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Joshua Turner
Joshua Turner

What You Need to Know About Spring Microservices in Action.pdf: A Comprehensive Book that Covers Everything from Design to Deployment of Microservices with Java and Spring



Spring Microservices in Action: A Comprehensive Guide




If you are a Java developer who wants to build scalable, resilient, and agile applications that can run on the cloud, you might have heard of microservices. Microservices are small, independent, and loosely coupled services that communicate with each other using well-defined APIs. They allow you to decompose your application into manageable modules that can be developed, tested, deployed, and scaled independently.




Spring Microservices In Action.pdf


Download Zip: https://www.google.com/url?q=https%3A%2F%2Furluso.com%2F2ud5KM&sa=D&sntz=1&usg=AOvVaw0vM7CGwvDg_SwRS-sHPUub



But how do you build microservices with Java? One of the most popular and powerful frameworks for building microservices is Spring Boot. Spring Boot is an opinionated framework that simplifies the development of stand-alone, production-grade applications based on the Spring Framework. It provides features such as auto-configuration, dependency management, embedded servers, actuator endpoints, and more.


However, Spring Boot alone is not enough to build cloud-native microservices. You also need tools that can help you with configuration management, service discovery, load balancing, fault tolerance, routing, security, monitoring, and more. That's where Spring Cloud comes in. Spring Cloud is a collection of projects that provide solutions for common patterns in distributed systems. It integrates well with Spring Boot and makes it easy to implement features such as Config Server, Eureka, Ribbon, Feign, Hystrix, Zuul, and more.


In this article, we will explore the benefits and challenges of microservices architecture. We will also learn how to use Spring Boot and Spring Cloud to build a simple microservice application that demonstrates some of the key features of these frameworks. Let's get started!


Benefits of Microservices Architecture




Microservices architecture has many advantages over the traditional monolithic architecture. Some of the main benefits are:


  • Scalability: Microservices can be scaled independently according to their demand and resource consumption. You can also use different scaling strategies for different services depending on their needs. For example, you can scale up or down a service, scale out or in a service, or use a combination of both.



  • Resilience: Microservices are isolated from each other and can tolerate failures without affecting the whole system. You can also use techniques such as circuit breaker, fallback, retry, and timeout to handle errors and prevent cascading failures.



  • Agility: Microservices enable faster and more frequent delivery of features and updates. You can use agile methodologies such as Scrum or Kanban to manage your development process. You can also use continuous integration and continuous delivery (CI/CD) pipelines to automate your testing and deployment process.



  • Modularity: Microservices are organized around business domains and capabilities. They have clear boundaries and interfaces that define their responsibilities and interactions. This makes them easier to understand, maintain, and reuse.



  • Testability: Microservices can be tested independently using different levels of testing such as unit, integration, contract, and end-to-end testing. You can also use tools such as Docker and Kubernetes to create isolated and reproducible environments for testing.



Challenges of Microservices Architecture




Microservices architecture also has some drawbacks and challenges that you need to be aware of. Some of the main challenges are:


  • Complexity: Microservices introduce more complexity in terms of design, development, deployment, and management. You need to deal with issues such as service decomposition, inter-service communication, data consistency, transaction management, distributed tracing, logging, etc.



  • Communication: Microservices communicate with each other using network calls that are prone to latency, errors, and failures. You need to choose the right communication protocol (such as HTTP, AMQP, gRPC, etc.) and the right communication style (such as synchronous, asynchronous, or event-driven) for your services. You also need to implement proper error handling and retry mechanisms for your communication.



  • Security: Microservices expose more endpoints and increase the attack surface of your application. You need to implement proper authentication, authorization, encryption, and auditing for your services. You also need to use tools such as API gateway, firewall, and VPN to protect your services from external threats.



  • Monitoring: Microservices generate more metrics, logs, and traces that need to be collected, aggregated, analyzed, and visualized. You need to use tools such as Prometheus, Grafana, ELK stack, Zipkin, etc. to monitor the health and performance of your services. You also need to use tools such as alertmanager, pagerduty, etc. to notify you of any issues or incidents.



  • Deployment: Microservices require more infrastructure and resources to run and manage. You need to use tools such as Docker, Kubernetes, Helm, etc. to package, deploy, orchestrate, and scale your services. You also need to use tools such as Jenkins, Spinnaker, etc. to automate your deployment process.



Spring Boot: A Powerful Framework for Building Microservices




Spring Boot is a framework that makes it easy to create stand-alone, production-grade applications based on the Spring Framework. It provides features such as:


  • Auto-configuration: Spring Boot automatically configures your application based on the dependencies that you have added in your pom.xml file. For example, if you add spring-boot-starter-web dependency, Spring Boot will automatically configure a web application with an embedded Tomcat server.



  • Dependency management: Spring Boot manages the versions of the dependencies that you need for your application. It provides a set of starter dependencies that include the most common libraries for building different types of applications. For example, if you want to build a RESTful web service with Spring MVC and Jackson, you can simply add spring-boot-starter-web dependency.



  • Embedded servers: Spring Boot allows you to run your application without needing to deploy it to an external server. It supports embedded servers such as Tomcat, Jetty, Undertow, etc. You can also switch between different servers by changing a single property in your application.properties file.



  • Actuator: Spring Boot provides a set of endpoints that expose information about your application such as health status, metrics, environment variables, configuration properties, etc. You can access these endpoints using HTTP or JMX protocols. You can also customize these endpoints or add your own endpoints.



Creating a Simple Spring Boot Application




To create a simple Spring Boot application that prints "Hello World" on the browser window when you access http://localhost:8080/, follow these steps:


  • Go to https://start.spring.io/ and fill in the details as follows:



  • Project: Maven Project



  • Language: Java



  • Spring Boot: 2.5.7



  • Project Metadata:



  • Group: com.example



  • Artifact: hello-world



  • Name: hello-world



  • Description: Demo project for Spring Boot



  • Package name: com.example.hello-world



  • Packaging: Jar



  • Java: 11



  • Dependencies: Spring Web



  • Click on Generate and download the zip file.



  • Extract the zip file and open it in your favorite IDE (such as IntelliJ IDEA).



  • Create a new class called HelloWorldController in the package com.example.hello-world and add the following code:



  • ```java package com.example.hello-world; import org.springframework.web.bind.annotation.GetMapping; import org.springframework.web.bind.annotation.RestController; @RestController public class HelloWorldController @GetMapping("/") public String hello() return "Hello World"; ``` Run the application by right-clicking on the HelloWorldApplication class and selecting Run.



  • Open your browser and go to http://localhost:8080/. You should see "Hello World" on the screen.



Configuring a Spring Boot Application




Spring Boot provides various ways to configure your application. One of the most common ways is to use the application.properties file that is located in the src/main/resources folder. This file allows you to define key-value pairs that can be used to customize your application. For example, you can change the server port, logging level, database connection, etc.


You can also use profiles to define different configurations for different environments such as development, testing, production, etc. You can create profile-specific properties files such as application-dev.properties, application-test.properties, application-prod.properties, etc. and activate them using the spring.profiles.active property.


Another way to configure your application is to use environment variables. You can set environment variables in your operating system or pass them as command-line arguments when running your application. Spring Boot will automatically map them to properties using relaxed binding rules. For example, you can set SERVER_PORT=8081 or server.port=8081 to change the server port.


Testing a Spring Boot Application




Spring Boot makes it easy to test your application using various tools and frameworks. You can use JUnit as the testing framework, Mockito as the mocking framework, and TestRestTemplate as the REST client. You can also use annotations such as @SpringBootTest, @WebMvcTest, @DataJpaTest, etc. to configure your test classes and run them with different slices of your application context.


To test our simple Spring Boot application that prints "Hello World" on the browser window when you access http://localhost:8080/, follow these steps:


  • Create a new Spring Boot application called config-server and add the spring-cloud-config-server dependency.



  • Add the @EnableConfigServer annotation to the ConfigServerApplication class.



  • Create a Git repository and add some configuration files for your microservices. For example, you can create a file called hello-world.properties and add some properties such as server.port=8081, message=Hello World from Config Server, etc.



  • Add the spring.cloud.config.server.git.uri property to the application.properties file of the config-server application and set it to the URL of your Git repository.



  • Run the config-server application and access http://localhost:8888/hello-world/default. You should see the properties from the hello-world.properties file in JSON format.



  • Create a new Spring Boot application called hello-world-client and add the spring-cloud-starter-config dependency.



  • Add the spring.application.name property to the bootstrap.properties file of the hello-world-client application and set it to hello-world.



  • Add the spring.cloud.config.uri property to the bootstrap.properties file of the hello-world-client application and set it to http://localhost:8888.



  • Create a new class called HelloWorldClientController in the package com.example.hello-world-client and add the following code:



  • ```java package com.example.hello-world-client; import org.springframework.beans.factory.annotation.Value; import org.springframework.web.bind.annotation.GetMapping; import org.springframework.web.bind.annotation.RestController; @RestController public class HelloWorldClientController @Value("$message") private String message; @GetMapping("/") public String hello() return message; ``` Run the hello-world-client application and access http://localhost:8081/. You should see "Hello World from Config Server" on the screen.



Registering and Discovering Microservices with Spring Cloud Eureka




To register and discover your microservices with Spring Cloud Eureka, follow these steps:


  • Create a new Spring Boot application called eureka-server and add the spring-cloud-starter-netflix-eureka-server dependency.



  • Add the @EnableEurekaServer annotation to the EurekaServerApplication class.



  • Add the following properties to the application.properties file of the eureka-server application:



  • ```properties server.port=8761 eureka.client.register-with-eureka=false eureka.client.fetch-registry=false ``` Run the eureka-server application and access http://localhost:8761/. You should see the Eureka dashboard with no registered instances.



  • Create a new Spring Boot application called hello-world-service and add the spring-cloud-starter-netflix-eureka-client dependency.



  • Add the @EnableEurekaClient annotation to the HelloWorldServiceApplication class.



