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How to prevent ajax from confirming on success content already inside a div

How to prevent ajax from confirming on success content already in in this case in $('.Mydiv').Append(data);
$(document).ready(function (ajaxCall) {
var offset = 0;
var limit = offset + 4;
var cats_in_home = '<?php echo $myCat ?>';
var request_in_progress = false;
$.ajax({
type: 'GET',
url: 'getActivity.php',
data: {
'offset': offset,
'limit': limit,
'cats_in_home': cats_in_home
},
success: function (data) {
$('.get_communication_with_div_class').html(data);
}
});
$('.MySeconddiv').onclick(function () {
if (request_in_progress) {
return;
}
request_in_progress = true;
$.ajax({
type: 'GET',
url: 'getActivity.php',
data: {
'offset': offset += 6,
'limit': limit,
'cats_in_home': cats_in_home
},
success: function (data) {
$('.Mydiv').append(data);
request_in_progress = false;
}
});
});
});
the problem is when i click the MySeconddiv tag its accept duplicates,
plese help
i cant find way to find a solution
i cant find way to find a solution

How to run javascript function periodically when the Apache tomcat server is starts instead of java class using ScheduledExecutorService?

I need to run my javascript function periodically on server starts. i dont know how to write the equivalent Java code as my javaScript function contains multiple ajax call and mathematical equations.
below is my javascript code which i need to run periodically on server start.
<script type="text/javascript">
$(document).ready(function(){
var polyLat = new Array();
polyLat[0] = 10.194027;
polyLat[1] = 10.226975;
polyLat[2] = 10.059987;
polyLat[3] = 10.002248;
polyLat[4] = 9.854925;
polyLat[5] = 9.835443;
polyLat[6] = 9.899107;
polyLat[7] = 9.993088;
polyLat[8] = 10.081425;
polyLat[9] = 9.992266;
polyLat[10] = 10.194027;//First point repeated to close polygon
var polySides = (polyLat.length)-1;//number of points in polygon
//vertical Longitude coordinates of polygon
var polyLng = new Array();
polyLng[0] = 76.201205;
polyLng[1] = 76.375022;
polyLng[2] = 76.775730;
polyLng[3] = 76.778940;
polyLng[4] = 76.584336;
polyLng[5] = 76.411473;
polyLng[6] = 76.368070;
polyLng[7] = 76.397007;
polyLng[8] = 76.317492;
polyLng[9] = 76.267905;
polyLng[10] = 76.201205;//First point repeated to close polygon
//Coordinates for bounding box
var maxLat = Math.max.apply(null,polyLat);
var minLat = Math.min.apply(null,polyLat);
var maxLng = Math.max.apply(null,polyLng);
var minLng = Math.min.apply(null,polyLng);
$.post('outboundupd.jsp',
{
mx_lat:maxLat,
mn_lat:minLat,
mx_lng:maxLng,
mn_lng:minLng,
ply_sds:polySides
},
function(response,status,xhr)
{
// alert(response.trim());
plotdata(response);
});
function plotdata(response)
{
var x;
var y;
var mob;
var jsonArray=JSON.parse(response.trim());
var jalen= jsonArray.length;
for(i=0;i<jalen;i++)
{
var obj=jsonArray[i];
pcode= obj.Pcode;
nplate= obj.N_plate;
driver= obj.Driver;
mob= obj.MobileNu;
x= obj.Latitude;
y= obj.Longitude;
time= obj.Time;
}
var j = polySides-1 ;
oddNodes = 0;
for (i=0; i<polySides; i++) {
if (polyLng[i]<y && polyLng[j]>=y || polyLng[j]<y && polyLng[i]>=y) {
if (polyLat[i]+(y-polyLng[i])/(polyLng[j]-polyLng[i])*(polyLat[j]-polyLat[i])<x) {
oddNodes=!oddNodes;
}
}
j=i; }
if(oddNodes!=true)
{
// alert("ob mobile:"+mob);
$.post('obsouth.jsp',
{
pcd:pcode,
npt:nplate,
drv:driver,
mobl:mob,
lat:x,
lon:y,
tm:time
},
function(response,status,xhr)
{
alert(response.trim());
});
}
return oddNodes;
}
});
</script>
My question:-
Is there any technique to call a javascript function from a java class extended with runnables or directly implement the exact javascript in java class?
If answer for 1 is no, can you please guide me to convert my entire javascript to Java code?
Any piece of code is highly appreciated and thanks in advance.

