Develop microservice application in minutes

Before you begin

Walk through the instructions in the Quick Start.

Develop BMI microservice application in minutes

The workflow of BMI application have been introduced in Quick start. It contains two separate microservices:

• BMI calculator service：provides computing services.

• Web service：provides both user interface and gateway service.

Before we start, we need to add some common dependencies in the parent project of the services’.

  <dependencyManagement>
    <dependencies>
      <dependency>
        <groupId>org.apache.servicecomb</groupId>
        <artifactId>java-chassis-dependencies</artifactId>
        <version>1.0.0-m1</version>
        <type>pom</type>
        <scope>import</scope>
      </dependency>
    </dependencies>
  </dependencyManagement>

  <dependencies>
    <dependency>
      <groupId>org.hibernate</groupId>
      <artifactId>hibernate-validator</artifactId>
    </dependency>
  </dependencies>

Notice: The java-chassis-dependencies is imported as pom to unify version management of dependencies.

Now we will introduce the detailed implementation of these two microservices. The full code is on github.

Implementation of calculator

The calculator service provides capability of calculating BMI. It contains three parts:

• Detailed calculation implementation

• Service endpoint definition

• Service startup entry

Detailed calculation implementation

Implement detailed calculation according to the formula \(BMI=\frac{weight}{height^2}\).

public interface CalculatorService {
  double calculate(double height, double weight);
}

@Service
public class CalculatorServiceImpl implements CalculatorService {
  @Override
  public double calculate(double height, double weight) {
    if (height <= 0 || weight <= 0) {
      throw new IllegalArgumentException("Arguments must be above 0");
    }
    double heightInMeter = height / 100;
    return weight / (heightInMeter * heightInMeter);
  }
}

Service endpoint definition

Service endpoint is defined to generate service contract. First of all, define the endpoint interface:

public interface CalculatorEndpoint {
  double calculate(double height, double weight);
}

Introduce ServiceComb dependency:

    <dependency>
      <groupId>org.apache.servicecomb</groupId>
      <artifactId>spring-boot-starter-provider</artifactId>
    </dependency>

Expose calculator service’s restful endpoint:

@RestSchema(schemaId = "calculatorRestEndpoint")
@RequestMapping("/")
public class CalculatorRestEndpoint implements CalculatorEndpoint {

  private final CalculatorService calculatorService;

  @Autowired
  public CalculatorRestEndpoint(CalculatorService calculatorService) {
    this.calculatorService = calculatorService;
  }

  @Override
  @GetMapping("/bmi")
  public double calculate(double height, double weight) {
    return calculatorService.calculate(height, weight);
  }
}

ServiceComb supports SpringMvc simplified annotations, e.g. GetMapping, since version 0.3.0.

Note that ServiceComb can auto-generate service contract when annotating endpoints with @RestSchema. Then configure the endpoint in microservice.yaml as follows to register the contract and microservice to service center.

APPLICATION_ID: bmi
service_description:
  name: calculator
  version: 0.0.1
servicecomb:
  service:
    registry:
      address: http://127.0.0.1:30100
  rest:
    address: 0.0.0.0:7777

Service startup entry

Enable ServiceComb microservice framework by adding @EnableServiceComb annotation.

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

Implementation of webapp service

The web service provides both the user interface and gateway service. It contains three parts:

• User interface

• Gateway and routing rules

• Service startup entry

The user interface was developed using Bootstrap.

Gateway and routing rules

The gateway service was implemented using the Netflix Zuul.

Introduce ServiceComb dependency:

    <dependency>
      <groupId>org.apache.servicecomb</groupId>
      <artifactId>spring-boot-starter-discovery</artifactId>
    </dependency>
    <dependency>
      <groupId>org.apache.servicecomb</groupId>
      <artifactId>spring-boot-starter-servicecomb</artifactId>
    </dependency>
    <dependency>
      <groupId>org.apache.servicecomb</groupId>
      <artifactId>spring-cloud-zuul</artifactId>
    </dependency>

ServiceComb added spring-cloud-zuul module to provide better compatibility with zuul since version 0.4.0-SNAPSHOT.

Configure routing rules and service endpoint in application.yaml.

zuul:
  routes:
    calculator: /calculator/**

# disable netflix eureka since it's not used for service discovery
ribbon:
  eureka:
    enabled: false

server:
  port: 8889

Enable service discovery with zuul by putting the application information and service center address in microservice.yaml.

APPLICATION_ID: bmi
service_description:
  name: gateway
  version: 0.0.1
servicecomb:
  service:
    registry:
      address: http://127.0.0.1:30100

Service startup entry

Add annotations to enable ServiceComb and Zuul:

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

Now you can refer to quick start to verify the services.

What’s next

• Learn advance microservice development