So I was wondering how to edit an entity using Spring JPA/ Hibernate.

Below is how my model looked like: 

public class Vehicle {
    @Id
    @GeneratedValue(strategy=GenerationType.AUTO)
    private Long id;

    @Column(name="brand")
    private String brand;

    @Column(name="type")
    private String type;

    @Column(name="model")
    private String model;

    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name="owner_id",nullable=false)
    @JsonBackReference
    private Owner owner;

  //getters and setters

And this is how originally I was exposing the method for editing Vehicle:

public Vehicle editVehicleDetails(long vehicleId , Vehicle vehicle) {

    Vehicle original = vehicleRepository.findById(vehicleId).orElse(null);
    if(vehicle.getBrand()!=null) {
    original.setBrand(vehicle.getBrand());
}
//setting other attributes if not null 

In the above snippet, I am checking if the given vehicle attribute is non-null and setting it to the original. The problem with this approach is that I have to check each and every attribute for not null and then set it to the original.

So I came up with the BeanUtils for solving it. First of all, I came up a generic method to get the null fields in any object as below:

public static Set<String> getNullPropertyNames (Object source,String... extra) {
    final BeanWrapper src = new BeanWrapperImpl(source);
    java.beans.PropertyDescriptor[] pds = src.getPropertyDescriptors();

    Set<String> emptyNames = new HashSet<String>();
    for(java.beans.PropertyDescriptor pd : pds) {
        Object srcValue = src.getPropertyValue(pd.getName());
        if (srcValue == null) {
        logger.info("attribute {}",pd.getName());
        emptyNames.add(pd.getName());
        }
    }

    for(String args : extra) {
    emptyNames.add(args);
    }
    return emptyNames;
}

Here I have given a var args extra . This is to give additional functionality: Like if we want to ignore additional fields in a model, it can be provided here, which will be added to the set as well.

Now in the service layer, I used BeanUtils to copy from the source to the target.

public Vehicle editVehicleDetails(long vehicleId , Vehicle vehicle) {

    Vehicle original = vehicleRepository.findById(vehicleId).orElse(null);
    Set<String> ignoreFields = com.amoebiq.product.vehiman.controller.utils.BeanUtils.getNullPropertyNames(vehicle,"id","owner");
    BeanUtils.copyProperties(original, vehicle,ignoreFields.toArray(new String[ignoreFields.size()]));
    serviceDetailsRepository.save(service);
}

This reduced a lot of work for me, and I am using it across all my services. Hope this helps.