Use node.js and execute your script using Runtime.exec(). you would run node on this or you can go for Rhino scripting engine to envoke methods in .js file from within a java class. Hope that helped.

Button on website for taking screenshot [duplicate]

Google's "Report a Bug" or "Feedback Tool" lets you select an area of your browser window to create a screenshot that is submitted with your feedback about a bug.
Screenshot by Jason Small, posted in a duplicate question.
How are they doing this? Google's JavaScript feedback API is loaded from here and their overview of the feedback module will demonstrate the screenshot capability.

JavaScript can read the DOM and render a fairly accurate representation of that using canvas. I have been working on a script which converts HTML into a canvas image. Decided today to make an implementation of it into sending feedbacks like you described.
The script allows you to create feedback forms which include a screenshot, created on the client's browser, along with the form. The screenshot is based on the DOM and as such may not be 100% accurate to the real representation as it does not make an actual screenshot, but builds the screenshot based on the information available on the page.
It does not require any rendering from the server, as the whole image is created on the client's browser. The HTML2Canvas script itself is still in a very experimental state, as it does not parse nearly as much of the CSS3 attributes I would want it to, nor does it have any support to load CORS images even if a proxy was available.
Still quite limited browser compatibility (not because more couldn't be supported, just haven't had time to make it more cross browser supported).
For more information, have a look at the examples here:
http://hertzen.com/experiments/jsfeedback/
edit
The html2canvas script is now available separately here and some examples here.
edit 2
Another confirmation that Google uses a very similar method (in fact, based on the documentation, the only major difference is their async method of traversing/drawing) can be found in this presentation by Elliott Sprehn from the Google Feedback team:
http://www.elliottsprehn.com/preso/fluentconf/

Your web app can now take a 'native' screenshot of the client's entire desktop using getUserMedia():
Have a look at this example:
https://www.webrtc-experiment.com/Pluginfree-Screen-Sharing/
The client will have to be using chrome (for now) and will need to enable screen capture support under chrome://flags.

PoC
As Niklas mentioned you can use the html2canvas library to take a screenshot using JS in the browser. I will extend his answer in this point by providing an example of taking a screenshot using this library ("Proof of Concept"):
function report() {
let region = document.querySelector("body"); // whole screen
html2canvas(region, {
onrendered: function(canvas) {
let pngUrl = canvas.toDataURL(); // png in dataURL format
let img = document.querySelector(".screen");
img.src = pngUrl;
// here you can allow user to set bug-region
// and send it with 'pngUrl' to server
},
});
}
.container {
margin-top: 10px;
border: solid 1px black;
}
<script src="https://cdnjs.cloudflare.com/ajax/libs/html2canvas/0.4.1/html2canvas.min.js"></script>
<div>Screenshot tester</div>
<button onclick="report()">Take screenshot</button>
<div class="container">
<img width="75%" class="screen">
