I use JSM serialization bundle, which is fine, in symfony 2.
The deal is that I use some User entity, on which I want to define some display var policy. The strategy is somehow the same for all the projet, but the user entity is searched through many different requests, for instance there are some community->users, or or some session->user, or some comment->owner, and if I define some expose strategy, I guess I have to do it for all the including entities, propagating threw all the parents entities.
For instance, if I have got a community entity, where I include community->owner and community->session->user, I want to be able the strategy only at the user level without adding it to session, and community. Now if i dont the serilization display nothing...
Any suggestions folks?
Related
In doctrine documentation I found: "By default, no operations are cascaded." (here http://bit.ly/1frPyLH)
But still one of my database entities is persisting it's associated objects, besides the fact that it has no cascade option in the association.
How can I prevent it from persisting the associated entities ?
It is true and the documentation is still not wrong. =P
Without going deeper on your problem, you need to be aware that by default Doctrine applies a concept called "persistence by reachability". This means that if you are creating a new entity and one of your associations is already managed by UnitOfWork (already known by Doctrine), it will "cascade" the operation.
The problem here is how you read about cascading. In reality, it's not the cascading factor that is updating the associated entity, but it's because it's already managed by Doctrine.
To solve this "problem", you need to modify the way you want Doctrine to deal with your entities by altering the Change Tracking Policy.
I hope this gives you enough information to solve your issue.
I have an entity (eg Image) which is related to many other entities (eg Product or Category). I would like to know which is the best way to prevent the removal of an entity if a relation exists somewhere else (eg I should not be able to delete an Image if it is related to a product). My thoughts are either searching for relations in a repository class and returning results, or doing 'something' at the preRemove lifecycle event of the entity. Which is the best Symfony2 way for preventing removal of related entities?
As long as cascade delete is not set, any directionally entity will prevent delete of the related entity. If your associations are not birectional, you'll have to query form the backside as well.
To expand upon CJ's answer, you may remove delete links, but you will also have to check the entity in controller as well, because any url hacker can delete an object if its id is known.
What I would suggest is you can better of disabled the form delete link when there is a relationship between entities. In that way you can even make the customer understand that there is related entity and he should not remove it before removing the relationship.
You can always check the entity before deleting it and when you actually call certain process in symfony on an entity you actually work on the entire object of that particular entity which gives access to all the values of that entity. So you can check it at that particular point and make conditional statement.
It my personal believe that you should not try to import excess library functions for minor things which can be achieved by you without them. this would make you code easier to understand and even lighter as the prospect for including extra libraries which will most likely have more than what you need
Let's say that in my ASP.NET MVC project, I have a ViewModel that is used on a form for editing a product. Among many other fields, I have a list of product types I want the user to be able to select from, in a dropdown.
When I map my domain object to my ViewModel, I'm calling a service to fetch the domain object, then using AutoMapper to map it to the ViewModel. To fill a dropdown for that list of product types, I call another service, which fetches that data from the database and uses it to populate another property on my ViewModel.
What I'm wrestling with is whether it's better to call that secondary service explicitly in the controller, versus potentially putting that call into a custom ValueResolver class and configuring my mapping to use it.
I like the prospect of removing the dependency on the product type service from my controller (because there are a lot of these, and the controller ends up with a lot of dependencies), but I'm worried that putting this sort of logic (which can hit the database) into a ValueResolver is an inappropriate use of a ValueResolver and might violate what I'd call the principle of least surprise. (I.e., I probably wouldn't expect mapping code to be causing database requests.)
Is this a common thing to use a ValueResolver for?
Answered by Jimmy Bogard on the AutoMapper Mailing List:
Yeah, it's definitely not uncommon. Drop-down list data sources....man, they're the toughest thing to figure out in our ViewModel world.
Keep in mind that you'll need to worry about the POST scenarios, refilling-in the information for validation failures, etc.
I've got to the point with Symfony 2 / Doctrine 2 where I've come to realise that we have build too much business logic in our application into services & controllers - and not enough into the model.
We wish to introduce configuration to our models (to modify behaviour) potentially giving models access to services directly in order to carry out their behaviours.
