Angular 11 + Spring Boot: File upload example

#angular #springboot #webdev #fullstack

In this tutorial, I will show you way to build Angular 11 File upload & download example with Spring Boot server.

Overview

We're gonna create a full-stack Angular 11 File upload to Spring Boot Server in that user can:

see the upload process (percentage)
view all uploaded files
download by clicking on the file name

All uploaded files will be saved in uploads folder:

Angular 11 + Spring Boot File upload Architecture

Let's look at the architecture below:

Angular 11 Client:

FileUpload Component calls UploadService functions for upload/download/display files
UploadService uses HttpClientModule to make HTTP requests

Spring Boot Server:

FilesController receives the HTTP requests from Client, then calls FilesStorageService functions for upload/download/getting files
FilesStorageService implements functions for storing and retrieving file systems using Java Files library

Technology

Server:

Java 8
Spring Boot 2 (with Spring Web MVC)
Maven 3.6.1

Client:

Angular 11
RxJS 6
Bootstrap 4

Spring Boot Rest APIs for File Upload & Storage

Spring Boot App will provide APIs

Methods	Urls	Actions
POST	/upload	upload a File
GET	/files	get List of Files (name & url)
GET	/files/[filename]	download a File

This is the project structure:

FileInfo contains information of the uploaded file.
FilesStorageService helps us to initialize storage, save new file, load file, get list of Files' info, delete all files.
FilesController uses FilesStorageService to export Rest APIs: POST a file, GET all files' information, download a File.
FileUploadExceptionAdvice handles exception when the controller processes file upload.
application.properties contains configuration for Servlet Multipart.
pom.xml for Spring Boot dependency.

You can find Step by Step to implement the Spring Boot Server at:
Spring Boot Multipart File upload (to static folder) example

Or: Spring Boot Multipart File upload (to database) example

Angular 11 Client for file upload/download UI

This is the project structure that we're gonna build:

We import necessary library, components in app.module.ts.
upload-file.service provides methods to save File and get Files from Spring Boot Server.
upload-files.component contains upload form, progress bar, display of list files.
app.component is the container that we embed all components.
index.html for importing the Bootstrap.

Angular Service for File Upload
This service will use Angular HTTPClient to send HTTP requests.
There are 2 functions:

upload(file): returns Observable<HttpEvent<any>> that we're gonna use for tracking progress
getFiles(): returns a list of Files' information as Observable object

export class UploadFileService {

  constructor(private http: HttpClient) { }

  upload(file: File): Observable&lt;HttpEvent&lt;any>> {
    ...
  }

  getFiles(): Observable&lt;any> {
    ...
  }
}

Angular Component for File Upload
File Upload Component has Progress Bar, Card, Button and Message. It injects UploadFileService to call uploadService.upload() method.

The upload progress will be calculated basing on event.loaded and event.total.
If the transmission is done, the event will be a HttpResponse object. At this time, we call uploadService.getFiles() to get the files' information and assign the result to fileInfos variable.

upload() {
  this.progress = 0;

  this.currentFile = this.selectedFiles.item(0);
  this.uploadService.upload(this.currentFile).subscribe(
    event => {
      if (event.type === HttpEventType.UploadProgress) {
        this.progress = Math.round(100 * event.loaded / event.total);
      } else if (event instanceof HttpResponse) {
        this.message = event.body.message;
        this.fileInfos = this.uploadService.getFiles();
      }
    },
    err => {
      this.progress = 0;
      this.message = 'Could not upload the file!';
    });
}

You can find step by step with more details in the tutorial:
Angular 11 File upload example with progress bar & Bootstrap

Run the App

Run Spring Boot Server with command: mvn spring-boot:run.
Refresh the project directory and you will see uploads folder inside it.

Because we configure CORS for origin: http://localhost:8081, so you need to run Angular 11 Client with command:
ng serve --port 8081

Open Browser with url http://localhost:8081/ and check the result.

Conclusion

Today we're learned how to build an example for upload Files from Angular 11 to Spring Boot server. We also provide the ability to show list of files, upload progress using Bootstrap, and to download file from the server.

Next tutorials will show you way to implement the full-stack (with source code):