Develop Reference

Repeated requests when I use struts2 to submit form

My project is build on struts2.Recently I found a problem that is when I submit my form,sometimes the request send 2 times.
my code:
document.searchForm.action = "${dynamicURL}/voucher/doAddIniAccountVoucherMake.action";
var para=$('#searchForm').serialize();
$('#para').val(para);
document.searchForm.submit();
In the method of the action,I log the time and param in database.Actually ,the Repeated requests is bare,but it did happen.I want to konw the reason of this problem, because it will cause big problem in procudution enviroment.Someone can give any means?

jquery/angular scheduler implementation

I have a chat application written on jquery. When user sends a message, this message is being sent to java REST endpoint. But I also want to listen for response. I think it would be good to listen other REST endpoint every second, because I have no idea how to implement it like in Facebook. So if there new message, get them and show. How to do that in jquery?

There are couple of solutions for that, but I'd suggest you do not create chat application using REST. If you want pure JS think about firebase from google (it will be realtime)/meteor or definitely using Websockets (you'll need a websocket server and you can use authobahnjs to subscribe to that server).
I do realize it's solution that's more complicated than REST, but if you ask me and probably your customers REST is really not the best choice for chat/realtime applications...
Just think of situation where you will have lots of users online and each of them will not only be sending a lot of queries (if they write fast) but as well checking for response every second. Now think if something goes wrong on the network what will happen with your server... you'll get tons of 'hanging' connections etc.
btw. ppl who tried it (like me in past) will tell you the same, no chats with polling for messages over REST! ;)
JQuery way...
Ok, just watch out for defining multiple events on the same element (that’s classic one when working with Jquery), here’s a function that should do what you want (its a post, but you can adapt it):
var interval = 1000; // 1000 = 1 second, 3000 = 3 seconds
function doAjax() {
$.ajax({
type: 'POST',
url: 'chatController.php',
data: {action: 'getMessagesForUser', user: {user: 'data'}},
dataType: 'json',
success: function (data) {
//do something with results
},
complete: function (data) {
// Schedule the next
setTimeout(doAjax, interval);
}
});
}
setTimeout(doAjax, interval);
You could also introduce some variable that would make sure you're not making another request before the previous one has completed etc.

Url Encoding Issue - Special Characters originate webserver crash

I have been searching about this info but since I'm new to web development the answers I'm getting are getting me even more confused.
Basically, I have a webserver established in a Java Modem (which uses 1.3IDE) which will handle requests. These requests were being processed as long as I kept it simple.
http://87.103.87.59/teste.html?a=10&b=10
This request is normally processed.
However, when applying the real deal, my webserver is crashing.
http://5.43.52.4/api.html?ATCOMMAND=AT%5EMTXTUNNEL=SMS,0035111111111,string sending test
The problem is due to two aspects. The "%" character and the string sending test.
To put everything clear, handlers I'm using are these:
public InputStream is = null;
private OutputStream os = null;
private byte buffer[] = new byte[];
String streamAux="";
is = socketX.openInputStream();
os = socketX.openOutputStream();
if ((is.available()>0)||(blockX==true))
{
//Read data sent from remote client
numDadosLidos=is.read(buffer);
for (int i=0;i<numDadosLidos;i++)
streamAux= streamAux + (char)buffer[i]; //where the url will be stored
Basically I will need those parameters so I can use them to operate my Java device so, I think I'll need to do some sort of encoding but there's a lot of information that I can't comprehend and my 1.3 IDE is kind of keeping me stuck.
I apologize for some sort of newbie behaviour in advance.
Hope you can lend me a hand,
Thanks

For those who are interested, I basically went around the issue obliging the message to be sent using '-' character. It doesn't solve the issue, it simply solves the question with the "not-ideal" method.
Still totally interested if someone figures this one out.
Thanks.

Asynchronous SSE Listener in Java Servlet

I am new here so forgive me if I am not familiar with standard operating procedure, but I have researched this topic at length and haven't found a lot of info.
I am trying to implement a client in a Java Http Servlet that can subscribe to a server-sent-event stream and parse data from that stream. Every time I have a client POST a request to my Http servlet, I need to pass on some data from that client to another server and then open an SSE listener, as that is how the other server will notify me it has data for me to hand back to the client.
It needs to be asynchronous and probably multi-threaded because I will have many requests from the client happening in a short time frame and I need to catch every event coming back from the server. The data I pass back from the server to the client can be large so I need threading so I don't miss new events coming in.
I am at a loss for where to start. I have tried implementing some of the example code using the Jersey SSE API (https://jersey.java.net/documentation/latest/sse.html) but when I implement their asynchronous SSE event handling example, the events coming in happen too fast for my handler to process all the data back to the client and the function gets called again from a new event before it finishes, or at least that's what seems to be happening.
Here is a synopsis of what I have written so far:
Client client = ClientBuilder.newBuilder().register(SseFeature.class).build();
WebTarget target = client.target("Target URL");
EventSource eventSource = new EventSource(target) {
#Override
public void onEvent(InboundEvent inboundEvent){
if ("in".equals(inboundEvent.getName())) {
//Check if the event is of the type we care about
//If it is, open an input stream to read the payload and store in a byte array via an HttpURLConnection object
//Open an output stream and stream the payload to a client via an HttpServletResponse Object - This never seems to happen
}
}
};
}
I know it's sloppy, I'm not as familiar with Java so I am just piecing things together so I apologize for that.
This gets called from within my servlet class but it never makes it to the point where I write to the output stream, I think because it's getting interrupted by another event coming in. If anyone has insight into how I can make this work, or another way to do it, I would greatly appreciate it. Thanks.

I recommend you the JEaSSE library (Java Easy Server-Sent Events): http://mvnrepository.com/artifact/info.macias/jeasse
You can find some usage examples here:
https://github.com/mariomac/jeasse

Smack api and Java

I am using Tapestry 5, Smack api 3.1.0.
I have established a connection and am able to communicate with a user through the xmpp server but the replies i get are sent to the standard output as they come in:
Chat chat = connection.getChatManager().createChat("blah#jabber.org", new MessageListener() {
public void processMessage(Chat chat, Message message) {
// Print out any messages we get back to standard out.
System.out.println("Received message: " + message.getBody()); // this works
showonbrowser = message.getBody();
System.out.println(showonbrowser) // this prints nothing
}
};
I am looking to get the replies to my html file so i can read them on the web instead of the console. However, when i try to set message.getBody() to showonbrowser (a property on the page) i see no result. Does anyone know how I get around this?
Regards,
Kace

Smack is multi-threading and it has a nasty habit of eating up exceptions that are thrown (silently.) Most likely you are not using a thread-safe GUI and its throwing an exception that you never get.

I think the processMessage method is being called after the page is rendered.
You are creating a MessageListener instance (through an anonymous class), so you don't know when the processMessage method will be called. I think you would have to do something with AJAX to do partial updates on the page, polling the server and getting any new messages to show them on the page.