Building A Microservices Application Using Spring Boot
With the advent of cloud computing & containerization, microservices has taken the world by storm. Organizations are hunting for professionals with Microservices Architecture Training. In this article, let me show how we can create Microservices Application for Top Sports Brands using Spring Boot and Netflix Eureka Server in detail.
So, let us get started, folks.
Why there is a need for Spring Boot?
Spring Boot enables building production-ready applications quickly and provides non-functional features:
- Embedded servers which are easy to deploy with the containers
- It helps in monitoring the multiples components
- It helps in configuring the components externally
Now, let us see what are the challenges with Microservices Architecture
Challenges With Microservice Architectures
While developing a number of smaller microservices might look easy, but there are a number of inherent complexities that are associated with microservices architectures. Let’s look at some of the challenges:
Automating the Components: It becomes difficult to automate everything because there are a number of smaller components instead of a monolith, i.e. Builds, Deployment, Monitoring, etc.
Perceptibility: There are number of small components to deploy and maintain which sometimes becomes difficult to monitor and identify problems. It requires great perceptibility around all the components.
Configuration Management: There is a great need to maintain the configurations for the components across the various environments.
Debugging: It becomes difficult to probe each and every service for an error. Centralized Logging and Dashboards are essential to make it easy to debug problems.
Consistency: You cannot have a wide range of tools solving the same problem. While it is important to foster innovation, it is also important to have some decentralized governance around the languages, platforms, technology and tools used for implementing/deploying/monitoring microservices.
Spring Boot Microservices: Building a Top Sports Brands Architecture with Spring Boot
In this spring boot microservices example, we will be creating Top Sports Brands application which will be having 3 services:-
Eureka Service
This Service will register every microservice and then the client microservice will look up the Eureka server to get a dependent microservice to get the job done. This Eureka Server is owned by Netflix and in this, Spring Cloud offers a declarative way to register and invoke services by Java annotation.
Item Catalog Service
This service will generate the list of Sports brands which are popular in the market.
Edge Service
It is similar to the standalone Item service created in Bootiful Development with Spring Boot and Angular. However, it will have fallback capabilities which prevent the client from receiving an HTTP error when the service is not available.
Let us see which of the following tools required to create this spring boot microservices example application.
Tools Required
- Java 8
- Eclipse IDE Oxygen
- Spring Tool
If you facing any difficulty in installing and running the above tools, please refer to the article on Install Spring Tool Suite.
Spring Boot Microservices: Creating a Eureka Service
To begin with, create a EurekaServer Spring Starter Project in Eclipse IDE. Click on Spring Starter Project and click on Next.
Name your Spring Starter Project as EurekaServer and other Information will be filled automatically.
Note:- Make sure your Internet is connected otherwise it will show an error.
Now, select Eureka Server as a dependency and click on Finish.
Now, modify EurekaServer/src/main/resources/application.properties file to add a port number and disable registration.
server.port=8761
eureka.client.register-with-eureka=false
Now, Open the following directory,
EurekaServer/src/main/java/com/example/EurekaServiceApplication.java and add @EnableEurekaServer above @SpringBootApplication.
import org.springframework.cloud.netflix.eureka.server.EnableEurekaServer;@EnableEurekaServer
@SpringBootApplication
This annotation will configure a registry that will allow other applications to communicate.
To start the Application: Right Click on the Project –> Run As –> Click on “Spring Boot App“.
Now open http://localhost:8761. Here Spring Eureka Server will open and will show no service will be running.
Spring Boot Microservices: Creating an Item Catalog Service
Again create a new project. Use Item-catalog-service for the artifact name and click on Next.
Add the following dependencies:
Actuator: features to help you monitor and manage your application
Eureka Discovery: for service registration
JPA: to save/retrieve data
H2: an in-memory database
Rest Repositories: to expose JPA repositories as REST endpoints
Web: Spring MVC and embedded Tomcat
DevTools: to auto-reload the application when files change
Lombok: to reduce boilerplate code
Click on Finish.
