I have a news project with comment feature. Any one who add a comment can see his comment immediately without reloading the page ( using ajax ). The problem is that when user1 ( for example ) comment on post1 , only user1 can see his comment immediately but all other users need to reload the page to see the comment of user1. How can I solve this problem ?
The code I am using to get the comment :
$(function () {
$("#AddComment").click(function () {
var CommentText = document.getElementById("CommetForm").innerHTML;
var UserName = document.getElementById("UserName").innerHTML;
var PostId = document.getElementById("PostId").innerHTML;
$.ajax({
url: '/PostComment/AddComment',
type: 'POST',
dataType: 'json',
cache: false,
data: { "PostId": PostId, "CommentText": OrignalCommentText },
success: function (data)
{
if (data == "P") // Commet Stored on database successfully
{
document.getElementById("PostComments-" + PostId).innerHTML +=
"<li>" +
"<div class='media'>" +
"<div class='media-body'>" +
"<a href='' class='comment-author'>"+UserName+"</a>" +
"<span class='CommetText' id='CommentText-" + PostId + "'>" + CommentText + "</span>" +
"</div>" +
"</div>" +
"</li>";
}
else // Some Error occur during storing database
{
document.getElementById("CommentError-" + PostId).innerHTML = "\nSomething went wrog, please try agin";
}
}
});
});
});
And This code for storing comment in database :
private SocialMediaDatabaseContext db = new SocialMediaDatabaseContext();
[HttpPost]
public JsonResult AddComment(string PostId, string CommentText)
{
try
{
Users CurrentUser = (Users)Session["CurrentUser"];
PostComment postcomment = new PostComment();
CommentText = System.Uri.UnescapeDataString(CommentText);
postcomment.PostId = int.Parse(PostId);
postcomment.CommentFromId = CurrentUser.UserId;
postcomment.CommentText = CommentText;
postcomment.CommentDate = DateTime.Now;
db.PostComments.Add(postcomment);
db.SaveChanges();
return Json("P");
}
catch
{
return Json("F");
}
}
I suggest you use SignalR for this. http://www.asp.net/signalr/overview/getting-started/introduction-to-signalr
TL;DR Use can use setInterval or Websockets to accomplish this. Below I explain how.
First of all, we need to understand what is behind this Publish/Subscribe pattern. Since you want to build a real-time application, you may create a function that asks to your server if some data was added since last time it was checked.
USING WindowTimers.setInterval()
Here is the simplest way to accomplish this in my point of view, assuming that's your first time and you never worked with websockets before. For instance, in your client-side project you create a function within a setInterval setInterval( checkNewData, time). Your method checkNewData() will make an ajax requisition to your server, asking if some data was added recently:
function checkNewData() {
// ajax call
// On response, if found some new comment, you will inject it in the DOM
}
Then, in your server-side method, get the timestamp of its call and verify in your database if there are some data. Something like this:
// Method written in PHP
public function ajax_checkNewData() {
$time = time();
// Asks to your model controller if has something new for us.
// SELECT comment FROM comments WHERE timestamp > $time
// Then return its response
}
You will use the response that came from your controller method ajax_checkNewData() to write on your comments-container.
USING WEBSOCKETS (beautiful way)
Now, there are another way to do this, using WebSockets. HTML5 WebSocket represents the first major upgrade in the history of web communications. Before WebSocket, all communication between web clients and servers relied only on HTTP. Now, dynamic data can flow freely over WebSocket connections that are persistent (always on), full duplex (simultaneously bi-directional) and blazingly fast. Amongst different libraries and frameworks, you can use socket.io. I believe this will solve your real-time application problem pretty good, but I am not sure how much of your project you will need to change to suit this solution.
Check it out the simple chat tutorial from SocketIo page and see for yourself if it fits to your needs. Its pretty neat and would be a good challenge to implement using it. Since its event-driven, I believe you wont have problems implementing it.
For further information check it out:
REFERENCES
Get Started: Chat application - http://socket.io/get-started/chat/
Websockets - http://en.wikipedia.org/wiki/WebSocket
WebSockets - https://developer.mozilla.org/en/docs/WebSockets
Good luck!
