I have an entity0 and it has 2 navigation properties created through ABP Suite. 1 is one to many relationship with entity1 and other is many to many relationship with entity2. When I'm making a call to get a list of entity0, it returns all values except for entity2 and within the repository I found that it assigns empty entity2 list without any query generated to get entity2. I know how this can be handled manually but why ABP suite is generating empty result for entity2. What needs to be changed in ABP suite to generate query for entity2 in below method?
protected virtual async Task> GetQueryForNavigationPropertiesAsync()
{
return from entity0 in (await GetDbSetAsync())
join entity1 in (await GetDbContextAsync()).Entities1 on entity0.entity1Id equals entity1.Id into entities1
from entity1 in entities1.DefaultIfEmpty()
select new entity0WithNavigationProperties
{
Entity0 = entity0,
Entity1 = entity1,
Entity2 = new List()
};
}
Related
I created a back API with Symfony and a front with React. To communicate between back and front I'm using API PLATFORM.
I created in Symfony one entity "users" and one entity "customers" with a relation OneToOne. In React when I create a new Customer I automatically create a new User for the same person. This works perfectly.
In my table Customer a column "user_id" has been automatically created by the relation. In this column I find the id of user which corresponds to the customer.
Via react I need to do a request with API Platform in direction of the Entity User to find the id of the customer which corresponds to the User. I don't have a column client_id because I made the relation OneToOne in the client entity.
I can't find the solution.
You have to complete your entity, by default a OneToOne relation is not bidirectionnal, adding cascade persist and above all JoinColumn on the two sides:
class Customer
{
/**
* #ORM\OneToOne(targetEntity=User::class, inversedBy="customer", cascade={"persist", "remove"})
* #ORM\JoinColumn(name="user_id", referencedColumnName="id", onDelete="SET NULL")
*/
private $user;
// getters / setters
}
class User
{
/**
* #ORM\OneToOne(targetEntity=Customer::class, mappedBy="customer", cascade={"persist", "remove"})
* #ORM\JoinColumn(name="customer_id", referencedColumnName="id", onDelete="SET NULL"))
*/
private $customer;
// getters / setters
}
then launch the command to create the migration:
php bin/console d:m:diff
I used json serialization to store list on ids in a field
Model:
public class Video
{
public int Id { get; set; }
public string Name { get; set; }
public virtual IList<int> AllRelatedIds { get; set; }
}
Context:
modelBuilder.Entity<Video>(entity =>
{
entity.Property(p => p.AllRelatedIds).HasConversion(
v => JsonConvert.SerializeObject(v, new JsonSerializerSettings { NullValueHandling = NullValueHandling.Ignore }),
v => JsonConvert.DeserializeObject<IList<int>>(v, new JsonSerializerSettings { NullValueHandling = NullValueHandling.Ignore })
);
});
It works fine, Adding, Editing, Deleting items is easy and in SQL Database it stores as json like
[11000,12000,13000]
Everything is fine BUT!! as soon as want to query on this list I get weird responses.
Where:
_context.Set<Video>().Where(t=>t.AllRelatedIds.contains(11000)) returns null however if I ask to return all AllRelatedIds items some records have 11000 value exp.
Count:
_context.Set<Video>().Count(t=>t.AllRelatedIds.contains(11000)) returns could not be translated. Either rewrite the query in a form that can be translated, or switch to client evaluation explicitly by inserting a call to either AsEnumerable(), AsAsyncEnumerable(), ToList(), or ToListAsync().
What's the matter with EF Core? I even tested t=>t.AllRelatedIds.ToList().contains(11000) but made no difference
What I should do? I don't want to have more tables, I used this methods hundreds of times but seems never queried on them.
The Json Serialization/Deserialization happens at application level. EF Core serializes the IList<int> object to value [11000,12000,13000] before sending it to database for storing, and deserializes the value [11000,12000,13000] to IList<int> object after retrieving it from the database. Nothing happens inside the database. Your database cannot operate on [11000,12000,13000] as a collection of number. To the database, its a single piece of data.
If you try the following queries -
var videos = _context.Set<Video>().ToList();
var video = _context.Set<Video>().FirstOrDefault(p=> p.Id == 2);
you'll get the expected result, EF Core is doing it's job perfectly.
The problem is, when you query something like -
_context.Set<Video>().Where(t=> t.AllRelatedIds.Contains(11000))
EF Core will fail to translate the t.AllRelatedIds.Contains(11000) part to SQL. EF Core can only serialize/deserialize it because you told it to (and how). But as I said above, your database cannot operate on [11000,12000,13000] as a collection of integer. So EF Core cannot translate the t.AllRelatedIds.Contains(11000) to anything meaningful to the database.
