Java back-end development is a very important technology that is the core of modern Internet applications. Java backend development mainly involves API MVC framework development. In this article, I will introduce how to use Java Spring MVC for API MVC framework development.

Java Spring MVC is a very powerful open source framework, which is mainly used for the development of web applications. It uses the MVC (Model-View-Controller) architectural pattern to enable developers to develop Web applications more efficiently. Java Spring MVC is very easy to learn and use. It uses Java EE standard technologies, including Servlets, JSP, JSTL, Hibernate and other Java EE frameworks.

First, we need to install Java and Eclipse IDE. Java is generally pre-installed. If not, you need to go to the official website (https://www.oracle.com/java/technologies/javase-downloads.html) to download Java and follow the installation program prompts to install it. Eclipse IDE can be downloaded from the official website (https://www.eclipse.org/downloads/packages/release/2020-09/r/eclipse-ide-enterprise-java-developers).

Next, we need to create a new Java Spring MVC project. In the Eclipse IDE, select File > New > Other, then select Spring Legacy Project in the pop-up dialog box, and then select Spring MVC Project. Then we need to specify the name and location of the project. We can choose the default configuration or a custom configuration. Once completed, we can start using the Java Spring MVC framework.

In Java Spring MVC, the controller is the core of the MVC framework. It is mainly responsible for processing HTTP requests and displaying corresponding responses. We can define the controller class and its methods through annotations. For example:

@Controller @RequestMapping("/hello") public class HelloWorldController { @RequestMapping(method = RequestMethod.GET) public String helloWorld(ModelMap model) { model.addAttribute("message", "Hello World!"); return "hello"; } }

The above code defines a controller class called HelloWorldController, which handles HTTP GET requests on the /hello URL. The method helloWorld adds a property called "message" to the ModelMap and returns a view name called "hello".

View is the HTML page that website users ultimately see. In Java Spring MVC, JSP is usually used as the view. We can return the view name in the controller and Java Spring MVC will automatically find the JSP file corresponding to that name. For example:

<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%>      
  
${message}
  

The above code is a JSP file named "hello". It uses an EL expression to display the value of the attribute named "message" added in the controller.

Between the controller and the view, we use the model to pass data. The model uses the ModelMap class to save attribute values. Controllers can add properties to the model, and views can use EL expressions to get properties from the model. For example:

@Controller public class LoginController { @RequestMapping(value = "/login", method = RequestMethod.POST) public String login(@RequestParam("username") String username, @RequestParam("password") String password, ModelMap model) { if (username.equals("admin") && password.equals("password")) { model.addAttribute("username", username); return "home"; } else { return "login"; } } }

The above code defines a controller named LoginController that handles HTTP POST requests on the /login URL. The method login compares the username and password obtained from the request with the hardcoded values. If the validation passes, it will add a property called "username" to the ModelMap and then return a view name called "home". Otherwise, it returns a view name called "login".

Finally, we need to configure DispatcherServlet in the Web.xml file. In Java Spring MVC, DispatcherServlet forwards all HTTP requests to the corresponding controller. We can define its URL mapping in the Web.xml file. For example:

 dispatcher org.springframework.web.servlet.DispatcherServlet 1   dispatcher / 

The above is a Web.xml file configuration example. It maps all URLs into a Servlet named "dispatcher". We can define the configuration file of the Spring MVC framework in DispatcherServlet. For example:

 contextConfigLocation /WEB-INF/dispatcher-servlet.xml 

The above is the location configuration of the Spring MVC configuration file. It indicates that the configuration file of the Spring MVC framework is located in the /WEB-INF/dispatcher-servlet.xml file. In this file we can define controllers, views and models and the relationships between them.

In short, Java Spring MVC is a very excellent API MVC framework. In this article, I introduced how to use the Java Spring MVC framework for API MVC framework development. In the actual development process, we can choose the appropriate framework according to project needs to improve the development efficiency and quality of Web applications.

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