</div>
In report() function in onrendered after getting image as data URI you can show it to the user and allow him to draw "bug region" by mouse and then send a screenshot and region coordinates to the server.
In this example async/await version was made: with nice makeScreenshot() function.
UPDATE
Simple example which allows you to take screenshot, select region, describe bug and send POST request (here jsfiddle) (the main function is report()).
async function report() {
let screenshot = await makeScreenshot(); // png dataUrl
let img = q(".screen");
img.src = screenshot;
let c = q(".bug-container");
c.classList.remove('hide')
let box = await getBox();
c.classList.add('hide');
send(screenshot,box); // sed post request with bug image, region and description
alert('To see POST requset with image go to: chrome console > network tab');
}
// ----- Helper functions
let q = s => document.querySelector(s); // query selector helper
window.report = report; // bind report be visible in fiddle html
async function makeScreenshot(selector="body")
{
return new Promise((resolve, reject) => {
let node = document.querySelector(selector);
html2canvas(node, { onrendered: (canvas) => {
let pngUrl = canvas.toDataURL();
resolve(pngUrl);
}});
});
}
async function getBox(box) {
return new Promise((resolve, reject) => {
let b = q(".bug");
let r = q(".region");
let scr = q(".screen");
let send = q(".send");
let start=0;
let sx,sy,ex,ey=-1;
r.style.width=0;
r.style.height=0;
let drawBox= () => {
r.style.left = (ex > 0 ? sx : sx+ex ) +'px';
r.style.top = (ey > 0 ? sy : sy+ey) +'px';
r.style.width = Math.abs(ex) +'px';
r.style.height = Math.abs(ey) +'px';
}
//console.log({b,r, scr});
b.addEventListener("click", e=>{
if(start==0) {
sx=e.pageX;
sy=e.pageY;
ex=0;
ey=0;
drawBox();
}
start=(start+1)%3;
});
b.addEventListener("mousemove", e=>{
//console.log(e)
if(start==1) {
ex=e.pageX-sx;
ey=e.pageY-sy
drawBox();
}
});
send.addEventListener("click", e=>{
start=0;
let a=100/75 //zoom out img 75%
resolve({
x:Math.floor(((ex > 0 ? sx : sx+ex )-scr.offsetLeft)*a),
y:Math.floor(((ey > 0 ? sy : sy+ey )-b.offsetTop)*a),
width:Math.floor(Math.abs(ex)*a),
height:Math.floor(Math.abs(ex)*a),
desc: q('.bug-desc').value
});
});
});
}
function send(image,box) {
let formData = new FormData();
let req = new XMLHttpRequest();
formData.append("box", JSON.stringify(box));
formData.append("screenshot", image);
req.open("POST", '/upload/screenshot');
req.send(formData);
}
.bug-container { background: rgb(255,0,0,0.1); margin-top:20px; text-align: center; }
.send { border-radius:5px; padding:10px; background: green; cursor: pointer; }
.region { position: absolute; background: rgba(255,0,0,0.4); }
.example { height: 100px; background: yellow; }
.bug { margin-top: 10px; cursor: crosshair; }
.hide { display: none; }
.screen { pointer-events: none }
<script src="https://cdnjs.cloudflare.com/ajax/libs/html2canvas/0.4.1/html2canvas.min.js"></script>
<body>
<div>Screenshot tester</div>
<button onclick="report()">Report bug</button>
<div class="example">Lorem ipsum</div>
<div class="bug-container hide">
<div>Select bug region: click once - move mouse - click again</div>
<div class="bug">
<img width="75%" class="screen" >
<div class="region"></div>
</div>
<div>
<textarea class="bug-desc">Describe bug here...</textarea>
</div>
<div class="send">SEND BUG</div>
</div>
</body>

