Send POST request open save as dialog to save file locally

README.md

• https://developer.mozilla.org/en-US/docs/Web/API/XMLHttpRequest/Sending_and_Receiving_Binary_Data
• https://github.com/eligrey/FileSaver.js/
• Why threre is no way to download file using ajax request?
• Using jquery ajax to download a binary file
• https://stackoverflow.com/questions/16086162/handle-file-download-from-ajax-post
• https://stackoverflow.com/questions/38975718/how-to-download-excel-xls-file-from-api-in-postman
• http://www.freeformatter.com/mime-types-list.html
• Downloading a file from spring controllers
• https://github.com/hellokoding/uploadingfiles-springboot

save_as.js

	var oReq = new XMLHttpRequest();
	oReq.open("POST", "/download2", true);
	oReq.responseType = "arraybuffer";
	
	oReq.onload = function(oEvent) {
	  var blob = new Blob([oReq.response], {type: "image/jpeg"});
	  saveAs(blob, "test.jpg"); // https://github.com/eligrey/FileSaver.js/
	};
	
	oReq.send();

UploadingController.java

/**
 * Copy from https://github.com/hellokoding/uploadingfiles-springboot
 */

package com.hellokoding.uploadingfiles;

import org.apache.tomcat.util.http.fileupload.IOUtils;
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.multipart.MultipartFile;

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.nio.file.Files;

import javax.servlet.http.HttpServletResponse;

@Controller
public class UploadingController {
    public static final String uploadingdir = System.getProperty("user.dir") + "/uploadingdir/";

    @RequestMapping("/")
    public String uploading(Model model) {
        File file = new File(uploadingdir);
        model.addAttribute("files", file.listFiles());
        return "uploading";
    }

    @RequestMapping(value = "/", method = RequestMethod.POST)
    public String uploadingPost(@RequestParam("uploadingFiles") MultipartFile[] uploadingFiles) throws IOException {
        for(MultipartFile uploadedFile : uploadingFiles) {
            File file = new File(uploadingdir + uploadedFile.getOriginalFilename());
            uploadedFile.transferTo(file);
        }

        return "redirect:/";
    }

    @RequestMapping(value = "/download", method = RequestMethod.POST)
    public File downloadPost() throws IOException {
        File file = new File(uploadingdir + "test.jpg");

        return file;
    }
    
    @RequestMapping(value = "/download2", method = RequestMethod.POST)
    public void getFile(
        HttpServletResponse response) {
        try {
          // get your file as InputStream
          InputStream is = new FileInputStream(uploadingdir + "test.jpg");
          // copy it to response's OutputStream
          IOUtils.copy(is, response.getOutputStream());
          response.setContentType("image/jpeg");      
          response.setHeader("Content-Disposition", "attachment; filename=\"somefile.jpg\"");
          // response.flushBuffer();
        } catch (IOException ex) {
          // log.info("Error writing file to output stream. Filename was '{}'", fileName, ex);
          throw new RuntimeException("IOError writing file to output stream");
        }

    }
}