Spring Cloud Zuul Overview

Zuul serves as an edge service providing load balancing, reverse proxying, authentication, dynamic routing, monitoring, and security. It acts as a protective layer for microservice architectures by handling non-business logic concerns at the routing level.

Routing Gateway Patterns

Consider three architectural approaches:

1. Direct Service Access: Clients connect directly to individual services
2. Gateway Routing: All requests pass through a single gateway before reaching services
3. Registry-Integrated Gateway: Gateway integrates with service discovery for dynamic routing

Development Environment

• Java Development Kit: 1.8+
• Spring Boot: 2.0.6.RELEASE
• Spring Cloud: Finchley.SR2

Service Implementation

Service Registry Configuration

Create a Eureka registry service with the following configuration:

Maven Dependencies

<dependencies>
  <dependency>
    <groupId>org.springframework.cloud</groupId>
    <artifactId>spring-cloud-starter-netflix-eureka-server</artifactId>
  </dependency>
</dependencies>

Application Properties

application.name=service-registry
server.port=8006
eureka.client.register-with-eureka=false
eureka.client.fetch-registry=false
eureka.client.service-url.default-zone=http://localhost:${server.port}/eureka/

Registry Main Class

@EnableEurekaServer
@SpringBootApplication
public class RegistryMain {
  public static void main(String[] args) {
    SpringApplication.run(RegistryMain.class, args);
  }
}

Gateway Configuration

Gateway Dependencies

<dependencies>
  <dependency>
    <groupId>org.springframework.cloud</groupId>
    <artifactId>spring-cloud-starter-netflix-zuul</artifactId>
  </dependency>
  <dependency>
    <groupId>org.springframework.cloud</groupId>
    <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
  </dependency>
</dependencies>

Gateway Properties

application.name=api-gateway
server.port=9009
eureka.client.service-url.default-zone=http://localhost:8006/eureka/

zuul.routes.service-a.path=/greeting/**
zuul.routes.service-a.url=http://localhost:9010/greeting
zuul.routes.service-b.path=/salutation/**
zuul.routes.service-b.url=http://localhost:9011/salutation

Gateway Main Class

@EnableZuulProxy
@EnableDiscoveryClient
@SpringBootApplication
public class GatewayMain {
  public static void main(String[] args) {
    SpringApplication.run(GatewayMain.class, args);
  }
}

Service Implementations

Service A Configuration

application.name=service-a
server.port=9010
eureka.client.service-url.default-zone=http://localhost:8006/eureka/

Service A Controller

@RestController
public class GreetingController {
  @GetMapping("/greeting/{user}")
  public String greetUser(@PathVariable String user) {
    return user + ", welcome!";
  }
}

Service B Configuraton

application.name=service-b
server.port=9011
eureka.client.service-url.default-zone=http://localhost:8006/eureka/

Service B Controller

@RestController
public class SalutationController {
  @GetMapping("/salutation")
  public String saluteUser(@RequestParam String name) {
    return name + ", greetings!";
  }
}

Verification Process

Start all services in sequence: registry, gateway, service A, and service B. Validate routing functionality through these endpoints: