Initiating httpservletrequest from inside Tomcat / TomEE

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Initiating httpservletrequest from inside Tomcat / TomEE

Paul Carter-Brown-3
Hi

I'm trying to design a Kafka consumer and producer that will run inside the
tomcat jvm and pick up messages off a Kafka topic and translate them into a
servlet request and pass it through tomcat and then when the response is
complete then translate it into a Kafka message and put it onto another
topic as a reply. This way I can reuse our existing jax-rs rest services
and expose them as an async api over Kafka. The idea is to make the Kafka
messages similar to http in that they would consist of headers and a body.
The body would be json.

Now I know this could be done by calling localhost with an http call to
trombone the requests back into tomcat but I'd like to avoid the associated
latency and overhead. Is it possible to call tomcat directly in-process.
This does not need to be portable to other containers so can be proprietary.

I'm using tomcat 8. In fact its tomee 8 but guessed this is more a tomcat
question than tomee but have sent to both groups just in case.

Thanks for any insights.

Paul
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Re: Initiating httpservletrequest from inside Tomcat / TomEE

John Dale
This is one of my favorite things.

You'll need to retransmit headers, but by and large it's doable.

Management of contexts can be tricky. Don't forget that the target
service will have a difference context (database connection context
has bitten me in the past on this type of task).

I do my session management in the database, bypassing tomcat's session
management.  The session affinity being in the database has proven
VERY useful to me when extending and integrating my code

I'm not sure if you'll have this luxury, though.

This type of Internet plumbing is powerful, but also can allude to
some scary topics.

Good luck!


On 4/29/19, Paul Carter-Brown <[hidden email]> wrote:

> Hi
>
> I'm trying to design a Kafka consumer and producer that will run inside the
> tomcat jvm and pick up messages off a Kafka topic and translate them into a
> servlet request and pass it through tomcat and then when the response is
> complete then translate it into a Kafka message and put it onto another
> topic as a reply. This way I can reuse our existing jax-rs rest services
> and expose them as an async api over Kafka. The idea is to make the Kafka
> messages similar to http in that they would consist of headers and a body.
> The body would be json.
>
> Now I know this could be done by calling localhost with an http call to
> trombone the requests back into tomcat but I'd like to avoid the associated
> latency and overhead. Is it possible to call tomcat directly in-process.
> This does not need to be portable to other containers so can be
> proprietary.
>
> I'm using tomcat 8. In fact its tomee 8 but guessed this is more a tomcat
> question than tomee but have sent to both groups just in case.
>
> Thanks for any insights.
>
> Paul
>
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Re: Initiating httpservletrequest from inside Tomcat / TomEE

John Dale
In reply to this post by Paul Carter-Brown-3
Another thought .. you can do some request dispatching, but without
knowing more about the tools you're using, I can't say for sure if
this is the direction you'll want to go.

On 4/29/19, Paul Carter-Brown <[hidden email]> wrote:

> Hi
>
> I'm trying to design a Kafka consumer and producer that will run inside the
> tomcat jvm and pick up messages off a Kafka topic and translate them into a
> servlet request and pass it through tomcat and then when the response is
> complete then translate it into a Kafka message and put it onto another
> topic as a reply. This way I can reuse our existing jax-rs rest services
> and expose them as an async api over Kafka. The idea is to make the Kafka
> messages similar to http in that they would consist of headers and a body.
> The body would be json.
>
> Now I know this could be done by calling localhost with an http call to
> trombone the requests back into tomcat but I'd like to avoid the associated
> latency and overhead. Is it possible to call tomcat directly in-process.
> This does not need to be portable to other containers so can be
> proprietary.
>
> I'm using tomcat 8. In fact its tomee 8 but guessed this is more a tomcat
> question than tomee but have sent to both groups just in case.
>
> Thanks for any insights.
>
> Paul
>
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Re: Initiating httpservletrequest from inside Tomcat / TomEE

Paul Carter-Brown-3
Hi John,

Thanks for your feedback.

