After some learning, i have found the answer to how to upload file(.zip/.txt/ any other file format) from angular (4/5) to spring/rest controller. Writing down my learning below for those who looking same thing.:)

Front-end coding ::

1. HTML (eg. UploadFile.component.html):

<input type="file" formControlName="uploadFile" (change)="uploadFileToServer($event)"/>

2. Component (eg. UploadFile.component.ts) :

import { Component } from '@angular/core';
import { RequestOptions, Headers, Http } from '@angular/http';
@Component({
  selector: 'file-uploader',
  templateUrl: './uploadFile.component.html',
  styleUrls: ['./uploadFile.component.css'],
})
export class FileUploadComponent {

public uploadFileToServer(event) {
  let fileList: FileList = event.target.files;
  if (fileList.length > 0) {
    let file: File = fileList[0];
    let formData: FormData = new FormData();
    formData.append('uploadFile', file, file.name);
    formData.append('fileType', 'zip');
    let headers = new Headers();
    headers.append('Accept', 'application/json');
    let options = new RequestOptions({ headers: headers });
    this.http.post('domain/urservice', formData, options)
      .map(res => res.json())
      .catch(error => Observable.throw(error))
      .subscribe(
      data => console.log('success'),
      error => console.log(error)
      )
  }
} 

}

(note - this server communication call should be present in some service not in component but for simplicity i am writing it in component)

server-side coding ::

1 . Spring/Rest controller (FileUploadController.java) :

    @RequestMapping(value = "/urservice", method = RequestMethod.POST)
    public void uploadFile(MultipartHttpServletRequest request) throws IOException {

    Iterator<String> itr = request.getFileNames();

    // directory to save file
    String tempDir = System.getProperty("jboss.server.temp.dir");

      MultipartFile file = request.getFile(itr.next());
      String fileType = request.getParameter("fileType");
      String fileName = file.getOriginalFilename();

      File dir = new File(tempDir);
      File fileToImport = null;
      if (dir.isDirectory()) {

        try {
            fileToImport = new File(dir + File.separator + fileName);
            BufferedOutputStream stream = new BufferedOutputStream(new FileOutputStream(fileToImport));
            stream.write(file.getBytes());
            stream.close();
        } catch (Exception e) {
            logger.error("Got error in uploading file.");
        }

}