How to limit the each file size of multipart file in springboot

Issue

I want to limit each file's size to 20 MB, but it's only validating the size of all the input files. I have used the below properties to limit the file size. Could you please guide me on how I can restrict the size of each file?

spring: servlet: multipart: max-file-size: 20MB max-request-size: 20MB enabled: true

Solution

Here's what you need to do:

1. Use custom annotation validation for all your input with different sizes.
2. Set a default maximum size that Spring Boot can accept in your application.properties

To achieve step 1, lets say you have an Entity: Post

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import jakarta.persistence.*;

@Entity
public class Post {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    private String image;

    @Transient
    private MultipartFile imageContent;

    // Getters and setters, constructors, etc.
}

With an interface, PostImageSize

import jakarta.validation.Constraint;
import jakarta.validation.Payload;

import java.lang.annotation.*;

@Documented
@Constraint(validatedBy = ImageSizeValidation.class)
@Target({ ElementType.METHOD, ElementType.FIELD })
@Retention(RetentionPolicy.RUNTIME)
public @interface PostImageSize {

    String message() default "Invalid image size";

    long maxSize() default 5 * 1024 * 1024; // Default size is 5MB

    Class<?>[] groups() default {};

    Class<? extends Payload>[] payload() default {};
}

and the class ImageSizeValidation mentioned in PostImageSize interface

import jakarta.validation.ConstraintValidator;
import jakarta.validation.ConstraintValidatorContext;
import org.springframework.web.multipart.MultipartFile;

public class ImageSizeValidation implements 
ConstraintValidator<PostImageSize, MultipartFile> {

    private long maxSize;

    @Override
    public void initialize(PostImageSize constraintAnnotation) {
        this.maxSize = constraintAnnotation.maxSize();
    }

    @Override
    public boolean isValid(MultipartFile multipartFile, 
    ConstraintValidatorContext cxt) {
        return multipartFile == null || multipartFile.getSize() <= 
        maxSize;
    }
}

Once you have set this up, using the annotation @PostImageSize in your entity will enable custom validation.

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;

@Entity
public class Post {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    private String image;

    @PostImageSize(message = "This image must not be more than 5MB")
    private MultipartFile imageContent;

    // Getters and setters, constructors, etc.
}

After this, you can customize the size according to the annotations you have and include in your entity which will enable it.

// Customizing to 1MB
@PostImageSize(message = "This image must not be more than 1MB", maxSize = 1024 * 1024)
private MultipartFile imageContent;

For step 2 in your application.properties

# Multipart settings
spring.servlet.multipart.max-file-size=256MB
spring.servlet.multipart.max-request-size=256MB
spring.servlet.multipart.enabled=true

Goodluck !!!

Answered By - Michael Chuks