I'm trying to incorporate MassTransit in a project that also uses NHibernate. NHibernate requires me to have at least a default constructor with protected internal visibility.
I run into the following problem. Messages can be published without any problem, however the handlers receive the message objects with uninitialized members. After some period of debugging and inspection of the MassTransit sources I found out that this is caused by the fact that MassTransit uses the setting ConstructorHandling.AllowNonPublicDefaultConstructor during deserialization, which causes my protected internal default constructor to be called instead of the parametrized constructor. I managed to reproduce this behavior, see code below.
What's the reason behind MassTransit's use of AllowNonPublicDefaultConstructor, and is there any way to change this behavior?
class Program
{
public class TestClass
{
private readonly string _someString;
public string SomeString {
get { return _someString; }
}
public TestClass(string someString)
{
_someString = someString;
}
protected internal TestClass()
{
_someString = "uninitialized";
}
}
static void Main(string[] args)
{
var obj = new TestClass("Hello World");
var serializerSettings = new JsonSerializerSettings
{
ConstructorHandling = ConstructorHandling.AllowNonPublicDefaultConstructor,
ContractResolver = new ... // MassTransit contract resolver that includes private setters
};
string serializedObject = JsonConvert.SerializeObject(obj, serializerSettings);
var deserializedObj = JsonConvert.DeserializeObject<TestClass>(serializedObject, serializerSettings);
// deserializedObj.SomeString == "uninitialized"
}
}
Messages shouldn't have any logic in them at all. Messages are contracts. Any logic in them will only end up bitting you again and again. :( We will always use a default, no parameter, constructor. If there isn't one we won't deserialize your message.
We suggest that you alway consume interfaces instead of concrete types to help enforce the removal of logic from message types. But if you really want to have this behaviour you'll need to write your own serializer.
If you want to discuss further, I suggest you join the mailing list: groups.google.com/group/masstransit-discuss.
Related
I'm new to GraphQL and I'm currently implementing a GraphQL API into an established Java code, using GraphQL-SPQR and I'm running into a couple issues when it comes extracting data from hierarchical classes.
The issues that I am running into are as follows.
Firstly I don't if there is an easy way to get all the data associated with a returned node. If there is, this would be most useful for my more complex classes.
Secondly when a method returns an abstract class, I only seem able to request the variables on the abstract class. I'm sure this should be possible I am just hitting my head against a wall.
As a simple example
public abstract class Animal {
private String name;
private int age;
// Constructor
#GraphQLQuery(name = "name")
public String getName() {
return name;
}
// Age getter
}
public class Dog extends Animal {
private String favouriteFood;
// Constructor
#GraphQLQuery(name = "favouriteFood")
public String getFavouriteFood() {
return favouriteFood;
}
}
public class Database {
#GraphQLQuery(name = "getanimal")
public Animal getAnimal(#GraphQLArgument(name = "animalname") String animalname) {
return database.get(name);
}
}
So in my first question what I am currently querying is.
"{animalname(name: \"Daisy\") {name age}}"
This works fine as expected. If you imagine the class however had 10 variables I would like to merely be able to write the equivalent of the following without having to look them up.
"{node(name: \"Daisy\") {ALL}}"
Is this possible?
In terms of my second question.
The follow query, throws an error ('Field 'favouriteFood' in type 'Animal' is undefined')
"{animalname(name: \"Bones\") {name age favouriteFood}}"
likewise (reading Inline Fragments of https://graphql.org/learn/queries/)
"{animalname(name: \"Bones\") {name age ... on Dog{favouriteFood}}}"
throws an error Unknown type Dog
This is annoying as I have a number of sub classes which could be returned and may require handling in different fashions. I think I can understand why this is occuring as GraphQL has no knowledge as to what the true class is, only the super class I have returned. However I'm wondering if there is a way to fix this.
Ultimately while I can get past both these issues by simply serialising all the data to JSON and sending it back, it kind of gets rid of the point of GraphQL and I would rather find an alternate solution.
Thank you for any response.
Apologies if these are basic questions.
Answering my own question to help anyone else who has this issue.
The abstract class needs to have #GraphQLInterface included, as shown below
#GraphQLInterface(name = "Animal ", implementationAutoDiscovery = true)
public abstract class Animal {
private String name;
private int age;
// Constructor
#GraphQLQuery(name = "name")
public String getName() {
return name;
}
// Age getter
}
The following code was found after much solution and was created by the creator of SPQR. Effectively, when setting up your schema you need to declare an interface mapping strategy. The code below can be copied wholesale with only the "nodeQuery" variable being replaced with the service you are using to containing your "#GraphQLQuery" and "#GraphQLMutation" methods.
final GraphQLSchema schema = new GraphQLSchemaGenerator()
.withInterfaceMappingStrategy(new InterfaceMappingStrategy() {
#Override
public boolean supports(final AnnotatedType interfase) {
return interfase.isAnnotationPresent(GraphQLInterface.class);
}
#Override
public Collection<AnnotatedType> getInterfaces(final AnnotatedType type) {
Class clazz = ClassUtils.getRawType(type.getType());
final Set<AnnotatedType> interfaces = new HashSet<>();
do {
final AnnotatedType currentType = GenericTypeReflector.getExactSuperType(type, clazz);
if (supports(currentType)) {
interfaces.add(currentType);
}
Arrays.stream(clazz.getInterfaces())
.map(inter -> GenericTypeReflector.getExactSuperType(type, inter))
.filter(this::supports).forEach(interfaces::add);
} while ((clazz = clazz.getSuperclass()) != Object.class && clazz != null);
return interfaces;
}
}).withOperationsFromSingleton(nodeQuery)// register the service
.generate(); // done ;)
graphQL = new GraphQL.Builder(schema).build();
As this solution took some hunting, I'm going to start a blog soon with the other solutions I've stumbled on.
With regards to having a query that just returns all results. This is not possible in GraphQL. One workaround I might write is to have a endpoint that returns JSON of the entire object and the name of the object, then I can just use ObjectMapper to convert it back.
I hope this helps other people. I'm still looking into an answer for my first question and will update this post when I find one.
i need to do something like this
String myVar = "myString";
...
#Preauthorize("customMethod(myVar)")
public void myMethod() {
...
}
but I'm failing at it. How can I do that? It says it cannot be resolved
EDIT:I'm decoupling few rest services and sometimes I have to share infos between them
#Value("${my-properties}")
String urlIWantToShare;
...
#PreAuthorize("isValid(#myValue,urlIWantToShare)")
#RequestMapping(value = "**/letsCheckSecurityConfig", method = RequestMethod.GET)
public boolean letsCheckSecurityConfig(#RequestHeader(name = "MY-VALUE") String myValue)) {
return true;
}
this "isValid" custom security method will call an external service, that doesn't know anything about the caller and his infos. I need to transmit few infos and I need to take them from different kind of sources
One of the sources is my application.properties
EDIT2: I managed to do this
#PreAuthorize("isValid(#myValue, #myProperty)")
#RequestMapping(value = "**/letsCheckSecurityConfig", method = RequestMethod.GET)
public boolean letsCheckSecurityConfig(#RequestHeader(name = "MY-VALUE") String myValue,
#Value("${my-property-from-app-properties}") String myProperty))
..but I want to use not only actual static properties but runtime one. Any help?
You can create a wrapper method without parameters which will call the desired method with parameters. In the annotation you can use the method without parameters
Apologies if I have misunderstood what you are trying to do, but from my understanding you're trying to set an annotation at runtime based on a variable / app.properties, so that you can then read this variable and then execute your class?
If this is the case, You cannot do this from an annotation alone as annotations cannot read local variables and cannot be set at runtime.
However, one option for you is to have an object which contains the 'values' of interest for you and then read the values from the object.
