Kotlin + SpringBoot JPA + MySQL- Save/retrieve Files/Images with @Lob annotation

In the tutorial, JavaSampleApproach will show you how to create a SpringBoot Kotlin project that uses SpringJPA with @Lob annotation to save Files/Images to MySQL database.

I. Technologies

– Kotlin 1.2.20
– Apache Maven 3.5.2
– Spring Tool Suite – Version 3.9.0.RELEASE
– MySQL
– Spring Boot – 1.5.10.RELEASE

II. Goal

– We create a SpringBoot project to save files/images to MySQL database as below structure:

Create MySQL table:

-> Run and check results:

III. Practice

Step to do:
– Create SpringBoot Kotlin project
– Create data model
– Create JPA Repository
– Implement Client to save/retrieve files/images
– Configure JPA connection & MySQL script

1. Create SpringBoot Kotlin project

Using SpringToolSuite to create a SpringBoot project with dependencies:

<dependency>
	<groupId>org.springframework.boot</groupId>
	<artifactId>spring-boot-starter-data-jpa</artifactId>
</dependency>
 
<dependency>
	<groupId>mysql</groupId>
	<artifactId>mysql-connector-java</artifactId>
	<scope>runtime</scope>
</dependency>

2. Create data model

package com.javasampleapproach.kotlin.springboot.saveimage2mysql.model

import javax.persistence.Column
import javax.persistence.Entity
import javax.persistence.Id
import javax.persistence.Lob
import javax.persistence.Table

@Entity
@Table(name="image_model")
data class ImageModel(
			@Id
		    @Column(name = "id")
		    val id: Long,
			
		    @Column(name = "name")
			val name: String,
		    
		    @Column(name = "type")
			val type: String,
			
			@Lob
		    @Column(name="pic")
		    val pic: ByteArray
){
	private constructor(): this(-1, "", "", byteArrayOf())
}

3. Create JPA Repository

package com.javasampleapproach.kotlin.springboot.saveimage2mysql.jpa

import org.springframework.data.jpa.repository.JpaRepository;
 
import com.javasampleapproach.kotlin.springboot.saveimage2mysql.model.ImageModel
 
interface ImageRepository: JpaRepository

4. Implement Client to save/retrieve files/images

package com.javasampleapproach.kotlin.springboot.saveimage2mysql

import java.nio.file.Files
import java.nio.file.Paths

import org.springframework.boot.SpringApplication
import org.springframework.boot.autoconfigure.SpringBootApplication
import org.springframework.core.io.ClassPathResource

import org.springframework.context.annotation.Bean
import org.springframework.boot.CommandLineRunner
import com.javasampleapproach.kotlin.springboot.saveimage2mysql.jpa.ImageRepository
import com.javasampleapproach.kotlin.springboot.saveimage2mysql.model.ImageModel

@SpringBootApplication
class KotlinSpringBootSaveImage2MySqlApplication{
	
	@Bean
	fun imageProcess(imageRepository: ImageRepository) = CommandLineRunner {
		// image 1
		val backImgFile = ClassPathResource("image/jsa_about_img_black_background.png")
		var arrayPic = ByteArray(backImgFile.contentLength().toInt())	
		backImgFile.getInputStream().read(arrayPic);
		val blackImage = ImageModel(1, "JSA-ABOUT-IMAGE-BLACK-BACKGROUND", "png", arrayPic)
		
		// image 2
		val blueImgFile = ClassPathResource("image/jsa_about_img_blue_background.png")
		arrayPic = ByteArray(blueImgFile.contentLength().toInt())
		blueImgFile.getInputStream().read(arrayPic)
		val blueImage = ImageModel(2, "JSA-ABOUT-IMAGE-BLUE-BACKGROUND", "png", arrayPic)
		
		// store image to MySQL via SpringJPA
		imageRepository.save(blackImage);
		imageRepository.save(blueImage);
		
		// retrieve image from MySQL via SpringJPA
		imageRepository.findAll().forEach{
			imageModel ->
					Files.write(Paths.get("retrieve-dir/" + imageModel.name + "." + imageModel.type), imageModel.pic);
		}
	}
}

fun main(args: Array) {
    SpringApplication.run(KotlinSpringBootSaveImage2MySqlApplication::class.java, *args)
}

5. Configure JPA connection & MySQL script

5.1 Configure connection info

– Open application.properties file, add connection info:

spring.datasource.url=jdbc:mysql://localhost:3306/testdb?useSSL=false
spring.datasource.username=root
spring.datasource.password=12345

5.2 MySQL script

– Implement MySQL creating table script:

CREATE TABLE image_model(
   id BIGINT NOT NULL,
   name VARCHAR(100) NOT NULL,
   type VARCHAR(10) NOT NULL,
   pic BLOB NOT NULL,
   PRIMARY KEY (id)
);

IV. Sourcecode

KotlinSpringBootSaveImage2MySQL

Last updated on April 13, 2021.