如何将使用jxl.jar生成的Excel文件从服务器计算机发送到客户端

Question

I am using struts to develop my web application. I wrote a method which generates excel file and saves it based on the data model I pass.. Works great on my local machine since tomcat is present locally.. But now I've moved my application to a central server.. Now if I use the method it stores generates the excel file in the server not in the client machine which are hitting the server.. I need to pass it from server to client through http.. How do I do that?

public static void populateExcelDoc(List<ColumnList> listOfColumns,RowList rowlist,String filename)
{
    try
    {
        WorkbookSettings ws = new WorkbookSettings();
        ws.setLocale(new Locale("en", "EN"));

        WritableWorkbook workbook = Workbook.createWorkbook(new File(filename+".xls"), ws);
        WritableSheet s = workbook.createSheet("Sheet1", 1);
        writeDataSheetifx1(s,listOfColumns,rowlist);
        workbook.write();
        workbook.close();

        Process p = 
                  Runtime.getRuntime()
                   .exec("rundll32 url.dll,FileProtocolHandler " + filename+".xls");
    }
    catch(IOException e)
    {
        e.printStackTrace();
    }
    catch(WriteException e)
    {
        e.printStackTrace();
    }
}  

This is what my current code looks like.. What change do I need to make? Should I be using HttpServletResponse response?

Answer 1

In Struts2 there is stream result for sending data to the HttpServletResponse.

In your struts.xml configure your action to use stream result.

<action name="exceldoc" method="populateExcelDoc" class="ExcelDocAction">
  <result name="success" type="stream">
    <param name="inputName">inputStream</param>
    <param name="contentType">application/vnd.ms-excel</param>
    <param name="contentDisposition">attachment;filename=excel.xls</param>
  </result>
</action>

And inside your action create private InputStream inputStream; with getters/setters and write your file to it inside your method.

Answer 2

You have several options, two of them are:

1) Save the file in a place where a client browser can access it

To do this, you will have to find out a decent directory to store the file. When you are using a Servlet, you can create an absolute file systems path from a relative URL path using this method:

String filePath = getServletContext().getRealPath("/MyFile.xls");
WritableWorkbook workbook = Workbook.createWorkbook(new File(filePath), ws);
...

Then users can access it from the browser using a URL like: http://host:port/AppName/MyFile.xls

You could also modify the response header, so that the browser has to read the file:

response.setHeader("Content-Disposition", "attachment;filename=/MyFile.xls");

Disadvantage of this method is that the file will be accessible for everybody and that you probably will have to think about generating unique file names, if there are multiple users generating the file again and again. Then you will also have to implement a delete routine for old files.

2) Send the file directly from the servlet to the browser.

If the response of your Servlet request can be the created Excel file, this is probably the best way.

Set the response header accordingly to the file type and size:

response.setContentLength(length);
response.setContentType("application/vnd.ms-excel");
response.getOutputStream().write(...);
response.getOutputStream().flush();

After writing the data, the file can be deleted from the servers file system.