Develop consumer with Rest Template

Concepts

Rest Template is a RESTful API provided by the Spring framework. ServiceComb provides the implementation class for service calling

Scenario

With ServiceComb's RestTemplate instance, users can call the service with a customized URL without knowing the service's address.

Sample Code

The RestTemplate instance is created by the static method RestTemplateBuilder.create(). Then, users can call the microservices with the instance and the customized URL. The code is as follows:

• Sample code for Sprint MVC consumer

import org.springframework.stereotype.Component;
import org.springframework.web.client.RestTemplate;

import org.apache.servicecomb.foundation.common.utils.BeanUtils;
import org.apache.servicecomb.foundation.common.utils.Log4jUtils;
import org.apache.servicecomb.provider.springmvc.reference.RestTemplateBuilder;
import org.apache.servicecomb.samples.common.schema.models.Person;

@Component
public class SpringmvcConsumerMain {
    private static RestTemplate restTemplate = RestTemplateBuilder.create();

    public static void main(String[] args) throws Exception {
        init();
        Person person = new Person();
        person.setName("ServiceComb/Java Chassis");
        String sayHiResult = restTemplate
                .postForObject("cse://springmvc/springmvchello/sayhi?name=Java Chassis", null, String.class);
        String sayHelloResult = restTemplate
                .postForObject("cse://springmvc/springmvchello/sayhello", person, String.class);
        System.out.println("RestTemplate consumer sayhi services: " + sayHiResult);
        System.out.println("RestTemplate consumer sayhello services: " + sayHelloResult);
    }

    public static void init() throws Exception {
        Log4jUtils.init();
        BeanUtils.init();
    }
}

• Sample code for JAX RS Consumer:

@Component
public class JaxrsConsumerMain {

    public static void main(String[] args) throws Exception {
        init();
        // The rest is just like the Spring MVC Consumer sample code, notice that if the provider only accepts GET requests, the consumer should use method getForObject()
        RestTemplate restTemplate = RestTemplateBuilder.create();
        String result = restTemplate.getForObject("cse://jaxrs/jaxrshello/saybye", String.class);
    }

    public static void init() throws Exception {
        Log4jUtils.init();
        BeanUtils.init();
    }
}

NOTE:

• The URL should be in format: cse//microserviceName/path?querystring. Taking the provider example from Develop micro service with SpringMVC, the micro service's name is springmvc, the basePath is /springmvchello, then the microserviceName in the URL is springmvc, the path to call sayhi is springmvchello/sayhi, so the URL for sayhi in the sample is cse://springmvc/springmvchello/sayhi?name=Java Chassis, below is the code for the provider:

@RestSchema(schemaId = "springmvcHello")
@RequestMapping(path = "/springmvchello", produces = MediaType.APPLICATION_JSON)
//这里 path = “/springmvchello” 中的 springmvchello 就是 上述的basePath
public class SpringmvcHelloImpl implements Hello {
    @Override
    @RequestMapping(path = "/sayhi", method = RequestMethod.POST)
    public String sayHi(@RequestParam(name = "name") String name) {
        return "Hello " + name;
    }

    @Override
    @RequestMapping(path = "/sayhello", method = RequestMethod.POST)
    public String sayHello(@RequestBody Person person) {
        return "Hello person " + person.getName();
    }
}

The following configuration is the file resources/microservice.yaml of the springmvc-provider module in the SpringMVC sample:

APPLICATION_ID: springmvc-sample
service_description:
  name: springmvc # The name of the micro service
  version: 0.0.2
servicecomb:
  service:
    registry:
      address: http://127.0.0.1:30100
  rest:
    address: 0.0.0.0:8080
  highway:
    address: 0.0.0.0:7070

• With the URL format, ServiceComb framework will perform internal microservice descovery, fallback, fault tolerance and send the requests to the microservice providers.