Imagine i have an entity like this:
#Entity
#Getter
#Setter
#ToString
#Table(name = "employeeSalary")
public class EmployeeSalary{
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private long id;
#Column(name = "fullName", nullable = false, length = 60)
private String fullName;
#Column(name = "salary", nullable = false)
private double salary;
#Column(name = "month", nullable = false)
#Enumerated(EnumType.STRING)
private Month month;
#Column(name = "year", nullable = false)
private Year year;
}
Now imagine i created DTO like this:
#Data
#NoArgsConstructor
#AllArgsConstructor
public class EmployeeSalaryDTO {
private String fullName;
private double salary;
private Month month;
private Year year;
}
The Question is following: is creating DTO in this case really a good practice? as we can see both DTO and entity is the same (the only difference is that DTO does not have id, but lets imagine adding id also in this DTO) does it make any sense to create this DTO. Because as i know its not a good idea to manipulate entity in service layer, its a better option to manipulate DTO and then convert this DTO to entity, but as we see DTO and entity are identically the same, so does it make any sense to create DTOs when we have 100% similarity in these two classes? Or is it a good practice to create them anyway? (because manipulating entity in service layer is not a good idea, better is to manipulate dto and then convert to entity)
So its a good practice to introduce another layer as DTO. Because manipulating data and operations on entity seems not a good practice. A good idea would be have manipulation of data in DTOs and then converting them to entity's using model mapper. So in a word its a good practice to have DTO even though we have exactly the same fields in entity and DTO.
Related
I know there has been multiple questions on bidirectional relations using spring jpa in the past but my case is a little bit different because i am using 3 entities with 2 relationships to implement a medical system
I have 3 entities : doctor/patient/appointment
here is the code for the 3 entities
please note all setters , getters and constructors implemented but ommited here for clarity
Patient class
#Entity
public class resPatient {
#Id
#GeneratedValue( strategy= GenerationType.IDENTITY )
private long code;
private String name;
private String gender;
private String email;
private String mobile;
private int age;
private String notes;
#OneToMany(mappedBy = "patient")
List<resPackageMembership> memberships;
#OneToMany(mappedBy = "patient")
List<resAppointment> appointments;
#OneToMany(fetch = FetchType.LAZY,mappedBy = "patient")
List<resMedImage> medImages;
Doctor class
#Entity
public class resDoctor {
#Id
#GeneratedValue( strategy= GenerationType.IDENTITY )
private long code;
private String name;
private String mobile;
private String email;
private String gender;
private int age;
private String speciality;
#OneToMany(mappedBy = "doctor")
List<resAppointment> appointments;
Appointment class
#Entity
public class resAppointment {
#Id
#GeneratedValue( strategy= GenerationType.IDENTITY )
private long code;
private String speciality;
#Basic
#Temporal(TemporalType.TIMESTAMP)
private Date dateCreated;
#Basic
#Temporal(TemporalType.TIMESTAMP)
private Date dateToVisit;
private String status;
private String notes;
#ManyToOne(fetch = FetchType.LAZY)
#JoinColumn(name = "doctorCode")
private resDoctor doctor;
#ManyToOne(fetch = FetchType.LAZY)
#JoinColumn(name = "patientCode")
private resPatient patient;
the way my medical system should work is that when i get a patient using my restful controller i want all the patient data including his appointments but this leads to an infinite loop as the appointment has the doctor which also has appointments and so on.
i cannot user #JSONIGNORE as there are 2 relationships i want to get the patient with his appointments which should have the doctor without the appointments array and should not have any patient data as i already am in the patient object
As a general best-practice, it's recommended to separate the entities from the data transfer objects used for the rest controllers. With DTO's in place, you have more control on which data to include and serialize within them to avoid the circlular references.
If you like check out https://bootify.io, it generates the DTOs from your database schema, but the custom endpoint you still need to define/build.
I develop an annotation processor called beanknife recently, it support generate DTO from any class. You need config by annotation. But you don't need change the original class. This library support configuring on a separate class. Of course you can choose which property you want and which you not need. And you can add new property by the static method in the config class. For your question:
// this will generate a DTO class named "resPatientView".
// You can change this name using genName attribute.
#ViewOf(value=resPatient.class, includePattern = ".*")
public class PatientViewConfigure {
// here tell the processor to automatically convert the property appointments from List<resAppointment> to List<resAppointmentWithoutPatient>.
// resAppointmentWithoutPatient is the generated class configured at the following.
// Note, although at this moment it not exists and your idea think it is an error.
// this code really can be compiled, and after compiled, all will ok.
#OverrideViewProperty("appointments")
private List<resAppointmentWithoutPatient> appointments;
}
// here generated a class named resAppointmentWithoutPatient whick has all properties of resAppointment except patient
#ViewOf(value=resAppointment.class, genName="resAppointmentWithoutPatient", includePattern = ".*", excludes={"patient"})
public class AppointmentWithoutPatientViewConfigure {
// the doctor property will be converted to its dto version which defined by the configure class DoctorWithoutAppointmentsViewConfigure.
