I see no such exception running the latest 7.0.x code.

(In reply to comment #1)
> I see no such exception running the latest 7.0.x code.

I using the 7.0.19 code.

The IllegalStateException not showed in the browser, 
but in the Tomcat/logs/localhost.2011-08-07.log

Observing this as well with current trunk@r1178371 (7.0.22) using Nio connector.
WinXP 32-bit, JDK 6u26.

Steps to reproduce:
1. Configure Tomcat with org.apache.coyote.http11.Http11NioProtocol
I also have logging configured with OneLineFormatter, but that should not matter.

2. Start it and open in web browser the following page:
http://localhost:8080/examples/async/async0

3. The following exception is in localhost.<date>.log: (not in catalina*.log !)

03-окт-2011 14:35:15.218 SEVERE [http-nio-8080-exec-2] org.apache.catalina.core.StandardWrapperValve.invoke Servlet.service() for servlet [async0] in context with path [/examples] threw exception [java.lang.RuntimeException: java.lang.IllegalStateException: Calling [asyncComplete()] is not valid for a request with Async state [DISPATCHED]] with root cause
 java.lang.IllegalStateException: Calling [asyncComplete()] is not valid for a request with Async state [DISPATCHED]
	at org.apache.coyote.AsyncStateMachine.asyncComplete(AsyncStateMachine.java:221)
	at org.apache.coyote.http11.Http11NioProcessor.actionInternal(Http11NioProcessor.java:476)
	at org.apache.coyote.http11.AbstractHttp11Processor.action(AbstractHttp11Processor.java:807)
	at org.apache.coyote.Request.action(Request.java:344)
	at org.apache.catalina.core.AsyncContextImpl.complete(AsyncContextImpl.java:89)
	at async.Async0.service(Async0.java:42)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:304)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
	at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:684)
	at org.apache.catalina.core.ApplicationDispatcher.doInclude(ApplicationDispatcher.java:593)
	at org.apache.catalina.core.ApplicationDispatcher.include(ApplicationDispatcher.java:530)
	at org.apache.catalina.core.AsyncContextImpl$1.run(AsyncContextImpl.java:173)
	at org.apache.catalina.core.AsyncContextImpl.doInternalDispatch(AsyncContextImpl.java:314)
	at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:219)
	at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:169)
	at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:472)
	at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:168)
	at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:100)
	at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:929)
	at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
	at org.apache.catalina.connector.CoyoteAdapter.asyncDispatch(CoyoteAdapter.java:296)
	at org.apache.coyote.http11.AbstractHttp11Processor.asyncDispatch(AbstractHttp11Processor.java:1486)
	at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:511)
	at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.run(NioEndpoint.java:1554)
	at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
	at java.lang.Thread.run(Thread.java:662)

In catalina.<date>.log one can see debug messages from Async0 servlet:
03-окт-2011 14:35:15.218 INFO [http-nio-8080-exec-2] async.Async0.service Received dispatch, completing on the worker thread.
03-окт-2011 14:35:15.218 INFO [http-nio-8080-exec-2] async.Async0.service After complete called started:false

What bothers me is that Async0 servlet is not annotated with @WebServlet(asyncSupported=true) as required by ch.2.3.3.3 of servlet-3_0-final-spec.pdf.  Page #12 (34/230) there: "It is illegal to call startAsync if the request is within the scope of a servlet or filter that does not support asynchronous operations"

The same chapter describes "isAsyncStarted()" saying that it should return false after a dispatch call. That is what we are observing here.

From description of "complete()" in the same chapter, it is container's responsibility to call complete() after service() method exits: "The complete method can be invoked by the container if
the request is dispatched to a servlet that does not support async processing, or
the target servlet called by AsyncContext.dispatch does not do a
subsequent call to startAsync. In this case, it is the container's responsibility
to call complete() as soon as that servlet's service method is exited."


So I think the IllegalStateException is valid here, but the Async0 example should be fixed by removing the complete() call and annotating the servlet with @WebServlet(asyncSupported=true).

(In reply to comment #3)
> What bothers me is that Async0 servlet is not annotated with
> @WebServlet(asyncSupported=true) as required by ch.2.3.3.3 of
> servlet-3_0-final-spec.pdf.  Page #12 (34/230) there: "It is illegal to call
> startAsync if the request is within the scope of a servlet or filter that does
> not support asynchronous operations"

You can also set async support in web.xml and this is what is done for the examples.

Fixed in trunk and 7.0.x and will be included in 7.0.23 onwards.