A solution will be to fetch the list of all videos, so that EF Core can deserialize the AllRelatedIds to IList<int>, then you can apply LINQ on it -
var allVideos = _context.Set<Video>().ToList();
var selectedVideos = allVideos.Where(t=> t.AllRelatedIds.Contains(11000)).ToList();
But isn't fetching ALL videos each time unnecessary/overkill or inefficient from performance perspective? Yes, of course. But as the comments implied, your database design/usage approach has some flaws.
I wanted to know if the {save} method in CrudRepository do an update if it finds already the entry in the database like :
#Repository
public interface ProjectDAO extends CrudRepository<Project, Integer> {}
#Service
public class ProjectServiceImpl {
#Autowired private ProjectDAO pDAO;
public void save(Project p) { pDAO.save(p); } }
So if I call that method on an already registred entry, it'll update it if it finds a changed attribute ?
Thanks.
I wanted to know if the {save} method in CrudRepository do an update
if it finds already the entry in the database
The Spring documentation about it is not precise :
Saves a given entity. Use the returned instance for further operations
as the save operation might have changed the entity instance
completely.
But as the CrudRepository interface doesn't propose another method with an explicit naming for updating an entity, we may suppose that yes since CRUD is expected to do all CRUD operations (CREATE, READ, UPDATE, DELETE).
This supposition is confirmed by the implementation of the SimpleJpaRepository
class which is the default implementation of CrudRepository which shows that both cases are handled by the method :
#Transactional
public <S extends T> S save(S entity) {
if (entityInformation.isNew(entity)) {
em.persist(entity);
return entity;
} else {
return em.merge(entity);
}
}
So if I call that method on an already registered entry, it'll update
it if it finds a changed attribute?
It will do a merge operation in this case. So all fields are updated according to how the merging cascade and read-only option are set.
Looking at the default implemantation of CrudRepository interface
/*
* (non-Javadoc)
* #see org.springframework.data.repository.CrudRepository#save(java.lang.Object)
*/
#Transactional
public <S extends T> S save(S entity) {
if (entityInformation.isNew(entity)) {
em.persist(entity);
return entity;
} else {
return em.merge(entity);
}
}
Save method manage two situations:
-If the person Id is null (a new entity is created) then save will call persist method => insert query will be executed.
-If the person id is not null then save will call merge: fetch the existing entity from entityManagerFactory(from the 2 level cache if it doesn't exist then it will be fetched from the database) and comparing the detached entity with the managed and finally propagate the changes to the database by calling update query.
To be precise, the save(obj) method will treat obj as a new record if the id is empty (therefore will do an insert) and will treat obj as an existing record if the id is filled in (therefore will do the merge).
Why is this important?
Let's say the Project object contains an auto-generated id and also a person_id which must be unique. You make a Project object and fill in the person_id but not the id and then try to save. Hibernate will try to insert this record, since the id is empty, but if that person exists in the database already, you will get a duplicate key exception.
How to handle
Either do a findByPersonId(id) to check if the obj is in the db already, and get the id from that if it is found,
Or just try the save and catch the exception in which case you know it's in the db already and you need to get and set the id before saving.
I wanted to know if the {save} method in CrudRepository do an update if it finds already the entry in the database:
The Answer is Yes, It will update if it finds an entry:
From Spring Documentation: Herehttps://docs.spring.io/spring-data/jpa/docs/1.5.0.RELEASE/reference/html/jpa.repositories.html?
Saving an entity can be performed via the CrudRepository.save(…)-Method. It will persist or merge the given entity using the underlying JPA EntityManager. If the entity has not been persisted yet Spring Data JPA will save the entity via a call to the entityManager.persist(…)-Method, otherwise the entityManager.merge(…)-Method will be called.
In my case I had to add the id property to the Entity, and put the annotation #Id like this.
#Id
private String id;
This way when you get the object has the Id of the entity in the database, and does the Update operation instead of the Create.
TL;DR What is the proper way of rehydrating an entity framework object with a self referential many to many relationship from a DTO and updating it with the new values so that the database updates correctly?
I have the following entity (irrelevant stuff trimmed)
public class Role
{
[Key]
[Required]
public String RoleId { get; set; }
public List<Role> Children { get; set; }
}
In my dbContext, I have set up a many to many relationship
modelBuilder.Entity<Role>().HasMany(r => r.Children).WithMany();
I'm using MVC front end, with a web-api backend for an n-tier setup, and an mssql database.
The following chain of events happens
Browser->MVC Controller->REST call to Web API->WebAPI Controller->DB Context Query
This chain happens twice, once to view the page in edit mode, and then again when the user pushes the save button to persist.
