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In this tutorial, we will learn what is @Controller and how to use it in Spring Boot web applications.

Spring @Controller Annotation Overview

The @Controller annotation is used in Spring MVC to mark a class as a controller component. It acts as a request handler and handles incoming HTTP requests, performing the necessary processing and returning a response.

Controllers in Spring MVC are responsible for processing user requests, interacting with business logic or services, and returning a view or response to the client.

Spring @Controller Annotation Example

Let's use Spring Boot to develop a simple web application.

Add Maven Dependencies

Add the following Maven dependencies to your Spring boot application:

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-thymeleaf</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

The spring-boot-starter-web starter is responsible for setting up the web-related components and configurations in a Spring Boot application. It includes the necessary dependencies and auto-configurations to develop web applications using Spring MVC.

The spring-boot-starter-thymeleaf starter includes the Thymeleaf templating engine for server-side rendering of views. Thymeleaf is a popular Java-based templating language that enables the creation of dynamic web pages.

By including the spring-boot-starter-web and spring-boot-starter-thymeleaf starters in your Spring Boot project, you can quickly set up a web application with the necessary web infrastructure, request handling capabilities, and Thymeleaf templating support. These starters simplify the configuration process and provide a solid foundation for building modern, scalable, and interactive web applications using Spring Boot.

Create Spring MVC HelloController

Next, create a class and annotate it with @Controller:

import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestParam;

@Controller
public class HelloController {

    @GetMapping({
        "/",
        "/hello"
    })
    public String hello(@RequestParam(value = "name",
        defaultValue = "World", required = true) String name, Model model) {
        model.addAttribute("name", name);
        return "hello";
    }
}

In the example above, the HelloController class is annotated with @Controller. The @GetMapping annotation is used to map the /hello and / URL paths to the home method, which returns a view name "hello". When a user visits the /hello URL, this method is executed and the associated view is rendered.

Spring boot will auto-configure the view resolver for Thymeleaf whenever it will find the spring-boot-starter-thymeleaf dependency on the classpath. Spring boot will pick Thymeleaf templates (HTML pages) from the resources/templates folder.

Create Thymeleaf Template View

Next, let's create a Thymeleaf template hello.html under /resources/templates folder and add the following code to it:

<!DOCTYPE html>
<html>
<head>
<meta charset="ISO-8859-1">
<title>Insert title here</title>
</head>
<body>
 <p th:text="'Hello, ' + ${name} + '!'" />
</body>
</html>

In the above code, th:text Thymeleaf attribute specifies that the content of the paragraph should be set using Thymeleaf's text substitution feature.

"Hello, ' + ${name} + '!'": This Thymeleaf expression concatenates the string "Hello, " with the value of the ${name} variable and then appends "!" at the end. The ${name} variable is expected to be passed as a model attribute when rendering the template. The result of this expression will be dynamically inserted into the paragraph element when the page is rendered, displaying a personalized greeting message.

Demo

Next, let's run the Spring boot application and see the result in the browser:

Root URL: http://localhost:8080/

The /hello?Ramesh URL: http://localhost:8080/hello?Ramesh

Conclusion

The @Controller annotation is a fundamental building block of Spring MVC, allowing developers to create web applications and handle HTTP requests with ease. By using the @Controller annotation, you can define request mapping methods and build flexible, modular, and maintainable web applications using the Spring Framework.

Related Spring and Spring Boot Annotations

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Spring @Controller Annotation Example Tutorial

Spring @Controller Annotation Overview

Spring @Controller Annotation Example

Add Maven Dependencies

Create Spring MVC HelloController

Create Thymeleaf Template View

Demo

Conclusion

Related Spring and Spring Boot Annotations

My Top and Bestseller Udemy Courses. The sale is going on with a 70 - 80% discount. The discount coupon has been added to each course below:

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Spring Boot 3 Paid Course Published for Free
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Spring @Controller Annotation Example Tutorial

Spring @Controller Annotation Overview

Spring @Controller Annotation Example

Add Maven Dependencies

Create Spring MVC HelloController

Create Thymeleaf Template View

Demo

Conclusion

Related Spring and Spring Boot Annotations

My Top and Bestseller Udemy Courses. The sale is going on with a 70 - 80% discount. The discount coupon has been added to each course below:

Build REST APIs with Spring Boot 4, Spring Security 7, and JWT

[NEW] Learn Apache Maven with IntelliJ IDEA and Java 25

ChatGPT + Generative AI + Prompt Engineering for Beginners

Spring 7 and Spring Boot 4 for Beginners (Includes 8 Projects)

Building Real-Time REST APIs with Spring Boot - Blog App

Building Microservices with Spring Boot and Spring Cloud

Java Full-Stack Developer Course with Spring Boot and React JS

Build 5 Spring Boot Projects with Java: Line-by-Line Coding

Testing Spring Boot Application with JUnit and Mockito

Spring Boot Thymeleaf Real-Time Web Application - Blog App

Master Spring Data JPA with Hibernate

Spring Boot + Apache Kafka Course - The Practical Guide

Java Testing: Mastering JUnit 5 Framework

Reactive Programming in Java: Spring WebFlux and Testing

Spring Boot + RabbitMQ Course - The Practical Guide

Functional Programming in Java (Includes Java Collections)

ChatGPT for Java Developers: Boost Your Productivity with AI

Comments

Post a Comment

Spring Boot 3 Paid Course Published for Free on my Java Guides YouTube Channel

Spring Boot 3 Paid Course Published for Free
on my Java Guides YouTube Channel