Question

I want to create a servlet method like below. In this method I want to perform some data download.So if request for data download comes I just do the download. If already a download is going on I want somehow the second request to wait till the first thread is done with download. Once the first thread is done with download the second thread can start automatically.

DoTheDownloadAction(){

}

How can i achieve the above requirement?

Answer 1

Considering you have a DownloadHelper class and in your Servlet you have created one instance of that class then you can do something like this :

DoTheDownloadAction() {
   synchronized(downloadHelper) {
      //Downloading something
   }
}

Lets imagine you have a button called as “download” with id=”download” in your jsp and you have this code in your javascript

var globalDownloadStatus = false;
jQuery(document).ready(function(){
   jQuery('#download'(.click(function(){
       if(globalDownloadStatus == true) {
           alert('download already in progress, please wait');
           return;
       }
       jQuery.get('yourservletpath', function(data){
          alert('Download Complete');
       });
   });
});