Something like the below:
PoJo
public class testObject{
#test
private String myVar;
private String myValue;
//Getters and Setters
}
Get Object values
public void getFields (Object obj){
Field fields = obj.getClass().getDeclaredFields();
for (Field f : fields){
test fieldAnnotation = f.getAnnotation(test.Class);
if (fieldAnnotation != null){
f.get(obj);
// Do checks based on this
}
}
}
Main Class
public static void main(String[] args){
//Create object
testObject test = new testObject();
test.setOne("testOne");
test.setTwo("testTwo");
getFields(test);
}
I've pulled this code based on what I had to do to get the fields - but in my case, I did not know the object types I was going to be passed. You are simply using the annotation to 'mark' the fields you want to retrieve and then reading the value from the object.
If you're in a similar situation, then you can see my answer here: initial answer
Let me know if i've misunderstood this and I can try and further clarify my answer.
I have been looking around for a non Parameter injection option for the WebApi attributes.
My question is simply whether this is actually possible using Structuremap?
I have been googling around but keep coming up with either property injection (which I prefer not to use) or supposed implementations of constructor injection that I have thus far been unable to replicate.
My container of choice is Structuremap however any example of this will suffice as I am able to convert it.
Anyone ever managed this?
Yes, it is possible. You (like most people) are being thrown by Microsoft's marketing of Action Filter Attributes, which are conveniently put into a single class, but not at all DI-friendly.
The solution is to break the Action Filter Attribute into 2 parts as demonstrated in this post:
An attribute that contains no behavior to flag your controllers and action methods with.
A DI-friendly class that implements IActionFilter and contains the desired behavior.
The approach is to use the IActionFilter to test for the presence of the attribute, and then execute the desired behavior. The action filter can be supplied with all dependencies (through the constructor) and then injected when the application is composed.
IConfigProvider provider = new WebConfigProvider();
IActionFilter filter = new MaxLengthActionFilter(provider);
config.Filters.Add(filter);
NOTE: If you need any of the filter's dependencies to have a lifetime shorter than singleton, you will need to use a GlobalFilterProvider as in this answer.
To wire this up with StructureMap, you will need to return an instance of the container from your DI configuration module. The Application_Start method is still part of the composition root, so you can use the container anywhere within this method and it is still not considered a service locator pattern. Note that I don't show a complete WebApi setup here, because I am assuming you already have a working DI configuration with WebApi. If you need one, that is another question.
public class DIConfig()
{
public static IContainer Register()
{
// Create the DI container
var container = new Container();
// Setup configuration of DI
container.Configure(r => r.AddRegistry<SomeRegistry>());
// Add additional registries here...
#if DEBUG
container.AssertConfigurationIsValid();
#endif
// Return our DI container instance to the composition root
return container;
}
}
public class MvcApplication : System.Web.HttpApplication
{
protected void Application_Start()
{
// Hang on to the container instance so you can resolve
// instances while still in the composition root
IContainer container = DIConfig.Register();
AreaRegistration.RegisterAllAreas();
// Pass the container so we can resolve our IActionFilter
WebApiConfig.Register(GlobalConfiguration.Configuration, container);
FilterConfig.RegisterGlobalFilters(GlobalFilters.Filters);
RouteConfig.RegisterRoutes(RouteTable.Routes);
BundleConfig.RegisterBundles(BundleTable.Bundles);
AuthConfig.RegisterAuth();
}
}
public static class WebApiConfig
{
// Add a parameter for IContainer
public static void Register(HttpConfiguration config, IContainer container)
{
config.Routes.MapHttpRoute(
name: "DefaultApi",
routeTemplate: "api/{controller}/{id}",
defaults: new { id = RouteParameter.Optional }
);
// Uncomment the following line of code to enable query support for actions with an IQueryable or IQueryable<T> return type.
// To avoid processing unexpected or malicious queries, use the validation settings on QueryableAttribute to validate incoming queries.
// For more information, visit http://go.microsoft.com/fwlink/?LinkId=279712.
//config.EnableQuerySupport();
// Add our action filter
config.Filters.Add(container.GetInstance<IMaxLengthActionFilter>());
// Add additional filters here that look for other attributes...
