Call a servlet using post request with large amount of data and open url in new tab [duplicate] - gwt

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Is it possible to download a file from server to my device having MGWT&GwtPhoneGap app?
(2 answers)
Closed 8 years ago.
I am using gwt canvas .
I am having 74kb string(image) data which I want to pass it to servlet. So that servlet process that data and throw the contents to the browser . In this way it will prompt user to download it.
From client side I am using RequestBuilder to call a servlet ,set request data to it ,data is large so I am using post request. It is hitting servlet also throwing contents on the browser but not showing anything downloading.
The current url having canvas .I thinks that's why it is not downloading anything this conclusion is because If am opening that servlet directly using http://localhost:8080/servlet then its downloading it property (In this case i am not proving any content from client side) but for the url having canvas its giving problem.
So is there any way where i can open a url in new tab and can call servlet using post request in gwt.

Answer 1

You can use a Form Panel for do the upload, the Form Panel will use a hidden iframe,
FormPanel form = new FormPanel();
form.setMethod(FormPanel.METHOD_POST);
form.setAction("/downloadServlet");
FlowPanel hiddenPanel = new FlowPanel();
hiddenPanel.add(new Hidden("name1", "value"));
hiddenPanel.add(new Hidden("name2", "value"));
form.setWidget(hiddenPanel);
RootPanel.get().add(form);
form.submit();
The content return by the servlet if you put the correct header will be downloaded by the user navigator.
public class ServletDownloadDemo extends HttpServlet{
private static final int BYTES_DOWNLOAD = 1024;
#Override
public void doPost(HttpServletRequest request,
HttpServletResponse response) throws IOException{
//Get Parameters
String name1 = request.getParameter("name1");
String name2 = request.getParameter("name2");
response.setContentType("text/plain");
response.setHeader("Content-Disposition",
"attachment;filename=downloadname.txt");
ServletContext ctx = getServletContext();
InputStream is = ctx.getResourceAsStream("/testing.txt");
int read=0;
byte[] bytes = new byte[BYTES_DOWNLOAD];
OutputStream os = response.getOutputStream();
while((read = is.read(bytes))!= -1){
os.write(bytes, 0, read);
}
os.flush();
os.close();
}
}