Question

if after rendering page i change src of an img tag from javascript like:

function changeImage(){
  img.src = 'getImage?imgId=232132'; //getImage is calling doGet() Method of Servlet   with  response content type "image/jpeg"
}

is this make asynchronous call and load image or not?

Answer 1

Yes, the call is asynchronous, except if it’s not really a distant call because the image is in cache (in this case, the image will be loaded before the next line of the script is executed).

If you want to be notified when it’s finished, do this :

img.onload = function(){alert('loaded!')};
img.src = 'getImage?imgId=232132';