Java EE中的Web数据流

Question

we have a design like this :

our installed service upon tomcat has a method getDatabaseData(String request) (RMI Client) which receive data from database using (RMI Server implementation) existing on the core.

we want to do something that our installed service which is inside tomcat make a xml file and send it to client now :

we have thought about a solution that :

• first make the whole xml file on our tomcat using the getDatabaseData(String request) & then our user can get a reference using a link to it & start downloading the data.

but this solution is not informative for us because the size of this file is so big and if we want to do this our tomcat server storage will get full so fast & get down, so we're looking for a solution for real time streaming data to user instead of creating the whole file. I mean a way to send the data to user in a xml template when data is receiving from the CORE.

Do you have any idea ?

(by the way the web service upon tomcat has been written using Spring MVC & Spring Security)

Answer 1

I can give you a pice of code from my current project, where we return a file in struts action:

response.setContentType("application/octet-stream");
response.setHeader("Content-Disposition", "attachment;filename=\"" + fileName + "\"");
ServletOutputStream out = response.getOutputStream();
out.write(file);

Is this what you are looking for?

Answer 2

using @Noofiz code, I wrote this code for testing this functionality & that worked for me!

we can read from a file and send it out on-time to user and let the user download the file !

1) I printed 'End!' to make sure that the file is sending to user on time when It's buffering and not finish buffering first & then send it to user !

2) the downloaded file & main file md5 checked and they were similar.

here is my servlet code :

protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    InputStream is = new FileInputStream("/home/Mehdi/Desktop/log.log");
    response.setContentType("application/octet-stream");
    ServletOutputStream out = response.getOutputStream();
    int i;
    byte[] buffer = new byte[10 * 1024];

    while ((i = is.read(buffer)) != -1) {
        if (i != 10240) {
            for (int j = 0; j < i; j++) {
                out.write(buffer[j]);
            }
        } else {
            out.write(buffer);
        }
    }
    System.out.println("End!");
}