I don't know where to put the business logic in spring mvc because I'm new to it. I have a clue on what to do but because of lack in knowledge in spring mvc, I don't know where to start. I would also like to ask if somebody knows where I can get a good tutorial on this or a complete sample of a spring mvc web application that has a business logic on it? Anyways, the business logic that I was talking about is all about database handling :)
#Controller classes serve as C from MVC. Note that the real controller in Spring MVC is DispatcherServlet that will use the specific #Controller class to handle the URL request.
#Service classes should serve for your service layer. Here you should put your business logic.
#Repository classes should serve for your data access layer. Here you should put CRUD logic: insert, update, delete, select.
#Service, #Repository and your entity classes will be M from MVC. JSP and other view technologies(e.g. JSP, Thymeleaf etc.) will conform V from MVC.
#Controller classes should only have access to #Service classes through interfaces. Similar, #Service classes should only have access to other #Service classes and for a specific set of #Repository classes through interfaces.
Many people would recommend to add the business logic to the service layer. I personally find out that's not a great idea, specially when you start testing: you may have to deal either with the persistence and business logic at the same time, or mocking everything around, and then things can get very messy.
I do recommend reading this article before taking any conclusions:
The Biggest Flaw of Spring Web Applications
Resuming, the idea would be to move the business logic to the model layer and simplify your services methods.
Generally, your business logic goes in the service layer. Though you can put basic validation rules in your pojos with JSR annotations.
For a Spring MVC app you have controllers, which handle http requests, and a domain layer, which are pojos representing your business models. You often have a persistence layer, or DAO. You might have a service layer as well, for helping with non-trivial logic.
Your comment about database handling doesn't make sense. Business rules are orthogonal to storing data. Your database handling should go in your persistence layer.
Related
I'm developing a set of microservices for a web application with Spring Boot, and I'm unsure if the pattern design I'm using is correct, or makes sense, or has any advantages.
What I'm using is a controller-facade-service design, which in my mind should work in this way:
The controller delegates everything to the facade, passing the input DTO to it
The facade implements all the business logic and uses one or more services to create an output DTO to send back to the controller
Services implement core and atomic functionalities, mostly CRUDs, without any or minimal business logic so that different facades with different business logic can use them, and return a JPA entity to the facade
Is this a good design pattern? Is the facade unnecessary?
More specifically, should the business logic be in the facade or in the service? I believe services should be logic agnostic so that they can be shared across multiple facades, which may implement different logic depending on the endpoint.
Also, in the case of a CRUD operation, should the service return an entity to the facade? Or should it be up to the service to create an output DTO for the facade?
Suppose I have a Spring application divided into 3 layers: controller, service and repository. In which layer should all the business logic go? From what I have read on the net, the controller should only consume the service and it is the service that should be the one that contains all the business logic. Is this correct? Should I handle the Exception that may occur in the service?, I'm quite new to Spring and not sure which is the correct way to approach and which are the best practices.
Into services.
Repo - interaction with database
Controller - Http communication handling (or other type if interaction like CLI)
Service - bussiness logic.
You should put all your business logic into the Service Layer.
Commonly, exceptions are, also, handled at the Service Layer. This happens mainly because of the reusability. However, in Spring Applications, generally, even the service layer throw the exceptions, so that you can centralize all the errors in a single handler class.
Read more at Spring MVC Exception Handling.
I am planning to build a web application with Java Server Faces but i am unsure how to handle the persistence of my entities. For php projects i am using the Symfony framework with Doctrine 2. I call the persist method of the entity manager mainly in the controllers. So there are no seperate classes for business logic. I tried Hibernate and i think that is a good replace for Doctrine. ;)
The java project is for university and i want to transfer the business logic from the controllers/beans to classes for business logic.
I read articles and tutorials about the data access object and repository pattern (http://docs.spring.io/spring-data/jpa/docs/1.3.0.RELEASE/reference/html/jpa.repositories.html).
In the data access object pattern i have a class for my Entity and an interface and a class for my DAO object/entity, in the repository pattern i have a class for my entity and a class for the repisitory.