  • Add the following properties to the application.properties file of the hello-world-service application:



  • ```properties server.port=8082 spring.application.name=hello-world-service eureka.client.service-url.defaultZone=http://localhost:8761/eureka ``` Create a new class called HelloWorldServiceController in the package com.example.hello-world-service and add the following code:



  • ```java package com.example.hello-world-service; import org.springframework.web.bind.annotation.GetMapping; import org.springframework.web.bind.annotation.RestController; @RestController public class HelloWorldServiceController @GetMapping("/") public String hello() return "Hello World from Eureka Service"; ``` Run the hello-world-service application and access http://localhost:8082/. You should see "Hello World from Eureka Service" on the screen.



  • Refresh the Eureka dashboard and you should see the hello-world-service instance registered.



  • Create a new Spring Boot application called hello-world-client and add the spring-cloud-starter-netflix-eureka-client dependency.



  • Add the @EnableEurekaClient annotation to the HelloWorldClientApplication class.



  • Add the following properties to the application.properties file of the hello-world-client application:



  • ```properties server.port=8083 spring.application.name=hello-world-client eureka.client.service-url.defaultZone=http://localhost:8761/eureka ``` Create a new class called HelloWorldClientController in the package com.example.hello-world-client and add the following code:



  • ```java package com.example.hello-world-client; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.web.bind.annotation.GetMapping; import org.springframework.web.bind.annotation.RestController; import org.springframework.web.client.RestTemplate; @RestController public class HelloWorldClientController @Autowired private RestTemplate restTemplate; @GetMapping("/") public String hello() return restTemplate.getForObject("http://hello-world-service/", String.class); ``` Create a new class called RestTemplateConfig in the package com.example.hello-world-client and add the following code:



  • ```java package com.example.hello-world-client; import org.springframework.cloud.client.loadbalancer.LoadBalanced; import org.springframework.context.annotation.Bean; import org.springframework.context.annotation.Configuration; import org.springframework.web.client.RestTemplate; @Configuration public class RestTemplateConfig @Bean @LoadBalanced public RestTemplate restTemplate() return new RestTemplate(); ``` Run the hello-world-client application and access http://localhost:8083/. You should see "Hello World from Eureka Service" on the screen.



Load Balancing and Rest Clients with Spring Cloud Ribbon and Feign




To load balance and communicate with your microservices using Spring Cloud Ribbon and Feign, follow these steps:


  • Create a new Spring Boot application called hello-world-service-2 and add the spring-cloud-starter-netflix-eureka-client dependency.



  • Add the @EnableEurekaClient annotation to the HelloWorldService2Application class.



  • Add the following properties to the application.properties file of the hello-world-service-2 application:



  • ```properties server.port=8084 spring.application.name=hello-world-service eureka.client.service-url.defaultZone=http://localhost:8761/eureka ``` Create a new class called HelloWorldService2Controller in the package com.example.hello-world-service-2 and add the following code:



  • ```java package com.example.hello-world-service-2; import org.springframework.web.bind.annotation.GetMapping; import org.springframework.web.bind.annotation.RestController; @RestController public class HelloWorldService2Controller @GetMapping("/") public String hello() return "Hello World from Eureka Service 2"; ``` Run the hello-world-service-2 application and access http://localhost:8084/. You should see "Hello World from Eureka Service 2" on the screen.



  • Refresh the Eureka dashboard and you should see two instances of hello-world-service registered.



  • Modify the HelloWorldClientController class in the hello-world-client application and add a loop to call the hello-world-service multiple times:



  • ```java package com.example.hello-world-client; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.web.bind.annotation.GetMapping; import org.springframework.web.bind.annotation.RestController; import org.springframework.web.client.RestTemplate; @RestController public class HelloWorldClientController @Autowired private RestTemplate restTemplate; @GetMapping("/") public String hello() StringBuilder sb = new StringBuilder(); for (int i = 0; i < 10; i++) sb.append(restTemplate.getForObject("http://hello-world-service/", String.class)); sb.append("\n"); return sb.toString(); ``` Run the hello-world-client application and access http://localhost:8083/. You should see alternating responses from hello-world-service and hello-world-service-2. This shows that Ribbon is load balancing the requests among the available instances of the service.



  • Create a new interface called HelloWorldServiceClient in the package com.example.hello-world-client and add the following code:



  • ```java package com.example.hello-world-client; import org.springframework.cloud.openfeign.FeignClient; import org.springframework.web.bind.annotation.GetMapping; @FeignClient(name = "hello-world-service") public interface HelloWorldServiceClient @GetMapping("/") String hello(); ``` Modify the HelloWorldClientController class in the hello-world-client application and use the HelloWorldServiceClient interface instead of RestTemplate:



  • ```java package com.example.hello-world-client; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.web.bind.annotation.GetMapping; import org.springframework.web.bind.annotation.RestController; @RestController public class HelloWorldClientController @Autowired private HelloWorldServiceClient helloWorldServiceClient; @GetMapping("/") public String hello() StringBuilder sb = new StringBuilder(); for (int i = 0; i < 10; i++) sb.append(helloWorldServiceClient.hello()); sb.append("\n"); return sb.toString(); ``` Run the hello-world-client application and access http://localhost:8083/. You should see the same result as before. This shows that Feign is a declarative REST client that simplifies the communication with your microservices.



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