Thanks Carl! Your method worked fine. It's almost fully implemented,
but the only question I have that remains is the proper way to
generate tokens. I haven't ever had to generate them before - is
there an automatic way of generating unique tokens, or is generateToken
() a function I would write myself and have to ensure that each token
generated was unique?
For now, I just hard coded a random string into the code, which worked
well enough to see that the PDF did indeed open in a new window and
display as expected.
I will also need to figure out the session settings so that they are
invalidated properly, although I think I will need to do a bit more
reading on this.
// RPC code in the class which extends RemoteServiceServlet
public String generatePDF(ReportDO report, int id) {
// initialize new document for PDF
Document document = new Document();
// generate one time token that the client can use to retrieve
the
PDF
String token = "258958395ai53";
// generate test PDF
try {
ByteArrayOutputStream baos = new ByteArrayOutputStream();
PdfWriter.getInstance(document, baos);
document.open();
document.add(new Paragraph("Hello World!"));
document.close();
byte[] pdf = baos.toByteArray();
HttpServletRequest request = this.getThreadLocalRequest();
HttpSession session = request.getSession();
session.setAttribute(token, pdf);
}
catch (Exception e) {
System.out.println("ReportServlet::generatePDF::Exception " +
e.getMessage());
}
return token;
}
// standard servlet
public class PDFServlet extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse
response) throws IOException, ServletException {
// create output stream from byte array in session
ByteArrayOutputStream baos = new ByteArrayOutputStream();
String token = request.getParameter("token");
byte[] pdf = (byte[]) request.getSession().getAttribute(token);
baos.write(pdf);
// setting some response headers
response.setHeader("Expires", "0");
response.setHeader("Cache-Control", "must-revalidate,
post-check=0,
pre-check=0");
response.setHeader("Pragma", "public");
response.setContentType("application/pdf");
// content length is needed for MSIE
response.setContentLength(baos.size());
// write ByteArrayOutputStream to ServletOutputStream
ServletOutputStream out = response.getOutputStream();
baos.writeTo(out);
out.flush();
}
}
// client side code section
ReportController.getInstance().generatePDF(report, id, new
AsyncCallback() {
public void onFailure(Throwable caught)
{
SC.say("Failed");
}
public void onSuccess(Object result) {
String token = (String) result;
Window.open("PDFService?token="
+ token, "_blank",
"menubar=yes,location=yes,resizable=yes,scrollbars=yes,status=yes");
}
});
}
});
On Apr 7, 1:04 am, Carl Pritchett <[email protected]> wrote:
> The simplest safest way I can think of is basically the same as other
> people have already stated in this thread.
> Using a token and storing data in the session means that the pdf data
> is unique to the user (as long as the session is invalidated
> properly).
>
> - Send an RPC call to generate the pdf (or at least send the
> information used to generate the pdf)
> - The RPC service saves the pdf (or request data) in the session:
>
> // use the data to create the PDF usingiTextetc
> byte[] pdf = generatePDF(requestData);
>
> // generate a one-time token that the client can use to
> retrieve the PDF
> String token = generateToken();
>
> HttpServletRequest req = this.getThreadLocalRequest();
> HttpSession session = req.getSession();
> session.setAttribute(token, pdf);
> return token;
>
> - Then the client calls a normal servlet with the token as a parameter
> (localhost:8080/myApp/pdfRetriever?token=...)
> - This servlet looks up the data in the session using the token,
> removes the attribute, and sends back the pdf
>
> String token = req.getParameter("token");
> byte[] pdf = (byte[])req.getSession().getAttribute(token);
>
> Carl.
>
> On Apr 7, 11:18 am, Superman859 <[email protected]> wrote:
>
> > Thanks for all the responses. I had (and still do) little
> > understanding of responses and requests as I rarely work directly with
> > them. However, I now see that GWT-RPC is not the way to go. From
> > what I've read and what I saw using Firebug, GWT-RPC sets up the
> > response variable for it's own purposes as part of GWT-RPC, so by
> > going in and modifying it myself I caused problems with GWT-RPC.
>
> > Instead of extending RemoteServiceServlet, I extended HttpServlet and
> > have been able to get a result. However, I was not able to get a
> > result from the GWT app yet using RequestBuilder. I attempted to do
> > so, and the function ran (I had some print statements which showed up
> > in the log) successfully and the RequestCallback received a response.
> > However, nothing happened.
>
> > Is it possible to do this using RequestBuilder? Using Firebug, I saw
> > a response was generated and it seemed to have the correct headers as
> > I had set. However, no PDF file opened, was offered, etc. and it
> > appeared as if nothing happened.
>
> > I was able to get it to generate a PDF by simply typing the URL into
> > my browser...
>
> >www.site.com/app-name/PDFServlet
>
> > that URL displayed a Hello World example PDF as expected. Ideally,
> > this would open by clicking from GWT app. I suppose I could create a
> > standard HTML link in the GWT app and that may work, but I wonder why
> > the RequestBuilder did not work, even though response was returned.
>
> > And finally - does anyone have any tips on ways to make it more secure
> > somehow? While there is a rare chance, and it probably wouldn't be
> > anything serious, anyone could type in the URL in the browser and view
> > the reports that will be generated, provided they pass in the report
> > ID, etc. Is there a way that it would only work if accessed from the
> > app (which is user protected) or are there any other tips on making it
> > a bit more secure?
