The project demonstrates the end-to-end implementation of the microservices. It has an API Gateway for routing with global filter, Naming Server for Load Balancing and Service Discovery, Configuration Server for centralized Git-based configuration, Microservices, it's call chaining, Circuit Breaker concept implementation. It uses Spring boot version 2.6.1 and Spring cloud version 2021.0.0, and Java 16. The project structure is a Spring boot multimodule project. It helps to define shared maven dependencies in the root (parent) pom.xml.
The project has five modules as list below and each has its own responsibility.
- API Gateway
- Configuration Server
- Naming Server
- Microservice-1: Currency Exchange Service
- Microservice-2: Currency Conversion Service
- Microservice-3: Limit Service
The API Gateway uses using the spring-cloud-start-gateway dependency. It demonstrates the dynamic routing configuration and global filter implementation feature. Also, it connects with the Configuration Server using the spring-cloud-starter-config dependency and registers to the service registry using the spring-cloud-starter-netflix-eureka dependency.
The Configuration Server uses using the spring-cloud-config-server dependency. It manages the configuration based upon the profile in the central git repository. The configuration files are present in the local-config folder at the root of the project repository. Also, it registers to the service registry using the spring-cloud-starter-netflix-eureka dependency.
It acts as a service registry of microservices as called as Naming Server. It uses spring-cloud-starter-netflix-eureka-server dependency. Each service registers itself whenever an instance comes up. It helps for auto-scaling up and down verify effectively. Also, It plays an important role in the load balancing in the microservice.
It is responsible for the Currency Exchange related information. It connects to the in-memory h2 database using JPA to maintain the currency exchange information. It demonstrates fault tolerance and circuit breaker functionality resilience4j-spring-boot2 and it's peer dependency spring-boot-starter-aop. Also, it registers to the service registry using the spring-cloud-starter-netflix-eureka dependency.
It is responsible for actual currency conversion functionality. For currency conversion, it takes the help of a currency exchange microservice to get currency exchange information. It calls y exchange microservice using three approaches. The first approach is using the RestTemplate it retrieves currency exchange objects. The second approach is using feign client proxy interface definition. It uses spring-cloud-starter-openfeign dependency. And the third approach is using the feign and eureka client with load balancing feature. It uses spring-cloud-starter-openfeign and spring-cloud-starter-netflix-eureka-client dependency. Also, it registers to the service registry using the spring-cloud-starter-netflix-eureka dependency.
It demonstrates the functionality of reading the configuration from the Spring Configuration Server using the spring-cloud-starter-config dependency. Also, it registers to the service registry using the spring-cloud-starter-netflix-eureka dependency.
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.6.1</version> <!-- lookup parent from repository -->
<relativePath />
</parent>
<groupId>com.manoj.ccm</groupId>
<artifactId>CurrencyConverterMicroservice</artifactId>
<version>1.0.0</version>
<packaging>pom</packaging>
<name>CurrencyConverterMicroservice</name>
<description>Currency Converter Microservice Application</description>
<properties>
<java.version>16</java.version>
<spring-cloud.version>2021.0.0</spring-cloud.version>
<lombok.version>1.18.22</lombok.version>
<archetype.version>3.2.0</archetype.version>
</properties>
<modules>
<module>LimitService</module>
<module>ConfigService</module>
<module>CurrencyExchangeService</module>
<module>CurrencyConversionService</module>
<module>NamingServer</module>
<module>APIGateway</module>
</modules>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter</artifactId>
<exclusions>
<exclusion>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-logging</artifactId>
</exclusion>
</exclusions>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-log4j2</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-configuration-processor</artifactId>
<optional>true</optional>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-actuator</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-devtools</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
</dependency>
</dependencies>
<dependencyManagement>
<dependencies>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-dependencies</artifactId>
<version>${spring-cloud.version}</version>
<type>pom</type>
<scope>import</scope>
</dependency>
</dependencies>
</dependencyManagement>
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
</plugin>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-archetype-plugin</artifactId>
<version>${archetype.version}</version>
<configuration>
<propertyFile>archetype.yml</propertyFile>
<encoding>UTF-8</encoding>
<filterProperties>java,xml,yaml,yml,properties</filterProperties>
</configuration>
</plugin>
</plugins>
</build>
</project>