Hibernate / Spring boot: when I update a product, I successfully update the variable I want to modify but the image disappears (which is of type blob) - spring-boot

Question

I am trying to update a product in Postman by changing only the name; when I do this, the name is updated successfully but I notice that the product photo (blob type) that was previously saved when the object was inserted disappears (it is automatically set to null).
How can I solve this problem?
Thank you all
Product.java
import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.Lob;
import javax.persistence.Table;
import Model.Product;
#Entity
#Table(name="product")
public class Product {
#Id
private String prodcode;
private String name;
#Lob
private byte[] photo;
public Product() {
}
public Product(String prodcode, String name, byte[] photo) {
this.prodcode = prodcode;
this.name = name;
this.photo = photo;
}
public String getProdcode() {
return prodcode;
}
public void setProdcode(String prodcode) {
this.prodcode = prodcode;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public byte[] getPhoto() {
return photo;
}
public void setPhoto(byte[] photo) {
this.photo = photo;
}
Product_DAO_Imp.java
package DAO;
import java.util.List;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.query.Query;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Repository;
import Model.Product;
#Repository
public class Product_DAO_Imp implements Product_DAO{
#Autowired
private SessionFactory sessionFactory;
#Override
public boolean updateProduct(Product product) {
boolean status=false;
try {
sessionFactory.getCurrentSession().update(product);
status=true;
} catch (Exception e) {
e.printStackTrace();
}
return status;
}
// ....
// ....
// ....
}
Product_Service_Imp
package Service;
import java.util.List;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;
import org.springframework.util.StringUtils;
import org.springframework.web.multipart.MultipartFile;
import java.io.IOException;
import DAO.Product_DAO;
import Model.Product;
#Service
#Transactional
public class Product_Service_Imp implements Product_Service {
#Autowired
private Product_DAO productdao;
#Override
public boolean updateProduct(Product product) {
return productdao.updateProduct(product);
}
// ....
// ....
// ....
}
Controller.java
import java.io.IOException;
import java.util.List;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.CrossOrigin;
import org.springframework.web.bind.annotation.DeleteMapping;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.multipart.MultipartFile;
import Model.Product;
import Service.Product_Service;
#RestController
#CrossOrigin(origins="http://localhost:4200")
#RequestMapping(value="/api")
public class Controller {
#Autowired
private Product_Service productservice;
#PostMapping("update-product/{prodcode}")
public boolean updateProduct(#RequestBody Product product,#PathVariable("prodcode") String prodcode) {
product.setProdcode(prodcode);
return productservice.updateProduct(product);
}
// ....
// ....
// ....
}

Answer 1

You can follow load and save approach to do the desired
It follows below steps
Read the row from DB, using prodcode
update the fields in the above read object and update
You can update the below method in the your Product_DAO_Imp.java
#Override
public boolean updateProduct(Product product) {
boolean status=false;
try {
Product productFrmDb = sessionFactory.getCurrentSession().get(Product.class,product.getProdcode());
productFrmDb.setName(product.getName());
sessionFactory.getCurrentSession().update(productFrmDb);
status=true;
} catch (Exception e) {
e.printStackTrace();
}
return status;
}