The request I'm initiating should not or need not carry any context from
the originating code. There is also no session to worry about as its just
for rest calls. So basically I have the headers, path and body and need to
generate a http servlet request and get an http servlet response (or
similar) back. I have this working by calling into localhost but ideally
want to skip the trombone out and back in.

Have you got any basic code examples?

Paul

On Tue, Apr 30, 2019 at 5:27 PM John Dale <[hidden email]> wrote:

> Another thought .. you can do some request dispatching, but without
> knowing more about the tools you're using, I can't say for sure if
> this is the direction you'll want to go.
>
> On 4/29/19, Paul Carter-Brown <[hidden email]> wrote:
> > Hi
> >
> > I'm trying to design a Kafka consumer and producer that will run inside
> the
> > tomcat jvm and pick up messages off a Kafka topic and translate them
> into a
> > servlet request and pass it through tomcat and then when the response is
> > complete then translate it into a Kafka message and put it onto another
> > topic as a reply. This way I can reuse our existing jax-rs rest services
> > and expose them as an async api over Kafka. The idea is to make the Kafka
> > messages similar to http in that they would consist of headers and a
> body.
> > The body would be json.
> >
> > Now I know this could be done by calling localhost with an http call to
> > trombone the requests back into tomcat but I'd like to avoid the
> associated
> > latency and overhead. Is it possible to call tomcat directly in-process.
> > This does not need to be portable to other containers so can be
> > proprietary.
> >
> > I'm using tomcat 8. In fact its tomee 8 but guessed this is more a tomcat
> > question than tomee but have sent to both groups just in case.
> >
> > Thanks for any insights.
> >
> > Paul
> >
>
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Re: Initiating httpservletrequest from inside Tomcat / TomEE

Paul Carter-Brown-3
lol on the Semaphore Telegraph,

I can't use a request dispatcher as the request is being initiated from
code that has no context. I already have it working with HTTP using
asynchttp library, but I want to avoid the overhead. E.g. lets say I wrote
my own server socket listener on port 10000 running in the Tomcat JVM and
got some request in some propriatary protocol called X. Now I want to call
a Tomcat servlet in the current JVM with some info I got over X without
going out on TCP and back in....

On Mon, May 6, 2019 at 4:40 PM John Dale <[hidden email]> wrote:

