.org by Santos Jha <sa...@adelphia.net> on 2003/04/11 03:36:33 UTC
Servlet Design Question
Hello Everybody,
I am developing a system which finds out the application specific status
of different servers( written in C++) and and this data is transmitted
to users for display.System should continuously
( every 15 seconds) poll these servers to get the data. Once user
requests it fetches the most recent data.
In order to get the data from these servers I am planning to use socket.
However I have few questions regarding socket and servlet.
1. Should I write a servlet with a init method which will have
a. for ever loop and inside the for ever loop I will be
continuously getting the data using socket.
2. Should I write a client outside the tomcat servlet container which
will get all the data and will be sent them to the container.
What will be the better approach? or there is something better than these.?
Santos
>
>
>
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Re: Servlet Design Question
Posted by Mark Pease <mp...@chartermi.net>.
I forgot to mention that the code I submitted is from a servlet, which is
initialized when Tomcat starts (using load on startup functions).
----- Original Message -----
From: "Santos Jha" <sa...@adelphia.net>
To: "Tomcat Users List" <to...@jakarta.apache.org>
Sent: Thursday, April 10, 2003 9:36 PM
Subject: Servlet Design Question
> Hello Everybody,
>
> I am developing a system which finds out the application specific status
> of different servers( written in C++) and and this data is transmitted
> to users for display.System should continuously
> ( every 15 seconds) poll these servers to get the data. Once user
> requests it fetches the most recent data.
>
> In order to get the data from these servers I am planning to use socket.
> However I have few questions regarding socket and servlet.
>
> 1. Should I write a servlet with a init method which will have
> a. for ever loop and inside the for ever loop I will be
> continuously getting the data using socket.
>
> 2. Should I write a client outside the tomcat servlet container which
> will get all the data and will be sent them to the container.
> What will be the better approach? or there is something better than
these.?
> Santos
>
>
> >
> >
> >
>
>
>
> ---------------------------------------------------------------------
> To unsubscribe, e-mail: tomcat-user-unsubscribe@jakarta.apache.org
> For additional commands, e-mail: tomcat-user-help@jakarta.apache.org
>
---------------------------------------------------------------------
To unsubscribe, e-mail: tomcat-user-unsubscribe@jakarta.apache.org
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Re: Servlet Design Question
Posted by Santos Jha <sa...@adelphia.net>.
Thank you. I guess I got the answer.
Santos
Mark Pease wrote:
>Hi Santos,
>
>You are probably going to want to make a seperate class that will handle
>your socket communications on a seperate thread for each connection. I have
>a similar application, which also listens on a socket port for XML data to
>be sent sporadically. I have a class defined to be run as a seperate
>thread, defined by:
>
>class SocketClient extends Thread implements Observer{
>
>
>The Observer isn't necessary, but I use it to notify various Java Beans when
>new data has come in. I establish the socket in a seperate method, then, in
>the run() method, I have this:
>
>
> public void run(){
> // Get XML data, send to ClientBean for parsing...
> // Slight problem with reading XML from sockets: the XML parser
> // does not know where the end of file is, so it hangs.
> // Workaround is to convert the XML data, which must have only one
> // CR LF at the end, into a string and send it. See java.sun.com
> // community discussion, search by "XML socket" to find.
> String inData;
> BufferedReader br;
> StringReader sr;
> InputSource in;
>
> try{
>
> while ( keepRunning ) {
>
> try{
> br = new BufferedReader(new
>InputStreamReader(socket.getInputStream()));
> inData = br.readLine();
>
> sr = new StringReader(inData);
>
> in = new InputSource(sr);
>
> // Do what you want with the string (in)
>
> }
> // This will be thrown when the socket connection is lost.
> // Will stop excecution even though the .readLine() method
>is
> // a blocking call.
> catch(NullPointerException npe){
> keepRunning = false;
>
> client.deleteObserver(this);
> client = null;
>
> try{
> socket.close();
> socket = null;
> }
> catch(IOException ioe){
> socket = null;
> }
> }
> }
>
> }
> catch(IOException ioe){
> Output.systemOut(99,"IOException:" + ioe.getMessage());
> }
> }
>
>
>Essentially, it keeps running the while loop until the socket connection is
>lost, which will raise an exception. You may want to start checking the
>Java forums if you need further information.
>
>Good luck!
