[JAVA] I want to control the maximum file size in file upload for each URL in Spring Boot

1. What you want to do

--Control things like spring.servlet.multipart.max-file-size = 1MB on a URL-by-URL basis

2. Version, conditions, etc.

• Java 12
• Spring Boot 2.1.4.RELEASE

3. What I did

--Create the following Intercecptor and determine MultipartFile # size

MultipartFileInterceptor.java

public class MultipartFileInterceptor extends HandlerInterceptorAdapter {

	private final long maxFileSize;

	public MultipartFileInterceptor(long maxFileSize) {
		this.maxFileSize = maxFileSize;
	}
	
	public MultipartFileInterceptor(String maxFileSize) {
		this(ByteSizeUnit.toBytes(maxFileSize));
	}

	@Override
	public boolean preHandle(HttpServletRequest request,
							 HttpServletResponse response,
							 Object handler) throws Exception {

		if (MultipartRequest.class.isInstance(request) && maxFileSize >= 0) {
			MultipartRequest multipartRequest = MultipartRequest.class.cast(request);

			multipartRequest.getFileMap()
				.values()
				.stream()
				.forEach(f -> {
					if (f.getSize() > maxFileSize) {
						throw new MaxUploadSizeExceededException(maxFileSize);
					}
				});
		}

		return super.preHandle(request, response, handler);
	}
}

--Create a WebMvcConfigurer like the one below and associate the Interceptor with the URL you want to control.

WebMvcConfig

@Configuration
public class WebMvcConfig implements WebMvcConfigurer {

	@Value("${app.file.max-file-size:-1}")
	private String fileMaxFileSize;

	@Override
	public void addInterceptors(InterceptorRegistry registry) {
		registry.addInterceptor(new MultipartFileInterceptor(fileMaxFileSize))
			.addPathPatterns("/file");
	}

}

--Although it is not directly related to this issue, by preparing the following class, it is possible to define it as 1MB in the application settings.

ByteSizeUnit.java

public enum ByteSizeUnit {

	KB {
		@Override
		long toBytes(long size) {
			return size * UNIT_SIZE;
		}
	},
	MB {
		@Override
		long toBytes(long size) {
			return size * UNIT_SIZE * UNIT_SIZE;
		}
	},
	GB {
		@Override
		long toBytes(long size) {
			return size * UNIT_SIZE * UNIT_SIZE * UNIT_SIZE;
		}
	};

	abstract long toBytes(long size);

	static final long UNIT_SIZE = 1024;

	public static long toBytes(String size) {
		if (Objects.isNull(size) || size.isEmpty()) {
			throw new IllegalArgumentException("size must not be empty");
		}

		for (ByteSizeUnit byteSizeUnit : values()) {
			if (size.toUpperCase().endsWith(byteSizeUnit.name())) {
				return byteSizeUnit.toBytes(Long.valueOf(size.substring(0, size.length() - byteSizeUnit.name().length())));
			}
		}

		return Long.valueOf(size);
	}

}

4. Example

• https://github.com/ShigeoTejima/spring-boot-demo

Please let me know if you can do it with Spring Boot settings. end.