> If you're wanting to forward control to another servlet deployed in
> the same context:
> https://www.javatpoint.com/requestdispatcher-in-servlet
>
> If you are okay going through TCP to facilitate some future or current
> distribution of services, Use HTTPURLConnection (not sure what you're
> wanting to do with the result of the request, if anything):
>
> https://stackoverflow.com/questions/2793150/how-to-use-java-net-urlconnection-to-fire-and-handle-http-requests
>
> If you need more sophisticated HTTP interactions, Apache maintains a
> very useful library for that:  http://hc.apache.org/
>
> If these don't work-out for you, rather than using .NET, PHP, Python,
> or some other Java facsimile at best, I recommend using the semaphore
> telegraph:
> https://en.wikipedia.org/wiki/Semaphore_telegraph
>
> Sincerely,
>
> John
> DB2DOM
>
> On 5/6/19, Paul Carter-Brown <[hidden email]> wrote:
> > Hi John,
> >
> > Thanks for your feedback.
> >
> > The request I'm initiating should not or need not carry any context from
> > the originating code. There is also no session to worry about as its just
> > for rest calls. So basically I have the headers, path and body and need
> to
> > generate a http servlet request and get an http servlet response (or
> > similar) back. I have this working by calling into localhost but ideally
> > want to skip the trombone out and back in.
> >
> > Have you got any basic code examples?
> >
> > Paul
> >
> > On Tue, Apr 30, 2019 at 5:27 PM John Dale <[hidden email]> wrote:
> >
> >> Another thought .. you can do some request dispatching, but without
> >> knowing more about the tools you're using, I can't say for sure if
> >> this is the direction you'll want to go.
> >>
> >> On 4/29/19, Paul Carter-Brown <[hidden email]> wrote:
> >> > Hi
> >> >
> >> > I'm trying to design a Kafka consumer and producer that will run
> inside
> >> the
> >> > tomcat jvm and pick up messages off a Kafka topic and translate them
> >> into a
> >> > servlet request and pass it through tomcat and then when the response
> >> > is
> >> > complete then translate it into a Kafka message and put it onto
> another
> >> > topic as a reply. This way I can reuse our existing jax-rs rest
> >> > services
> >> > and expose them as an async api over Kafka. The idea is to make the
> >> > Kafka
> >> > messages similar to http in that they would consist of headers and a
> >> body.
> >> > The body would be json.
> >> >
> >> > Now I know this could be done by calling localhost with an http call
> to
> >> > trombone the requests back into tomcat but I'd like to avoid the
> >> associated
> >> > latency and overhead. Is it possible to call tomcat directly
> >> > in-process.
> >> > This does not need to be portable to other containers so can be
> >> > proprietary.
> >> >
> >> > I'm using tomcat 8. In fact its tomee 8 but guessed this is more a
> >> > tomcat
> >> > question than tomee but have sent to both groups just in case.
> >> >
> >> > Thanks for any insights.
> >> >
> >> > Paul
> >> >
> >>
> >
>
> ---------------------------------------------------------------------
> To unsubscribe, e-mail: [hidden email]
> For additional commands, e-mail: [hidden email]
>
>
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Re: Initiating httpservletrequest from inside Tomcat / TomEE

Paul Carter-Brown-3
I think we are completely missing each other. Forget sockets - that was
just an example. I have code running in a Tomcat App server which is not
managed by Tomcat and is not initiated by anything within Tomcat. That code
now wants to call a servlet hosted in that very same JVM. Any way to do
that without going out and back in on TCP?


On Mon, May 6, 2019 at 5:14 PM John Dale <[hidden email]> wrote:

