I realize that the Web API is REST focused, but I would still like to configure a single controller method that can handle a Command/Response scenario. So far I haven't been successful... is there a way to have the following class structure recognized by a single API endpoint?
[Serializable]
public abstract class Command{
public int CommandId{get; set;}
}
[Serializable]
public class RegisterNewPersonCommand:Command{
public string Name{get; set;}
}
//etc... various Command subclasses. Similar thing for Responses.
//now have a single endpoint to Handle Commands
public class CommandsController : ApiController{
public Response HandleCommand(Command command){
//handle Command based on which subclass it is
//return appropriate Response subclass
}
}
Thus far it doesn't seem the serialization system can handle this scenario, but I hope someone out there has found a way to do it :)
In order for polymorphism to work in Web API, you will need to enable type name handling and the data has to contain the type information.
You'll need to turn on TypeNameHandling in WebApiConfig.cs if you're using JSON in your scenario:
config.Formatters.JsonFormatter.SerializerSettings.TypeNameHandling =
Newtonsoft.Json.TypeNameHandling.All;
Then, the content body that you are sending to your HandleCommand(...) action must contain the type information:
{"$type":"MvcApplication.Models.RegisterNewPersonCommand, MvcApplication", ... }
For XML, you'll need to use DataContract's KnownType...
By the way, is there any specific reason why you are using [Serializable] (since POCO types and [DataContract] types are also supported...)?
Related
Please find my HomeController and DemoController
class HomeController{
#RequestMapping(value="index")
public void home(){
}
}
class DemoController{
#RequestMapping(value="index")
public void demo(){
}
}
when I try to send a request to index, which one will get executed?
I wanted to know how can we have same request mapping value for multiple controllers
https://stackoverflow.com/a/34590355/2682499 is only partially correct at this point.
You can have multiple controller methods use the same URI so long as you provide Spring enough additional information on which one it should use. Whether or not you should do this is a different question. I would certainly not recommend using the same URI in two separate controller classes to avoid confusion, though.
You can do something like this:
class HomeController{
#RequestMapping(value="/index", params = {"!name", "!foo"})
public List<Something> listItems(){
// retrieve Something list
}
#RequestMapping(value="/index", params = "name")
public List<Something> listItems(String name) {
// retrieve Something list WHERE name LIKE %name%
}
#RequestMapping(value="/index", params = {"!name", "foo"})
public List<Something> listItems(String foo) {
// Do something completely different
}
}
For the full documentation on what is possible when overloading URIs you should reference the #ReqeustMapping documentation: https://docs.spring.io/spring/docs/current/javadoc-api/org/springframework/web/bind/annotation/RequestMapping.html. And, specifically https://docs.spring.io/spring/docs/current/javadoc-api/org/springframework/web/bind/annotation/RequestMapping.html#params-- for the section request parameters.
In Spring Web MVC this is not possible. Each mapping must be unique in your context. If not, you will receive a RuntimeException during context initialization.
You cannot even use parameters to differentiate your endpoints because they are not evaluated while searching for a suitable handler (applicable for Servlet environments). From #RequestMapping javadoc:
In a Servlet environment, parameter mappings are considered as restrictions that are enforced at the type level. The primary path mapping (i.e. the specified URI value) still has to uniquely identify the target handler, with parameter mappings simply expressing preconditions for invoking the handler.
Note that you can do the opposite, so multiple URLs can point to the same handler. Have a look at Spring MVC: Mapping Multiple URLs to Same Controller
Unfortunately, this is not possible. The request mapping has to be unique otherwise the application can't determine which method the incoming request should be mapped to.
What you can do instead is to extend the request mapping:
class HomeController{
#RequestMapping(value="home/index")
public void home(){
}
}
class DemoController{
#RequestMapping(value="demo/index")
public void demo(){
}
}
I have some validation logic, which is based a user's session.
Сan I access the session from a class inherited from AbstractValidator?
Or is there another way to check RequestDTO based session?
For example I can use filters for that (and I can access the session via IRequest parameter req in overrided Execute method), but I don't know how to return the response from the class of the filter, bypassing the main method of the operation. If I will throw the Exception, the service will not work properly because RequestDTO declared outside of my project and it is not inherited from IReturn<> and does not contain a ResponseStatus field.
Thanks in advance for any help (and sorry for my English)
If your validator implements IRequiresRequest then it will injected with the current IRequest which you can use in your lambda expressions, e.g:
public class CustomValidator : AbstractValidator<Request>, IRequiresRequest
{
public IRequest Request { get; set; }
...
}
I have written a Web API to be used as a webhook with a 3rd party service so they can send me data when an event occurs in their service. They have dictated what the posted data coming in will be. So I created a class for the incoming data such that each property name matches the field names coming from the posted form urlencoded data.
What I would LIKE to do is name things in my class in a more user-friendly manner than the names they are sending in their POST request. I cannot find if there is a way, maybe using attributes, that will tell the ModelBinder which form data to put into which property. Is there a way to do this?
Incidentally, when I thought they were sending JSON as the POSTED data, I was able to do this with JSON.NET and their JsonProperty attribute. But now that it's coming as application/x-www-form-urlencoded, I don't know how to do this same thing.
