JSON Object with File Upload in Spring Rest API Example

When we are working on a real-time project at that time we have scenarios like user registration with an image, adding a product with an image, add some data with the file into the database through rest API. This kind of scenario we achieve with help of ObjectMapper class.
In this example, we can send a JSON object and files through ObjectMapper to Spring Rest API.
ObjectMapper is helping to convert JSON to Java class and vice versa.

Development Process:
1. Keep eclipse IDE ready(STS Integrated) 
2. Create a Spring Boot Starter Project
3. Configure Object Mapper
4. Enable Multipart File configuration in the application.properties file
5. Create a FileStorage class
6. Create a Service
7. Create a  Rest Controller class
8. Run the Project

1. Keep eclipse IDE ready(STS Integrated) 
Refer to this article How to Create Spring Project in IDE to create Spring Boot Project in Eclipse IDE.

2. Create a Spring Boot Starter Project
Add the following dependencies: 
    • Spring Web
    • Spring Configuration Processor   

Maven Dependency
pom.xml:

<?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>2.6.3</version>
		<relativePath/>
		<!-- lookup parent from repository -->
	</parent>
	<groupId>com.example</groupId>
	<artifactId>Json_Object_With_File_Spring_Boot_Rest_Api</artifactId>
	<version>0.0.1-SNAPSHOT</version>
	<packaging>war</packaging>
	<name>Json_Object_With_File_Spring_Boot_Rest_Api</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-web</artifactId>
		</dependency>
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-configuration-processor</artifactId>
			<optional>true</optional>
		</dependency>
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-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>

3. Configure Object Mapper

package com.example;

import org.springframework.boot.SpringApplication;

import org.springframework.boot.autoconfigure.SpringBootApplication;

import org.springframework.context.annotation.Bean;

import com.fasterxml.jackson.databind.ObjectMapper;

@SpringBootApplication

public class JsonObjectWithFileSpringBootRestApiApplication {

  public static void main(String[] args) {

    SpringApplication.run(JsonObjectWithFileSpringBootRestApiApplication.class, args);

  }

  @Bean

  public ObjectMapper getObjectMapper() {

    return new ObjectMapper();

  }
}

4. Enable Multipart File configuration in the application.properties file

## MULTIPART (MultipartProperties)
# Enable multipart uploads
spring.servlet.multipart.enabled=true
# Threshold after which files are written to the disk.
spring.servlet.multipart.file-size-threshold=2KB
# Max file size.
spring.servlet.multipart.max-file-size=500KB
# Max Request Size
spring.servlet.multipart.max-request-size=500KB
## File Storage Properties
file.upload-dir=./uploads
server.port=8082

5. Create a FileStorage class
FileStorageProperties.java:

package com.example.property;

import org.springframework.boot.context.properties.ConfigurationProperties;

import org.springframework.stereotype.Component;

@Component

@ConfigurationProperties(prefix = "file")

public class FileStorageProperties {

  private String uploadDir;

  public String getUploadDir() {

    return uploadDir;

  }

  public void setUploadDir(String uploadDir) {

    this.uploadDir = uploadDir;

  }
}

→ @ConfigurationProperties allows mapping the entire Properties and Yaml files into an object. By default, this annotation reads values from the  application.properties file.
6. Create a Service
FileStorageService.java:

package com.example.service;

import java.io.IOException;

import java.nio.file.Files;

import java.nio.file.Path;

import java.nio.file.Paths;

import java.nio.file.StandardCopyOption;

import org.springframework.beans.factory.annotation.Autowired;

import org.springframework.stereotype.Service;

import org.springframework.util.StringUtils;

import org.springframework.web.multipart.MultipartFile;

import com.example.property.FileStorageProperties;

@Service

public class FileStorageService {

  private final Path fileStorageLocation;

  @Autowired

  public FileStorageService(FileStorageProperties fileStorageProperties) {

    this.fileStorageLocation = Paths.get(fileStorageProperties.getUploadDir()).toAbsolutePath().normalize();

    try {

      Files.createDirectories(this.fileStorageLocation);

    } catch (Exception ex) {

      throw new RuntimeException("Couldn't create the directory where the upload files will be saved.", ex);

    }

  }

  public String storeFile(MultipartFile file) {

    // Normalize file name

    String fileName = StringUtils.cleanPath(file.getOriginalFilename());

    try {

      // Check if the file's name contains valid  characters or not

      if (fileName.contains("..")) {

        throw new RuntimeException("Sorry! File name which contains invalid path sequence " + fileName);

      }

      // Copy file to the target place (Replacing existing file with the same name)

      Path targetLocation = this.fileStorageLocation.resolve(fileName);

      Files.copy(file.getInputStream(), targetLocation, StandardCopyOption.REPLACE_EXISTING);

      return fileName;

    } catch (IOException ex) {

      ex.printStackTrace();

    }

  }
}

7. Create a Rest Controller class
UserController.java:

package com.example.api;

import org.springframework.beans.factory.annotation.Autowired;

import org.springframework.web.bind.annotation.PostMapping;

import org.springframework.web.bind.annotation.RequestParam;

import org.springframework.web.bind.annotation.RestController;

import org.springframework.web.multipart.MultipartFile;

import org.springframework.web.servlet.support.ServletUriComponentsBuilder;

import com.example.response.User;

import com.example.service.FileStorageService;

import com.fasterxml.jackson.core.JsonProcessingException;

import com.fasterxml.jackson.databind.ObjectMapper;

@RestController

public class UserController {

  @Autowired

  private FileStorageService fileStorageService;

  @Autowired

  private ObjectMapper objectMapper;

  @PostMapping("/json-object-file-upload")

  public User uploadFile(@RequestParam("model") String jsonObject, @RequestParam("file") MultipartFile file) {

    User response = null;

    try {

      String fileName = fileStorageService.storeFile(file);

      ServletUriComponentsBuilder.fromCurrentContextPath().path(fileName).toUriString();

      response = objectMapper.readValue(jsonObject, User.class);

      response.setImage(file.getOriginalFilename());

    } catch (JsonProcessingException e) {

      e.printStackTrace();

    }

    return response;

  }
}

8. Run the Project
JSON: 

{    

"userName":"Peter",

"mobileNo":"1111111111",

"emailId":"peter@gmail.com"

}

→ JSON is a simple string format. It can be understood by us and technologies.
→ “{ }” represents a JSON object.
→ “[ ]” represents a JSON array.
We can test API via postman.
POST type: http://localhost:8082/json-object-file-upload

Conclusion:
This example is explained How to send the JSON object with a file in the Spring Boot Rest API? What is an Object Mapper? How to configure an Object Mapper? How to convert JSON to Java class through Object Mapper?