> Sockets are an implementation of TCP/UDP inherently.
>
> Perhaps a mountaintop signal fire?
>
> ;)
>
> John
>
>
> On 5/6/19, Paul Carter-Brown <[hidden email]> wrote:
> > lol on the Semaphore Telegraph,
> >
> > I can't use a request dispatcher as the request is being initiated from
> > code that has no context. I already have it working with HTTP using
> > asynchttp library, but I want to avoid the overhead. E.g. lets say I
> wrote
> > my own server socket listener on port 10000 running in the Tomcat JVM and
> > got some request in some propriatary protocol called X. Now I want to
> call
> > a Tomcat servlet in the current JVM with some info I got over X without
> > going out on TCP and back in....
> >
> > On Mon, May 6, 2019 at 4:40 PM John Dale <[hidden email]> wrote:
> >
> >> If you're wanting to forward control to another servlet deployed in
> >> the same context:
> >> https://www.javatpoint.com/requestdispatcher-in-servlet
> >>
> >> If you are okay going through TCP to facilitate some future or current
> >> distribution of services, Use HTTPURLConnection (not sure what you're
> >> wanting to do with the result of the request, if anything):
> >>
> >>
> https://stackoverflow.com/questions/2793150/how-to-use-java-net-urlconnection-to-fire-and-handle-http-requests
> >>
> >> If you need more sophisticated HTTP interactions, Apache maintains a
> >> very useful library for that:  http://hc.apache.org/
> >>
> >> If these don't work-out for you, rather than using .NET, PHP, Python,
> >> or some other Java facsimile at best, I recommend using the semaphore
> >> telegraph:
> >> https://en.wikipedia.org/wiki/Semaphore_telegraph
> >>
> >> Sincerely,
> >>
> >> John
> >> DB2DOM
> >>
> >> On 5/6/19, Paul Carter-Brown <[hidden email]> wrote:
> >> > Hi John,
> >> >
> >> > Thanks for your feedback.
> >> >
> >> > The request I'm initiating should not or need not carry any context
> >> > from
> >> > the originating code. There is also no session to worry about as its
> >> > just
> >> > for rest calls. So basically I have the headers, path and body and
> need
> >> to
> >> > generate a http servlet request and get an http servlet response (or
> >> > similar) back. I have this working by calling into localhost but
> >> > ideally
> >> > want to skip the trombone out and back in.
> >> >
> >> > Have you got any basic code examples?
> >> >
> >> > Paul
> >> >
> >> > On Tue, Apr 30, 2019 at 5:27 PM John Dale <[hidden email]> wrote:
> >> >
> >> >> Another thought .. you can do some request dispatching, but without
> >> >> knowing more about the tools you're using, I can't say for sure if
> >> >> this is the direction you'll want to go.
> >> >>
> >> >> On 4/29/19, Paul Carter-Brown <[hidden email]> wrote:
> >> >> > Hi
> >> >> >
> >> >> > I'm trying to design a Kafka consumer and producer that will run
> >> inside
> >> >> the
> >> >> > tomcat jvm and pick up messages off a Kafka topic and translate
> them
> >> >> into a
> >> >> > servlet request and pass it through tomcat and then when the
> >> >> > response
> >> >> > is
> >> >> > complete then translate it into a Kafka message and put it onto
> >> another
> >> >> > topic as a reply. This way I can reuse our existing jax-rs rest
> >> >> > services
> >> >> > and expose them as an async api over Kafka. The idea is to make the
> >> >> > Kafka
> >> >> > messages similar to http in that they would consist of headers and
> a
> >> >> body.
> >> >> > The body would be json.
> >> >> >
> >> >> > Now I know this could be done by calling localhost with an http
> call
> >> to
> >> >> > trombone the requests back into tomcat but I'd like to avoid the
> >> >> associated
> >> >> > latency and overhead. Is it possible to call tomcat directly
> >> >> > in-process.
> >> >> > This does not need to be portable to other containers so can be
> >> >> > proprietary.
> >> >> >
> >> >> > I'm using tomcat 8. In fact its tomee 8 but guessed this is more a
> >> >> > tomcat
> >> >> > question than tomee but have sent to both groups just in case.
> >> >> >
> >> >> > Thanks for any insights.
> >> >> >
> >> >> > Paul
> >> >> >
> >> >>
> >> >
> >>
> >> ---------------------------------------------------------------------
> >> To unsubscribe, e-mail: [hidden email]
> >> For additional commands, e-mail: [hidden email]
> >>
> >>
> >
>
> ---------------------------------------------------------------------
> To unsubscribe, e-mail: [hidden email]
> For additional commands, e-mail: [hidden email]
>
>
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Re: Initiating httpservletrequest from inside Tomcat / TomEE

Paul Carter-Brown-3
Yea, but the issue is that only works when calling in the context of a
current servlet call.

Here is the kind of problem I want to solve:

@WebServlet(name = "MyExample", urlPatterns = {"/example"}, loadOnStartup =
1)
public class Example extends HttpServlet {

    @PersistenceContext
    private EntityManager em;

    @Override
    public void init(ServletConfig config) {
        Thread t = new Thread(() -> {
            while (true) {
                try {
                    // Do a GET to /example/ and get the response without
going out on localhost and back in....
                    // We cant just call doGet as we want the request to
flow through the servlet filters, do the entitymanager injection etc
                    Thread.sleep(10000);
                } catch (Exception e) {
                }
            }
        });
        t.start();

    }

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {
        // do stuff like use em
        resp.setStatus(200);
        resp.getWriter().write("Hello World");
    }

}




On Mon, May 6, 2019 at 5:35 PM John Dale <[hidden email]> wrote:

