Spring Boot send only changed data - spring

Question

I am building a game in Spring Boot on a server and classic Javascript on a backend.
Right now I have this:
...
#Autowired
private SimpMessagingTemplate template;
...
#Scheduled(fixedRate = 1000 / Constants.FPS)
public void renderClients() {
for(Game g : games) {
template.convertAndSend("/game/render/" + g.getId(), g);
}
}
...
Basically I have a multiple Games running and I send each with it's id to the client.
However the data I am sending (or the most of the data) is static (not changing)...
What if I want not to send the whole data but only parts which have changed.
Btw the response JSON looks like this:
{"id":"862b1dd8-48d5-4562-802a-7d669a5a5ed5","players":[{"id":"da8dcbec-7028-4a39-9547-a4e2dc321c3c","name":"John Doe","position":{"x":100.0,"y":100.0},"rotation":0.0,"hero":{"maxHealth":1300.0,"movementSpeed":4.5,"attackDamage":32.75,"width":68,"height":71,"heroName":"drowRanger","radius":34.0},"stats":{"kills":0,"lastHits":0},"lastClick":null}],"duration":380107.12}
and the only thing that is changing is duration and sometimes the x and y when the player moves...
Is it even possible?
Could I write some middleware that will do that at the time the objects are converted to JSON?

Answer 1

Maintain a data structure stores your changed value, and attach it to your Game Object.
When the time to send ,convert the map to a json ,and clear it.
Using this way may use more memory than before , but won't cost much time.

Answer 2

I DID IT!!
In my GameController I do:
#Scheduled(fixedRate = 1000 / Constants.FPS)
public void renderClients() throws Exception {
for(Game g : games) {
template.convertAndSend("/game/render/" + g.getId(), g.formatToSend());
}
}
Notice the g.formatToSend() method
here is how a Game class looks like:
public class Game {
private BandWidthOptimizer optimizer = new BandWidthOptimizer();
...
...
public String formatToSend() throws Exception {
return optimizer.optimize(this);
}
}
And Here Comes THE BandWidthOptimizer:
package com.iddqd.doto.optimization;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.sun.tools.classfile.Opcode;
import org.json.simple.JSONArray;
import org.json.simple.JSONObject;
import org.json.simple.parser.JSONParser;
import java.util.Iterator;
import java.util.Set;
import java.util.function.BiConsumer;
public class BandWidthOptimizer {
import com.fasterxml.jackson.databind.ObjectMapper;
import org.json.simple.JSONArray;
import org.json.simple.JSONObject;
import org.json.simple.parser.JSONParser;
private String[] preserveKeys;
public BandWidthOptimizer() {
this.preserveKeys = new String[0];
}
public BandWidthOptimizer(String[] preserveKeys) {
this.preserveKeys = preserveKeys;
}
public String optimize(Object obj) throws Exception {
String json = mapper.writeValueAsString(obj);
Object nobj = parser.parse(json);
Object oobj = parser.parse(lastJSON);
JSONObject newJsonObj = (JSONObject)nobj;
JSONObject oldJsonObj = (JSONObject)oobj;
JSONObject res = getJSONObjectDiff(newJsonObj, oldJsonObj);
lastJSON = json;
return res.toJSONString();
}
private JSONObject getJSONObjectDiff(JSONObject obj1, JSONObject obj2) {
JSONObject res = new JSONObject();
Set set = obj1.keySet();
for (Object key : set) {
// If doesn't exist put it in the diff
if (!obj2.containsKey(key)) {
res.put(key, obj1.get(key));
} else {
// Get the values from both objects
Object val1 = obj1.get(key);
Object val2 = obj2.get(key);
// If their instances are of the same type
if(val1 == null) {
continue;
}
if(val2 == null) {
res.put(key, val1);
continue;
}
if (val1.getClass().equals(val2.getClass())) {
// If they are JSONObject
if (val1 instanceof JSONObject) {
// Recursively parse JSONObject with all of it's properties
JSONObject nested = getJSONObjectDiff((JSONObject) obj1.get(key), (JSONObject) obj2.get(key));
// If it contains any keys
if(nested.keySet().size() > 0) {
// Store the diff into final diff
res.put(key, nested);
}
// If they are JSONArrays
} else if (val1 instanceof JSONArray) {
// If val1 contains some values (is not empty)
if(((JSONArray) val1).size() > 0) {
// Get their diff
JSONArray arr = getJSONArrayDiff((JSONArray) val1, (JSONArray) val2);
// If array is not empty
if (arr.size() > 0) {
// put it into the diff
res.put(key, arr);
}
}
// If they are just a pure values
} else {
// Compare them - If they're not equal
if(!val1.equals(val2)) {
// put the val1 into diff
res.put(key, val1);
}
}
} else {
res.put(key, val1);
}
}
}
return res;
}
private JSONArray getJSONArrayDiff(JSONArray arr1, JSONArray arr2) {
JSONArray res = new JSONArray();
// For every element
for(int i = 0; i < arr1.size(); i++) {
Object val1 = arr1.get(i);
// If i is out of arr2 bounds
if(i > arr2.size()) {
// put the arr1 item into the diff
res.add(val1);
}
Object val2 = arr2.get(i);
if(val1 == null) {
continue;
}
if(val2 == null) {
res.add(val1);
continue;
}
// If their types are equal
if(val1.getClass().equals(val2.getClass())) {
// If they are JSONObjects
if(val1 instanceof JSONObject) {
// Get their diff
JSONObject obj = getJSONObjectDiff((JSONObject) val1, (JSONObject) val2);
// If it contains any keys
if(obj.keySet().size() > 0) {
// Store the diff into final diff
res.add(obj);
}
// If they are JSONArrays
} else if (val1 instanceof JSONArray) {
// Get their diff
JSONArray arr = getJSONArrayDiff((JSONArray) val1, (JSONArray) val2);
// If array is not empty
if(arr.size() > 0) {
// put it into the diff
res.add(arr);
}
// If they are just a pure values
} else {
// Compare them - If they're not equal
if(val1 != val2) {
// add the val1 into diff
res.add(val1);
}
}
} else {
res.add(val1);
}
}
return res;
}
}
This is it, now if nothing moves on the map the result JSON looks like this:
{"duration":282964.56}
because only the duration changes
But when my Player moves on the map see what happens:
{"duration":386676.06,"players":[{"position":{"x":556.5914801003707,"y":153.55964799554002}}]}
TODO
I have to implement a preserveKeys functionallity because I always want to send some keys like id and so on...