Get screenshot as Canvas or Jpeg Blob / ArrayBuffer using getDisplayMedia API:
FIX 1: Use the getUserMedia with chromeMediaSource only for Electron.js
FIX 2: Throw error instead return null object
FIX 3: Fix demo to prevent the error: getDisplayMedia must be called from a user gesture handler
// docs: https://developer.mozilla.org/en-US/docs/Web/API/MediaDevices/getDisplayMedia
// see: https://www.webrtc-experiment.com/Pluginfree-Screen-Sharing/#20893521368186473
// see: https://github.com/muaz-khan/WebRTC-Experiment/blob/master/Pluginfree-Screen-Sharing/conference.js
function getDisplayMedia(options) {
if (navigator.mediaDevices && navigator.mediaDevices.getDisplayMedia) {
return navigator.mediaDevices.getDisplayMedia(options)
}
if (navigator.getDisplayMedia) {
return navigator.getDisplayMedia(options)
}
if (navigator.webkitGetDisplayMedia) {
return navigator.webkitGetDisplayMedia(options)
}
if (navigator.mozGetDisplayMedia) {
return navigator.mozGetDisplayMedia(options)
}
throw new Error('getDisplayMedia is not defined')
}
function getUserMedia(options) {
if (navigator.mediaDevices && navigator.mediaDevices.getUserMedia) {
return navigator.mediaDevices.getUserMedia(options)
}
if (navigator.getUserMedia) {
return navigator.getUserMedia(options)
}
if (navigator.webkitGetUserMedia) {
return navigator.webkitGetUserMedia(options)
}
if (navigator.mozGetUserMedia) {
return navigator.mozGetUserMedia(options)
}
throw new Error('getUserMedia is not defined')
}
async function takeScreenshotStream() {
// see: https://developer.mozilla.org/en-US/docs/Web/API/Window/screen
const width = screen.width * (window.devicePixelRatio || 1)
const height = screen.height * (window.devicePixelRatio || 1)
const errors = []
let stream
try {
stream = await getDisplayMedia({
audio: false,
// see: https://developer.mozilla.org/en-US/docs/Web/API/MediaStreamConstraints/video
video: {
width,
height,
frameRate: 1,
},
})
} catch (ex) {
errors.push(ex)
}
// for electron js
if (navigator.userAgent.indexOf('Electron') >= 0) {
try {
stream = await getUserMedia({
audio: false,
video: {
mandatory: {
chromeMediaSource: 'desktop',
// chromeMediaSourceId: source.id,
minWidth : width,
maxWidth : width,
minHeight : height,
maxHeight : height,
},
},
})
} catch (ex) {
errors.push(ex)
}
}
if (errors.length) {
console.debug(...errors)
if (!stream) {
throw errors[errors.length - 1]
}
}
return stream
}
async function takeScreenshotCanvas() {
const stream = await takeScreenshotStream()
// from: https://stackoverflow.com/a/57665309/5221762
const video = document.createElement('video')
const result = await new Promise((resolve, reject) => {
video.onloadedmetadata = () => {
video.play()
video.pause()
// from: https://github.com/kasprownik/electron-screencapture/blob/master/index.js
const canvas = document.createElement('canvas')
canvas.width = video.videoWidth
canvas.height = video.videoHeight
const context = canvas.getContext('2d')
// see: https://developer.mozilla.org/en-US/docs/Web/API/HTMLVideoElement
context.drawImage(video, 0, 0, video.videoWidth, video.videoHeight)
resolve(canvas)
}
video.srcObject = stream
})
stream.getTracks().forEach(function (track) {
track.stop()
})
if (result == null) {
throw new Error('Cannot take canvas screenshot')
}
return result
}
// from: https://stackoverflow.com/a/46182044/5221762
function getJpegBlob(canvas) {
return new Promise((resolve, reject) => {
// docs: https://developer.mozilla.org/en-US/docs/Web/API/HTMLCanvasElement/toBlob
canvas.toBlob(blob => resolve(blob), 'image/jpeg', 0.95)
})
}
async function getJpegBytes(canvas) {
const blob = await getJpegBlob(canvas)
return new Promise((resolve, reject) => {
const fileReader = new FileReader()
fileReader.addEventListener('loadend', function () {
if (this.error) {
reject(this.error)
return
}
resolve(this.result)
})
fileReader.readAsArrayBuffer(blob)
})
}
async function takeScreenshotJpegBlob() {
const canvas = await takeScreenshotCanvas()
return getJpegBlob(canvas)
}
async function takeScreenshotJpegBytes() {
const canvas = await takeScreenshotCanvas()
return getJpegBytes(canvas)
}
function blobToCanvas(blob, maxWidth, maxHeight) {
return new Promise((resolve, reject) => {
const img = new Image()
img.onload = function () {
const canvas = document.createElement('canvas')
const scale = Math.min(
1,
maxWidth ? maxWidth / img.width : 1,
maxHeight ? maxHeight / img.height : 1,
)
canvas.width = img.width * scale
canvas.height = img.height * scale
const ctx = canvas.getContext('2d')
ctx.drawImage(img, 0, 0, img.width, img.height, 0, 0, canvas.width, canvas.height)
resolve(canvas)
}
img.onerror = () => {
reject(new Error('Error load blob to Image'))
}
img.src = URL.createObjectURL(blob)
})
}
DEMO:
document.body.onclick = async () => {
// take the screenshot
var screenshotJpegBlob = await takeScreenshotJpegBlob()
// show preview with max size 300 x 300 px
var previewCanvas = await blobToCanvas(screenshotJpegBlob, 300, 300)
previewCanvas.style.position = 'fixed'
document.body.appendChild(previewCanvas)
// send it to the server
var formdata = new FormData()
formdata.append("screenshot", screenshotJpegBlob)
await fetch('https://your-web-site.com/', {
method: 'POST',
body: formdata,
'Content-Type' : "multipart/form-data",
})
}
// and click on the page