> For reference, I did find this after searching "calling a servlet
> programmatically":
> https://docs.oracle.com/cd/E19146-01/819-2634/abxbn/index.html
>
> On 5/6/19, Paul Carter-Brown <[hidden email]> wrote:
> > I think we are completely missing each other. Forget sockets - that was
> > just an example. I have code running in a Tomcat App server which is not
> > managed by Tomcat and is not initiated by anything within Tomcat. That
> code
> > now wants to call a servlet hosted in that very same JVM. Any way to do
> > that without going out and back in on TCP?
> >
> >
> > On Mon, May 6, 2019 at 5:14 PM John Dale <[hidden email]> wrote:
> >
> >> Sockets are an implementation of TCP/UDP inherently.
> >>
> >> Perhaps a mountaintop signal fire?
> >>
> >> ;)
> >>
> >> John
> >>
> >>
> >> On 5/6/19, Paul Carter-Brown <[hidden email]> wrote:
> >> > lol on the Semaphore Telegraph,
> >> >
> >> > I can't use a request dispatcher as the request is being initiated
> from
> >> > code that has no context. I already have it working with HTTP using
> >> > asynchttp library, but I want to avoid the overhead. E.g. lets say I
> >> wrote
> >> > my own server socket listener on port 10000 running in the Tomcat JVM
> >> > and
> >> > got some request in some propriatary protocol called X. Now I want to
> >> call
> >> > a Tomcat servlet in the current JVM with some info I got over X
> without
> >> > going out on TCP and back in....
> >> >
> >> > On Mon, May 6, 2019 at 4:40 PM John Dale <[hidden email]> wrote:
> >> >
> >> >> If you're wanting to forward control to another servlet deployed in
> >> >> the same context:
> >> >> https://www.javatpoint.com/requestdispatcher-in-servlet
> >> >>
> >> >> If you are okay going through TCP to facilitate some future or
> current
> >> >> distribution of services, Use HTTPURLConnection (not sure what you're
> >> >> wanting to do with the result of the request, if anything):
> >> >>
> >> >>
> >>
> https://stackoverflow.com/questions/2793150/how-to-use-java-net-urlconnection-to-fire-and-handle-http-requests
> >> >>
> >> >> If you need more sophisticated HTTP interactions, Apache maintains a
> >> >> very useful library for that:  http://hc.apache.org/
> >> >>
> >> >> If these don't work-out for you, rather than using .NET, PHP, Python,
> >> >> or some other Java facsimile at best, I recommend using the semaphore
> >> >> telegraph:
> >> >> https://en.wikipedia.org/wiki/Semaphore_telegraph
> >> >>
> >> >> Sincerely,
> >> >>
> >> >> John
> >> >> DB2DOM
> >> >>
> >> >> On 5/6/19, Paul Carter-Brown <[hidden email]> wrote:
> >> >> > Hi John,
> >> >> >
> >> >> > Thanks for your feedback.
> >> >> >
> >> >> > The request I'm initiating should not or need not carry any context
> >> >> > from
> >> >> > the originating code. There is also no session to worry about as
> its
> >> >> > just
> >> >> > for rest calls. So basically I have the headers, path and body and
> >> need
> >> >> to