When setting children on the entity, they always already exist first (IE, you don't create the parent and the children at the same time, you are just adding an existing child to a parent)
There is a DTO used by the MVC model and web API, which I re-hydrate to the entity on the web-api side.
public IHttpActionResult UpdateRoleInfo(RoleVM roleInfo){
//lookup existing entity to update
var existing = db.Roles.FirstOrDefault(y => y.RoleId == roleInfo.ExistingRoleId);
...Something happens here (see below for things i've tried)...
db.SaveChanges();
}
My first try was this :
existing.Children = roleInfo.Children
This tried to recreate all of the existing children as part of the save. (Primary key constraint violation on the roles table)
I changed that to
//Fetch all of the roles from the database to lookup the existing children
var allRoles = GetRoles();
//Have to reselect the roles from the DB so the DB doesn't try to recreate new ones for the children.
var childrenToAdd = roleInfo.Roles.Select(role2 => allRoles.FirstOrDefault(r => r.RoleId == role2.RoleId)).ToList();
existing.Children = childrenToAdd;
This correctly works for updating a role that does not already have any children, to add some the first time, but if you update a role that already has children, it tries to re-add the children to the database a second time, getting a primary key violation on the roles_role table
I then tried pre-pending this code to the second one above,
existing.Children.Clear();
db.SaveChanges();
I would expect this to delete all the existing parent-child relationships from the many to many table for this parent, and then recreate them with the new children. Why not?
TL;DR What is the proper way of rehydrating an entity framework object with a self referential many to many relationship from a DTO and updating it with the new values so that the database updates correctly?
Try turning off auto detect changes (before retrieving from the DB) via
context.Configuration.AutoDetectChangesEnabled = false;
Then set the state to modified on the specific role object you are updating
context.Entry(role).State = EntityState.Modified;
Haven't tried this myself on a self-referencing many-to-many table, but adding & updating entities in the manner can save all sorts of headaches where EF incorrectly infers what you are adding/updating
Found the problem.
On the initial load of the entity, I was using an include statement to eager load the children.
When I updated the entity, when I fetched it from the db again, I did not eager load the children. Therefore the additions/updates were getting confused. Once I put the include in during the upload Scenario #2 above worked (the explicit clear was not needed)
db.Roles.Include("Children").FirstOrDefault(z => z.RoleId == RoleId);
Also related, if you have this same problem when dealing with relationships across different tables, make sure all the entities that are involved in the graph are from the same DB context!
https://msdn.microsoft.com/en-us/magazine/dn166926.aspx
I'm currently developing a mobile application who uses a Google App Engine-hosted web service.
But i'm facing an issue. I just want to add a field in one my database's table.
App Engine doesn't use classic SQL syntax, but GQL. So i cannot use the ALTER TABLE statement. How can i do this with GQL ? I looked for a solution on the web, but there's not a lot of help.
public MyEntity() {
}
#Id
#GeneratedValue(strategy=GenerationType.IDENTITY)
private Key idStation;
private String name;
private double longitude;
private double latitude;
private java.util.Date dateRefresh = new Date(); //the field i want to add in DB
So, now when i create a "MyEntity" object, it should add the "dateRefresh" field into the database... I create my object like this:
MyEntity station = new MyEntity();
station.setName("test");
station.setLatitude(0);
station.setLongitude(0);
station.setDateRefresh(new Date("01/01/1980"));
DaoFactory.getStationDao().addStation(station);
addStation method:
#Override
public MyEntity addStation(MyEntity station) {
EntityManager em = PersistenceManager.getEntityManagerFactory().createEntityManager();
try {
em.getTransaction().begin();
em.persist(station);
em.getTransaction().commit();
} finally {
if(em.getTransaction().isActive()) em.getTransaction().rollback();
em.close();
}
return station;
}
The field "dateRefresh" is never created into my DB...
Someone to help me please ?
Thanks in advance
Just add another field to your data structure, maybe providing a default clause, and that's all. For example, if you have a UserAccount:
class UserAccount(db.Model):
user = db.UserProperty()
user_id = db.StringProperty()
you may easily add:
class UserAccount(db.Model):
user = db.UserProperty()
user_id = db.StringProperty()
extra_info = db.IntegerProperty(default=0)
timezone = db.StringProperty(default="UTC")
and let it go.
While the datastore kinda mimics tables, data is stored on a per entity basis. There is no schema or table.
All you need to do is update your model class, and new entities will be saved with the structure (fields) of the new entity.
Old entities and indexes, however, are not automatically updated. They still have the same fields as they had when they were originally written to the datastore.
There's two ways to do this. One is to make sure your code can handle situations where your new properties are missing, ie make sure no exceptions are thrown, or handle the exceptions properly when you're missing the properties.
The second way is to write a little function (usu a mapreduce function) to update every entity with appropriate or null values for your new properties.
Note that indexes are not updated unless the entity is written. So if you add a new indexed property, old entities won't show up when you query for the new property. In this case, you must use the second method and update all the entities in the datastore so that they are indexed.