You could write a JavaScript code which makes ajax call to a servlet that checks for updates in the database.
Return a flag to the success function of the ajax call and If the state has changed or any comment added to the database, you can reload the page or refresh the consisting of the comments with the new comments.
It's not posting on other pages, because the user1 page is making an AJAX call, so it loads correctly. However, the other pages don't 'know' they are supposed to reload via AJAX. You need some kind of timed loop running that checks for any changes. Either of the above answers should work for it.
You could use SignalR for this, you can send realtime messages to the server, here is a sample to know how to implement SignalR in ASP.NET MVC
https://github.com/WaleedChayeb/SignalRChatApp
Related
I am writing a page update which works with PHP to read a SQL database the page echo's the contents in a div section 'track_data'. yet it doesn't do this update idk
I have JavaScript script which I dont really fully understand and hopeful someone could explain its principally the check response section I think is failing ? :
in my PHP page :
<script type="text/javascript">
function InitReload() {
new Ajax.PeriodicalUpdater('track_data', 'fetch_sql.php', {
method: 'get', frequency: 60, decay: 1});
}
</script>
Thanks for looking and hopefully someone undersstands this and can put a smile on my face for the second time today :)
Steps to fix
Thanks for the suggestions of syntax errors. I haven't really got very far with this here are the changes you suggested which I have changed but I still think there is something wrong with last function as it doesn't update div section.
Code in JS file
// Start Clock refresh
// uses new new Ajax.PeriodicalUpdater(
// in main fetch file to trigger the auto update of the page.
// Written by Denise Rose
var gUpdateDiv;
var gContentURL;
var gcheckInterval;
var gcheckURL = "";
var gCurrentCheck ="";
_fetchUpdater('track_data','/fetch_sql.php','/fetch_sql.php',8000);
function _fetchUpdater(updateDiv,contentURL,checkURL,checkInterval)
{
gUpdateDiv = updateDiv;
gContentURL = contentURL;
gcheckInterval = checkInterval;
gcheckURL = checkURL;
setTimeout('check();',gCheckInterval);
}
//Called by _fetchUpdater every (n) seconds determins if content should be updated.
function check()
{
new Ajax.Request(gContentUrl,{method:'get', onSuccess:'checkResponse'});
setTimeout('check();',gCheckInterval);
}
// looks for the response and determines if the div should be updated.
function checkResponse(transport)
{
var content = transport.response.Text;
if(gCurrentCheck != content) {
gCurrentCheck = content;
new Ajax.Request(gContentUrl, {method: 'get',onSuccess:function t() {
$(gUpdateDiv).innerHTML = t.responseText; /*t.response.json()*/}
});
}
}
This is the bit I dont understand
function checkResponse(transport)
{
var content = transport.response.Text;
if(gCurrentCheck != content) {
gCurrentCheck = content;
new Ajax.Request(gContentUrl, {method: 'get',onSuccess:function t() {
$(gUpdateDiv).innerHTML = t.response.json();/*t.responseText;*/}
});
}
}
Method and Issues
What is transport here and what is t? if it stores the contents of the body text from the second in gCurrentCheck and compares to transport version content then why doesn't it update if its different please which it is if the SQL has created a different page?
I did find this https://api.jquery.com/jquery.ajaxtransport/
First Answer not using Ajax
I was given a neat and JS version as an answer, which is not really what I was looking for. I was hopeful to get the one working with one with Ajax but I appreciate your efforts is very kind. I just really wanted to send a refresh to the div area so that the PHP rebuilt the page from the SQL.
I might have been missing the MIT javascript http://www.prototypejs.org/ lol but I dont think it was.
Just to help:
AJAX stands for Asynchronous JavaScript And XML. In a nutshell, it is the use of the XMLHttpRequest object to communicate with servers. It can send and receive information in various formats, including JSON, XML, HTML, and text files. ... Make requests to the server without reloading the page.