But where goes my business logic? Do I have to write an interface and a class per entity for the business logic layer and inside the classes i simply call my dao/repository methods? If so, what is the difference between both patterns?
If I am totally wrong: What is the (industry) standard for data persistence (with Hibernate/JPA) with Java Server Faces?
The architecture of the project must be well organized according to principle "low coupling and high cohesion"
The system layers should be well seperated. The basic architecture have 3 layers.
Presentation Tier: JSF managed beans are in this layer. The task of this layer is to correspond user actions, hold user data and show the data to the user. Basically, its responsibility is bounded by MVC pattern regardless of which implementation you use (JSF, Spring MVC or Struts)
Bussimess Logic Tier: The data and actions which was collected from page was sent to this layer to operate on data. You should not manipulte the data and prepare the response inside Presentation Tier. It is the responsibility of Bussiness Logic Tier.(Spring, CDI)
Integration Tier: Database access should be done in this layer regardless of the library technology used (Hibernate, JPA, JDBC).
As you can see in the pic. your JSF managed beans should only be capable of requests from the pages(controller) and page data (model). You can have a look to this answer to understand JSF MVC. Therefore, It is better to not to connect DB inside JSF managed beans. It is not a good practice.
The second part of your question. All technologies, Hibernate, JPA, Spring JDBC, uses JDBC driver of the related DB. JDBC Drivers is the just thing which connects to the DB. However, it is beter to select a method how to connect to DB, Hibernate, JPA or Spring JDBC.
You can download my example application which implements this architecture basically.
I have a design/architectural problem:
I've started developing a java web application. I thought of using 3 layers: a persistence layer (with jpa and hibernate), a business layer and a presentation layer. My problem now is:
the jpa entities would make the model but can or may I use the entities as business objects?
Is this a practice? My common sense says I shouldn't, but then, I need to duplicate these entities as business objects?
Finally, I'd like the presentation layer to be really decoupled from the other layers. While using spring mvc with jsp at first, I'd like. if it's suitable, at some moment to switch to javascript-based application that communicates with the backend through rest requests.
Yes, you can. Outside the persistence context, the JPA Entities are like simple POJOs. It is legal to use them in business code (actually, as hinted by JB Nizet, you usually ALWAYS use them in your business layer without DAO). If it is tightly related to the Entity, you can even add business logic into your JPA beans. Nevertheless, it will be harder to read and understand what the code does. But if you have a reason to do that - there is nothing illegal. It all comes down to software design practices and what you need most.
When you want to change your app into the REST-powered service, it is not difficult. You will have to change the Servlet you are currently running your app with for a JAX-RS or other framework Servlet which will handle HTTP requests in a REST manner for you. It is done in web.xml. Then, you will place your html-pages in any place, where it is accesible for the remote hosts, and connect them to your REST-service with the Javascript AJAX or sth. You should take care of CORS then.
I've participated in several projects of Spring-based web-application - and have written a quantity myself. Usually we have (roughly speaking) following folders to divide our classes by categories like dao, models, web (for controllers if we use Spring MVC or backing beans for JSF for example) and also service - here we keep what we think is business-logic (even when sometimes classes here simply forward methods to dao).
Now I am faced with development of EJB application - I've learnt that I will have some web and model classes anyway. Also I may use dedicated dao layer or may put data access into facades (I prefer dedicated folder though it increases verbosity).
But I do not understand clearly whether facades are exactly the place to put business-logic in it, or I should add services folder for it and use facades more like dao (eliminating dao itself).
I also would be glad for short and comprehensive compilation of hints on EJB application architecture.
I would go with a similar setup with EJB as you have done with Spring. You have your web package (MVC stuff), then your service layer which contains most business logic and then DAO layer which contains basic CRUD operations and some database queries.
In this scenario you can test the possibly complex business logic in the session beans with fast unit tests that don't need database and you can mock the DAO access here. Then you can have relatively simple tests for your DAO layer, so the number of tests requiring database (ie. that are consirably slower) is smaller.
Normally I would call facade a set of session beans that offer simple methods for operating the system via for example Web services. These beans would use the normal service layer beans. With just a web layer and no integration layers I don't see a reason to create an extra facade layer.