Thanks for your help!
please try something like this
[DataContract]
public class TestSerialization
{
[DataMember(Name = "field_one")]
public string ItemOne { get; set; }
[DataMember(Name = "field_two")]
public string ItemTwo { get; set; }
}
Does WebAPI can handle ValidationAttribute on action parameter?
For instance:
public class SampleController : ApiController
{
public string Get([RegularExpression("sampleExpression")]string id)
{
return "result";
}
}
In this sample WebAPI doesn't invoke any methods of RegularExpressionAttribute (or any other data annotation attribute) to validate input parameter. But in case if we passing an object as parameter, for instance a class then WebAPI can validate properties.
Is it a bug? Or I'm doing something wrong?
UPD: It's an open issue:
http://aspnetwebstack.codeplex.com/workitem/24?PendingVoteId=24
Does anyone can suggest a workaround?
This is a genuine question, I'm curious why not just do something like :
public class SampleController : ApiController
{
public string Get(string id)
{
RegularExpressionHelper.ValidateWith("sampleExpression",id);
return "result";
}
}
To me this seems to be equivalently concise. It is obvious when the validation occurs. I can safely assume that if the validation fails then an exception will be thrown. I can easily add additional validation and be confident of the order in which they occur.
Regarding the attribute method, I don't know if the validation is used as part of the route matching, I have no idea what happens if it fails. I don't know what filters run before or after the validation. I'm sure if I knew MVC better I would know the answer to these questions, but I don't see the advantage of using an attribute that makes my code's behaviour dependent on some framework controlled infrastructure.
Am I missing some significant benefit?
I had the same doubt. My workaround consists in creating a class just for encapsulating the parameter, so I can decorate it with the validation attribute I want. I could use the workaround proposed by Darrel in his answer, but I have a filter that checks if ModelState.IsValid before entering the action, so I need to validate before the action gets executed.
[ModelBinder]
public class Item
{
[RegularExpression("sampleExpression")]
public string Id { get; set; }
}
The class must be annotated with [ModelBinder], otherwise the parameter binding mechanism will try to extract the id field from the body of the request. Read this article for more info.
Also, note that Id is now in PascalCase instead of camelCase. Read this article to understand how the conversion is made.
The action signature is:
public string Get(Item item)
What's a good way to validate a model when information external to the model is required in order for the validation to take place? For example, consider the following model:
public class Rating {
public string Comment { get; set; }
public int RatingLevel { get; set; }
}
The system administrator can then set the RatingLevels for which a comment is required. These settings are available through a settings service.
So, in order to fully validate the model I need information external to it, in this case the settings service.
I've considered the following so far:
Inject the service into the model. The DefaultModelBinder uses System.Activator to create the object so it doesn't go through the normal dependency resolver and I can't inject the service into the model without creating a new model binder (besides which, that doesn't feel like the correct way to go about it).
Inject the service into an annotation. I'm not yet sure this is possible but will investigate further soon. It still feels clumsy.
Use a custom model binder. Apparently I can implement OnPropertyValidating to do custom property validation. This seems the most preferable so far though I'm not yet sure how to do it.
Which method, above or not, is best suited to this type of validation problem?
Option 1 doesn't fit. The only way it would work would be to pull in the dependency via the service locator anti-pattern.
Option 2 doesn't work. Although I couldn't see how this was possible because of the C# attribute requirements, it is possible. See the following for references:
Resolving IoC Container Services for Validation Attributes in ASP.NET MVC
NInjectDataAnnotationsModelValidatorProvider
Option 3: I didn't know about this earlier, but what appears to be a very powerful way to write validators is to use the ModelValidator class and a corresponding ModelValidatorProvider.
First, you create your custom ModelValidatorProvider:
public class CustomModelValidatorProvider : ModelValidatorProvider
{
public CustomModelValidatorProvider(/* Your dependencies */) {}
public override IEnumerable<ModelValidator> GetValidators(ModelMetadata metadata, ControllerContext context)
{
if (metadata.ModelType == typeof(YourModel))
{
yield return new YourModelValidator(...);
}
}
}
ASP.NET MVC's IDependencyResolver will attempt to resolve the above provider, so as long as it's registered with your IoC container you won't need to do anything else. And then the ModelValidator:
public class EntryRatingViewModelValidatorMvcAdapter : ModelValidator
{
public EntryRatingViewModelValidatorMvcAdapter(
ModelMetadata argMetadata,
ControllerContext argContext)
: base(argMetadata, argContext)
{
_validator = validator;
}
public override IEnumerable<ModelValidationResult> Validate(object container)
{
if (/* error condition */)
{
yield return new ModelValidationResult
{
MemberName = "Model.Member",
Message = "Rating is required."
};
}
}
}
As the provider is retrieved through the IDependencyResolver and the provider has full control over the returned ModelValidators I was easily able to inject the dependencies and perform necessary validation.
You could try fluent validation. It supports asp.net mvc and DI so you can inject external services into your validators.
Assuming that you want both client and server-side validation of the model based upon the values returned from the service, I would opt for 2., Inject the service into an annotation.
I give some sample code in my response to this question about adding validators to a model. The only additional step in your case is that you will need to inject your service into your class inheriting from DataAnnotationsModelValidatorProvider.
What about just simply using IValidateableObject and in that method determine if validation is appropriate or not and setting the errors there?
How do I use IValidatableObject?