Researching
I found this Update div with the result of an Ajax-call but it did not really explain as the OP was using PHP like me not HTML. The answer was given:
$.ajax({
url: 'http://dowmian.com/xs1/getcam.php',
type: 'GET',
data: {id: <?php echo $cam_id; ?>},
success: function(responseText){
$('#update-div').html(responseText);
},
error: function(responseText){
}
});
I dont think above it answered posters question or mine as ajax is a server based push how is this relevant? as if its PHP driven the needs a refresh at server to refresh the contents not to provide new html. It is this refresh I am not interested in to re-copy PHP code elsewhere in JS as its already in my PHP. Does that make more sense?
Update
I did find a bracket missing and a set of single quotes inserted by editor. Which I have updated above but there was no significant change.
Cheers Nicolas . I am still hopeful that someone knows about Ajax as it sits underneath these technologies. I have a server side PHP file that I was hoping to use AJAX to pull just the PHP from the section it was pointing to an gUpdateDiv . As its derived from the server and created on the fly from SQL. I dont see how your answer would help push this data back in to the from the server . The $(gUpdateDiv).innerHTML was supposed to be acted upon not the whole page . What I am unsure of is how a trigger from this can update timer just this $(gUpdateDiv).innerHTML . I am also not aware if a server based refresh would do this or if the transport id provided from the file would be able to deliver just that . I think I am missing something a vital part that I dont have or have grasped yet. The reason there is two timers is effectively it checks the same file at a different point in time as its created by PHP it might be different from the first if it is i.e. the SQL data has changed, I want this to update this $(gUpdateDiv).innerHTML with the data which it compared it to the second 'Get' in the second request. It sounds, simple in practice but have got stuck comparing two versions and insuring second version gets used .
Further update placing an alert in the Javascript file did not pop up like it does here https://www.w3schools.com/jsref/tryit.asp?filename=tryjsref_alert however the same alert in the initiating PHP worked fine and created the alert. called the same function from the main PHP nd the alert occurred so the JavaScript is running next visit F12 on the page to see if there is any warnings or errors. Ok after adding JQuery which I thought I had added this started working however It is not doing what i Expected it to do. As the contained both text and graphics created by PHP I expected this all to be updated The graphics are not the text is any ideas? .
Further to the image problems I placed an extra line to update the image however I used this too in PHP
<script type="text/javascript">
//initpage() ;
function updateArtworkDisplay() {
document.querySelector('#np_track_artwork').src = 'images/nowplaying_artwork_2.png?' + new Date().getTime();
}
</Script>
But it didnt work to update the image in php?
<div id='outer_img'><img id='#np_track_artwork' src='/images/nowplaying_artwork_2.png' alt='Playing track artwork' width='200' height='200'></div>
in js change
/ looks for the response and determines if the div should be updated.
function checkResponse(transport)
{
var content = transport.response.Text;
if(gCurrentCheck != content) {
gCurrentCheck = content;
new Ajax.Request(gContentUrl, {method: 'get',onSuccess:function t() {
$(gUpdateDiv).innerHTML = t.responseText; /*t.response.json()*/}
});
updateArtworkDisplay(); // fire up the redraw in php file.
}
}
Nearly there it does almost what it needs to apart from the redraw which is not happening
// Start Clock refresh
// uses new new Ajax.PeriodicalUpdater(
// in main fetch file to trigger the auto update of the page.
// Written by Denise Rose
var gUpdateDiv="";
var gContentURL="";
var gcheckInterval=0;
var gcheckURL = "";
var gCurrentCheck ="";
_fetchUpdater('track_data','/fetch_sql.php','/fetch_sql.php',8000);
function _fetchUpdater(updateDiv,contentURL,checkURL,checkInterval)
{
gUpdateDiv = updateDiv;
gContentURL = contentURL;
gcheckInterval = checkInterval;
gCheckURL = checkURL;
setTimeout('check();',gcheckInterval);
}
//Called by _fetchUpdater every (n) seconds determins if content should be updated.
function check()
{
new Ajax.Request(gCheckURL,{method:'get', onSuccess:'CheckResponse()'});
setTimeout('check();',gcheckInterval);
}
// looks for the response and determines if the div should be updated.
function checkResponse(transport)
{
var content = transport.response.Text;
if(gCurrentCheck != content) {
gCurrentCheck = content;
new Ajax.Request(gContentUrl, {method: 'get',onSuccess:function t() {
$(gUpdateDiv).innerHTML = t.responseText; /*t.response.json()*/}
});
$time = new Date().getTime();
new Ajax.Request('outer_img', {method: 'get',onSuccess:function s() {
$('outer_img').innerHTML = "<img id='#np_track_artwork' src='/images/nowplaying_artwork_2.png?t='"+$time+" alt='Playing track artwork' width='200' height='200'>"}
});
}
}
GIVEN UP WITH THIS PLEASE DELETE MY PERSONAL INFORMATION AND POSTSript-fetch-async-await/
I am trying to display how many rows are there in the database. This should be dynamically updated, so when the number of rows change, the displayed number is also updated. I tried to print it with PHP but it is not dynamic.
Here is the index file:
<script>
$(document).ready(function() {
setInterval("ajaxcall()",2000);
});
function ajaxcall() {
$.ajax({
type: "GET",
url: "count.php"
success: function(response){
json_object = JSON.parse(response)
var count = json_object.count
// HOW TO DISPLAY COUNT SO IT IS DYNAMIC
}
});
}
</script>
And here is the count.php
$num_rows = mysql_num_rows($result);
echo json_encode($num_rows);
You need to either -
Periodically make ajax calls to check for updated value.(This is what you are currently doing.) -- Usually a bad idea if users are going to be connected for very long.
Or, a better solution would be to use HTML5 web sockets instead.
Projects like socket.io make it very easy to implement websockets on a javascript server(node). But PHP also has a few options. -
Ratchet - Similar to socket.io but built for PHP.
Elephant.io - Also a PHP implementation of websockets but it is a ws 'client' which is meant to work on the server. So, you'll probably have to deploy node and socket.io on the server as well and drive it using elephant.io to handle websocket communication with the other clients.
phpsocket.io - "A server side alternative implementation of socket.io in PHP based on Workerman." - according to its github page.
There isn't much documentation on phpsocket.io but the API looks simple enough from the examples in their readme. Something like this should work for you --
<?
use PHPSocketIO\SocketIO;
// listen port 2021 for socket.io client
$io = new SocketIO(2021);
$io->on('connection', function($socket)use($io){
$socket->on('get count', function($msg)use($io){
$num_rows = mysql_num_rows($result);
$io->emit($num_rows, $msg);
});
});
and on the client--
var count = 0;
// check if browser supports websockets
if ("WebSocket" in window) {
var ws = new WebSocket("ws://yourdomain.com:2021/");
ws.onopen = function() {
// Web Socket is connected, send data using send()
ws.send("get count");
};
ws.onmessage = function (evt) {
var received_msg = evt.data;
json_object = JSON.parse(response)
count = json_object.count
$("#database-results").text(count);
};
}
*Disclaimer -- I haven't tested the code above or used the phpsocket.io library before. So the code might not work. Also, Ratchet looks to be a more mature project so you should investigate it further if you want a more robust solution for your app.
I got a lot of the above info from this so thread. Some info there is however a few years out of date and the top rated answers there don't offer the best solutions for today.
You can update a DOM element with the count variable from the AJAX response.
Something like the following:
<span id="database-results">
</span>
Then in your AJAX success call, append the count variable to the HTML element:
success: function(response) {
json_object = JSON.parse(response)
var count = json_object.count
$("#database-results").text(count);
}
As an additional note, you would be spamming the server with AJAX requests every 2 seconds, depending on your user base this may be something to consider.
So I made a website that displays FPS information stored in a mysql database. For each second of gameplay I have a pair of number(fps)-image(screenshot).
I display the numbers in a line chart made with JavaScript. The behaviour desired is when I click on a bullet in the chart, the screenshot for that particular second is displayed in a div on the page.