I've noticed that the following question has the completely wrong answer marked as correct with 8 upvotes - so I know the approach we have taken up to now (anaemic model) is considered the 'correct' way to do things by a lot of Symfony 2 users. After reading more into domain driven design I know this is not the case.
Symfony2 MVC: where does my code belong?
I see a lot of bundles define the behaviour in the model and extend this in entities/documents. This pattern works to a certain extent - but I think we need to introduce an additional stage. Some of the behaviour of our models is optional and having that behaviour will depend on what additional bundles are registered in our application (so including X bundle will allow the application to do more things). An Example.
We have an order object which at the moment has a bidirectional relationship with entities in the courier bundle meaning there is a hard dependency. I want to decouple this and have the courier bundle(s) optionally add behaviour to the order. Consider this method call.
// no courier bundle is registered
$order->getShippingMethods();
// throws NoAvailableShippingMethodsException;
// one bundle registered
$order-getShippingMethods();
// returns an array with one shipping method
etc....
Now currently we have an OrderProvider service which just sits on top of the Entity Manager - so if you call
$orderProvider->GetOrder($id);
You just get the entity returned 'direct' from the database. My question here is what pattens are other people using here? I'm thinking about moving all 'business logic' into a model class that the entity extends, having the service layer pull the entity out (entity being dumb record with properties in the database and getters), and then configure the model using configuration (the configuration being injected into the OrderProvider service), which will modify the behaviour of the model. For the example given I might do something like (within the OrderProvider)..
// trimmed down for example purposes by removing exceptions etc.
public function getOrder($id)
{
$order = $this->orderRepository->findOneById($id);
if ($this->couriers){
$order->addCouriers($couriers);
}
return $order;
}
// this function would be called by the courier bundle automatically using semantic configuration / tags / setter injection
public function addCourier(CourierInterface $courier)
{
$this->couriers[] = $courier;
}
The other option that I have is to create a new type of object - which decorates the base order and is already configured (as it ITSELF will be defined as a service in the DIC) and inject the order into that. The difference is subtle and both approaches would work but I'm wondering which is the best path.
Finally I have one issue with all of this that I can't get my head around. If my base Order entity has relationships with other entities and THOSE entities need to be configured - where should this happen? For example if I access my customer thus.
$order->getCustomer();
I get the customer (entity). But It may be the case that I need to add some configuration to the customer object too - like
$customer->getContactMethods();
Now the behaviour of this method might differ depending on whether my application has registered a twitter bundle or a facebook bundle or something else. Given the above example I'm not going to get a sufficiently configured customer - but rather the 'vanilla' base entity. Only way I can see around this is to cut relationships between entities which require configuration and pull the entity from a CustomerProvider service:
$customerProvider->getCustomerByOrder($order);
This seems to me to be removing information from the model layer and moves back towards a reliance on using multiple services for simple tasks (which I'm trying to get away from). Thoughts and links to resources appreciated.
Edit: Relevant - I see the cons listed in the first answer every single day which is why I've asked this question -> Anemic Domain Model: Pros/Cons
It seems like a complexity of your project is the modularity requirement - application behavior must be extensible via bundles. I'm not familiar with Symfony 2 / Doctrine 2 but a typical DDD tactic is to try and make sure that domain entities such as Order and Customer are unaware of bundle configurations. In other words, surrounding services should not add bundle-specific behaviors to entities. Delegating the responsibility for bundle awareness to entities will make them too complex. Fabricating entity class hierarchies to support extensive behavior is also too complex. Instead, this extensibility should be managed by application services. An application service would determine which bundles are loaded and orchestrate the appropriate entities as a result.
Another strategic pattern to consider is bounded contexts. Is it possible to partition your application into bounded contexts which align with the modules? For example, to address the $order-getShippingMethods() method you can create two BCs, one where there is an order model that has a getShippingMethods() method and another without it. Having two models may seem like a violation of DRY but if the models represent different things (ie an order that has shipping data vs an order that doesn't) then nothing is actually repeated.