> >> >> > generate a http servlet request and get an http servlet response
> (or
> >> >> > similar) back. I have this working by calling into localhost but
> >> >> > ideally
> >> >> > want to skip the trombone out and back in.
> >> >> >
> >> >> > Have you got any basic code examples?
> >> >> >
> >> >> > Paul
> >> >> >
> >> >> > On Tue, Apr 30, 2019 at 5:27 PM John Dale <[hidden email]>
> wrote:
> >> >> >
> >> >> >> Another thought .. you can do some request dispatching, but
> without
> >> >> >> knowing more about the tools you're using, I can't say for sure if
> >> >> >> this is the direction you'll want to go.
> >> >> >>
> >> >> >> On 4/29/19, Paul Carter-Brown <[hidden email]>
> wrote:
> >> >> >> > Hi
> >> >> >> >
> >> >> >> > I'm trying to design a Kafka consumer and producer that will run
> >> >> inside
> >> >> >> the
> >> >> >> > tomcat jvm and pick up messages off a Kafka topic and translate
> >> them
> >> >> >> into a
> >> >> >> > servlet request and pass it through tomcat and then when the
> >> >> >> > response
> >> >> >> > is
> >> >> >> > complete then translate it into a Kafka message and put it onto
> >> >> another
> >> >> >> > topic as a reply. This way I can reuse our existing jax-rs rest
> >> >> >> > services
> >> >> >> > and expose them as an async api over Kafka. The idea is to make
> >> >> >> > the
> >> >> >> > Kafka
> >> >> >> > messages similar to http in that they would consist of headers
> >> >> >> > and
> >> a
> >> >> >> body.
> >> >> >> > The body would be json.
> >> >> >> >
> >> >> >> > Now I know this could be done by calling localhost with an http
> >> call
> >> >> to
> >> >> >> > trombone the requests back into tomcat but I'd like to avoid the
> >> >> >> associated
> >> >> >> > latency and overhead. Is it possible to call tomcat directly
> >> >> >> > in-process.
> >> >> >> > This does not need to be portable to other containers so can be
> >> >> >> > proprietary.
> >> >> >> >
> >> >> >> > I'm using tomcat 8. In fact its tomee 8 but guessed this is more
> >> >> >> > a
> >> >> >> > tomcat
> >> >> >> > question than tomee but have sent to both groups just in case.
> >> >> >> >
> >> >> >> > Thanks for any insights.
> >> >> >> >
> >> >> >> > Paul
> >> >> >> >
> >> >> >>
> >> >> >
> >> >>
> >> >> ---------------------------------------------------------------------
> >> >> To unsubscribe, e-mail: [hidden email]
> >> >> For additional commands, e-mail: [hidden email]
> >> >>
> >> >>
> >> >
> >>
> >> ---------------------------------------------------------------------
> >> To unsubscribe, e-mail: [hidden email]
> >> For additional commands, e-mail: [hidden email]
> >>
> >>
> >
>
> ---------------------------------------------------------------------
> To unsubscribe, e-mail: [hidden email]
> For additional commands, e-mail: [hidden email]
>
>
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Re: Initiating httpservletrequest from inside Tomcat / TomEE