>Mark
>
>----- Original Message -----
>From: "Santos Jha" <sa...@adelphia.net>
>To: "Tomcat Users List" <to...@jakarta.apache.org>
>Sent: Thursday, April 10, 2003 9:36 PM
>Subject: Servlet Design Question
>
>
>
>
>>Hello Everybody,
>>
>>I am developing a system which finds out the application specific status
>>of different servers( written in C++) and and this data is transmitted
>>to users for display.System should continuously
>>( every 15 seconds) poll these servers to get the data. Once user
>>requests it fetches the most recent data.
>>
>>In order to get the data from these servers I am planning to use socket.
>>However I have few questions regarding socket and servlet.
>>
>>1. Should I write a servlet with a init method which will have
>> a. for ever loop and inside the for ever loop I will be
>>continuously getting the data using socket.
>>
>>2. Should I write a client outside the tomcat servlet container which
>>will get all the data and will be sent them to the container.
>>What will be the better approach? or there is something better than
>>
>>
>these.?
>
>
>>Santos
>>
>>
>>
>>
>>>
>>>
>>>
>>
>>---------------------------------------------------------------------
>>To unsubscribe, e-mail: tomcat-user-unsubscribe@jakarta.apache.org
>>For additional commands, e-mail: tomcat-user-help@jakarta.apache.org
>>
>>
>>
>
>
>---------------------------------------------------------------------
>To unsubscribe, e-mail: tomcat-user-unsubscribe@jakarta.apache.org
>For additional commands, e-mail: tomcat-user-help@jakarta.apache.org
>
>
>
>
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Re: Servlet Design Question
Posted by Mark Pease <mp...@chartermi.net>.
Hi Santos,
You are probably going to want to make a seperate class that will handle
your socket communications on a seperate thread for each connection. I have
a similar application, which also listens on a socket port for XML data to
be sent sporadically. I have a class defined to be run as a seperate
thread, defined by:
class SocketClient extends Thread implements Observer{
The Observer isn't necessary, but I use it to notify various Java Beans when
new data has come in. I establish the socket in a seperate method, then, in
the run() method, I have this:
public void run(){
// Get XML data, send to ClientBean for parsing...
// Slight problem with reading XML from sockets: the XML parser
// does not know where the end of file is, so it hangs.
// Workaround is to convert the XML data, which must have only one
// CR LF at the end, into a string and send it. See java.sun.com
// community discussion, search by "XML socket" to find.
String inData;
BufferedReader br;
StringReader sr;
InputSource in;
try{
while ( keepRunning ) {
try{
br = new BufferedReader(new
InputStreamReader(socket.getInputStream()));
inData = br.readLine();
sr = new StringReader(inData);
in = new InputSource(sr);
// Do what you want with the string (in)
}
// This will be thrown when the socket connection is lost.
// Will stop excecution even though the .readLine() method
is
// a blocking call.
catch(NullPointerException npe){
keepRunning = false;
client.deleteObserver(this);
client = null;
try{
socket.close();
socket = null;
}
catch(IOException ioe){
socket = null;
}
}
}
}
catch(IOException ioe){
Output.systemOut(99,"IOException:" + ioe.getMessage());
}
}
Essentially, it keeps running the while loop until the socket connection is
lost, which will raise an exception. You may want to start checking the
Java forums if you need further information.
Good luck!
Mark
----- Original Message -----
From: "Santos Jha" <sa...@adelphia.net>
To: "Tomcat Users List" <to...@jakarta.apache.org>
Sent: Thursday, April 10, 2003 9:36 PM
Subject: Servlet Design Question
> Hello Everybody,
>
> I am developing a system which finds out the application specific status
> of different servers( written in C++) and and this data is transmitted
> to users for display.System should continuously
> ( every 15 seconds) poll these servers to get the data. Once user
> requests it fetches the most recent data.
>
> In order to get the data from these servers I am planning to use socket.
> However I have few questions regarding socket and servlet.
>
> 1. Should I write a servlet with a init method which will have
> a. for ever loop and inside the for ever loop I will be
> continuously getting the data using socket.
>
> 2. Should I write a client outside the tomcat servlet container which
> will get all the data and will be sent them to the container.
> What will be the better approach? or there is something better than
these.?
> Santos
>
>
> >
> >
> >
>
>
>
> ---------------------------------------------------------------------
> To unsubscribe, e-mail: tomcat-user-unsubscribe@jakarta.apache.org
> For additional commands, e-mail: tomcat-user-help@jakarta.apache.org
>
---------------------------------------------------------------------
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