Author: fhanik
Date: Fri Jun 15 14:31:45 2007
New Revision: 547792
URL: http://svn.apache.org/viewvc?view=rev&rev=547792
Log:
Added in AJAX with delayed response example
Modified:
tomcat/trunk/webapps/docs/aio.xml
Modified: tomcat/trunk/webapps/docs/aio.xml
URL:
http://svn.apache.org/viewvc/tomcat/trunk/webapps/docs/aio.xml?view=diff&rev=547792&r1=547791&r2=547792
==============================================================================
--- tomcat/trunk/webapps/docs/aio.xml (original)
+++ tomcat/trunk/webapps/docs/aio.xml Fri Jun 15 14:31:45 2007
@@ -282,6 +282,133 @@
</subsection>
<subsection name="Example code snippets">
+ <p>Let's start with a real world example of how you could use Comet to
handle AJAX requests.
+ An AJAX request is a complete HTTP request, followed by a complete HTTP
response.
+ The next request is a new HTTP request.
+ There are many AJAX frameworks, and they can be used with regular
servlets, so why
+ would I want to do this using Comet?
+ The answer is simply, with Comet you can do the response asynchronously
and therefor
+ release the Tomcat thread to handle other requests.
+
+ </p>
+ <source>
+Non blocking read and writes
+
+public class ExampleDelayedAjaxResponse implements CometProcessor {
+ ...
+ public class DelayedResponder extends Thread {
+ public void run() {
+ ...
+ Client[] clients = getClients();
+ for (int i=0; i<clients.length; i++ ) {
+ CometEvent event = client.getEvent();
+ byte[] data = getDelayedResponse(event);
+ if (data!=null) {
+ if (event.isWriteable()) {
+ event.getHttpServletResponse().getOutputStream().write(data);
+ if (event.isWriteable()) { //did we write it all?
+ event.close(); //close the event, in anticipation of the next
request
+ event.register(OP_CALLBACK); //triggers an END event
+ } else { //we didn't write it all, trigger a WRITE event when we
are done with the write event.register(OP_WRITE);
+ }
+ } else {
+ //we are not able to write, let us know when we can
+ event.register(OP_WRITE);
+ }
+ //remove the client from the async thread
+ //since we have received the data for this client.
+ clients.remove(event);
+ }
+ }
+ ...
+ }
+ }
+ ...
+ public void event(CometEvent event) throws IOException, ServletException {
+ ...
+ if ( event.getEventType() == CometEvent.EventType.BEGIN ) {
+ //configure non blocking
+ event.configureBlocking(false);
+ //deregister for READ since we want to enable pipe lining on the
connection //for the next HTTP request
+ event.unregister(OP_READ);
+ //add the client to the list
+ clients.add(event);
+ } if ( event.getEventType() == CometEvent.EventType.READ ) {
+ //read client Id and stock list from client
+ //and add the event to our list
+ assert("this should never happen");
+ } if ( event.getEventType() == CometEvent.EventType.WRITE ) {
+ //unregister from the write event
+ event.unregister(OP_WRITE);
+ //we can now write
+ byte[] data = getDelayedResponse(event);
+ if ( data != null ) {
+ event.getHttpServletResponse().getOutputStream().write(data);
+ }
+ if( data==null || event.isWriteable() ) {
+ event.close();
+ }
+ } if ( event.getEventType() == CometEvent.EventType.END ) {
+ clients.remove(event); } else if (...) {
+ ...
+ }
+ ...
+ }
+}
+
+Blocking read and writes
+public class ExampleDelayedAjaxResponse implements CometProcessor {
+ ...
+ public class DelayedResponder extends Thread {
+ public void run() {
+ ...
+ Client[] clients = getClients();
+ for (int i=0; i<clients.length; i++ ) {
+ CometEvent event = client.getEvent();
+ byte[] data = getDelayedResponse(event);
+ if (data!=null) {
+ //register for a write, better do that on a thread pool thread
+ //since write is blocking
+ event.register(OP_WRITE);
+ //remove the client from the async thread
+ clients.remove(event);
+ }
+ }
+ ...
+ }
+ }
+ ...
+ public void event(CometEvent event) throws IOException, ServletException {
+ ...
+ if ( event.getEventType() == CometEvent.EventType.BEGIN ) {
+ //configure blocking
+ event.configureBlocking(true);
+ //deregister for READ since we want to enable pipe lining on the
connection //for the next HTTP request
+ event.unregister(OP_READ);
+ //add the client to the list
+ clients.add(event);
+ } if ( event.getEventType() == CometEvent.EventType.READ ) {
+ //read client Id and stock list from client
+ //and add the event to our list
+ assert("this should never happen");
+ } if ( event.getEventType() == CometEvent.EventType.WRITE ) {
+ //unregister from the write event
+ event.unregister(OP_WRITE);
+ //we can now write
+ byte[] data = getDelayedResponse(event); //note we don't have
to check for null data here
+ event.getHttpServletResponse().getOutputStream().write(data);
+ event.close();
+ } if ( event.getEventType() == CometEvent.EventType.END ) {
+ clients.remove(event);
+ } else if (...) {
+ ...
+ }
+ ...
+ }
+}
+
+ </source>
+
<p>
Imagine you are writing a servlet that is updating a set of
stock tickers. You have a back ground thread that is receiving
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