Paul Carter-Brown-3
Hi John,

See original request. It's pretty much a Kafka/Servlet proxy/gateway:

I'm trying to design a Kafka consumer and producer that will run inside the
tomcat jvm and pick up messages off a Kafka topic and translate them into a
servlet request and pass it through tomcat and then when the response is
complete then translate it into a Kafka message and put it onto another
topic as a reply. This way I can reuse our existing jax-rs rest services
and expose them as an async api over Kafka. The idea is to make the Kafka
messages similar to http in that they would consist of headers and a body.
The body would be json.


On Mon, May 6, 2019 at 6:13 PM John Dale <[hidden email]> wrote:

> You could try debugging the tomcat code and find out how, right after
> it parses the TCP request, it invokes the servlet.  You can then
> create your own harness for tomcat code after initializing the
> appropriate context for the request to tomcat.  I don't know off hand
> where in the tomcat code this cut point can be found.
>
> Is this a performance issue, or are you building a proxy?
>
> What is the problem you're trying to solve?
>
> On 5/6/19, Paul Carter-Brown <[hidden email]> wrote:
> > Yea, but the issue is that only works when calling in the context of a
> > current servlet call.
> >
> > Here is the kind of problem I want to solve:
> >
> > @WebServlet(name = "MyExample", urlPatterns = {"/example"},
> loadOnStartup =
> > 1)
> > public class Example extends HttpServlet {
> >
> >     @PersistenceContext
> >     private EntityManager em;
> >
> >     @Override
> >     public void init(ServletConfig config) {
> >         Thread t = new Thread(() -> {
> >             while (true) {
> >                 try {
> >                     // Do a GET to /example/ and get the response without
> > going out on localhost and back in....
> >                     // We cant just call doGet as we want the request to
> > flow through the servlet filters, do the entitymanager injection etc
> >                     Thread.sleep(10000);
> >                 } catch (Exception e) {
> >                 }
> >             }
> >         });
> >         t.start();
> >
> >     }
> >
> >     @Override
> >     protected void doGet(HttpServletRequest req, HttpServletResponse
> resp)
> > throws ServletException, IOException {
> >         // do stuff like use em
> >         resp.setStatus(200);
> >         resp.getWriter().write("Hello World");
> >     }
> >
> > }
> >
> >
> >
> >
> > On Mon, May 6, 2019 at 5:35 PM John Dale <[hidden email]> wrote:
> >
> >> For reference, I did find this after searching "calling a servlet
> >> programmatically":
> >> https://docs.oracle.com/cd/E19146-01/819-2634/abxbn/index.html
> >>
> >> On 5/6/19, Paul Carter-Brown <[hidden email]> wrote:
> >> > I think we are completely missing each other. Forget sockets - that
> was
> >> > just an example. I have code running in a Tomcat App server which is
> >> > not
> >> > managed by Tomcat and is not initiated by anything within Tomcat. That
> >> code
> >> > now wants to call a servlet hosted in that very same JVM. Any way to
> do
> >> > that without going out and back in on TCP?
> >> >
> >> >
> >> > On Mon, May 6, 2019 at 5:14 PM John Dale <[hidden email]> wrote:
> >> >
> >> >> Sockets are an implementation of TCP/UDP inherently.
> >> >>
> >> >> Perhaps a mountaintop signal fire?
> >> >>
> >> >> ;)
> >> >>
> >> >> John
> >> >>
> >> >>
> >> >> On 5/6/19, Paul Carter-Brown <[hidden email]> wrote:
> >> >> > lol on the Semaphore Telegraph,
> >> >> >
> >> >> > I can't use a request dispatcher as the request is being initiated
> >> from
> >> >> > code that has no context. I already have it working with HTTP using
> >> >> > asynchttp library, but I want to avoid the overhead. E.g. lets say
> I
> >> >> wrote
> >> >> > my own server socket listener on port 10000 running in the Tomcat
> >> >> > JVM
> >> >> > and
> >> >> > got some request in some propriatary protocol called X. Now I want
> >> >> > to
> >> >> call
> >> >> > a Tomcat servlet in the current JVM with some info I got over X
> >> without
> >> >> > going out on TCP and back in....
> >> >> >
> >> >> > On Mon, May 6, 2019 at 4:40 PM John Dale <[hidden email]>
> wrote:
> >> >> >
