Stream data in response for Spring MVC 4.3 Using Java 8, Tomcat 7

Question

Below is the piece of code that causes OutOfMemory issue when I run my xyz.war in tomcat 7 with Java 8.

In Below code I am creating a CSV response of the data that was fetched from MongoDB via cursor.

@RequestMapping(value = "/elements/{elementname}/records", method = RequestMethod.GET)
public ModelAndView getAllRecords(
  HttpServletRequest request, HttpServletResponse response,
  @RequestParam(value = "customerid", required = true) long customerId,
  @RequestParam(value = "userid", required = true) long userId,
  @RequestParam(value = "query", required = false) String query,
  throws Exception {
    Map < String, Object > model = new HashMap < String, Object > ();
    JsonObject records = elementService.searchRecords(query);
    ModelAndViewData msvd = elementService.commonRestService
                                .getModelAndView("dataObject", "streamingView");
    return new ModelAndView(msvd.getViewName(), handleCsvReportTypeRequest(records, customerId, userId));
}

public Map < String, Object > handleCsvReportTypeRequest(JsonObject records,
        String elementName, long customerId, long userId) throws Exception {
    StringBuffer csvData = new StringBuffer();
    // create csv data
    ModelAndViewData modelAndStreamingViewData = commonRestService.getModelAndView(
    "dataObject", "streamingView");
    byte[] byteArray = String.valueOf(csvData).getBytes();
    InputStream byteArrayInputStream = new ByteArrayInputStream(byteArray);
    model.put(modelAndStreamingViewData.getModelAttributeName(), byteArrayInputStream);

    model.put(DownloadConstants.CONTENT_TYPE, DownloadConstants.CSV_CONTENT_TYPE);
    model.put(DownloadConstants.FILENAME, "XYZ.csv");
    model.put(DownloadConstants.LAST_MODIFIED, new Date(System.currentTimeMillis()));
    model.put(DownloadConstants.CONTENT_LENGTH, Integer.valueOf(byteArray.length));
    return model;
}

How can I stream CSV data back to the user without creating a huge data in memory and then passing to the user?

Answer 1

Use a Buffered read and write the response in HttpResponse object.

Try this way: Spring MVC : large files for download, OutOfMemoryException