Module 2: Spring Boot

Introduction to Spring Boot

Spring Boot is an extension of the Spring framework that simplifies the building and development of applications. It takes an opinionated approach to configuration, automatically configuring your application based on the dependencies you've added to your project. This allows you to get started with minimal setup and configuration.

Spring Boot makes it easier to create stand-alone, production-grade Spring based applications that you can "just run". It's designed to be fast, require minimal configuration, and provide a platform to create microservices and cloud-ready applications.

REST APIs and Spring

REST (Representational State Transfer) APIs provide a way to expose data and business logic safely through endpoints or routes. Spring Boot is an excellent framework for building REST APIs because it provides built-in support for HTTP methods, request routing, and response handling.

A REST API typically follows the CRUD (Create, Read, Update, Delete) operations through HTTP methods:

• CREATE - POST: Creates new resources
• READ - GET: Retrieves data from the server
• UPDATE - PUT/PATCH: Updates existing resources
• DELETE - DELETE: Removes resources

Key Topics

Building REST Services with Spring Boot

Setting Up a Spring Boot Application

To create a Spring Boot application, you need to add the necessary dependencies to your build.gradle file:

implementation 'org.springframework.boot:spring-boot-starter-web'
developmentOnly 'org.springframework.boot:spring-boot-devtools'
testImplementation 'org.springframework.boot:spring-boot-starter-test'

Then, create your main application class with the @SpringBootApplication annotation:

package com.example.demo;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
public class DemoApplication {

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

Creating a REST Controller

Controllers in Spring Boot handle HTTP requests. Here's an example of a simple REST controller:

@RestController
public class DogController {
    
    @Autowired
    private DogRepository dogRepos;

    @GetMapping(value = "/dogs/name/{findname}", produces = {"application/json"})
    public ResponseEntity<?> findADogs(@PathVariable String findname) {
        return new ResponseEntity<>(dogRepos.findByName(findname), HttpStatus.OK);
    }
}

Understanding Spring Boot Annotations

• @RestController: Identifies this class as a controller where every method returns a domain object instead of a view.
• @GetMapping: Maps HTTP GET requests to specific handler methods.
• @PathVariable: Extracts values from the URI path.
• @RequestParam: Extracts query parameters from the request URL.
• @Autowired: Automatically injects dependencies.

Different Types of Request Parameters

Spring Boot supports different ways to handle request parameters:

Path Variables

Used in URL paths like /dogs/name/dottie, where "dottie" is the path variable.

@GetMapping(value = "/dogs/name/{findname}")
public ResponseEntity<?> findADogs(@PathVariable String findname) {
    // Method implementation
}

Request Parameters

Added to the URL with a question mark like /dogs/name?name=dottie.

@GetMapping(value = "/dogs/name")
public ResponseEntity<?> findADogs(@RequestParam(name = "findname", required = false) String theName) {
    // Method implementation
}

Key Benefits of Spring Boot

• Rapid Development: Reduces boilerplate code and simplifies configuration
• Embedded Servers: Includes embedded servers (Tomcat, Jetty) for easy deployment
• Production-Ready: Provides health checks, metrics, and monitoring out of the box
• No XML Configuration: Uses Java annotations and properties files instead of XML
• Microservices Support: Designed with cloud-native applications in mind

Resources