Java Applet hangs in IE when getting HttpUrlConnection outputstream

Question

I have a signed file uploader applet that works in Chrome but seems to hang when run in IE. In IE, I can successfully upload a file (or set of files) one time but the next time I try to upload another file, the browser freezes and I have to close the browser. It seems to be happening when I attempt to retrieve the outputstream of the HttpUrlConnection object. Here is my code:

public void upload(URL url, URL returnUrl, List<FileIconPanel> files) {
    HttpURLConnection conn = null;

    try {
        conn = (HttpURLConnection) url.openConnection();
        conn.setDoOutput(true);
        conn.setDoInput(true);
        conn.setUseCaches(false);
        conn.setChunkedStreamingMode(1024);
        HttpURLConnection.setFollowRedirects(false);
        conn.setRequestProperty("content-type", "application/zip");
        conn.setRequestMethod("POST");

        //This zip output stream will server as our stream to the server and will zip each file while 
        // it sends it to the server.
        ZipOutputStream out = new ZipOutputStream(conn.getOutputStream());
        for (int i = 0; i < files.size(); i++) {
            //For each file we will create a new entry in the ZIP archive and stream the file into that entry.

            File f = (File) files.get(i).getFile();
            ZipEntry entry = new ZipEntry(f.getName());
            out.putNextEntry(entry);
            InputStream in = new FileInputStream(f);
            int read;
            byte[] buf = new byte[1024];

            while ((read = in.read(buf)) > 0) {
                out.write(buf, 0, read);
            }

            out.closeEntry();
        }

        //Once we are done writing out our stream we will finish building the archive and close the stream.
        out.finish();
        out.close();

        // Now that we have set all the connection parameters and prepared all
        //  the data we are ready to connect to the server.
        conn.connect();

        // read & parse the response
        InputStream is = conn.getInputStream();
        StringBuilder response = new StringBuilder();
        byte[] respBuffer = new byte[4096];
        while (is.read(respBuffer) >= 0) {
            response.append(new String(respBuffer).trim());
        }
        is.close();
    } catch (IOException ioE) {
        ioE.printStackTrace();
        logger.info("An unexpected exception has occurred. Contact your system administrator");
    } catch (Exception e) {
        e.printStackTrace();
        logger.info("An unexpected exception has occurred. Contact your system administrator");
    } finally {
        //Once we are done we want to make sure to disconnect from the server.
        if (conn != null) conn.disconnect();
    }
}

I can see in the log files that it is freezing a this line:

ZipOutputStream out = new ZipOutputStream(conn.getOutputStream());

the second time I try to upload a file. This code also does work in IE under java 6. It has had this problem since I updated to the latest.

Is there something I'm leaving open that I need to make sure to close out before using the applet again? Been beating my head against this for the last two days. Sure hope someone can help...

Answer 1

I have an idea of what's going on but I don't know exactly the details of the what's causing the problem. I at least figured it out a workaround...I was using a jquery dialog box to display the applet. I was doing this on the fly so every time I open the dialog box, it was building the applet again. It's strange because I was in fact removing the div element that contained the applet every time the dialog box was closed so I would have thought that would ensure the old applet instance was destroyed as well. Chrome seems to be smart enough to destroy it and create a new one (or something to that effect) but IE has problems.