This blog offers both theoretical insights and practical applications for mastering Spring MVC.
Explore the concept of Spring MVC, starting with an introduction to its role as a Java framework utilizing the MVC architecture. Understand the workings of Spring MVC, covering request processing, controller invocation, model preparation, and more.
Table of Contents:
What is Spring MVC?
Spring MVC is a Java-based framework that provides a Model-View-Controller architecture. This framework is used for developing web applications. This design pattern specifies that an application comprises a data model, presentation information, and control information. This framework is structured around a DispatcherServlet, which is responsible for directing incoming HTTP requests to appropriate handlers. The meaning of the terms Model, View, and Controller is:
Model: It encapsulates application data, serving as a representation of the underlying information.
View: It is responsible for rendering the data from the model and generating HTML output, which the client’s browser can then interpret visually.
Controller: It functions to process user requests, orchestrate the interaction by receiving inputs, managing the logic, and passing the processed data to the View for presentation. This separation into Model, View, and Controller components contributes to a structured and efficient code organization, promoting a clean and maintainable design in application development.
What is Dispatcher Servlet?
The Dispatcher Servlet acts as the front controller or the entry point for managing the flow of requests in a Spring MVC application. It helps in handling and dispatching incoming HTTP requests to the appropriate controllers for processing. It serves as the front controller in the Spring MVC (Model-View-Controller) architecture.
When a client makes a request, the DispatcherServlet receives the request, consults a handler that maps which controller should handle the request, and then forwards the request to the chosen controller. After the controller processes the request and produces a response, the DispatcherServlet engages a view resolver to determine the appropriate view for rendering the response.
For example, imagine a scenario where a website named “university.com” receives a client request to save student data through the URL “university.com/save.” This request is initially directed to the front controller, acting as the central entry point. Upon accepting the request, the front controller delegates the task to “DataController” since it specializes in handling operations related to data storage, including the “/save” operation. Subsequently, the DataController processes the request and sends back the response to the client, completing the cycle.
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Working of Spring MVC
The workings of Spring MVC involve a systematic process that manages the flow of web requests in a Java web application. When a user initiates an HTTP request, the central component, DispatcherServlet, intercepts the request and analyzes its headers, path, and HTTP method to extract relevant information. Throughout this process, Spring MVC’s exception-handling mechanism ensures robust error management, contributing to a well-organized and efficient development framework.
Given below is a step-by-step explanation of how to work with an MVC framework:
Receiving the request: When you go to a website, the DispatcherServlet checks the information you’re sending, like where you want to go (request path), how you want to get there (HTTP method), and any additional details(headers).
Request Routing: The DispatcherServlet consults the HandlerMapping component to determine the suitable controller method, ensuring the request is directed to the correct handler based on the URL.
Controller Invocation: The identified controller method is invoked, executing application-specific logic, such as database operations, form data processing, or business operations.
Model Preparation: The controller method prepares and stores data in the model object, encapsulating information to be rendered in the view.
View Resolution: Upon completing the controller method, a ModelAndView object is returned, containing the prepared model data and the name of the view template.
View Rendering: The DispatcherServlet delegates rendering to the ViewResolver, which identifies the view template based on the provided name.
View Template Processing: The selected view template is processed by the respective view technology, converting model data into the desired output format.
Response Generation: The rendered view template becomes an HTTP response, with the DispatcherServlet sending it back to the client, concluding the request-response cycle.
Exception Handling: Spring MVC handles exceptions throughout the process, employing mechanisms to catch and manage errors and offering strategies like logging, redirection, or specific error codes.
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Creating a Spring MVC Application
Creating a project in Spring MVC is not as complex as it seems to be. We will create a simple MVC application that will simply give a greeting message. The process for creating the application is mentioned below:
Step 1. Create a project directory named “spring-mvc-example.” Within this directory, initiate a Maven project using the Maven project creation wizard provided by your IDE. In the project’s pom.xml file, add the following dependencies:
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-webmvc</artifactId>
<version>5.3.18</version>
</dependency>
Step 2. In the “src/main/java/com/example” package, establish a controller class named “GreetingController.java.” This class is designed to manage requests for displaying a greeting message.
@Controller
public class GreetingController {
@RequestMapping("/")
public String greeting(Model model) {
model.addAttribute("message", "Hello, Spring MVC!");
return "greeting";
}
}
Step 3. Create a JSP file named greeting.jsp in the src/main/webapp/WEB-INF/views directory. This template will render the greeting message.
<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head>
<title>Spring MVC Greeting</title>
</head>
<body>
<h1>${message}</h1>
</body>
</html>
Step 4: To deploy and run the application:
- Package the application into a WAR file using Maven.
- Deploy the WAR file to a configured web server, such as Apache Tomcat.
- Start the web server.
- Access the application in a web browser using the URL http://localhost:8080/spring-mvc-example/. You should see the message “Hello, Spring MVC!” displayed on the page.
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Advantages and Disadvantages of Spring MVC
Spring MVC stands as a robust Java framework for web application development, renowned for its extensive feature set, flexibility, and broad acceptance in the development community. Some advantages of Spring MVC are listed below:
- Saves developers time and effort as it reduces the amount of boilerplate code required to develop web applications.
- The Model-View-Controller (MVC) architectural pattern of Spring MVC provides code separation and organization, making web applications easier to understand.
- It makes debugging easier.
- It can be seamlessly integrated with other Spring Framework features.
The following are the disadvantages of Spring MVC:
- It is not beginner-friendly because of its complexity.
- It relies on XML configuration in some cases.
- May not be suitable for smaller projects.
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Conclusion
Spring MVC has completely changed the field of web development, as it has introduced a systematic approach to building web applications. Its impact has changed how developers approach web development tasks, making the process more scalable and effective. Creating a basic application is simple and fast using Spring MVC. Its widespread acceptance and seamless integration with the broader Spring ecosystem have firmly established it as a leading Java framework for web development.