}
}
The implementation of MaxLengthActionFilter would look something like this:
// Used to uniquely identify the filter in StructureMap
public interface IMaxLengthActionFilter : System.Web.Http.Filters.IActionFilter
{
}
public class MaxLengthActionFitler : IMaxLengthActionFilter
{
public readonly IConfigProvider configProvider;
public MaxLengthActionFilter(IConfigProvider configProvider)
{
if (configProvider == null)
throw new ArgumentNullException("configProvider");
this.configProvider = configProvider;
}
public Task<HttpResponseMessage> ExecuteActionFilterAsync(
HttpActionContext actionContext,
CancellationToken cancellationToken,
Func<Task<HttpResponseMessage>> continuation)
{
var attribute = this.GetMaxLengthAttribute(filterContext.ActionDescriptor);
if (attribute != null)
{
var maxLength = attribute.MaxLength;
// Execute your behavior here (before the continuation),
// and use the configProvider as needed
return continuation().ContinueWith(t =>
{
// Execute your behavior here (after the continuation),
// and use the configProvider as needed
return t.Result;
});
}
return continuation();
}
public bool AllowMultiple
{
get { return true; }
}
public MaxLengthAttribute GetMaxLengthAttribute(ActionDescriptor actionDescriptor)
{
MaxLengthAttribute result = null;
// Check if the attribute exists on the action method
result = (MaxLengthAttribute)actionDescriptor
.GetCustomAttributes(typeof(MaxLengthAttribute), false)
.SingleOrDefault();
if (result != null)
{
return result;
}
// Check if the attribute exists on the controller
result = (MaxLengthAttribute)actionDescriptor
.ControllerDescriptor
.GetCustomAttributes(typeof(MaxLengthAttribute), false)
.SingleOrDefault();
return result;
}
}
And, your attribute which should not contain any behavior should look something like this:
// This attribute should contain no behavior. No behavior, nothing needs to be injected.
[AttributeUsage(AttributeTargets.Method | AttributeTargets.Class, AllowMultiple = false)]
public class MaxLengthAttribute : Attribute
{
public MaxLengthAttribute(int maxLength)
{
this.MaxLength = maxLength;
}
public int MaxLength { get; private set; }
}
I struggled with custom action filter providers, without getting it to work for my auth attributes. I also trying out various approaches with constructor and property injection, but did not find a solution that felt nice.
I finally ended up injecting functions into my attributes. That way, unit tests can inject a function that returns a fake or mock, while the application can inject a function that resolves the dependency with the IoC container.
I just wrote about this approach here: http://danielsaidi.com/blog/2015/09/11/asp-net-and-webapi-attributes-with-structuremap
It works really well in my project and solves all problems I had with the other approaches.
I really like #SubscribeMapping approach to implement RPC-like semantic with STOMP-over-Websocket.
Unfortunately its "magic" requires that annotated method returns a value. But what if return value is not readily available? I want to avoid blocking inside the method waiting for it. Instead I'd like to pass a callback that will publish a value when it's ready. I thought I could use messaging template's convertAndSendToUser() inside a callback to do that. Turns out #SubscribeMapping handling is quite special and is not possible with instance of SimpMessageSendingOperations.
I was able to achieve my goal by calling handleReturnValue() on a SubscriptionMethodReturnValueHandler, but the overall mechanics of this is very tedious if not hackish (like providing dummy instance of MethodParameter to handleReturnValue()):
public class MessageController {
private final SubscriptionMethodReturnValueHandler subscriptionMethodReturnValueHandler;
#Autowired
public MessageController(SimpAnnotationMethodMessageHandler annotationMethodMessageHandler) {
SubscriptionMethodReturnValueHandler subscriptionMethodReturnValueHandler = null;
for (HandlerMethodReturnValueHandler returnValueHandler : annotationMethodMessageHandler.getReturnValueHandlers()) {
if (returnValueHandler instanceof SubscriptionMethodReturnValueHandler) {
subscriptionMethodReturnValueHandler = (SubscriptionMethodReturnValueHandler) returnValueHandler;
break;
}
}
this.subscriptionMethodReturnValueHandler = subscriptionMethodReturnValueHandler;
}
#SubscribeMapping("/greeting/{name}")
public void greet(#DestinationVariable String name, Message<?> message) throws Exception {
subscriptionMethodReturnValueHandler.handleReturnValue("Hello " + name, new MethodParameter(Object.class.getMethods()[0], -1), message);
}
}
So my question is simple: Is there a better way?