I have to mention that the screenshots are stored in the database and they are very low in size. I display then using PHP like this:
$query = "SELECT `image` FROM `logs` WHERE `session_id`=".$_GET['session']." AND `second`=".$second;
$sth = $mysqli->query($query);
$result=mysqli_fetch_array($sth);
if (!empty($result))
echo ' <img id="screen" src="data:image/jpg;base64,'.base64_encode($result['image']).'"/>';
The method I'm using now is when I click on a bullet in the chart (action recorded in JS), I send it as a GET parameter and read it with PHP afterwards, like this:
window.location.href = url + "?second=" + second;
This method obviously will refresh my page. The problem is, the chart I made also has a zoom/scroll option and that resets whenever the page is refreshed, making the experience very bad for the user.
Is there any method to display the screenshots without refreshing the page, for this particular case (where I have to query the database for each click/picture)? Maybe there is a better way of approaching this problem?
Thanks.
I think you've got 2 solutions which are Ajax or Websocket depending your needs.
AJAX
Ajax permit to asynchronously, only when you need, call the server and get datas from an URL which could be a webservice or PHP page... Perhaps, it's the better solution in your case.
To make it easy, you can use JQuery library by donwloading the script and insert it in your HTML :
<script src="jquery-3.0.0.min.js"></script>
To call the server, using JQuery :
$.ajax({
url: url + "/yourphppage.php",
data: "parameter=" + yourOptionelParameter,
async: false,
success: function(data) {
refreshYourChart(data);
},
error: function() {
alert("Your error");
},
contentType: 'charset=utf-8'
});
Or if your prefer pure javascript.
Now, you just have to work on the presentation of your data, on the server side. It could be what you want HTML, TXT, JSON, XML...
Websocket
Websocket is like a permanent tunnel opened between your server and the client. Each side can ask or send datas in real time.
It seems to be a library server side :
http://socketo.me/
And client side, it's very easy :
Nice documentation on mozilla website
Hope it helps. Good luck.
To change a picture source, as I see the easiest way is using an ajax call, so you can send any kind of parameters to your server, and in return your will get your new picture source.
$.get('urlToYourServer.com?parameter=1', function(data){
$('#img').attr('src', data.imgSrc);
})
I have been working on an ajax code in which I need to update a SQL table. I am not sure if I could write SQL code inside ajax or not as I am completely new to AJAX. While I was trying, I was having issue i.e when I write code for SQL update inside the ajax code, it gives me an error saying "Uncaught Syntax Error: Missing catch or finally after try". Here is the code that I am working on:
$("#ktId").change(function(){
var cataid = $("#ktId option:selected").val();
var tktid = $(this).attr('tktid');
if (tktid != '') {
$.ajax({
async: false,
type : 'POST',
url : 'ajax/ticketload_test.asp',
data : { cataid: cataid, tktid: tktid },
success : function(responseData) {
try {
SQL = "UPDATE tbltkt SET ticketType = '& cataid &' WHERE id = '" & Request("tktid")& "'"
}
}
catch(e) {/*ignore*/}
}
});
} else {
alert("Please fill in the catagory!");
}
});
Background:
In classic ASP, I have to create and select the value from the drop-down list. So "#ktId" above mentioned is the id for the drop-down. After selecting an option from drop-down, I just need to update the table i.e tbltkt mentioned above. "ticketType" is the field or column for the options in the drop-down. So can anyone please mention or point out my mistake here. Can I use SQL update code in the ajax?
Please don't do that. Read about SQL injection here: SQL INJECTION
All your SQL code must be present ONLY in the server side or as a Stored Procedure. Just send your variables to the server and make the query in the server side. Please read about SQL Injection in order to avoid hacking.
It's not really safe. Maybe you should reconsider your architecture? However, your syntax error is because of extra brace after SQL. But still, any your SQL procedures won't work if you write it in callback
The main point here is that who should actually access the database is your application server (IIS if you're using ASP in the backend), which is in turn listening to your AJAX requests. So, the code that access your database may be in the server side, and not mixed with the javascript functions, what could lead to SQL injection attacks as described in another answer above.
So you should have to code some server handler to listen to your AJAX call on wich you put the parameters that this handler will use to construct the SQL query, launch it against the database server, and return a view (or JSON data) with the results.
Sorry but I cannot be more specfic if you don't give more details about the architecture of your application and the technologies you're using.