Here is a complete screenshot example that works with chrome in 2021. The end result is a blob ready to be transmitted. Flow is: request media > grab frame > draw to canvas > transfer to blob. If you want to do it more memory efficient explore OffscreenCanvas or possibly ImageBitmapRenderingContext
https://jsfiddle.net/v24hyd3q/1/
// Request media
navigator.mediaDevices.getDisplayMedia().then(stream =>
{
// Grab frame from stream
let track = stream.getVideoTracks()[0];
let capture = new ImageCapture(track);
capture.grabFrame().then(bitmap =>
{
// Stop sharing
track.stop();
// Draw the bitmap to canvas
canvas.width = bitmap.width;
canvas.height = bitmap.height;
canvas.getContext('2d').drawImage(bitmap, 0, 0);
// Grab blob from canvas
canvas.toBlob(blob => {
// Do things with blob here
console.log('output blob:', blob);
});
});
})
.catch(e => console.log(e));

Heres an example using: getDisplayMedia
document.body.innerHTML = '<video style="width: 100%; height: 100%; border: 1px black solid;"/>';
navigator.mediaDevices.getDisplayMedia()
.then( mediaStream => {
const video = document.querySelector('video');
video.srcObject = mediaStream;
video.onloadedmetadata = e => {
video.play();
video.pause();
};
})
.catch( err => console.log(`${err.name}: ${err.message}`));
Also worth checking out is the Screen Capture API docs.

You can try my new JS library: screenshot.js.
It's enable to take real screenshot.
You load the script:
<script src="https://raw.githubusercontent.com/amiad/screenshot.js/master/screenshot.js"></script>
and take screenshot:
new Screenshot({success: img => {
// callback function
myimage = img;
}});
You can read more options in project page.

Change default Service Unavailable message when REST api call fails

When user tries to do api call but if our server is down (due to many reasons) then my website UI gives following error:
Service Unavailable
The server is temporarily unable to service your request due to
maintenance downtime or capacity problems. Please try again later.
Additionally, a 406 Not Acceptable error was encountered while trying
to use an ErrorDocument to handle the request.
Apache/2.4.7 (Win32) OpenSSL/1.0.1e PHP/5.5.6 Server at localhost Port 80
I don't want this message to be this much detailed. I want to customize this message. How can I do this? Better if you suggest something change on my ajax request (from where I do api calls)
Here is the javascript from where I do all my api request (if it helps)
function request(url, request_type, datatype, callback, postdata){
if(typeof(postdata) == "object"){
postdata = JSON.stringify(postdata);
} else if(typeof(postdata) == "string") {
SY.setContentType("text/plain");
}
$.ajax({
beforeSend: function(xhr){
for(var key in requestHeaders){
if(key == ANOTHER_CONTENT_TYPE)
continue;
xhr.setRequestHeader(key, requestHeaders[key]);
}
var client_id = readCookie(CLIENT_ID);
var client_token = readCookie(CLIENT_TOKEN);
if(client_id != null && client_token != null){
xhr.setRequestHeader(CLIENT_ID, client_id);
xhr.setRequestHeader(CLIENT_TOKEN, client_token);
}
//if there is another content type defined then modify the xhr content-type header
var newContentType = requestHeaders[ANOTHER_CONTENT_TYPE];
if(newContentType != undefined) {
SyUtils.log("Changing request content type to ="+newContentType);
xhr.setRequestHeader("Content-Type", newContentType);
delete requestHeaders[ANOTHER_CONTENT_TYPE];
}
var loadingDivId = callback.loadingDivId;
if(loadingDivId){
$("#"+loadingDivId).addClass("loader-small");
}else{
$("body").append("<div id=\"loader\"></div>");
}
},
url: url,
data: postdata,
dataType: datatype,
type: request_type,
success: function(data) {
var loadingDivId = callback.loadingDivId;
if(loadingDivId){
$("#"+loadingDivId).removeClass("loader-small");
}else{
$("#loader").remove();
}
// Write back cookie again so that expiry time refreshes
var client_id = readCookie(CLIENT_ID);
var client_token = readCookie(CLIENT_TOKEN);
if(client_id != null && client_token != null){
saveCredentials(client_id, client_token);
}
callback("success", data);
},
error: function(xhr, status, error) {
var loadingDivId = callback.loadingDivId;
if(loadingDivId){
$("#"+loadingDivId).removeClass("loader-small");
}else{
$("#loader").remove();
}
try{
var errorMessageObj = JSON.parse(xhr.responseText);
}catch(err){
errorMessageObj = {type:"ERROR", message:xhr.responseText};
}
var st = xhr.status;
var currentPage = window.location.pathname; // to avoid infinite redirect loop
if (st == 401 && currentPage != "/login"){
SY.removeCurrentUser();
deleteCookie(CLIENT_ID);
deleteCookie(CLIENT_TOKEN);
window.location.replace("/login?toPage="+currentPage);
}else if(st == 403 && currentPage != "/unauthorized"){
window.location.replace("/unauthorized");
}else if(st == 500 && currentPage != "/error"){
window.location.href = "/error";
}else if(st == 404 && currentPage != "/404"){
window.location.href = "/404";
}else{
callback(error, errorMessageObj);
}
}
});
};