I have a repository pattern i created on top of the ado.net entity framework. When i tried to implement StructureMap to decouple my objects, i kept getting StackOverflowException (infinite loop?). Here is what the pattern looks like:
IEntityRepository where TEntity : class
Defines basic CRUD members
MyEntityRepository : IEntityRepository
Implements CRUD members
IEntityService where TEntity : class
Defines CRUD members which return common types for each member.
MyEntityService : IEntityService
Uses the repository to retrieve data and return a common type as a result (IList, bool and etc)
The problem appears to be with my Service layer. More specifically with the constructors.
public PostService(IValidationDictionary validationDictionary)
: this(validationDictionary, new PostRepository())
{ }
public PostService(IValidationDictionary validationDictionary, IEntityRepository<Post> repository)
{
_validationDictionary = validationDictionary;
_repository = repository;
}
From the controller, i pass an object that implements IValidationDictionary. And i am explicitly calling the second constructor to initialize the repository.
This is what the controller constructors look like (the first one creates an instance of the validation object):
public PostController()
{
_service = new PostService(new ModelStateWrapper(this.ModelState));
}
public PostController(IEntityService<Post> service)
{
_service = service;
}
Everything works if i don't pass my IValidationDictionary object reference, in which case the first controller constructor would be removed and the service object would only have one constructor which accepts the repository interface as the parameter.
I appreciate any help with this :) Thanks.
It looks like the circular reference had to do with the fact that the service layer was dependent on the Controller's ModelState and the Controller dependent on the Service layer.
I had to rewrite my validation layer to get this to work. Here is what i did.
Define generic validator interface like below:
public interface IValidator<TEntity>
{
ValidationState Validate(TEntity entity);
}
We want to be able to return an instance of ValidationState which, obviously, defines the state of validation.
public class ValidationState
{
private readonly ValidationErrorCollection _errors;
public ValidationErrorCollection Errors
{
get
{
return _errors;
}
}
public bool IsValid
{
get
{
return Errors.Count == 0;
}
}
public ValidationState()
{
_errors = new ValidationErrorCollection();
}
}
Notice that we have an strongly typed error collection which we need to define as well. The collection is going to consist of ValidationError objects containing the property name of the entity we're validating and the error message associated with it. This just follows the standard ModelState interface.
public class ValidationErrorCollection : Collection<ValidationError>
{
public void Add(string property, string message)
{
Add(new ValidationError(property, message));
}
}
And here is what the ValidationError looks like:
public class ValidationError
{
private string _property;
private string _message;
public string Property
{
get
{
return _property;
}
private set
{
_property = value;
}
}
public string Message
{
get
{
return _message;
}
private set
{
_message = value;
}
}
public ValidationError(string property, string message)
{
Property = property;
Message = message;
}
}
The rest of this is StructureMap magic. We need to create validation service layer which will locate validation objects and validate our entity. I'd like to define an interface for this, since i want anyone using validation service to be completely unaware of the StructureMap presence. Besides, i think sprinkling ObjectFactory.GetInstance() anywhere besides the bootstrapper logic a bad idea. Keeping it centralized is a good way to insure good maintainability. Anyway, i use the decorator pattern here:
public interface IValidationService
{
ValidationState Validate<TEntity>(TEntity entity);
}
And we finally implement it:
public class ValidationService : IValidationService
{
#region IValidationService Members
public IValidator<TEntity> GetValidatorFor<TEntity>(TEntity entity)
{
return ObjectFactory.GetInstance<IValidator<TEntity>>();
}
public ValidationState Validate<TEntity>(TEntity entity)
{
IValidator<TEntity> validator = GetValidatorFor(entity);
if (validator == null)
{
throw new Exception("Cannot locate validator");
}
return validator.Validate(entity);
