Springboot Mapping and DTO

I'm new to Spring and I'm encountering a lot of doubts when making an insertion of the example below.
I currently have three tables whose models are those below:

@Entity
@Table(name = "namespace")
public class Namespace {
	
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Integer id;

    @NotNull
    @Size(max = 100)
    @Column(unique = true)
    private String namespacename;
}

@Entity
@Table(name = "services")
public class Services {
	
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Integer id;

    @NotNull
    @Size(max = 100)
    @Column(unique = true)
    private String servicename;
}

@Entity
@Table(name = "historiquedeploiement")
public class HistoriqueDeploiement {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Integer id;    

    @ManyToOne(fetch = FetchType.LAZY, optional = false)
    @JoinColumn(name = "idnamespace", nullable = false)    
    @JsonIdentityInfo(generator=ObjectIdGenerators.PropertyGenerator.class, property="id")
    @JsonIdentityReference(alwaysAsId=true)
    @JsonProperty("idnamespace")
    private Namespace namespace;
    
    @ManyToOne(fetch = FetchType.LAZY, optional = false)
    @JoinColumn(name = "idservices", nullable = false)    
    @JsonIdentityInfo(generator=ObjectIdGenerators.PropertyGenerator.class, property="id")
    @JsonIdentityReference(alwaysAsId=true)
    @JsonProperty("idservices")
    private Services services;

    @NotNull
    @Size(max = 100)
    @Column(unique = true)
    private String tagvalue;
}

And this is my DTO :

public class HistoriqueDeploiementReadingDTO {
	    @NotNull
	    private Integer id;

	    @NotNull
	    private String namespacename;

	    @NotNull
	    private String servicename;
	    
	    @NotNull
	    private String tagvalue;

}

So the problem is :
I receive an object of type HistoriqueDeploiementReadingDTO and i have to insert it in historiquedeploiement table.
The problem is that i receive "namespacename", "servicename" and i need to save the id of each one that i can find in the table namespace and service.

When i have the id of each one, i can save it in historiquedeploiement table.

I hope you understand that little problem and hope you can purpose me something
Thanks !

You have 2 ways:

First of all

if relation is many to one your field is List of services and List of namespaces instead services and namespaces.

if you mean OneToOne

HistoriqueDeploiementReadingDTO historiqueDeploiementReadingDTO;

NameSpace nameSpace = new Namespace();
namespace.setNameSpaceName(historiqueDeploiementReadingDTO.getNameSpaceName());

Services service = new Service();
service.setServicename(historiqueDeploiementReadingDTO.getServiceName())

HistoriqueDeploiement historiqueDeploiement = new HistoriqueDeploiement;
historiqueDeploiement.setTagValue(historiqueDeploiementReadingDTO.getTagValue())
historiqueDeploiement.setService(service)
historiqueDeploiement.setNameSpaceName(nameSpace)

IHistoriqueDeploiementRepository.save(historiqueDeploiement);

2 -

You should first validate what you receive(against db records of each table). More or less the following will give you a highlight, so you should do for the others too.
Don't forget that all should be on the same transaction.

== updated==

@Transactional(rollbackFor=Exception.class) 
public boolean saveHistoriqueDeploiement(HistoriqueDeploiementReadingDTO  dto) {
	Services service = getServices(dto.getServicename());
	// do the same for the others

	HistoriqueDeploiement deploiment = new HistoriqueDeploiement();
	deploiment.setService(service);
	//same for the others

	deploiementRepository.save(deploiment);
}

public Services getServices(String serviceName) {
	Services service = serviceRepository.findByServicename(serviceName); //if it exists, use the existing

	if(service == null) {
		service = new Services();
		service.setServicename(dto.getServicename());
		service = serviceRepository.save(service);
	}
	
	return service;
}