Pushing complete data from Spring Boot server through Web Socket to Client - html

Question

I have a spring boot server and i am able to generate a streaming table on client side by sending json one after the another. The problem is if a user logs in say after 10 minutes, he is only able to access data starting from 10th minute i.e he is not able to access data from 0 to 10th minute. What i want is to push the data from 0th to 10th minute first and at the same time continue the streaming process. How can this be done? I am using jquery datatable to generate the table.
I am attaching the controller and client side html for reference
1) Controller
#Controller
public class ScheduledUpdatesOnTopic {
#Autowired
private SimpMessagingTemplate template;
int count=0;
#Scheduled(fixedDelay=500)
public void trigger() {
DateFormat df = new SimpleDateFormat("yyyy/MM/dd HH:mm:ss");
Date date = new Date();
String str[] = {"name"+count,""+Math.round(Math.random()*100),"India"+Math.round(Math.random()*100),df.format(date)};
this.template.convertAndSend("/topic/message",str);
++count;
}
}
2) Client HTML
var _self = this;
$(document).ready(function() {
var message ;
$('#tbl').DataTable( {
data: message,
"aLengthMenu" : [[25,50,75,-1],[25,50,75,"All"]],
"pageLength" :25,
columns: [
{ title: "Name" },
{ title: "Age" },
{ title: "Country" },
{ title: "Date"}
]
});
subscribeSocket();
});
function addRow(message){
var table = $('#tbl').DataTable();
if(table && message ){
table.row.add(message).draw();
}
}
function subscribeSocket(){
var socket = new SockJS('/gs-guide-websocket');
var stompClient = Stomp.over(socket);
stompClient.connect({ }, function(frame) {
stompClient.subscribe("/topic/message", function(data) {
message = JSON.parse(data.body);
_self.addRow(message);
});
});
};

Answer 1

If you don't save previous sent datas, you can't send them back to new customers.
On the front side, you have to subscribe to an "history" resource and make a call to get it.
Front:
function subscribeSocket() {
var socket = new SockJS('/gs-guide-websocket');
stompClient = Stomp.over(socket);
var firstCounterReceived = null;
stompClient.connect({}, function (frame) {
setConnected(true);
stompClient.subscribe('/topic/history', function (response) {
console.log(JSON.parse(response.body));
});
stompClient.subscribe('/topic/message', function (response) {
var message = JSON.parse(response.body);
if (firstCounterReceived == null) {
firstCounterReceived = message[0];
console.log(`Calling history endpoint with ${firstCounterReceived}`);
stompClient.send("/app/topic/history", {}, message[0]);
}
console.log(message);
});
});
}
Back:
#Controller
#EnableScheduling
public class ScheduledUpdatesOnTopic {
Map<Integer, String[]> history = new LinkedHashMap<>();
#Autowired
private SimpMessagingTemplate template;
private Integer count = 0;
#MessageMapping("/topic/history")
#SendTo("/topic/history")
public List<String[]> history(Integer to) {
return history.keySet()
.stream()
.filter(counter -> counter < to)
.map(counter -> history.get(counter))
.collect(Collectors.toList());
}
#Scheduled(fixedRate = 500)
public void sendMessage() {
DateFormat df = new SimpleDateFormat("yyyy/MM/dd HH:mm:ss");
Date date = new Date();
String[] str = {count.toString(), "name"+count,""+Math.round(Math.random()*100),"India"+Math.round(Math.random()*100),df.format(date)};
history.put(count, str);
this.template.convertAndSend("/topic/message",str);
++count;
}
}
In this sample, saved datas are stored in a map, be aware that it will consume some memory at some point.