Get remote data sorted with grand total in jQuery using Java

I am using jQuery for UI and my programming language is Java. Now I want to get remote data using an Ajax call to Java servlet and get the records from remote site in sorted order with also grand total. How can I do that?
I found many examples, but that was in PHP only. I want to implement it in Java, and I am not able to understand PHP.
Example which I found is as below.
JavaScript code
jQuery("#48remote2").jqGrid({
url:'server.php?q=2',
datatype: "json",
colNames:['Inv No','Date', 'Client', 'Amount','Tax','Total','Notes'],
colModel:[
{name:'id',index:'id', width:55, editable:true, sorttype:'int',summaryType:'count', summaryTpl : '({0}) total'},
{name:'invdate',index:'invdate', width:90, sorttype:'date', formatter:'date', datefmt:'d/m/Y'},
{name:'name',index:'name', width:100},
{name:'amount',index:'amount', width:80, align:"right", sorttype:'number',formatter:'number',summaryType:'sum'},
{name:'tax',index:'tax', width:80, align:"right",sorttype:'number',formatter:'number',summaryType:'sum'},
{name:'total',index:'total', width:80,align:"right",sorttype:'number',formatter:'number', summaryType:'sum'},
{name:'note',index:'note', width:150, sortable:false,editable:true}
],
rowNum:10,
rowList:[10,20,30],
height: 'auto',
pager: '#p48remote2',
sortname: 'invdate',
viewrecords: true,
sortorder: "desc",
caption:"Grouping with remote data",
grouping: true,
groupingView : {
groupField : ['name'],
groupColumnShow : [true],
groupText : ['<b>{0}</b>'],
groupCollapse : false,
groupOrder: ['asc'],
groupSummary : [true],
groupDataSorted : true
},
footerrow: true,
userDataOnFooter: true
});
jQuery("#48remote2").jqGrid('navGrid','#p48remote',{add:false,edit:false,del:false});
And PHP code is as below,
PHP MySQL code
examp = $_REQUEST["q"]; //Query number
$page = $_REQUEST['page']; // Get the requested page
$limit = $_REQUEST['rows']; // Get how many rows we want to have into the grid
$sidx = $_REQUEST['sidx']; // Get index row - i.e. user click to sort
$sord = $_REQUEST['sord']; // Get the direction
if(!$sidx) $sidx =1;
...
$result = mysql_query("SELECT COUNT(*) AS count FROM invheader a, clients b WHERE a.client_id=b.client_id".$wh);
$row = mysql_fetch_array($result,MYSQL_ASSOC);
$count = $row['count'];
if( $count >0 ) {
$total_pages = ceil($count/$limit);
}
else {
$total_pages = 0;
}
if ($page > $total_pages)
$page=$total_pages;
$start = $limit*$page - $limit; // Do not put $limit*($page - 1)
if ($start<0)
$start = 0;
$SQL = "SELECT a.id, a.invdate, b.name, a.amount,a.tax,a.total,a.note FROM invheader a, clients b WHERE a.client_id=b.client_id".$wh." ORDER BY ".$sidx." ".$sord. " LIMIT ".$start." , ".$limit;
$result = mysql_query( $SQL ) or die("Could not execute query.".mysql_error());
$responce->page = $page;
$responce->total = $total_pages;
$responce->records = $count;
$i=0; $amttot=0; $taxtot=0; $total=0;
while($row = mysql_fetch_array($result,MYSQL_ASSOC)) {
$amttot += $row[amount];
$taxtot += $row[tax];
$total += $row[total];
$responce->rows[$i]['id']=$row[id];
$responce->rows[$i]['cell']=array($row[id],$row[invdate],$row[name],$row[amount],$row[tax],$row[total],$row[note]);
$i++;
}
$responce->userdata['amount'] = $amttot;
$responce->userdata['tax'] = $taxtot;
$responce->userdata['total'] = $total;
$responce->userdata['name'] = 'Totals:';
echo json_encode($responce);
But I am not able to understand the code in PHP. How can I do that?

If I understand you correct you need include summary line in the bottom of the grid. To do this you don't need the grouping part from the posted example. The only parameters which are important in your case are:
footerrow: true,
userDataOnFooter: true
If you use both from the jqGrid options you need just calculate the sum for the columns where you need it has and include "userdata" part in the JSON which produce the servlet. See here, here and here for more information.