Spring Webflux File Upload - Single&Multiple - REST API Example

This article shows you how to upload Single|Multiple files in the Spring Webflux application. 

Technologies Used:
  • Spring Boot 2.5.4
  • Spring Webflux 2.5.4
  • Java 11
  • Maven 3


Project Structure:



Project Dependency

Spring boot dependencies, no need for an extra library for file upload.
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0
https://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.5.4</version>
<relativePath/> <!-- lookup parent from repository -->
</parent>
<groupId>com.knf.dev.demo</groupId>
<artifactId>springwebfluxfileuploaddownload</artifactId>
<version>0.0.1-SNAPSHOT</version>
<name>springwebfluxfileuploaddownload</name>
<description>Demo project for Spring Boot</description>
<properties>
<java.version>11</java.version>
</properties>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-webflux</artifactId>
</dependency>

<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
</dependency>
<dependency>
<groupId>io.projectreactor</groupId>
<artifactId>reactor-test</artifactId>
<scope>test</scope>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
</plugin>
</plugins>
</build>
</project>


Rest Controller
package com.knf.dev.demo.controller;

import org.springframework.http.codec.multipart.FilePart;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestPart;
import org.springframework.web.bind.annotation.RestController;
import reactor.core.publisher.Flux;
import reactor.core.publisher.Mono;
import java.nio.file.Path;
import java.nio.file.Paths;

@RestController
@RequestMapping("api/v1")
public class UploadDownloadController {

private final Path basePath = Paths.
get("./src/main/resources/files/");

//single file upload
@PostMapping("single/upload")
public Mono<Void> uploadFile(@RequestPart("file")
Mono<FilePart> filePartMono){
return filePartMono
.doOnNext(fp -> System.out.println
("Received File : " + fp.filename()))
.flatMap(fp -> fp.
transferTo(basePath.resolve(fp.filename())))
.then();
}

//multiple file upload
@PostMapping("multi/upload")
public Mono<Void> uploadMultipleFiles(@RequestPart("files")
Flux<FilePart> partFlux){
return partFlux
.doOnNext(fp ->
System.out.println(fp.filename()))
.flatMap(fp ->
fp.transferTo(basePath.resolve(fp.filename())))
.then();
}
}


Main Class
package com.knf.dev.demo;

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

@SpringBootApplication
public class SpringwebfluxfileuploaddownloadApplication {

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


Run

Step 1: Download or clone the source code to a local machine.

Step 2mvn clean install

Step 3: Run the Spring Boot application
mvn spring-boot:run


API testing using postman:

Single file upload:




Multiple file upload:




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