We are writing a mostly single-page, client-side app, but server-side/DB endpoints are still required of course, so the natural choice is SpringMVC (since we are a Java / Spring shop).
But this got me thinking why we need the cluttered, very old design for this app:
- Controller layer
- Service layer
- DAO layer
This app is mostly just the client side making AJAX calls with JSON for DB retrieval/persistence. Do I really need to go thru the Controller layer to receive requests, then invoke a Service method, which in turn invokes a DAO method?
At the same time, I don't want to write a REST Service because it could result in overhead and we may not support all of the REST requirements... but is it the right choice here? If I understand correctly, I would still need a RESTController on the presentation layer?
My goal is to just directly hit a Service method or, maybe even more directly, a DAO method. Is that how modern apps are written?
You cannot hit a DAO unless you expose it through an API of some sort that can be invoked remotely by the UI application; as a consequence, you need to write a service.
A convenient way of exposing a service is to either:
Use Spring MVC and use the controllers as stateless endpoints that provide a JSON/Protobuffer/XML sort of payload that is then parsed by your API (with JSON being the simplest option of them all, perhaps) or
Use Spring Boot, which uses Spring MVC under the hood.
Hope this helps and good luck with your project.
Related
I have a spring application. It exposes an endpoint, which when hit, needs to make an call to some other API. So, where should I make this API call, inside my controller itself or should I do it in the service class?
Based on any Architectural style (DDD, Microservices, etc), we should follow separation of concerns.
Best practice would be to create a Rest Client class for the API you want to consume and make all rest calls inside that.
Then you create a Service class to call the method consuming the API, performing the operation, data filter, anything you want to do with data.
Next would be to inject your service class inside the controller and return the data you just consumed and did some operation on it.
It might not sound well in a small project/feature, but it is the best practice when things get complicated and grow.
I'm trying to learn SI (Spring Integration) but i'm a bit confused on the real usage of this.
As first example i would like to interact with a WebService but i dont understand what could be the difference from
Invoke a WebService Using SI
Invoke a Webservice using RestTemplate
So, what is the benefit of using SI (in Webservice context, or in other context)?
Looking the web, i havent find an article that explain:
Usually you will do in this way....
With SI you can do better - in this another way - and the benefit are....
To be more explicit on what i have to realize, this is an example:
1) I have to write an application (Standalone application) that have to collect some data in the system periodically and then invoke a Web Service that will store it.
2) The Web Service receive the call from the "clients" and store in the database.
My webservice will use REST.
The reason because i've think to use SI is that the Standalone Application should interact with different system
Webservice in first instance
A Web Mail, if the webservice is not achievable
File system if Web mail is not achievable too
If you only need to pull some data in a simple way and push it onwards to a REST service this does not "justify" the use of Spring Integration. A simple Spring (Boot) application combined with a scheduler will be sufficient.
But if you want to use a more complex data source for which an endpoint is available, you need transformations, complex and flexible routing is a high priority or even Enterprise Integration Patterns (EIP) then Spring Integration is for you. Have a look at the Overview and decide if it mentions something you consider as valuable to you.
Perhaps you will create additional value by mixing in Spring Batch if you need to process a lot of data.
But as I understand your current demand starting with just a RESTTemplate should do for the moment. Starting small will not prevent you from switching to Spring Integration later on.
Have a look at the various tutorials and guides provided by the Spring Boot project. There is even an example for Spring Integration.
I have following architecture in my application.
Client (GWT) <--calls--> Servlet <--calls--> Service <--calls--> Dao
I want to make this architecture easier for changes.
For example: when I want return the inserted id of an object from the Dao layer, because I need it in the client, I have to update the service and the servlet layer as well. So for this little change I have to update all 3 layers (3 classes and 3 interfaces) makes a change on 6 places.
I see why I need the Dao Layer.
I also get why I need the service layer.
What I don't get is why the service layer can't also be a servlet. At the moment all my servlets do is forwarding the request to the service layer.
The Wikipedia Article about Java Servlets says:
Servlets are most often used to
1 process or store data that was submitted from an HTML form
2 provide dynamic content such as the results of a database query
3 manage state information that does not exist in the stateless HTTP protocol
1 and 2 are just database calls, which I make in my dao layer and the service layer makes extra business logic already possible.
3 I am currently not working with sessions. I don't have a login so far and I am just playing around with my architecture, but I think the service layer could handle this as well.
I want to know the cos and pros for this architecture change:
pros:
One layer less to update if a change happens.
cons
Service Layer gets complexer.