#OverrideViewProperty("doctor")
private resDoctorWithoutAppointments doctor;
}
// here we generate a class which has all properties of resDoctor except appointments
#ViewOf(value=resDoctor.class, genName="resDoctorWithoutAppointments", includePattern = ".*", excludes={"appointments"})
public class DoctorWithoutAppointmentsViewConfigure {}
// in you rest controller. return the dto instead of the entities.
resPatient patient = ...
resPatientView dto = resPatientView.read(patient);
List<resPatient> patients = ...
List<resPatientView> dto = resPatientView.read(patients);
At the end, the class resPatientView will has the same shap with resPatient except its appointments not having patient property and its doctor property is replaced with a version without appointments property.
Here are more examples.
The version 1.10 is ready. Will fix some bug and support the configure bean to be managed by spring.
I've a question about One to One unidirectional Mapping in Spring Boot.
I've a Customer class with a One to One unidirectional mapping to an Address class.
But when I try to associate a new customer with an existing Address, the database is updated.
So two Customers are now associated with the one Address.
As I understand it only one Customer should be associated with one unique Address. Do I understand the concept correctly, or am I doing something wrong in Spring Boot/ Spring Data JPA/ Hibernate?
Customer
#Entity
public class Customer {
#Id
private Long cId;
private String cName;
#OneToOne(cascade = CascadeType.ALL)
#JoinColumn(name="aid")
private Address cAddr;
:
}
Address
#Entity
public class Address {
#Id
private Long aid;
private String town;
private String county;
:
}
data.sql
insert into address values (100, "New York", "NY");
insert into customer values (1, "John Smith", 100);
Application.java
#Override
public void run(String... args) throws Exception {
Customer c1 = new Customer((long)5, "Mr. Men");
Optional<Address> a100 = ar.findById((long)100);
c1.setcAddr(a100.get());
cr.save(c1);
}
Database
There are 2 options on how to make #OneToOne relation: unidirectional and bidirectional: see hibernate doc.
When you scroll down a little bit you will find the following:
When using a bidirectional #OneToOne association, Hibernate enforces the unique constraint upon fetching the child-side. If there are more than one children associated with the same parent, Hibernate will throw a org.hibernate.exception.ConstraintViolationException
It means that you'll have the exception only on fetching and when you have a bidirectional association. Because Hibernate will make an additional query to find the dependent entities, will find 2 of them, which doesn't fit #OneToOne relation and will have to throw an exception.
One way to "fix" uniqueness for your entities, is to make cAddr unique:
#OneToOne(cascade = CascadeType.ALL)
#JoinColumn(name="aid", unique=true)
private Address cAddr;
If you create your db tables, by setting hbm2ddl property this will add a unique constraint to the aid column.
I really recommend to read the following:
#OneToOne javadoc itself provides examples of how to do everything correctly (for you Examples 1 and 2 are the most useful)
Check Vlad's blog about #OneToOne. It must be the best you can find. At least jump to the chapter "The most efficient mapping" and implement it bidirectional and sharing the PK, using #MapsId.
Also maybe you will come up to the idea to use #ManyToOne option (at least i can imagine that customer can have multiple addresses)
This is not One-to-Many relation. It's One-to-Many as One object has multiple related objects. Checkout this article.
Example:
Post.java
#Getter
#Setter
#AllArgsConstructor
#NoArgsConstructor
#Entity
#Table
public class Post {
#Id
#GeneratedValue
#Column(name = "post_id")
private Long id;
#Column
private String postHeader;
#OneToMany(
cascade = CascadeType.ALL,
orphanRemoval = true
)
private List<Comment> comments = new ArrayList<>();
public void addComment(Comment comment) {
comments.add(comment);
}
public void removeComment(Comment comment) {
comments.remove(comment);
}
// equals() and hashCode()
}
Comment:
#Getter
#Setter
#AllArgsConstructor
#NoArgsConstructor
#Entity
#Table
public class Comment {
#Id
#GeneratedValue
#Column(name = "postcom_id")
private Long id;
#Column
private String text;
// equals() and hashCode()
}
Check out step "3. Uni-directional one-to-one mapping demonstration" at this site basically carbon copy of what you're trying to do.
I have a rare scenario where i have to maintain two tables say
Student_failed and Student_passed. both have exactly same schema.
#Entity
#Table(name = "student_failed")
public class StudentFailed {
#Id
#Column(name="id")
private String id;
#Column(name="student_name")
private String studentName;
#Column(name="home_town")
private String homeTown;
...