}
#endregion
}
I'm going to be using validation service in my controller. We could move it to the service layer and have StructureMap use property injection to inject an instance of controller's ModelState to the service layer, but i don't want the service layer to be coupled with ModelState. What if we decide to use another validation technique? This is why i'd rather put it in the controller. Here is what my controller looks like:
public class PostController : Controller
{
private IEntityService<Post> _service = null;
private IValidationService _validationService = null;
public PostController(IEntityService<Post> service, IValidationService validationService)
{
_service = service;
_validationService = validationService;
}
}
Here i am injecting my service layer and validaton service instances using StructureMap. So, we need to register both in StructureMap registry:
ForRequestedType<IValidationService>()
.TheDefaultIsConcreteType<ValidationService>();
ForRequestedType<IValidator<Post>>()
.TheDefaultIsConcreteType<PostValidator>();
That's it. I don't show how i implement my PostValidator, but it's simply implementing IValidator interface and defining validation logic in the Validate() method. All that's left to do is call your validation service instance to retrieve the validator, call the validate method on your entity and write any errors to ModelState.
[AcceptVerbs(HttpVerbs.Post)]
public ActionResult Create([Bind(Exclude = "PostId")] Post post)
{
ValidationState vst = _validationService.Validate<Post>(post);
if (!vst.IsValid)
{
foreach (ValidationError error in vst.Errors)
{
this.ModelState.AddModelError(error.Property, error.Message);
}
return View(post);
}
...
}
Hope i helped somebody out with this :)
I used a similar solution involving a generic implementor of IValidationDictionary uses a StringDictionary and then copied the errors from this back into the model state in the controller.
Interface for validationdictionary
public interface IValidationDictionary
{
bool IsValid{get;}
void AddError(string Key, string errorMessage);
StringDictionary errors { get; }
}
Implementation of validation dictionary with no reference to model state or anything else so structuremap can create it easily
public class ValidationDictionary : IValidationDictionary
{
private StringDictionary _errors = new StringDictionary();
#region IValidationDictionary Members
public void AddError(string key, string errorMessage)
{
_errors.Add(key, errorMessage);
}
public bool IsValid
{
get { return (_errors.Count == 0); }
}
public StringDictionary errors
{
get { return _errors; }
}
#endregion
}
Code in the controller to copy the errors from the dictionary into the model state. This would probably be best as an extension function of Controller.
protected void copyValidationDictionaryToModelState()
{
// this copies the errors into viewstate
foreach (DictionaryEntry error in _service.validationdictionary.errors)
{
ModelState.AddModelError((string)error.Key, (string)error.Value);
}
}
thus bootstrapping code is like this
public static void BootstrapStructureMap()
{
// Initialize the static ObjectFactory container
ObjectFactory.Initialize(x =>
{
x.For<IContactRepository>().Use<EntityContactManagerRepository>();
x.For<IValidationDictionary>().Use<ValidationDictionary>();
x.For<IContactManagerService>().Use<ContactManagerService>();
});
}
and code to create controllers is like this
public class IocControllerFactory : DefaultControllerFactory
{
protected override IController GetControllerInstance(RequestContext requestContext, Type controllerType)
{
return (Controller)ObjectFactory.GetInstance(controllerType);
}
}
Just a quick query on this. It's helped me out quite a lot so thanks for putting the answer up, but I wondered which namespace TEntity exists in? I see Colletion(TEntity) needs System.Collections.ObjectModel. My file compiles without anything further but I see your TEntity reference highlighted in Blue which suggests it has a class type, mine is Black in Visual Studio. Hope you can help. I'm pretty keen to get this working.
Have you found any way to seperate validation into the service layer at all? My gut tells me that validating in the Controller is a bit smelly but I've looked high and low to find a way to pass validation error messages back to the controller without tightly coupling the service layer to the controller and can't find anything. :(
Again, thanks for the great post!
Lloyd