Thx for your answers.
You need the servlet layer because that is what allows access to the session.
Also, you don't want your service layer to need to know anything about HTTP since you want to be able to re-use the service and DAO layers in other applications (e.g. if you write a desktop application re-using those layers) and needing to include the servlet API would not make sense there.
If needed you could call the DAO layer directly from a servlet for simple cases in order to not duplicate methods in the service and DAO layers.
The servlet API has filters which are a good place to implement security in your web application.
You can use Spring Security if you are already using the Spring framework for your web application.
So we've decided to rebuild an application in our business since it's been sitting in Sharepoint for no apparent reason other than to make use of its document indexing feature.
We've decided to create our new app in ASP.NET MVC3 using C#. We're trying to decide on the overall architecture.
I was thinking something like the following:
Core - domain objects (poco's)
Data - Entity Framework (Code First) or nHibernate exposed as Repositories
Service - This layer would encapsulate any business logic and act as a facade. This could be broken down into further modules.
UI (MVC) - Controllers and Views.
This would all be tied together using a DI container such as Autofac.
We also want to be able to write unit tests so we need to be able to mock our service layer and data repositories for testing our controllers etc.
So - does the above sound like a good overall architectural pattern for a pretty standard business application?
The idea being that data, service, ui can reference Core but the UI would only really talk to the service level components and not know about the implementation details of data etc.
My next question is that at some point we're going to want to expose some functionality outside our application i.e. WCF Services/ASP.NET Web API.
What, in your view, would be the best option. Build the service layer in WCF and call this from our Controllers in MVC? If so would this be testable or would we need to write a wrapper around the web service? Could this be time consuming?
OR
Continue writing a service layer (i.e. Service1.CreateObject(object obj);) in C# classes and create a web service as a separate entity exposing just the functionality we need that calls our service layer?
Any thoughts would be really helpful as I don't know what best route would be.
Should we use a WCF service as our service layer facade in nTier application
Depends on if any other application than the MVC application is going to talk to the service.
MVC3 is the only app: You aint gonno need it
Other apps too: Sure. Do it.
What, in your view, would be the best option. Build the service layer in WCF and call this from our Controllers in MVC? If so would this be testable or would we need to write a wrapper around the web service? Could this be time consuming
Don't use the concrete service classes. Use the service interfaces. Problem solved.
My next question is that at some point we're going to want to expose some functionality outside our application i.e. WCF Services/ASP.NET Web API
I hope that you mean the same WCF service.
Continue writing a service layer (i.e. Service1.CreateObject(object obj);) in C# classes and create a web service as a separate entity exposing just the functionality we need that calls our service layer?
ehh. What kind of method is Service1.CreateObject(object obj)? That looks just wrong.
Using WCF Service is the right approach. (As you need to host this as web-api and web-api is over http).
In your mvc application you can consume the service by endpoint url.
Time factor depends on the connectivity between your servers(WebServer for MVC app and the Server to host WCFservices).ideally it should not be a bottle neck.
Still you can do unit testing of MVC code (as service layer call can be mocked.(using Moq/NMock?RhinoMock...))
I'd like to call methods of my DAOs by AJAX. I'm quite new in that so I would like to ask what is the best way to do that. Is it possible to publish my beans as web services and call them with e.g. jQuery? I think it is not possible :) I've also read about Direct Web Remoting but I don't know which way to go...
As I see, there are lot of experienced guys here so I think you can show me direction.. thanks in advance
Rather than exposing your DAO beans directly, you should create some Spring MVC controller beans, and call those from the client-side (using AJAX). Ideally, the controllers should not call the DAOs directly, but should instead call service beans (and the service beans should call the DAOs). One advantage of this approach is that you can define your service methods to be transactional, i.e. whenever a service method begins a transaction is started, and whenever a service method returns (without an exception) the transaction is committed. If the boundaries of your transactions are your DAO methods then it is not possible to wrap several database calls in a single transaction.
Of course there's no reason why you need to use Spring MVC - any web framework would suffice.
You have to expose your DAO's or beans by means of http. Typically you create a layer above the DAO layer to expose your services through HTTP, which are available to any AJAX framework such as jQuery. What jQuery and other frameworks ends up doing is using a special asynchronous request called XMLHttpRequest and then parse the server response (can be anything, pure HTML, JSON, XML, etc) and process it.
Here's a link I found that shows Spring & DWR with AJAX: Bram Smeets Blog.