(No implementation example) Configuration of web application to which MVC model 2 by Java is applied to us who are having a hard time in new employee training
Notes
- For beginners
- Or rather, I'm a beginner
- Implementation is not listed
- Conceptual
- I wrote it to solve the question "Where are you making now?" When making an app.
- I'm sorry I can't improve the class relationship due to various reasons.
Overview
- Introduction of MVC model 2
- Explanation of the configuration of the web application assuming implementation using Servlet + JSP + Java Beans
MVC model 2
Nowadays, it is often called the MVC model. A type of design pattern that can be used when implementing an application with a UI. MVC is an abbreviation of Model View Controller, and the controller plays the role of holding data and business logic as Model, displaying as View, and connecting them.
Web application with MVC model 2 applied
Since Servlet and JSP are used this time, Controller and View correspond to Servlet and JSP, respectively.
In addition, data is passed between Servlet and JSP via Bean. Bean is a data class and is included in Model. From now on, the class that manipulates data for the purpose of the application will be referred to as BusinessLogic.
Since it is a web application, there are users. In addition, the user accesses the application via a web browser. The request from the user is received by the Servlet, and the model is instructed to perform appropriate processing by input. The Servlet confirms that it is ready to return the response to the request and passes control to the JSP. JSP formats the passed data into HTML.
Here, "appropriate processing" includes validation of input from the user. The Servlet asks FormBean to check the validity, and if the input from the user is appropriate, performs the desired operation (business logic part in the figure).
For example, if you want to make an addition app, follow the steps below.
- Servlet receives GET request from user
- The user receives HTML from the Servlet with two numeric boxes and a submit button.
- Each of the two number boxes should be entered by the user ...
- Servlet receives POST request from user
- FormBean receives a user request from Servlet and checks its validity (not empty, etc.)
- If not valid, the JSP will generate HTML to display the error message.
- If valid, the function to add two numbers is called from Servlet and a bean for sending is returned.
- The sum of the two numbers is sent from the Servlet to the JSP as a bean.
- HTML that displays the sum is generated by JSP
The above is an example that does not use DB, but when using DB, DAO is used. DAO is an abbreviation for Data Access Object, which wraps operations from an application to a DB. The data extracted from the DB by DAO is stored in DTO (Data Transfer Object) and passed. DTO is a data type and follows Java Beans conventions.
