Java Reference
In-Depth Information
The
post()
method consumes plain-text data. The first thing we do is store a
UriBuilder
in
a local variable of the base URI of our service. We then queue up a task for our writer thread.
We cannot use the
UriInfo
member variable in this background task. The
CustomerChat
class is a singleton and can accept requests concurrently. Because of this, the
UriInfo ur-
iInfo
member variable is a proxy that delegates to the request's actual
UriInfo
by using an
underlying
ThreadLocal
in most JAX-RS vendor implementations. If the
writer
background
thread invokes on this proxy, it would get an error because
ThreadLocal
data is not trans-
ferred between different threads.
writer
.
submit
(
new
new
Runnable
());
{
@Override
public
public
void
void
run
()
{
synchronized
synchronized
(
messages
)
{
Message message
=
new
new
Message
();
message
.
id
=
Long
.
toString
(
counter
.
incrementAndGet
());
message
.
message
=
text
;
Each new message post is queued up for the
writer
thread in an implementation of the
Run-
nable
interface. This task starts off by synchronizing on the
messages
variable. This pro-
tects the critical parts of our message service by serializing access to the
messages
map. The
code then creates a
Message
instance using an
id
generated from the
counter
.
iif
(
messages
.
size
() ==
0
)
{
first
=
message
;
}
else
else
{
last
.
next
=
message
;
}
The
writer
thread next checks to see if this is the initial message to the system. If so, it sets
the
first
member variable to point to the first message posted to the service. Otherwise, it
points the tail of the
Message
linked list to this new
Message
instance.
messages
.
put
(
message
.
id
,
message
);
last
=
message
;
The code then stores the new message in the
messages
map and sets the
last
member vari-
able to point to this new message.