Now, create an Item entity, toItemCatalogServiceApplication.java . The code below assumes you’re putting all classes in the same file.
@Data
@AllArgsConstructor
@NoArgsConstructor
@ToString
@Entity
class Item {public Item(String name) {
this.name = name;
}@Id
@GeneratedValue
private Long id;private String name;
}@RepositoryRestResource
interface ItemRepository extends JpaRepository<Item, Long> {}@Component
class ItemInitializer implements CommandLineRunner {private final ItemRepository ItemRepository;ItemInitializer(ItemRepository itemRepository) {
this.itemRepository = itemRepository;
}@Override
public void run(String... args) throws Exception {
Stream.of(""Lining", "PUMA", "Bad Boy", "Air Jordan", "Nike", "Adidas", "Reebok")
.forEach(item -> itemRepository.save(new Item(item)));itemRepository.findAll().forEach(System.out::println);
}
}
If you’re using an editor that doesn’t auto-import classes, here’s the list of imports needed at the top of ItemCatalogServiceApplication.java.
import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;
import lombok.ToString;
import org.springframework.boot.CommandLineRunner;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.data.rest.core.annotation.RepositoryRestResource;
import org.springframework.stereotype.Component;import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import java.util.stream.Stream;
Add an application name in item-catalog-service/src/main/resources/application.properties file to display in the Eureka service, and set the port to 8088.
server.port=8088
spring.application.name=item-catalog-service
Now, Create the Cloud Properties file
Click on File –> New –> Other –> File and add the below code in this file and save it.
eureka.instance.hostname=${vcap.application.uris[0]:localhost}
eureka.instance.nonSecurePort=80
eureka.instance.metadataMap.instanceId=${vcap.application.instance_id:${spring.application.name}:${spring.application.instance_id:${server.port}}}
eureka.instance.leaseRenewalIntervalInSeconds = 5eureka.client.region = default
eureka.client.registryFetchIntervalSeconds = 5
eureka.client.serviceUrl.defaultZone=${vcap.services.pwa-eureka-service.credentials.uri}/eureka/
Now, to start the Application:
Right Click on Project –> Run As –> Click on “Spring Boot App“.
Note: In case of error try this step: Right Click on the Project –> Run As –> Click on “Maven Build“
Now open http://localhost:8761. Here you will see Item Catalog service will be running.
You will see the list of items from the catalog service.
Open http://localhost:8088/items
Now let us move forward and create the Edge Service.
Spring Boot Microservices: Creating an Edge Service
It is similar to the standalone Item service created in Bootiful Development with Spring Boot and Angular. However, it will have fallback capabilities which prevent the client from receiving an HTTP error when the service is not available.
Again create a new project. Use edge-service for the artifact name.
Eureka Discovery: for service registration
Feign: a declarative web service client
Zuul: provides intelligent routing
Rest Repositories: to expose JPA repositories as REST endpoints
Web: Spring MVC and embedded Tomcat
Hystrix: a circuit breaker to stop cascading failure and enable resilience
Lombok: to reduce boilerplate code
Click on Finish.
Since the item-catalog-service is running on port 8088, you’ll need to configure this application to run on a different port. Modify edge-service/src/main/resources/application.properties to set the port to 8089 and set an application name.
server.port=8089
spring.application.name=edge-serviceNow, Create the Cloud Properties file
Click on File –> New –> Other –> File and add below code in this file and save it.
