jQuery.ajax servlet return a file [duplicate]

问题

I'm pretty new to jQuery and ajax and i have a question. In a jsp I call

function downloadDocument(documentId){
    var action = "attachment.do";
    var method = "downloadDocument";
    var url = action + "?actionType="+method+"&documentId=" + documentId;
    $.ajax({
          url: url,
          dataType: "json",
          type: 'POST',
          success: function(data){
              alert("downloaded!");
          },
          error: function (request, status, error) {
              alert(request.responseText);
            }
    });

then in the servlet I do

public void downloadDocument(ActionMapping mapping, ActionForm actionForm, HttpServletRequest request, HttpServletResponse response) throws IOException{

    AttachmentActionForm form = (AttachmentActionForm)actionForm;

    ServletOutputStream out = response.getOutputStream();

    try{
        // Get the downloadFileName, the name of the file when it will be downloaded by user
        String downloadFileName = "hello.txt";

        String  mimetype = "application/x-download"

        // Get the byte stream of the file
        FileInputStream in = new FileInputStream(Global.ATTACHMENTS_SHARED_FOLDER_PATH + downloadFileName);

        // Print out the byte stream
        byte[] buffer = new byte[4096];
        int length;
        while ((length = in.read(buffer)) > 0){
            out.write(buffer, 0, length);
        }

        response.addHeader("Content-Disposition", "attachment; filename="+downloadFileName);
        response.setHeader("Content-Length", Integer.toString(length));
        response.setContentType(mimetype);  

        in.close();
    }
    catch(Exception e){
        response.setContentType("text/text;charset=utf-8");
        response.setHeader("cache-control", "no-cache");
        System.out.println(e.getMessage());
        out.println(e.getMessage());
    }finally{
        out.flush();
    }
}

But in the ajax function, I never get a success, all the time I get the error message, even if the message is composed by the string inside of the file. What can I do?

回答1:

dont use Ajax call use //use hidden form approach

<form action='../servletname' method='POST' id='formid'>
                <input type='hidden' value='' name='name' id='id'/>
                <input type='hidden' value=' ' name='name'  id='id' />
            </form>

on click of button submit form

$('#formid').submit();

in servlet

response.setContentType("application/vnd.ms-excel");
            response.setHeader("Content-Disposition", "attachment; filename=filnemae.fileformat");

 ServletOutputStream out = res.getOutputStream();

write on ouput stream then close or flush

if you are sending large data through post update postsize in server.xml

回答2:

Remove your dataType: "json", options and you will see some debug informations.

By the way, there is a jQuery option that meet you need:

$.fileDownload('some/file.pdf')
    .done(function () { alert('File download a success!'); })
    .fail(function () { alert('File download failed!'); })

Taken from this answer: https://stackoverflow.com/a/9970672/1420186

EDIT:

Your JSP

function downloadDocument(documentId){
    var action = "attachment.do";
    var method = "downloadDocument";
    var url = action + "?actionType="+method+"&documentId=" + documentId;
    $.ajax({
          url: url,
          dataType: "text", // Change dataType to "text"
          type: 'POST',
          success: function(data){
              if (data == "FAIL") {
                  alert("File not found!");
              } else {
                  window.location.href = data; // Download the file
              }
          },
          error: function (request, status, error) {
              alert("The request failed: " + request.responseText);
          }
    });
}

In your Servlet, if the file is not exists, just return a "FAIL" string, else return the file URL.

Hope that helps.

来源：https://stackoverflow.com/questions/19661011/jquery-ajax-servlet-return-a-file

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java

jquery

ajax

servlets