> >> >> >> If you're wanting to forward control to another servlet deployed
> in
> >> >> >> the same context:
> >> >> >> https://www.javatpoint.com/requestdispatcher-in-servlet
> >> >> >>
> >> >> >> If you are okay going through TCP to facilitate some future or
> >> current
> >> >> >> distribution of services, Use HTTPURLConnection (not sure what
> >> >> >> you're
> >> >> >> wanting to do with the result of the request, if anything):
> >> >> >>
> >> >> >>
> >> >>
> >>
> https://stackoverflow.com/questions/2793150/how-to-use-java-net-urlconnection-to-fire-and-handle-http-requests
> >> >> >>
> >> >> >> If you need more sophisticated HTTP interactions, Apache maintains
> >> >> >> a
> >> >> >> very useful library for that:  http://hc.apache.org/
> >> >> >>
> >> >> >> If these don't work-out for you, rather than using .NET, PHP,
> >> >> >> Python,
> >> >> >> or some other Java facsimile at best, I recommend using the
> >> >> >> semaphore
> >> >> >> telegraph:
> >> >> >> https://en.wikipedia.org/wiki/Semaphore_telegraph
> >> >> >>
> >> >> >> Sincerely,
> >> >> >>
> >> >> >> John
> >> >> >> DB2DOM
> >> >> >>
> >> >> >> On 5/6/19, Paul Carter-Brown <[hidden email]> wrote:
> >> >> >> > Hi John,
> >> >> >> >
> >> >> >> > Thanks for your feedback.
> >> >> >> >
> >> >> >> > The request I'm initiating should not or need not carry any
> >> >> >> > context
> >> >> >> > from
> >> >> >> > the originating code. There is also no session to worry about as
> >> its
> >> >> >> > just
> >> >> >> > for rest calls. So basically I have the headers, path and body
> >> >> >> > and
> >> >> need
> >> >> >> to
> >> >> >> > generate a http servlet request and get an http servlet response
> >> (or
> >> >> >> > similar) back. I have this working by calling into localhost but
> >> >> >> > ideally
> >> >> >> > want to skip the trombone out and back in.
> >> >> >> >
> >> >> >> > Have you got any basic code examples?
> >> >> >> >
> >> >> >> > Paul
> >> >> >> >
> >> >> >> > On Tue, Apr 30, 2019 at 5:27 PM John Dale <[hidden email]>
> >> wrote:
> >> >> >> >
> >> >> >> >> Another thought .. you can do some request dispatching, but
> >> without
> >> >> >> >> knowing more about the tools you're using, I can't say for sure
> >> >> >> >> if
> >> >> >> >> this is the direction you'll want to go.
> >> >> >> >>
> >> >> >> >> On 4/29/19, Paul Carter-Brown <[hidden email]>
> >> wrote:
> >> >> >> >> > Hi
> >> >> >> >> >
> >> >> >> >> > I'm trying to design a Kafka consumer and producer that will
> >> >> >> >> > run
> >> >> >> inside
> >> >> >> >> the
> >> >> >> >> > tomcat jvm and pick up messages off a Kafka topic and
> >> >> >> >> > translate
> >> >> them
> >> >> >> >> into a
> >> >> >> >> > servlet request and pass it through tomcat and then when the
> >> >> >> >> > response
> >> >> >> >> > is
> >> >> >> >> > complete then translate it into a Kafka message and put it
> >> >> >> >> > onto
> >> >> >> another
> >> >> >> >> > topic as a reply. This way I can reuse our existing jax-rs
> >> >> >> >> > rest
> >> >> >> >> > services
> >> >> >> >> > and expose them as an async api over Kafka. The idea is to
> >> >> >> >> > make
> >> >> >> >> > the
> >> >> >> >> > Kafka
> >> >> >> >> > messages similar to http in that they would consist of
> headers
> >> >> >> >> > and
> >> >> a
> >> >> >> >> body.
> >> >> >> >> > The body would be json.
> >> >> >> >> >
> >> >> >> >> > Now I know this could be done by calling localhost with an
> >> >> >> >> > http
> >> >> call
> >> >> >> to
> >> >> >> >> > trombone the requests back into tomcat but I'd like to avoid
> >> >> >> >> > the
> >> >> >> >> associated
> >> >> >> >> > latency and overhead. Is it possible to call tomcat directly
> >> >> >> >> > in-process.
> >> >> >> >> > This does not need to be portable to other containers so can
> >> >> >> >> > be
> >> >> >> >> > proprietary.
> >> >> >> >> >
> >> >> >> >> > I'm using tomcat 8. In fact its tomee 8 but guessed this is
> >> >> >> >> > more
> >> >> >> >> > a
> >> >> >> >> > tomcat
> >> >> >> >> > question than tomee but have sent to both groups just in
> case.
> >> >> >> >> >
> >> >> >> >> > Thanks for any insights.
> >> >> >> >> >
> >> >> >> >> > Paul
> >> >> >> >> >
> >> >> >> >>
> >> >> >> >
> >> >> >>
> >> >> >>
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