I have been reading about entity framework over the past couple of days and have managed to get a fair idea of using it but I still have a couple of questions some of which might seem a bit too basic. For perspective I am using entity framework 4.0 in an asp.net web application.If you can answer any of the questions please go ahead.
What advantage do I get by using POCO templates. I understand that if I wish to get persistence ignorance and keep my Entities clear of any information related to storage POCO entities are the way to go. Also I could switch from Entity framework to say NHibernate with relative ease when using POCO entities? Apart from loose coupling is there any significant reason for me to go towards POCO entities. Also if I do use POCO do I end up losing anything. I still get change tracking and lazy loading with the help of proxies?
Is it normal practice to use the Entities of the EF model as Data transfer Objects or Business Objects. i.e for example I have a separate class library for my entity model.Supposing I am using MVP , where I want a list of Employee's in a company. The presenter would request my business logic functions which would query the entity model for the list of Employee's and return the list of entities to the presenter. In this case my presenter would need to have a reference to the EF model. Is this the correct way? In the case of my asp.net web applciation it shouldnt be a problem but if I am using web services how does this work? Is this the reason to go towards POCO entities?
Supposing The Employee entity has a navigation property to a company table. If I use and wrap the data context in an 'using' block , and try to access the navigation property in the BL I am assuming I would get an exception. Would I also get an exception if I turned off lazyloading and used the 'include' linq query to get the entity? On a previous post someone recommended I use an context per request implying that the context remains active even when I am in the BL. I am assuming I would still need to detach the object and attach it to the context on my next request if I wish to persist any changes I make? or Instead should I just query for the object again with the new context and update it?
This question has more to do with organizing files/best practices and is a followup to a question i posted earlier. When I am using separate files based on entities to organize my data access layer, what is the best practice to organize my queries involving joins between multiple tables. I am still a bit hazy on organization. Have tried searching online but havent had much help.
Terrific question. My first recommendation is to think in patterns. With that said...
You pretty much nailed the advantages of using POCO. There are some distinct advantages to decoupling your business objects (POCO entities) from your data access layer. But the primary reason is like you said the ability to change or modify layers below. However using POCO you are essentially following the Code First (CF) approach. Personally, I consider it Code In Parallel depending upon your software development life cycle. You still have all the bells and whistles that data or model first approach have and some since you can extend the DbContext which is ObjectContext under the hood. I read an article, which I cannot seem to find, that CF is the future of Entity Framework. Lastly the nice thing with POCO is you are able to incorporate validation rules here or else where. You can also provide projections. Lets say you have Date of Birth but you want an Age property as well. That now becomes a no brainer as the Age property is ignored when mapping to the database.
Personally I create my own business objects (POCO) for large projects that tend to have a life of its own where change is a way of life. Another thought is scalability and maintainability. What if down the road I choose to split functionality between applications where, like you mentioned web services, functionality is now delivered from two disparate locations. If you have encapsulated your business objects and DAL within the same code block separation or scalability has now become a bit more complex. However, consider the project. It may be small with very little future change so no need to throw a grenade to kill a fly. At which time data first might be the way to go and let edmx file represent your objects. So don't marry yourself to one technology or one methodology/pattern. Do what makes sense for your time and business.
Using statements are perfectly fine. In fact I've recently been turned on to then wrapping that within a TransactionScope. If an error occurs rollbacks are inherent. Next, something to consider is the UnitOfWork. UnitOfWork pattern encapsulates a snapshot of what needs to be performed where the Data Context is the boundaries from which you work within. For each UnitOfWork you have a subject for which work is to be performed on. For example an Employee. So if you are to save Employee information to keep it simple you would make a call to the BL service or repository (which ever). There you pass in the Employee Id, perform some work under that UnitOfWork where it is either instantiated in the constructor or using Dependency Injections (DI or IoC). Easy starter is StructureMap. There the service makes the necessary calls to your UnitOfWork (DbContext) then returns control back upstream (e.g. UI).
The best way to learn here is to view others code. I'd start with some Microsoft examples. I'd start with Nerd Dinner (http://nerddinner.codeplex.com/) then build off that.
