quick-hello-world.md

Hello World Example

Code reference : https://github.com/GlueCoders/springboot-guide/releases/tag/quickhelloworld
Let's add a simple webservice method in the project, to see some action. First include spring-boot-starter-web dependency as shown below.

<dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
            <version>${spring.version}</version>
        </dependency>

This will bring in a lot of dependencies, of which major are related to spring-web, tomcat. Now let's create a class which we will the start point of the application and will also serve as our webservice entry point.

package org.gluecoders.library;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

@SpringBootApplication
@RestController
public class Application {

    public static void main(String[] args) {
        SpringApplication.run(Application.class, args);
    }

    @RequestMapping("/")
    @GetMapping
    public String hello(){
        return "Hi ! Welcome to Spring Boot Guide";
    }
}

Now run this class from IDE, Spring Boot logs should appear in console.

On browser hit http://localhost:8080/, and a response will appear in return with text "Hi ! Welcome to Spring Boot Guide".

Let's start one by one with the details going on in class

• @SpringBootApplication - Under the hood it enables a lot of annotations which are needed to enable Spring to be able to integrate with project like ComponentScan, Configuration etc.
• @RequestController - Notifies Spring that this class is to be mapped to incoming HTTP requests.
• Main method - This is the entry point when project is started. This delegates control to SpringApplication which in turn will start embedded Tomcat container and bootstrap code and other Spring related libraries together.
• @RequestMapping @GetMapping - Used for configuring mapping of hello method to incoming HTTP request. In this case hello method will map to / path with GET HTTP method.

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