Java Reference
In-Depth Information
ent's first pull request. Injecting the
async
parameter via the
@Suspended
annotation de-
taches HTTP response processing from this request thread.
The method then begins by defining a
synchronized
block on the
messages
variable. This
block allows the
receive()
method to perform atomic actions that do not conflict with the
writer
thread. Within the block, the code looks up the
current
query parameter in the
mes-
sages
map. If the message is
null
, then the code sets this variable to the
first
member
variable of the class. Otherwise, it sets the message to the found message's
next
field. If the
message is still
null
, then there is no message available and the
AsyncResponse
is queued
for the
writer
thread to pick up when a message is available.
Finally, after the
synchronized
block, if the message is not
null
, it is sent immediately
back to the chat client.
protected
protected
void
void
queue
(
AsyncResponse async
)
{
listeners
.
add
(
async
);
}
The
queue()
method just adds the
AsyncResponse
to the
listeners
list so the
writer
thread
can pick it up.
protected
protected
void
void
send
(
UriBuilder base
,
AsyncResponse async
,
Message message
)
{
URI nextUri
=
base
.
clone
().
path
(
CustomerChat
.
class
)
.
queryParam
(
"current"
,
message
.
id
).
build
();
Link next
=
Link
.
fromUri
(
nextUri
).
rel
(
"next"
).
build
();
Response response
=
Response
.
ok
(
message
.
message
,
MediaType
.
TEXT_PLAIN_TYPE
)
.
links
(
next
).
build
();
async
.
resume
(
response
);
}
The
send()
method can be called by the
writer
thread or the
receive()
method. It creates a
Response
populated with the message that will be sent back to the chat client. It also calcu-
lates and adds a
next Link
header to send back with the response. At the end of the method,
the
AsyncResponse.resume()
method is invoked with the built
Response
.
Build and Run the Example Program
You'll need multiple console windows to run this example. In the first console window, per-
form the following steps:
1. Change to the
ex13_1
directory of the workbook example code.