I have come across a situation that doesn't make much sense to me. Just as some background information, I'm using the Laravel framework. The page in question calls a query when the page is requested using Laravel's '->with('var', $array)' syntax. This query (which I will post later) works perfectly fine on page load, and successfully inserts dummy data I fed it.
I call this same query via an Ajax $.post using jQuery, on click of a button. However, when I do this $.post and call this query, I get an Internal Server Error every time. Everything is exactly the same, information passed included; the only difference seems to be whether or not it is called on page load or via the $.post.
Here is the error:
Below is the code that performs the query on page load:
routes.php sends the HTTP get request to a file called AppController.php
routes.php
AppController.php
The page is then made with the following array acquired from DeviceCheckoutController.php
Which then goes to DeviceCheckout.php
I am able to echo $test on the page, and it returns the ID of a new row every time the page is reloaded (which obviously mean the 'insertGetId' query worked). However, I hooked this query up to the page load just to test. What I really want to happen is on click of a button. Here is the code for that:
$("#checkoutFormbox").on('click', '#checkoutButton', function() {
var checkoutInformation = Object();
var accessories = [];
var counter = 0;
var deviceName = checkoutDeviceTable.cell(0, 0).data();
$(".accessoryCheckbox").each(function() {
//add accessory ID's to this list of only accessories selected to be checked out
if($(this).val() == "1")
{
accessories[counter] = $(this).data('id') + " ";
}
counter++;
});
checkoutInformation['deviceID'] = $(".removeButton").val(); //deviceID was previously stored in the remove button's value when the add button was clicked
checkoutInformation['outBy'] = '';
checkoutInformation['outNotes'] = $("#checkOutDeviceNotes").val();
checkoutInformation['idOfAccessories'] = 2;
checkoutInformation['dueDate'] = $("#dueDate").val();
if($("#studentIdButton").hasClass('active'))
{
checkoutInformation['renterID'] = 0;
checkoutInformation['emplid'] = 1778884;
console.log(checkoutInformation);
$.post("http://xxx.xxx.xxx.xxx/testing/public/apps/devicecheckout-checkoutdevices", {type: "checkoutDeviceForStudent", checkoutInformation: checkoutInformation}, function(returnedData) {
alert(returnedData);
});
}
});
Which is also then routed to AppController.php, specifically to the 'checkoutDeviceForStudent' part of the switch statement:
And then back to that query that is shown previously in DeviceCheckout.php
Finally, here is my DB structure for reference:
Any explanation as for why this would be happening? Also, any Laravel or other general best practice tips would be greatly appreciated as I'm inexperienced in usage of this framework and programming overall.
Sorry for such a long post, I hope there is enough information to diagnose this problem. Let me know if I need to include anything else.
Edit: Included picture of error at the top of the page.
Everything is exactly the same, information passed included
No, it isn't. If it was exactly the same you wouldn't be getting the error you're getting.
These sorts of issues are too difficult to solve by taking guesses at what the problem might be. You need to
Setup your system so Laravel's logging errors to the laravel.log file
Setup you PHP system so errors Laravel can't handled are logged to your webserver's error log (and/or PHP's error log)
Put Laravel in debug mode so errors are output the the screen, and the view the output of your ajax request via Firebug or Chrome
Once you have the actual PHP error it's usually pretty easy to see what's different about the request you think is the same, and address the issue.
I found a resolution to my problem after some advice from a friend; much easier than I anticipated and much easier than any solution that has been offered to me here or other places.
Essentially, what I needed to do was place a try, catch clause in my model function, and then if an exception is encountered I store that in a variable, return it, and use console.log() to view the exception. Here is an example to emulate my point:
public function getUserFullname($userID)
{
try
{
$myResult = DB::connection('myDatabase')->table('TheCoolestTable')->select('fullName')->where('userID', '=', $userID)->get();
return $myResult;
}
catch(Exception $e)
{
$errorMessage = 'Caught exception: ' . $e->getMessage();
return $errorMessage;
}
}
And then on the View (or wherever your model function returns to), simply console.log() the output of your POST. This will display the results of the successful query, or the results of the Exception if it encountered one as opposed to an unhelpful Internal Server Error 500 message.