In our domain-driven application, we use a type called ServiceResponse<> to send data between layers of our application - specifically, one is returned by every method in the domain. As of right now, it encapsulates the data (if any) which was returned from the method, or any errors that it may have generated.
My question, then, is this: is it an acceptable practice to add fields to this object that may be useful in other layers of the application? For example, is it good form to add a Status or StatusCode field to it that may be interpreted later by the service layer for use as an HTTP status code (with or without some mapping)?
It sounds like a fine place to me. The idea that every method returns a "response" of some sort smells a bit like trying to decouple too much, but there are some cases where such extreme decoupling is warranted.
In any case, the ServiceResponse could easily have a status, and if it needed one, that is where I would put it.
Related
What if we make one type that includes all state user can get from the backend. Lets call it AppState.
And there will be only one query getAppState, and all mutations will return AppState as well so that clients can access any field they need, and if you use apolloClient, clients' cache will update automatically.
We can get all state on user login without any problem.
Is it a bad idea?
Following this pattern would exactly contradict the reasoning behind the existence of GraphQL itself.
The idea is for your queries and mutations to exactly fit a pre-defined expected outcome. If you actually implemented such a concept, unless you provide all the data a query or mutation expects, it will throw an error. Subsequently, if you would actually end up trying it, you will quickly realize how cluttered and resource-heavy it actually is. Imagine fetching all your databases with each request because of this schema .... that would be awful.
Well I have a few pipes in the application I'm working on and I'm starting to think they actually should be guards or even interceptors.
One of them is called PincodeStatusValidationPipe and its job as simple as snow. It checks the cache for a certain value if that value is the one expected then it returns what it gets otherwise it throws the FORBIDEN exception.
Another pipe is called UserExistenceValidationPipe it operates on the login method and checks if a user exists in DB and some other things related to that user (e.g. wheter a password expected in the login method is present and if it does then whether it matches that of the retrieved user) otherwise it throws appropriate exceptions.
I know it's more of a design question but I find it quite important and I would appreciate any hints. Thanks in advance.
EDIT:
Well I think UserExistenceValidationPipe is definitely not the best name choice, something like UserValidationPipe fits way better.
If you are throwing a FORBIDEN already, I would suggest migrating the PincodeStatusValidationPipe to be PincodeStatusValidationGuard, as returning false from a guard will throw a FORBIDEN for you. You'll also have full access to the Request object which is pretty nice to have.
For the UserExistenceValidationPipe, a pipe is not the worst thing to have. I consider existence validation to be a part of business logic, and as such should be handled in the service, but that's me. I use pipes for data validation and transformation, meaning I check the shape of the data there and pass it on to the service if the shape looks correct.
As for interceptors, I like to use those for logging, caching, and response mapping, though I've heard of others using interceptors for overall validators instead of using multiple pipes.
As the question is mostly an opinionated one, I'll leave the final decision up to you. In short, guards are great for short circuiting requests with a failure, interceptors are good for logging, caching, and response mapping, and pipes are for data validation and transformation.
I did a google search, but I could not find what I really need.
I need to query an API, which have the same route, but with different parameters.
Example:
router.get('/items/:query, function(){})
In this case, I would search for all items
router.get('/items/:id, function(){})
Here, I would look for a specific item
At the core of your issue is that you are trying to specify two different resources at the same location. If you design your API to adhere to restful principles you'll see why that's not a wise choice. Here are two good starting points:
https://en.wikipedia.org/wiki/Representational_state_transfer
http://www.restapitutorial.com/lessons/whatisrest.html
In restful api's the root resource represents the item collection:
/api/items
...and when you specify an id that indicates you want only one item:
/api/items/abc123
If you really still want to accomplish what you asked in your question you'll need to add a url parameter like /items/query?query=true or /items/abc123?detail=true but this will be confusing to 99% of web developers who ever look at your code.
Also I'm not sure if you really meant this, but when you pass a variable named "query" to the server that seems to indicate that you're going to send a SQL query (or similar data definition language) from the client into the server. This is a dangerous practice for several reasons - it's best to leave all of this type of code on your server.
