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What is MVC?

I remember my first interview with phper (php is another web development language that I can get started quickly). When people asked me about MVC, I only knew that m was model and v was view. c is the Controller. I don’t know anything about the other details. As a result, I was asked many questions and I didn’t know anything! ! I just realized how bad I am. So I decided not to give up until I figured it out! Found the following information

2006-12-17 12:02:37

Large, Medium, Small
Model-View-Controller (MVC) is the Xerox and PARC programming language Smalltalk in the 1980s -A software design pattern invented in the 1980s that has been widely used to this day. In recent years, it has been recommended as the design pattern of Sun's J2EE platform, and is welcomed by more and more developers using ColdFusion and PHP. The Model-View-Controller pattern is a useful toolbox that has many benefits, but also some drawbacks.
How MVC works

MVC is a design pattern that enforces the separation of input, processing and output of an application. Applications using MVC are divided into three core components: model, view, and controller. They each handle their own tasks.

View
A view is the interface that users see and interact with. For old-fashioned Web applications, the view is an interface composed of HTML elements. In new-style Web applications, HTML still plays an important role in the view, but some new technologies have emerged in endlessly, including Macromedia Flash and Some markup languages and Web services like XHTML, XML/XSL, WML, etc.

How to handle the interface of the application becomes more and more challenging. One of the big benefits of MVC is that it can handle many different views for your application. No real processing occurs in the view, whether the data is stored online or a list of employees. As a view, it just serves as a way to output the data and allow the user to manipulate it.

Model
Model represents enterprise data and business rules. Among the three components of MVC, the model has the most processing tasks. For example, it might use component objects like EJBs and ColdFusion Components to handle databases. The data returned by the model is neutral, which means that the model has nothing to do with the data format, so that a model can provide data for multiple views. Code duplication is reduced because the code applied to the model only needs to be written once and can be reused by multiple views.

Controller
The controller accepts user input and calls models and views to complete the user's needs. So when a hyperlink in a Web page is clicked and an HTML form is sent, the controller itself does not output anything or do any processing. It just receives the request and decides which model component to call to handle the request, and then determines which view to use to display the data returned by the model processing.

Now we summarize the MVC processing process. First, the controller receives the user's request and decides which model should be called for processing. Then the model uses business logic to process the user's request and returns the data. Finally, the controller uses the corresponding The view formats the data returned by the model and presents it to the user through the presentation layer.

Why use MVC

Most web applications are created using procedural languages like ASP, PHP, or CFML. They mix data-level code like database queries with presentation-level code like HTML. More experienced developers will separate the data from the presentation layer, but this is usually not easy to do and requires careful planning and constant trial and error. MVC fundamentally forces them to be separated. Although constructing MVC applications requires some extra work, the benefits it brings to us are unquestionable.

First and foremost, it’s important that multiple views share a model. As I mentioned, there are now more and more ways to access your application. One solution to this is to use MVC, whether your users want a Flash interface or a WAP interface; one model can handle them all. Since you have separated the data and business rules from the presentation layer, you can maximize the reuse of your code.

Since the data returned by the model is not formatted, the same component can be used by different interfaces. For example, a lot of data may be represented in HTML, but they may also be represented in Macromedia Flash and WAP. Models also have state management and data persistence capabilities. For example, session-based shopping carts and e-commerce processes can also be reused by Flash websites or wireless network applications.

Because models are self-contained and decoupled from controllers and views, it’s easy to change your application’s data layer and business rules. If you want to migrate your database from MySQL to Oracle, or change your RDBMS-based data source to LDAP, just change your model. Once you implement the model correctly, whether your data comes from a database or an LDAP server, the view will display it correctly. Since the three components of an application using MVC are mutually exclusive, changing one of them will not affect the other two, so you can construct good loosely coupled components based on this design idea.

For me, the controller also provides a benefit, that is, the controller can be used to connect different models and views to complete the user's needs. In this way, the controller can provide a powerful tool for constructing applications. means. Given some reusable models and views, the controller can select the model for processing according to the user's needs, and then select the view to display the processing results to the user.

Disadvantages of MVC
The disadvantage of MVC is that it is not very easy to fully understand MVC because it is not clearly defined. Using MVC requires careful planning, and because its internal principles are complex, it takes some time to think about.

You will have to spend considerable time thinking about how to apply MVC to your application. At the same time, since the model and view must be strictly separated, it also makes debugging the application difficult. Every component needs to be thoroughly tested before use. Once your components are tested, you can reuse them without worry.

According to my personal experience, since we divide an application into three parts, using MVC also means that you will have to manage more files than before, which is obvious. This may seem like our workload has increased, but please remember that this is nothing compared to the benefits it can bring us.

MVC is not suitable for small or even medium-sized applications. Spending a lot of time applying MVC to applications that are not very large will usually result in more loss than gain.

MVC is a good way to create software
MVC design pattern is a good way to create software. Some of the principles it advocates, such as the separation of content and display, may be easier to understand. But if you want to isolate the components of the model, view, and controller, you may need to rethink your application, especially the architectural aspects of the application. If you are willing to accept MVC and have the ability to deal with the extra work and complexity it brings, MVC will take your software to a new level in terms of robustness, code reuse, and structure.

Java development Web Application has several development methods that conform to the MVC design pattern.

1:Jsp+Servlet+JavaBean(EJB)

2:Jsp+JavaBean(Controller)+JavaBean(EJB)(Model)

3:TDK(Turbine, Velocity...)

4:Xsp

5:Jsp+Struts+JavaBean(EJB)