Additional Reading:
Use prototype pattern or not
http://weblogs.asp.net/manavi/archive/2011/05/17/associations-in-ef-4-1-code-first-part-6-many-valued-associations.aspx
[EDIT]
NightHawk457, I'm terribly sorry for not responding to your questions. Hopefully you figured it out but for future readers...
To help everyone visualize, imagine the below Architecture using the Domain Model and Repository as an example. Remember, there are many ways to skin a cat so take this and make it your own and don't forget my Grenade comment above.
Data Layer (Data Access): MyDbContext : DbContext, IUnitOfWork, where IUnitWork contracts the CRUD operations.
Data Repository (Data Access / Business Logic): MyDomainObjectRepository : IMyDomainObjectRepository, which receives IUnitOfWork by Factory class or Dependency Injection. Calls MyDomainObject validation on CRUD operations.
Domain Model (Business Logic): MyDomainObject using [Custom] Validation Attributes. Read this for pros/cons.
MVVM / MVC / WCF (Presentation / Service Layers): What ever additional layers you chose, you now have access to your data which is wrapped nicely in smaller modules who are self encapsulating of their function. The presentation layer (e.g. ViewModel, Controller, Code-Behind, etc.) can then receive an IMyObjectRepository by a Factory class or by Dependency Injection.
Tips:
Pass connection string into MyDbContext so you can reuse MyDbContext.
MySql does not play well with System.Transactions.TransactionScope, example. I don't recall exactly but it was something MySql did not support. This makes Testing a bit difficult since we have created this level of separation.
Create a Test project for each layer and at the minimum test general functionality/rules.
Each Domain Object should extend base object with ID field at minimum. Also do not implement Key attributes here. Domain Object should not describe architecture but rather the specific data as an entity. Even on Code First this can be achieved by the Fluent API.
Think generics when creating MyDbContext. ;) Read Diego's post.
In ASP.NET, the repositories are nice to use with ObjectDataSources.
As you can see, there is clear separation of roles where IUnitOfWork and IMyDomainObjectRepository are the Interfaces which expose the above layers functionality. And as an example, IUnitOfWork could be NHibernate, Entity Framework, LinqToSql or ADO.NET where a change to the factory class or dependency injection registration is all that has to change. FYI, I've heard the Repository called the Service Layer as well. Personally I like the first name to not be confused with Web Services. The next big take away from this structure is realizing the scope for you Database Context (IUnitOfWork). A simple example would be a ASP.NET page where for each page there is one and only one IUnitOfWork for either each repository or for that scope of work. Same holds true for ViewModels, Controllers, etc. So let's say you need to utilize two repositories, EmployeeRepository and HRRepository. You then could share the IUnitOfWork between both or not. To cross page, ViewModel or Controller boundaries, we use the ID for entities where they are then pulled from the DB and work is performed. You could alternatively pass a DTO across boundaries and attach to the context but then you begin losing separation of layers.
To continue, POCO classes do not have to be auto generated. In fact you can create your Entity Classes from scratch and perform the mapping in your extended DbContext class inside the OnModelCreating(DbModelBuilder mb) method. Start here, then here and note the Additional Resources, google Fluent API and read this post by Diego.
As for validation, this is an interesting point because it would be GREAT if all Business Rules could be validated in one location. Well, as we all know that doesn't work real well. So here is my recommendation, keep all data level validation (i.e. required, range, format, etc.) with data annotation as much as possible in the domain object and leave process validation in the Repository with clear roles of the Repository (i.e. if (isEmployee) do this, else that). I say clear, such that you do not want to add an Employee in two different Repositories where validation has to be duplicated. To call the validation, start here. Capture the ValidationResults and send upstream with a MyRepositoryValidationException which contains a collection of validations errors (e.g. Employee is required) which can be presented to the presentation layer. With all that said, don't forget to perform validation at the presentation layer. You don't want post backs to make sure an Employee has a valid Email, for example.
Just remember to balance time and effort with complexity. For something simple, use Data First or Model First with your EDMX file. Then lay a repository on top of that which also contains all the validation rules.