I don't know how to save a record in SDR with a link to an existing table.
For example:
There is a lookup-table Flag and another table Account with name and n:1 relation to Flag-ID.
The IDs in Flag-table are already created.
#Entity
public class Account{
public Account(String name, Flag flag){
this.name = name;
this.flag = flag;
}
#Id
private int id;
#Column
private String name;
#ManyToOne
private Flag flag;
// Getter & Setter
}
#Entity
public class Flag{
public Flag(String title){
this.title = title;
}
#Id
private int id;
#Column
private String title;
// Getter & Setter
}
Now I want to add an account and link it to the flag-id like this:
AccountRepo accountRepo;
accountRepo.save(new Account("Name", 0));
But I declared an object in my account-function and if I want to execute the save-function, I have to add a flag-object like this:
accountRepo.save(new Account("Name", new Flag("title")));
However in this case, the framework will add a new Flag-record, what I don't want. I only want to link it.
So I need help for solving my problem.
Thanks!
Edit:
The two answers from #piotr-sołtysiak and #upesh-m helped and worked for me. Thanks for your help!
You can use 'merge' of hibernate, ie. entityManager.merge(new Account("Name", new Flag("title"))). But the Id of the Flag should be an existing Id , so that it just adds an entry to Account.
ie. If you already have a flag record existing in db with id = 1, and you want to add an account linked to this flag, then use entityManager.merge(new Account("Name", existingFlagObject)
Find desired flag entity using dedicated repository, e.g
Flag flag = flagRespository.findByTitle("title");
Set it in Account entity and save:
accountRepo.save(new Account("Name", flag));
Related
I see in most of the coders save data(using spring data) as:
savedEntity = repo.save(savedEntity);
Long id = savedEntity.getId();
I am confused about why most of them assign back the returned value to the saved Entity while the following code also works exact(I have tested myself):
repo.save(savedEntity);
Long id = savedEntity.getId();
Did I miss some benefit of assigning back?
for example, let the entity be:
#Entity
public class SavedEntity {
#Id
private int id;
private String name;
//getter, setters, all arg-constructor, and no-arg constructor
}
Consider the object of SavedEntity is
SavedEntity entity = new SavedEntity(1,"abcd");
now for your first question,
SavedUser entity1 = repo.save(entity);
Long id = entity1.getId();
this entity1 object is the return object getting from the database, which means the above entity is saved in the database succesfully.
for the Second Question,
repo.save(entity);
Long id = entity.getId();//which you got it from SavedEntity entity = new SavedEntity(1,"abcd");
here the value of id is the integer you mentioned in place of id(the raw value).
Most of the time the id (primary key) is generated automatically while storing the entity to the database using strategies like AUTO, Sequence etc. So as to fetch those id's or autogenerated primary key values we assign back the saved entity.
For example:
#Entity
public class Customer {
#Id
#GeneratedValue(strategy=GenerationType.AUTO)
private Long id;
private String firstName;
private String lastName;
}
In this case you'll not pass the id externally but it will create a value for it automatically while storing the data to DB.
I am using Spring Data's Rest Repositories from spring-boot-starter-data-rest, with Couchbase being used as the underlining DBMS.
My Pojo for the object is setup as so.
#Document
public class Item{
#Id #GeneratedValue(strategy = UNIQUE)
private String id;
#NotNull
private String name;
//other items and getters and setters here
}
And say the Item has an id of "xxx-xxx-xxx-xxx" and name of "testItem".
Problem is, that when I want to access the item, I need to be accessible by /items/testItem, but instead it is accessible by /items/xxx-xxx-xxx-xxx.
How do I get use its name instead of its generated id, to get the data.
I found out the answer to my own question.
I just need to override the config for the EntityLookup.
#Component
public class SpringDataRestCustomization extends RepositoryRestConfigurerAdapter {
#Override
public void configureRepositoryRestConfiguration(RepositoryRestConfiguration config) {
config.withEntityLookup().forRepository(UserRepository.class).
withIdMapping(User::getUsername).
withLookup(UserRepository::findByUsername);
}
}
Found the info here, though the method name changed slightly.
https://github.com/spring-projects/spring-data-examples/tree/master/rest/uri-customization
If you want query the item by name and want it perform as querying by id,you should make sure the name is unique too.You cant identify a explicit object by name if all objects have a same name,right?
