How to upload multiple files in Java Spring Boot

In this tutorial, I will show you how to upload multiple files and download with a Spring Boot Rest APIs. We also use Spring Web MultipartFile interface to handle HTTP multi-part requests and Postman to check the result.

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Deployment: Deploy Spring Boot App on AWS – Elastic Beanstalk


Spring Boot Rest APIs for uploading multiple Files

Our Spring Boot Application will provide APIs for:

  • uploading multiple Files to Server
  • downloading File from server with the link
  • getting list of Files’ information (file name & url)

These are APIs to be exported:

MethodsUrlsActions
POST/uploadupload multiple Files
GET/filesget List of Files (name & url)
GET/files/[filename]download a File

Technology

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

Project Structure

upload-multiple-files-java-spring-boot-rest-api-project-structure

Let me explain it briefly.

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 multiple files, 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.

Setup Spring Boot Multiple Files upload project

Use Spring web tool or your development tool (Spring Tool Suite, Eclipse, Intellij) to create a Spring Boot project.

Then open pom.xml and add these dependencies:

<dependency>
  <groupId>org.springframework.boot</groupId>
  <artifactId>spring-boot-starter-web</artifactId>
</dependency>

Create Service for File Storage

First we need an interface that will be autowired in the Controller.
In service folder, create FilesStorageService interface like following code:

service/FilesStorageService.java

package com.bezkoder.spring.files.uploadmultiple.service;

import java.nio.file.Path;
import java.util.stream.Stream;

import org.springframework.core.io.Resource;
import org.springframework.web.multipart.MultipartFile;

public interface FilesStorageService {
  public void init();

  public void save(MultipartFile file);

  public Resource load(String filename);

  public void deleteAll();

  public Stream<Path> loadAll();
}

Now we create implementation of the interface.

service/FilesStorageServiceImpl.java

package com.bezkoder.spring.files.uploadmultiple.service;

import java.io.IOException;
import java.net.MalformedURLException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.stream.Stream;

import org.springframework.core.io.Resource;
import org.springframework.core.io.UrlResource;
import org.springframework.stereotype.Service;
import org.springframework.util.FileSystemUtils;
import org.springframework.web.multipart.MultipartFile;

@Service
public class FilesStorageServiceImpl implements FilesStorageService {

  private final Path root = Paths.get("uploads");

  @Override
  public void init() {
    try {
      Files.createDirectory(root);
    } catch (IOException e) {
      throw new RuntimeException("Could not initialize folder for upload!");
    }
  }

  @Override
  public void save(MultipartFile file) {
    try {
      Files.copy(file.getInputStream(), this.root.resolve(file.getOriginalFilename()));
    } catch (Exception e) {
      throw new RuntimeException("Could not store the file. Error: " + e.getMessage());
    }
  }

  @Override
  public Resource load(String filename) {
    try {
      Path file = root.resolve(filename);
      Resource resource = new UrlResource(file.toUri());

      if (resource.exists() || resource.isReadable()) {
        return resource;
      } else {
        throw new RuntimeException("Could not read the file!");
      }
    } catch (MalformedURLException e) {
      throw new RuntimeException("Error: " + e.getMessage());
    }
  }

  @Override
  public void deleteAll() {
    FileSystemUtils.deleteRecursively(root.toFile());
  }

  @Override
  public Stream<Path> loadAll() {
    try {
      return Files.walk(this.root, 1).filter(path -> !path.equals(this.root)).map(this.root::relativize);
    } catch (IOException e) {
      throw new RuntimeException("Could not load the files!");
    }
  }
}

Define Data Models

In model package, let’s create FileInfo which has fields: name & url.

model/FileInfo.java

package com.bezkoder.spring.files.uploadmultiple.model;

public class FileInfo {
  private String name;
  private String url;

  public FileInfo(String name, String url) {
    this.name = name;
    this.url = url;
  }

  public String getName() {
    return this.name;
  }

  public void setName(String name) {
    this.name = name;
  }

  public String getUrl() {
    return this.url;
  }

  public void setUrl(String url) {
    this.url = url;
  }
}

Define Response Message

ResponseMessage will be used for sending message to client in Controller and Exception Handler.

message/ResponseMessage.java

package com.bezkoder.spring.files.uploadmultiple.message;

public class ResponseMessage {
  private String message;

  public ResponseMessage(String message) {
    this.message = message;
  }

  public String getMessage() {
    return message;
  }

  public void setMessage(String message) {
    this.message = message;
  }

}

Create Controller for upload multiple Files & download

In controller package, we create FilesController.

controller/FilesController.java

package com.bezkoder.spring.files.uploadmultiple.controller;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.stream.Collectors;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.core.io.Resource;
import org.springframework.http.HttpHeaders;
import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.CrossOrigin;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.multipart.MultipartFile;
import org.springframework.web.servlet.mvc.method.annotation.MvcUriComponentsBuilder;

import com.bezkoder.spring.files.uploadmultiple.model.FileInfo;
import com.bezkoder.spring.files.uploadmultiple.model.ResponseMessage;
import com.bezkoder.spring.files.uploadmultiple.service.FilesStorageService;

@Controller
@CrossOrigin("http://localhost:8081")
public class FilesController {

  @Autowired
  FilesStorageService storageService;