>
> > Below is my current servlet code, followed by the RequestBuilder part
> > of the app that failed to work as expected.
>
> > public class PDFServlet extends HttpServlet {
>
> > public void doGet(HttpServletRequest request, HttpServletResponse
> > response) throws IOException, ServletException {
> > System.out.println("Hello World! to follow");
>
> > Document document = new Document();
>
> > // generate test PDF
> > try {
>
> > ByteArrayOutputStream baos = new ByteArrayOutputStream();
> > //PdfWriter.getInstance(document, new FileOutputStream
> > ("HelloWorld.pdf"));
> > PdfWriter.getInstance(document, baos);
> > document.open();
> > document.add(new Paragraph("Hello World!"));
> > document.close();
>
> > // setting some response headers
> > response.setHeader("Expires", "0");
> > response.setHeader("Cache-Control", "must-revalidate,
> > post-check=0,
> > pre-check=0");
> > response.setHeader("Pragma", "public");
>
> > response.setContentType("application/pdf");
>
> > // content length is needed for MSIE
> > response.setContentLength(baos.size());
>
> > // write ByteArrayOutputStream to ServletOutputStream
> > ServletOutputStream out = response.getOutputStream();
> > baos.writeTo(out);
> > out.flush();
> > }
> > catch (Exception e) {
> > System.out.println("PDFServlet::doGet::Exception "
> > + e.getMessage
> > ());
> > }
>
> > }
>
> > }
>
> > /*
> > * Code in GWT app - ultimately I will pass report type, ID to the
> > servlet to generate the
> > * appropriate report
> > */
> > public void onRecordClick(RecordClickEvent event) {
> > //need to add report ID, etc. to the
> > request in the future
> > RequestBuilder request = new
> > RequestBuilder(RequestBuilder.GET,
> > "PDFService");
> > request.setCallback(new RequestCallback() {
>
> > public void onError(Request
> > request, Throwable exception) {
> > SC.say("onError"); // this
> > is just an alert
>
> > }
>
> > public void
> > onResponseReceived(Request request,
> > Response response) {
> >
> > SC.say("onResponseReceived"); // alert
>
> > }
>
> > });
>
> > On Apr 6, 5:45 pm, Daniel Jue <[email protected]> wrote:
>
> > > There is a PDF generation demo using a GWT entrypoint on the DynamicJasper
> > > website (a wrapper for Jasper, which I think still usesiTextdeep inside).
>
> > >http://dynamicjasper.sourceforge.net/
>
> > > Anyway you can look at the relevant servlet code there, and the hand-off
> > > from the GWT "run report" button.
>
> > > On Mon, Apr 6, 2009 at 4:55 PM, [email protected]
> > > <[email protected]>wrote:
>
> > > > Foritextjust do a like to like a jsp page that will run theitext
> > > > gen. Thats how i do it and it works great.
>
> > > > On Apr 6, 11:55 am, Peter Ondruška <[email protected]> wrote:
> > > > > I think you should not use GWT RPC servlet, just use normal servlet.
>
> > > > > 2009/4/6, Superman859 <[email protected]>:
>
> > > > > > I want to useiTextto generate a PDF file. Ideally, I can
> > > > > > incorporate a generatePDF() method into my interface and my Servlet
> > > > > > that is involved in GWT-RPC. When that method is called, I want it
> > > > > > to
> > > > > > generate a PDF file and either display it to the user in a new
> > > > > > window
> > > > > > or present a save dialog box or anything - something that leaves the
> > > > > > GWT app as it was and allows the user to view / save / print the
> > > > > > PDF.
>
> > > > > > Generating the PDF is not a problem. I can generate one and write
> > > > > > it
> > > > > > to a file on the server without any trouble. However, I am having
> > > > > > trouble presenting the user with it (I would rather NOT write them
> > > > > > to
> > > > > > files on the server, and just let the user save on their own machine
> > > > > > if they wish to do so).
>
> > > > > > Here is code for a sample "Hello World"
>
> > > > > > public boolean generatePDF(ReportDO report, int id) {
> > > > > > System.out.println("hello world to follow");
> > > > > > // get request
> > > > > > //HttpServletRequest request = getThreadLocalRequest();
>
> > > > > > // get response
> > > > > > HttpServletResponse response = getThreadLocalResponse();
>
> > > > > > Document document = new Document();
>
> > > > > > // generate test PDF
> > > > > > try {
>
> > > > > > ByteArrayOutputStream baos = new ByteArrayOutputStream();
> > > > > > //PdfWriter.getInstance(document, new FileOutputStream
> > > > > > ("HelloWorld.pdf"));
> > > > > > PdfWriter.getInstance(document, baos);
> > > > > > document.open();
> > > > > > document.add(new Paragraph("hello world"));
> > > > > > document.close();
>
> > > > > > // setting some response headers
> > > > > > response.setHeader("Expires", "0");
> > > > > > response.setHeader("Cache-Control", "must-revalidate,
> > > > post-check=0,
> > > > > > pre-check=0");
> > > > > > response.setHeader("Pragma", "public");
>
> > > > > > response.setContentType("application/pdf");
>
> > > > > > // content length is needed for MSIE
> > > > > > response.setContentLength(baos.size());
>
> > > > > > // write ByteArrayOutputStream to ServletOutputStream
> > > > > > ServletOutputStream out = response.getOutputStream();
> > > > > > baos.writeTo(out);
> > > > > >
>
> ...
>
> read more »
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