}
and
#Entity
#Table(name = "student_passed")
public class StudentPassed {
#Id
#Column(name="id")
private String id;
#Column(name="student_name")
private String studentName;
#Column(name="home_town")
private String homeTown;
...
}
as both entities are same i want to use single entity for both table. I have two different controllers that do crud operations on either of the tables.
Can i use single entity and map it to both the tables? I came across #SecondaryTables annotation but i am not sure it if will work.
PS: i know its a bad approach to keep two different tables with same fields but due to some specific requirement i am not allowed to do that).
I have two pojo classes with one-to-many relationship in hibernate
CustomerAccountEnduserOrderDetails.class
#Entity #Table(name="customer_account_enduser_order_details")
public class CustomerAccountEnduserOrderDetails implements Serializable{
private static final long serialVersionUID = 1L;
#Id
#GeneratedValue(strategy=GenerationType.AUTO)
#Column(name="id")
private Long id;
#ManyToOne(fetch=FetchType.EAGER)
#JoinColumn(name = "product_id", insertable = false, updatable = false)
private CustomerCmsProduct customerCmsProduct;
}
Second is CustomerCmsProduct.class
#Entity
#Table(name="customer_cms_product")
#JsonIgnoreProperties(ignoreUnknown = true)
public class CustomerCmsProduct {
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
#Column(name="id")
private Long id;
#Column(name="name")
private String name;
#Column(name="offer_price")
private String offerPrice;
#Column(name="original_price")
private String originalPrice;
#Column(name="discount")
private String discount;
}
Here if I fetch the object of CustomerAccountEnduserOrderDetails class,then i will get the CustomerCmsProduct class also , my problem is that here i want the specific column of CustomerCmsProduct table (not all by default i am getting all) like only id and originalPrice.
How i can do like that projection here?
In the service layer or at a webservice layer( if this is a web project) Create two different classes other than #Entity as DTO(Data Transfer Objects) which helps is data transfer from one layer to the other.
public class CustomerAccountEnduserOrderDetailsPojo {
private List<CustomerCmsProductPojo> productPojoList = new ArrayList<> ();
// getter and setter
}
public class CustomerCmsProductPojo {}
Follow the below steps
Retrieve the #Entity class data by executing the query from service layer.
Iterate over all the fields and copy only required fields to pojo layer
Expose the data to other layers using service method.
This way, we can avoid changing the custom hibernate behavior as it is linked with many parameters like cache, one to many queries that are fired per iteration.
And also, do any customization that you want in this layer. Hope this is multi layered project where you have different layers which servers different purpose.
Hi I am new to Spring Data JPA and I am wondering even though I pass the Id to the entity, the Spring data jpa is inserting instead of merge. I thought when I implement the Persistable interface and implement the two methods:
public Long getId();
public Boolean isNew();
It will automatically merge instead of persist.
I have an entity class called User like:
#Entity
#Table(name = "T_USER")
public class User implements Serializable, Persistable<Long> {
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
#Column(name = "USER_ID")
private Long id;
#Column(name = "CREATION_TIME", nullable = false)
private Date creationTime;
#Column(name = "FIRST_NAME", nullable = false)
private String firstName;
#Column(name = "LAST_NAME", nullable = false)
private String lastName;
#Column(name = "MODIFICATION_TIME", nullable = false)
private Date modificationTime;
And have another class
#Entity
#Table(name = "T_USER_ROLE")
public class UserRole implements Serializable, Persistable<Long> {
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
private Long roleId;
#Column(name = "ROLE_NAME")
private String userRole;
}
I have a custom repository called UserRepostory extending JpaReopistory. I am hitting the save for merge and persist as I see the implementation demonstrate that Spring Data Jpa uses above two methods to either update or insert.
#Repository
public interface UserRepository extends JpaRepository<User, Long> {
}
I have been trying to figure out but didn't get any clue. Maybe you
guys can help.
I ran into this issue, tried to implement Persistable to no avail, and then looked into the Spring Data JPA source. I don't necessarily see this in your example code, but I have a #Version field in my entity. If there is a #Version field Spring Data will test that value to determine if the entity is new or not. If the #Version field is not a primitive and is null then the entity is considered new.
This threw me for a long time in my tests because I was not setting the version field in my representation but only on the persisted entity. I also don't see this documented in the otherwise helpful Spring Data docs (which is another issue...).
Hope that helps someone!
By default Spring Data JPA inspects the identifier property of the given entity. If the identifier property is null, then the entity will be assumed as new, otherwise as not new. It's Id-Property inspection Reference
If you are using Spring JPA with EntityManager calling .merge() will update your entity and .persist() will insert.
#PersistenceContext
private EntityManager em;
#Override
#Transactional
public User save(User user) {
if (user.getId() == null) {
em.persist(user);
return user;
} else {
return em.merge(user);
}
}
There is no need to implement the Persistable interface.