I was studying about Context Class and the functions it is responsible for;
What does it mean that Context class is reponsible for :to materialize the raw data returned from the database as entity objects??
Related
What is the difference between a Container and Context in Entity Framework and how they are related? I cannot find the explanation. Someone talks like they are the same. Someone talks about first or second, but never in compare. Thanks.
Check the below link.
Container:
An entity container is a logical grouping of entity sets, association sets, and function imports.
Context:
The Entity Framework enables you to query, insert, update, and delete data, using common language runtime (CLR) objects (known as entities). The Entity Framework maps the entities and relationships that are defined in your model to a database. The Entity Framework provides facilities to do the following: materialize data returned from the database as entity objects; track changes that were made to the objects; handle concurrency; propagate object changes back to the database; and bind objects to controls.
Container VS Context
I was reading a question about EJBContext.setRollbackOnly() method in a mock exam, one of the accepted answers is
It cannot be used by JPA Entities. [because] Entities do not have EJBContext. Remember that persistent entities are not same as Entity Beans. Entity Beans do not exist in EJB 3.x.
API reference states that
The EntityContext interface provides an instance with access to the container-provided runtime context of an entity bean instance.
and EntityContext extends EJBContext.
Now, what does it mean that persistent entities are not same as Entity Beans?
I've been scouring the net, but haven't found anything useful. I have a POCO class that I want to wire up to a stored procedure in Entity Framework 6.x. I've see how to do it in the Fluent API for Inserts, Updates, and Deletes.... but not for just straight Reading.
I found this: EF 6 Code First Stored Procedure - Read Only, but it looks like it's just a method on some controller somewhere.
Is there a way where I can call the context like I would any other Entity. I.E.,
ctx.Products.Where( p => p.ProductId == productId )?
I would approach this is one of two ways.
Domain / POCO mapping
If the underlying issue is a mismatch between your Entity Framework model POCO's and your (presumably purely logical) domain, I would match the EF model directly to the database schema and them map them across to domain types accordingly. I.e have a separate domain model to your EF poco's. The mapping work previously done by your proc would then be done within the domain mapper.
Abstract DbContext usage behind Repositories
Rather than having consumers directly query the context, you could abstract the context behind entity repositories and map between a SqlQuery calling a proc and your POCO's in the repository methods
E.g. here is some rough code:
public class MyEntityRepository()
{
public ICollection<MyEntity> GetAll()
{
return _myContext.SqlQuery<MyEntity>("exec myProc", params);
}
}
Neither of these options would be quick to implement and introduce into your codebase though.
If i havea JPA class Person and Person has reference to a JPA class Address. If I call Person.persist(), will Address.persist() be called implicitly?What if the hierarchy was longer. Would all the child classes be persisted implicitly?
From the JPA specification:
The semantics of the persist operation, applied to an entity X are as
follows: ...
the persist operation is cascaded to entities referenced by X, if the relationships from X to these other entities is annotated with the
cascade=PERSIST or cascade=ALL annotation element value or speciļ¬ed
with the equivalent XML descriptor element.
I am having trouble in understanding what is the difference between the service context and the object context.
I mean, where are they used? What is the basic difference?
ObjectContext is a class that is
generated inside the generated
DomainService class that you made.
while
Object Services is a component of the Entity Framework that enables you to query, insert, update, and delete data, expressed as strongly typed CLR objects that are instances of entity types. Object Services supports both Language-Integrated Query (LINQ) and Entity SQL queries against types that are defined in an Entity Data Model (EDM). Object Services materializes returned data as objects, and propagates object changes back to the data source. It also provides facilities for tracking changes, binding objects to controls, and handling concurrency. Object Services is implemented by classes in the System.Data.Objects and System.Data.Objects.DataClasses namespaces.