Spring Cloud Gateway — Microservices example

In this example, we’ll make the implement small Microservices POC using Spring Cloud API Gateway, Eureka and Spring Cloud. In this example, we will show to configure routes by making the use Spring Cloud API Gateway

In this diagram, I’ve shows two microservices (User Service and Account Management), but focused on single microservices to show the intelligent routing can be done using Spring Cloud API Gateway. For now there is no database is used in the code, but in future tutorials I will do that.

Service Discovery

pom.xml

<?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>2.5.2</version>
      <relativePath/> <!-- lookup parent from repository -->
   </parent>
   <groupId>com.example</groupId>
   <artifactId>PhotoAppDiscoveryService</artifactId>
   <version>0.0.1-SNAPSHOT</version>
   <name>PhotoAppDiscoveryService</name>
   <description>Photo App Eureka Discovery Service</description>
   <properties>
      <java.version>1.8</java.version>
      <spring-cloud.version>2020.0.3</spring-cloud.version>
   </properties>
   <dependencies>
      <dependency>
         <groupId>org.springframework.cloud</groupId>
         <artifactId>spring-cloud-starter-netflix-eureka-server</artifactId>
      </dependency>

      <dependency>
         <groupId>org.springframework.boot</groupId>
         <artifactId>spring-boot-starter-test</artifactId>
         <scope>test</scope>
      </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>
      </plugins>
   </build>

</project>

application.properties

server.port=8010
spring.application.name=discoveryservice

eureka.client.register-with-eureka=false
eureka.client.fetch-registry=false
eureka.client.serviceUrl.defaultZone=http://localhost:8010/eureka

eureka.instance.hostname=localhost
eureka.instance.prefer-ip-address=true

MainApp.java

@SpringBootApplication
@EnableEurekaServer
public class PhotoAppDiscoveryServiceApplication {

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

}

Users Service

pom.xml

<properties>
   <java.version>1.8</java.version>
   <spring-cloud.version>2020.0.3</spring-cloud.version>
</properties>
<dependencies>
   <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-validation</artifactId>
   </dependency>
   <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-web</artifactId>
   </dependency>
   <dependency>
      <groupId>org.springframework.cloud</groupId>
      <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
   </dependency>

   <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-test</artifactId>
      <scope>test</scope>
   </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>

application.properties

server.port=0
spring.application.name=users-ws

eureka.client.register-with-eureka=true
eureka.client.fetch-registry=true
eureka.client.serviceUrl.defaultZone=http://localhost:8010/eureka

eureka.instance.hostname=localhost
eureka.instance.prefer-ip-address=true

UsersController.java

@RestController
@RequestMapping("/users")
public class UsersController {

   @GetMapping("/status/check")
   public String status() {
      return "Working";
   }
}

MainApp.java

@EnableEurekaClient
@SpringBootApplication
public class PhotoAppApiUsersApplication {

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

}

API Gateway

pom.xml

<properties>
   <java.version>1.8</java.version>
   <spring-cloud.version>2020.0.3</spring-cloud.version>
</properties>
<dependencies>
   <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-webflux</artifactId>
   </dependency>
   <dependency>
      <groupId>org.springframework.cloud</groupId>
      <artifactId>spring-cloud-starter-gateway</artifactId>
   </dependency>
   <dependency>
      <groupId>org.springframework.cloud</groupId>
      <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
   </dependency>

   <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-test</artifactId>
      <scope>test</scope>
   </dependency>
   <dependency>
      <groupId>io.projectreactor</groupId>
      <artifactId>reactor-test</artifactId>
      <scope>test</scope>
   </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>

application.properties

server.port=8082
spring.application.name=api-gateway
eureka.client.serviceUrl.defaultZone=http://localhost:8010/eureka


spring.cloud.gateway.discovery.locator.enabled=true
spring.cloud.gateway.discovery.locator.lower-case-service-id=true


spring.cloud.gateway.routes[0].id=users-status-check
spring.cloud.gateway.routes[0].uri=lb://users-ws
spring.cloud.gateway.routes[0].predicates[0]=Path=/spring-ws/users/status/check
spring.cloud.gateway.routes[0].predicates[1]=Method=GET
spring.cloud.gateway.routes[0].filters[0]=RemoveRequestHeader=Cookie

# If request is coming /spring-ws/users/status/check, then Spring cloud API gateway will route it to /users/status/check
#spring.cloud.gateway.routes[0].filters[1]=RewritePath=/spring-ws/users/status/check, /users/status/check
spring.cloud.gateway.routes[0].filters[1]=RewritePath=/spring-ws/(?<segment>.*), /$\{segment}

MainApp.java

@SpringBootApplication
public class ApiGatewayApplication {

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

}

Output