  @PostMapping("/upload")
  public ResponseEntity<ResponseMessage> uploadFiles(@RequestParam("files") MultipartFile[] files) {
    String message = "";
    try {
      List<String> fileNames = new ArrayList<>();

      Arrays.asList(files).stream().forEach(file -> {
        storageService.save(file);
        fileNames.add(file.getOriginalFilename());
      });

      message = "Uploaded the files successfully: " + fileNames;
      return ResponseEntity.status(HttpStatus.OK).body(new ResponseMessage(message));
    } catch (Exception e) {
      message = "Fail to upload files!";
      return ResponseEntity.status(HttpStatus.EXPECTATION_FAILED).body(new ResponseMessage(message));
    }
  }

  @GetMapping("/files")
  public ResponseEntity<List<FileInfo>> getListFiles() {
    List<FileInfo> fileInfos = storageService.loadAll().map(path -> {
      String filename = path.getFileName().toString();
      String url = MvcUriComponentsBuilder
          .fromMethodName(FilesController.class, "getFile", path.getFileName().toString()).build().toString();

      return new FileInfo(filename, url);
    }).collect(Collectors.toList());

    return ResponseEntity.status(HttpStatus.OK).body(fileInfos);
  }

  @GetMapping("/files/{filename:.+}")
  public ResponseEntity<Resource> getFile(@PathVariable String filename) {
    Resource file = storageService.load(filename);
    return ResponseEntity.ok()
        .header(HttpHeaders.CONTENT_DISPOSITION, "attachment; filename=\"" + file.getFilename() + "\"").body(file);
  }
}

@CrossOrigin is for configuring allowed origins.
@Controller annotation is used to define a controller.
@GetMapping and @PostMapping annotation is for mapping HTTP GET & POST requests onto specific handler methods:

  • POST /upload: uploadFiles()
  • GET /files: getListFiles()
  • GET /files/[filename]: getFile()

– We use @Autowired to inject implementation of FilesStorageService bean to local variable.

The main method is uploadFiles() in which we use MultipartFile[] files as an argument, and Java 8 Stream API to work with each file in the array.

Configure Multipart File for Servlet

Let’s define the maximum file size that can be uploaded in application.properties as following:

spring.servlet.multipart.max-file-size=500KB
spring.servlet.multipart.max-request-size=500KB

spring.servlet.multipart.max-file-size: max file size for each request.
spring.servlet.multipart.max-request-size: max request size for a multipart/form-data.

Handle File Upload Exception

This is where we handle the case in that a request exceeds Max Upload Size. The system will throw MaxUploadSizeExceededException and we’re gonna use @ControllerAdvice with @ExceptionHandlerannotation for handling the exceptions.

exception/FileUploadExceptionAdvice.java

package com.bezkoder.spring.files.uploadmultiple.exception;

import org.springframework.web.multipart.MaxUploadSizeExceededException;
import org.springframework.web.servlet.mvc.method.annotation.ResponseEntityExceptionHandler;

import com.bezkoder.spring.files.uploadmultiple.model.ResponseMessage;

import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.ControllerAdvice;
import org.springframework.web.bind.annotation.ExceptionHandler;

@ControllerAdvice
public class FileUploadExceptionAdvice extends ResponseEntityExceptionHandler {

  @ExceptionHandler(MaxUploadSizeExceededException.class)
  public ResponseEntity<ResponseMessage> handleMaxSizeException(MaxUploadSizeExceededException exc) {
    return ResponseEntity
        .status(HttpStatus.EXPECTATION_FAILED)
        .body(new ResponseMessage("One or more files are too large!"));
  }
}

Initialize Storage

We need to run init() method of FilesStorageService (and also deleteAll() if necessary). So open SpringBootUploadMultipleFilesApplication.java and implement CommandLineRunner for run() method like this:

package com.bezkoder.spring.files.uploadmultiple;

import javax.annotation.Resource;

import org.springframework.boot.CommandLineRunner;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

import com.bezkoder.spring.files.uploadmultiple.service.FilesStorageService;

@SpringBootApplication
public class SpringBootUploadMultipleFilesApplication implements CommandLineRunner {
  @Resource
  FilesStorageService storageService;

  public static void main(String[] args) {
    SpringApplication.run(SpringBootUploadMultipleFilesApplication.class, args);
  }

  @Override
  public void run(String... arg) throws Exception {
    storageService.deleteAll();
    storageService.init();
  }
}

Spring Boot upload Multiple Files with Postman

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

Let’s use Postman to make some requests.

– Upload some files: In the Body tab, chose form-data, key files as File type. For value column, choose several files from your PC.

upload-multiple-files-java-spring-boot-rest-api-example

– Upload files which contains certain file with size larger than max file size (500KB):

upload-multiple-files-java-spring-boot-rest-api-handle-exception

– Check uploads folder:

upload-multiple-files-java-spring-boot-rest-api-static-folder

– Retrieve list of Files’ information:

upload-multiple-files-java-spring-boot-rest-api-example-get

– Now you can download any file from one of the paths above.
For example: http://localhost:8080/files/bezkoder.doc.

Conclusion

Today we’ve learned how to create Java Spring Boot Application to upload multiple files and get files’ information via Rest API.

You can find the complete source code for this tutorial on Github.

This post explains how to build Angular Client to work with Spring Boot Server.

Happy Learning! See you again.

Further Reading

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