Live Coding Cheatsheet

cheatsheet_livecoding.md

Live-Coding Cheatsheet

Image-Handling JPA+Upload

• Explain ImageController
• Move #loadImage from ImageController to BookController
• Book entity: add LOB field
• Insert example via LOAD_FILE
• book/edit.html: Add input to form + change to multipart
• Controller anpassen (loadImage)
• MultipartFileToByteArrayConverter + WebConfig
• application.properties: Adapt file POST limits
• JpegValidator

SHOW VARIABLES WHERE variable_name='secure_file_priv';
UPDATE book SET image=LOAD_FILE('/var/lib/mysql-files/Refactoring.jpeg');

# File Upload limits
spring.servlet.multipart.max-file-size=1024KB
spring.servlet.multipart.max-request-size=1024KB

@Documented
@Constraint(validatedBy = JPEGValidator.class)
@Target( { ElementType.PARAMETER, ElementType.FIELD })
@Retention(RetentionPolicy.RUNTIME)
public @interface JPEGConstraint {
    String message() default "Bild hat kein JPEG-Format!";
    Class<?>[] groups() default {};
    Class<? extends Payload>[] payload() default {};
}

public class JPEGValidator implements
ConstraintValidator<JPEGConstraint, byte[]> {

	private ImageService imageService;
	
	@Autowired
	public void setImageService(ImageService imageService) {
		this.imageService = imageService;
	}

	@Override
	public void initialize(JPEGConstraint image) {
	}

	@Override
	public boolean isValid(byte[] imageArray,
			ConstraintValidatorContext validatorContext) {
		
		// initialize result variable
		boolean valid = false;
		
		// if image was passed
		if (imageArray.length > 0 ) {

			valid = imageService.getImageType(imageArray) == "JPEG";
		
		} else {
			valid = true;
		}
				
		return valid;

	}

}