Edit: if you really absolutely positively have to do it this way then maybe have a query parameter that says ?collection=true. This would at least be understood by other developers that might have to maintain the code in future. Also make sure you add comments to explain why you weren't able to implement rest so you're not leaving behind a bad reputation :)
The issue is that without additional pattern matching there isn't a way Express will be able to distinguish between /items/:query and /items/:id, they are the same route pattern, just with different aliases for the parameter.
Depending on how you intend to structure your query you may want to consider having the route /items and then use query string parameters or have a separate /items/search/:query endpoint.
I use MEAN stack to develop an application.
I'm trying to develop a restful API to get users by first name or lastname
Should I write one get function to get the users for both firstname and lastname?
What is the best practice to write the URL to be handled by the backend?
Should I use the following?
To get user by firstname: localhost:3000/users?firstname=Joe
To get user by name:localhost:3000/users?firstname=Terry
And then check what is the parameter in my code and proceed.
In other words,What is the best practice if I want to pass one of multiple parameters to restful API and search by only one parameter?
Should I use content-location header?
There is no single best practice. There are lots of different ways to design a REST interface. You can use a scheme that is primarily path based such as:
http://myserver.com/query/users?firstname=Joe
Or primarily query parameter based:
http://myserver.com/query?type=users&firstname=Joe
Or, even entirely path based:
http://myserver.com/query/users/firstname/Joe
Only the last scheme dictates that only one search criteria can be passed, but this is likely also a limiting aspect of this scheme because if you, at some time in the future, want to be able to search on more than one parameter, you'd probably need to redesign.
In general, you want to take into account these considerations:
Make a list of all the things you think your REST API will want to do now and possibly in the future.
Design a scheme that anticipates all the things in your above list and feels extensible (you could easily add more things on to it without having to redesign anything).
Design a scheme that feels consistent for all of the different things a client will do with it. For example, there should be a consistent use of path and query parameters. You don't want some parts of your API using exclusively path segments and another part looking like a completely different design that uses only query parameters. An appropriate mix of the two is often the cleanest design.
Pick a design that "makes sense" to people who don't know your functionality. It should read logically and with a good REST API, the URL is often fairly self describing.
So, we can't really make a concrete recommendation on your one URL because it really needs to be considered in the totality of your whole API.
Of the three examples above, without knowing anything more about the rest of what you're trying to do, I like the first one because it puts what feels to me like the action into the path /query/users and then puts the parameters to that action into the query string and is easily extensible to add more arguments to the query. And, it reads very clearly.
There are clearly many different ways to successfully design and structure a REST API so there is no single best practice.
I'm looking into converting part of an large existing VB6 system, into .net. I'm trying to use domain driven design, but I'm having a hard time getting my head around some things.
One thing that I'm completely stumped on is how I should handle complex find statements. For example, we currently have a screen that displays a list of saved documents, that the user can select and print off, email, edit or delete. I have a SavedDocument object that does the trick for all the actions, but it only has the properties relevant to it, and I need to display the client name that the document is for and their email address if they have one. I also need to show the policy reference that this document may have come from. The Client and Policy are linked to the SavedDocument but are their own aggregate roots, so are not loaded at the same time the SavedDocuments are.
The user is also allowed to specify several filters to reduce the list down. These to can be from properties that are stored on the SavedDocument or the Client and Policy.
I'm not sure how to handle this from a Domain driven design point of view.
Do I have a function on a repository that takes the filters and returns me a list of SavedDocuments, that I then have to turn into a different object or DTO, and fill with the additional client and policy information? That seem a little slow as I have to load all the details using multiple calls.
Do I have a function on a repository that takes the filters and returns me a list of SavedDocumentsForList objects that contain just the information I want? This seems the quickest but doesn't feel like I'm using DDD.
Do I load everything from their objects and do all the filtering and column selection in a service? This seems the slowest, but also appears to be very domain orientated.
I'm just really confused how to handle these situations, and I've not really seeing any other people asking questions about it, which masks me feel that I'm missing something.
Queries can be handled in a few ways in DDD. Sometimes you can use the domain entities themselves to serve queries. This approach can become cumbersome in scenarios such as yours when queries require projections of multiple aggregates. In this case, it is easier to use objects explicitly designed for the respective queries - effectively DTOs. These DTOs will be read-only and won't have any behavior. This can be referred to as the read-model pattern.