With jpa you could do it like:
#NotNull
#Column(name="name",nullable=false,unique=true)
private String name;
I get an Post request that would give me a List<PersonApi> Objects
class PersonApi {
private String name;
private String age;
private String pincode ;
}
And I have an Entity Object named Person
#Entity
#Table(name = "person_master")
public class Person{
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
Long id;
#Column(name = "name")
String name;
#Column(name = "age")
String age;
#Column(name = "pincode ")
String pincode ;
}
My record from Post request would look something like this (pseudocode representation of the data below)
[
"Arun","33","09876gh"
"James","34","8765468"
]
I need to do a bulk-validation using Spring JPA.. Give the List<PersonApi> and get a True or False based on the condition that all the entries in the PersonApi objects list should be there in the database.
How to do this ?
The selected answer is not a right one. (not always right)
You are selecting the whole database to check for existence. Unless your use case is very special, i.e. table is very small, this will kill the performance.
The proper way may start from issuing repository.existsById(id) for each Person, if you never delete the persons, you can even apply some caching on top of it.
exists
Pseudo Code:
List<PersonApi> personsApiList = ...; //from request
List<Person> result = personRepository.findAll();
in your service class you can access your repository to fetch all database entities and check if your list of personapi's is completeley available.
boolean allEntriesExist = result.stream().allMatch(person -> personsApiList.contains(createPersonApiFromPerson(person)));
public PersonApi createPersonApiFromPerson(Person person){
return new PersonApi(person.getName(), person.getAge(), person.getPincode());
}
i'm new to Javers, and i`m currently using it to create a patch update for my entity. But i'm having some struggle with one specific scenario
I want to compare a Entity against a EntityDTO/VO and get only the changes in values, the current comparison only returns that is a NewObject and ObjectRemoved changes.
Example:
public class Entity{
private ObjectId id;
private String name;
private String description;
}
public class EntityDTO{
private String name;
}
//
Entity oldState = new Entity(new ObjectId(), "oldName" , "oldDescription);
EntityDTO newState = new EntityDTO( "newName" );
JaversBuilder.javers().build().compare(oldState, newState).getChanges();
//This is returning only NewObject/ObjectRemoved changes, and the intended is to be ValueChange/ReferenceChange
The questions is, is there a way to compare only the similar attributes between the objects?
No, in JaVers, you can compare only objects of the same type.
I am not so into Spring Data JPA and I have the following doubt about how to implement a simple query.
I have this AccomodationMedia entity class mapping the accomodation_media on my database:
#Entity
#Table(name = "accomodation_media")
public class AccomodationMedia {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
#Column(name = "id")
private Long id;
#Column(name = "id_accomodation")
private Long idAccomodation;
#Column(name = "is_master")
private boolean isMaster;
#Lob
#Column(name = "media")
private byte[] media;
private String description;
private Date time_stamp;
public AccomodationMedia() {
}
...............................................................
...............................................................
...............................................................
// GETTER AND SETTER METHODS
...............................................................
...............................................................
...............................................................
}
The instance of this class represents the photo associated to an accomodation (an hotel)
So as you can see in the prvious code snippet I have this field :
#Column(name = "id_accomodation")
private Long idAccomodation;
that contains the id of an accomodation (the id of an hotel on my database).
I also have this boolean field that specify if an image is the master image or not:
#Column(name = "is_master")
private boolean isMaster;
So, at this time, in my repository class I have this method that should return all the images associated to a specific hotel:
#Repository
public interface AccomodationMediaDAO extends JpaRepository<AccomodationMedia, Long> {
List<AccomodationMedia> findByIdAccomodation(Long accomodationId);
}
I want to modify this method passing also the boolean parameter that specify if have to be returned also the master image or only the images that are not master.
So I tryied doing in this way:
List<AccomodationMedia> findByIdAccomodationAndIsMaster(Long accomodationId, boolean isMaster);
but this is not correct because setting to true the isMaster parameter it will return only the master image (because it is first selecting all the Accomodation having a specific accomodation ID and then the one that have the isMaster field setted as true).
So, how can I correctly create this query that use the isMaster boolean parameter to include or exclude the AccomodationMedia instance that represent my master image?
I know that I can use also native SQL or HQL to do it but I prefer do it using the "query creation from method names"
I don't have how to test this, but essentially your final query should be:
id_accomodation = ?1 AND (is_master = ?2 OR is_master = false)
So I would try the following method signature:
findByIdAccomodationAndIsMasterOrIsMasterFalse(Long accomodationId, boolean isMaster);
I would go with two methods one for isMaster true, while second for false value like this:
List<AccomodationMedia> findByIdAccomodationAndIsMasterFalse(Long accomodationId);
List<AccomodationMedia> findByIdAccomodationAndIsMasterTrue(Long accomodationId);
Change your acommodation id as accomodationId instead of idAccomodation. When you write findByIdAccomodationAndIsMaster spring confusing findByIdAccomodationAndIsMaster
Try this this convention
#Column(name = "accomodation_id")
private Long accomodationId;