eureka.instance.hostname=${vcap.application.uris[0]:localhost}
eureka.instance.nonSecurePort=80
eureka.instance.metadataMap.instanceId=${vcap.application.instance_id:${spring.application.name}:${spring.application.instance_id:${server.port}}}
eureka.instance.leaseRenewalIntervalInSeconds = 5eureka.client.region = default
eureka.client.registryFetchIntervalSeconds = 5
eureka.client.serviceUrl.defaultZone=${vcap.services.pwa-eureka-service.credentials.uri}/eureka/package com.example.edgeservice;import com.netflix.hystrix.contrib.javanica.annotation.HystrixCommand;
import lombok.Data;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.circuitbreaker.EnableCircuitBreaker;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
import org.springframework.cloud.netflix.feign.EnableFeignClients;
import org.springframework.cloud.netflix.feign.FeignClient;
import org.springframework.cloud.netflix.zuul.EnableZuulProxy;
import org.springframework.hateoas.Resources;
import org.springframework.web.bind.annotation.*;import java.util.ArrayList;
import java.util.Collection;
import java.util.stream.Collectors;@EnableFeignClients
@EnableCircuitBreaker
@EnableDiscoveryClient
@EnableZuulProxy
@SpringBootApplication
public class EdgeServiceApplication {public static void main(String[] args) {
SpringApplication.run(EdgeServiceApplication.class, args);
}
}
Create a Item DTO (Data Transfer Object) in this same file. Lombok’s @Data will generate a toString() methods, getters, setters, and appropriate constructors.
@Data
class Item {
private String name;
}Create a ItemClient interface that uses Feign to communicate to the Item-catalog-service.
public class EdgeServiceApplication {public static void main(String[] args) {
SpringApplication.run(EdgeServiceApplication.class, args);
}
}@Data
class Item {
private String name;
}public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
@FeignClient("item-catalog-service")
interface ItemClient {@GetMapping("/items")
Resources<Item> readItems();
}
Create a RestController below the ItemClient that will filter out less-than-top brands and shows a /top-brandsendpoint.
@RestController
class GoodItemApiAdapterRestController {private final ItemClient itemClient;public GoodItemApiAdapterRestController(ItemClient ItemClient) {
this.itemClient = itemClient;
}@GetMapping("/top-brands")
public Collection<Item> goodItems() {
return itemClient.readItems()
.getContent()
.stream()
.filter(this::isGreat)
.collect(Collectors.toList());
}private boolean isGreat(Item item) {
return !item.getName().equals("Nike") &&
!item.getName().equals("Adidas") &&
!item.getName().equals("Reebok");
}
}
Start the edge-service application with Maven or your IDE and verify it registers successfully with the Eureka server.
Now invoke localhost:8089/top-brands, you will see the list of top brands from the catalog service.
Note: If you shut down the
item-catalog-serviceapplication, you’ll get a 500 internal server error.
$ http localhost:8089/top-brands
HTTP/1.1 500
Connection: close
Content-Type: application/json;charset=UTF-8
Date: Fri, 16 Mar 2018 12:51:22 GMT
Transfer-Encoding: chunked
X-Application-Context: edge-service:8089{
"error": "Internal Server Error",
"exception": "feign.RetryableException",
"message": "connect timed out executing GET http://item-catalog-service/items",
"path": "/top-brands",
"status": 500,
"timestamp": 1328088897672
}
To fix this, you can use Hystrix to create a fallback method and tell the goodItems() method to use it.
public Collection<Item> fallback() {
return new ArrayList<>();
}@HystrixCommand(fallbackMethod = "fallback")
@GetMapping("/top-brands")
public Collection<Item> goodItems() {
return …
}
Restart the edge-service and you should see an empty list returned.
$ http localhost:8089/top-brands
HTTP/1.1 200
Content-Type: application/json;charset=UTF-8
Date: Fri, 16 Mar 2018 12:59:02 GMT
Transfer-Encoding: chunked
X-Application-Context: edge-service:8089
[]Start the item-catalog-service again and this list should eventually return the full list of top brands names.
This brings us to the end of our article on Building Microservices Using Spring Boot. I hope you found this article informative and added value to your knowledge.
If you wish to check out more articles on the market’s most trending technologies like Artificial Intelligence, DevOps, Ethical Hacking, then you can refer to Edureka’s official site.
Do look out for other articles in this series which will explain the various other aspects of Microservices.
Originally published at www.edureka.co on May 10, 2018.
