单击html中的锚点调用文件下载servlet？

Question

I wrote a file download servlet and registered in web.xml as below.

<servlet>
    <servlet-name>downloadFile</servlet-name>
    <servlet-class>com.hibu.HibuProspector.FileDwonloadServlet</servlet-class>
</servlet>

<servlet-mapping>
    <servlet-name>downloadFile</servlet-name>
    <url-pattern>/</url-pattern>
</servlet-mapping>

FileDownloadServlet.java

public class FileDownloadServlet extends HttpServlet{

  private static final int BYTES_DOWNLOAD = 1024;

  public void doGet(HttpServletRequest request, 
   HttpServletResponse response) throws IOException{
    response.setContentType("application/vnd.openxmlformats-officedocument.spreadsheetml.sheet");
    response.setHeader("Content-Disposition",
                     "attachment;filename=SampleFile.xlsx");
    ServletContext ctx = getServletContext();
    InputStream is = ctx.getResourceAsStream("/SampleFile.xlsx");

    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(); 
   }
}

I have a link in html page as below. on click of the link i need to get the file downloaded.

<a class="button right" target="_blank">Download</a>

Now how can I link the download servlet with the anchor?
Any suggestions?

Answer 1

It is not good practice to give the root mapping of the web application to do specific operations, therefore update your web.xml with proper servlet mapping as follows:-

  <servlet-mapping>
      <servlet-name>fileDownload</servlet-name>
      <url-pattern>/fileDownload</url-pattern>
 </servlet-mapping>

then update the anchor tag with new mapping as below. (you should mention the url-pattern insde the href attribute of the anchor tag.)

<a class="button right" target="_blank" href="/fileDownload">Download</a>

This should work!!!

Answer 2

Give proper mapping in web.xml

  <servlet-mapping>

                <servlet-name>downloadFile</servlet-name>

                <url-pattern>/downloadFile</url-pattern>

        </servlet-mapping>

You just have to call the servlet through your anchor

<a href="/downloadFile"  class="button right" target="_blank">Download</a>

Answer 3

Change your mapping to something specific:

<servlet-mapping>
   <servlet-name>downloadFile</servlet-name>
   <url-pattern>/download</url-pattern>
</servlet-mapping>

And specify the href attribute of a tag :

<a class="button right" target="_blank" href="/download">Download</a>

You can read the specs of the anchor#href tag :

This attribute specifies the location of a Web resource, thus defining a link between the current element (the source anchor) and the destination anchor defined by this attribute.

Answer 4

在所有三个答案中，所有内容都是正确的，除了href =“ / downloadFile”省略'/'来产生-href =“ downloadFile”为我工作。