立即流式下载CSV文件，无需等待

Question

我有REST API，该方法调用一种检索CSV的方法，因为csv可能有数百万行，我一次要检索5万行，我希望在收到第一个查询结果后立即开始下载，然后继续写入同一文件。

我已经编写了以下代码，但是仍然只有在检索到所有结果之后才开始文件下载。

@GET
    @Path("network/all/stats/csv/download")
    @Produces({"text/csv"})
    public Response downloadCSV(UIAffiliateRequest uiInstallsRequest) {StreamingOutput stream = new StreamingOutput() {
                @Override
                public void write(OutputStream os) throws IOException, WebApplicationException {
                    Writer writer = new BufferedWriter(new OutputStreamWriter(os));
                    int off=0;
                    try {
                        CSVResponseType rs;

                        do {
                            rs = installsDao.getCSVResult(uiInstallsRequest, off);
                            String lines[] = rs.getFileName().split("\\r?\\n");
                            for (String path : lines) {
                                writer.write(path.toString() + "\n");
                            }
                            writer.flush();
                            off+=50000;
                        }
                        while (rs.isEmpty());
                    }
                    catch (DaoException e) {
                        ResponseUtils.getDataAccessErrorResponse(e);
                    }
                }
            };

            return Response.ok(stream).header("Content-Disposition", "attachment;filename=resp.csv").build();

    }