Java Reference
In-Depth Information
Server-side push
With server-side push, the server is sending events back to the client. A typical example is
stock quotes. The client wants to be notified when a new quote is available. It does a long-
poll GET request until the quote is ready.
Client client
=
ClientBuilder
.
newClient
();
final
final
WebTarget target
=
client
.
target
(
"http://quote.com/quote/RHT"
);
target
.
request
().
async
().
get
(
new
new
InvocationCallback
<
String
> {
public
public
void
void
completed
(
String quote
) {
System
.
out
.
println
(
"RHT: "
+
quote
);
target
.
request
().
async
().
get
(
this
this
);
}
public
public
void
void
failed
(
Throwable t
) {}
}
The preceding continuously polls for a quote using
InvocationCallback
. On the server
side, we want our JAX-RS resource classes to use suspended requests so that we can have
one thread that writes quotes back to polling clients. With one writer thread, we can scale this
quote service to thousands and thousands of clients, as we're not beholden to a “one thread
per request” model. Here's what the JAX-RS resource class might look like:
@Path
(
"quote/RHT"
)
public
public class
class
RHTQuoteResource
RHTQuoteResource
{
protected
protected
List
<
AsyncResponse
>
responses
;
@GET
@Produces
(
"text/plain"
)
public
public
void
void
getQuote
(
@Suspended
AsyncResponse response
) {
synchronized
synchronized
(
responses
) {
responses
.
put
(
response
);
}
}
}
The example code is overly simplified, but the idea is that there is a
List
of
AsyncResponse
objects that are waiting for the latest stock quote for Red Hat. This
List
would be shared by
a background thread that would send a response back to all waiting clients when a new quote
for Red Hat became available.
Executor executor
=
Executors
.
newSingleThreadExecutor
();
final
final
List
<
AsyncResponse
>
responses
= ...;
