Spring Boot is a Java-based Spring framework that makes it easy to develop stand-alone (build microservices) applications. Most Spring Boot applications require minimal configuration due to its auto-configuration and embedded application server support like Tomcat, Jetty, etc.
Spring Boot differs from Spring in several ways:
The advantages of Spring Boot include:
The features of Spring Boot include:
The key components of Spring Boot are:
Some important Spring Boot annotations are:
Spring Initializr is used to create new or skeleton Spring Boot projects.
Steps to create a Spring project using Spring Initializr:
Spring Boot provides various properties that can be configured in the application.properties file, such as spring.datasource.url, server.port, spring.profiles.active, etc.
Use @EnableAutoConfiguration(exclude = .class) to disable specific auto-configuration.
Example:
@EnableAutoConfiguration(exclude = SpringTestApplication.class)Spring Boot works through the automatic configuration of your application based on dependencies. It primarily uses the @SpringBootApplication annotation and a main method to run the application.
Thymeleaf is a popular templating engine used in Spring Boot applications to build dynamic web pages.
Commonly used Spring Boot starters include:
Add the thymeleaf-spring-boot-starter dependency in your pom.xml file.
Example:
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-thymeleaf</artifactId>
</dependency>@SpringBootApplication is equivalent to using @Configuration, @EnableAutoConfiguration, and @ComponentScan.
@RestController is a combination of @Controller and @ResponseBody, used to create RESTful web services. It converts the response to JSON or XML.
The key dependencies of Spring Boot include:
@Controller maps the model object to a view or template, making it readable. @RestController simply returns the object, with the object data directly written in the HTTP response as JSON or XML.
Spring Actuator provides additional features for monitoring and managing your application in production, such as metrics, health checks, and configuration properties.
Add the spring-boot-starter-actuator dependency in your pom.xml file.
Example:
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-actuator</artifactId>
</dependency>Change the default port by specifying the server.port property in the application.properties file.
Example:
server.port=8081Spring Boot DevTools provides additional development-time features like automatic restarts, live reload, and configurations for faster application development.
Add the spring-boot-devtools dependency in your pom.xml file.
Example:
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-devtools</artifactId>
</dependency>Enable scheduling by adding the @EnableScheduling annotation to a configuration class.
Example:
@Configuration
@EnableScheduling
public class SchedulingConfig {
}Spring Cloud provides tools for developers to quickly build distributed systems with common patterns such as configuration management, service discovery, circuit breakers, routing, etc.
Microservices architecture is a design style that structures an application as a collection of small, loosely coupled services that can be developed, deployed, and scaled independently.
The advantages of microservices include:
A distributed system is a network that consists of multiple autonomous computers that communicate and coordinate with each other to achieve a common goal.
Spring Boot simplifies the creation of production-ready applications and provides a wide range of tools for building and deploying microservices.
Netflix Eureka is a service registry that allows microservices to register themselves and discover other registered services.
Zuul is an edge service that provides dynamic routing, monitoring, resiliency, and security for microservices.
Load balancing is a way to distribute incoming network traffic across multiple servers, ensuring that no single server becomes overloaded.
Add spring-cloud-starter-netflix-eureka-client dependency in your pom.xml and configure application properties.
Communication between microservices can happen via:
Spring Cloud Config provides server and client-side support for externalized configuration in a distributed system.
Service discovery can be implemented using Netflix Eureka in Spring Cloud.
Hystrix is a latency and fault-tolerance library designed to isolate access points to remote systems and services, preventing cascading failures.
API Gateways handle routing requests, composition, and providing protocol translations. They act as an entry point for client requests.
Feign is a declarative web service client, making it easier to write web service clients by simplifying HTTP API calls using annotations.
Zuul is an edge server that provides dynamic routing, monitoring, security, and resilience in microservices architecture.
A service registry is a database of services and their locations, which enables dynamic discovery and connection of services.
@EnableDiscoveryClient is used to register a service with a discovery service like Eureka.
Ribbon is a client-side load balancer that allows for configuring a list of servers to distribute the load.
A circuit breaker pattern is a design pattern used to detect failures and encapsulate the logic of preventing the failure from constantly recurring.
Implement circuit breaker pattern using Hystrix with annotations like @HystrixCommand.
DevOps ensures continuous integration and deployment, making it easier to manage the microservices lifecycle.
Common challenges with microservices include:
Best practices for designing microservices include: