Develop Microservice with Transparent RPC

Concept Description

The transparent remote procedure call(RPC) development mode is a development mode based on API and API implementation. The service developer does not need to use the description of Spring MVC and JAX-RS.

Development Example

• Step 1 Import dependencies into your maven project:

    <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>
      <!--transport can optional import through endpoint setting in microservice.yaml, we import both rest and highway as example-->
      <dependency>
        <groupId>org.apache.servicecomb</groupId>
        <artifactId>transport-rest-vertx</artifactId>
      </dependency>
      <dependency>
        <groupId>org.apache.servicecomb</groupId>
        <artifactId>transport-highway</artifactId>
      </dependency>
      <dependency>
        <groupId>org.apache.servicecomb</groupId>
        <artifactId>provider-pojo</artifactId>
      </dependency>
      <dependency>
        <groupId>org.slf4j</groupId>
        <artifactId>slf4j-log4j12</artifactId>
      </dependency>
    </dependencies>
  

• Step 2 Define a service API. Compile the Java API definition based on the API definition defined before development. The code is as follows:

   public interface Hello {
     String sayHi(String name);
     String sayHello(Person person);
   }
  

• Step 3 implement the service. The implementation of the Hello service is as follows:

   import org.apache.servicecomb.samples.common.schema.Hello;
   import org.apache.servicecomb.samples.common.schema.models.Person;
  
   public class HelloImpl implements Hello {
     @Override
     public String sayHi(String name) {
       return "Hello " + name;
     }
  
     @Override
     public String sayHello(Person person) {
       return "Hello person " + person.getName();
     }
   }
  

• Step 4 Release the service. The transparent RPC development mode supports two service release mode: Spring XML configuration and Annotation configuration:

• Spring XML configuration Mode: Create the pojoHello.bean.xml file in the resources/META-INF/spring directory and declare the schema in the file. The content of the file is as follows:

  <?xml version="1.0" encoding="UTF-8"?>
  <beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xmlns:p="http://www.springframework.org/schema/p" xmlns:util="http://www.springframework.org/schema/util"
         xmlns:cse="http://www.huawei.com/schema/paas/cse/rpc"
         xmlns:context="http://www.springframework.org/schema/context"
         xsi:schemaLocation="http://www.springframework.org/schema/beans classpath:org/springframework/beans/factory/xml/spring-beans-3.0.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-3.0.xsd http://www.huawei.com/schema/paas/cse/rpc classpath:META-INF/spring/spring-paas-cse-rpc.xsd">
  
      <cse:rpc-schema schema-id="pojoHello" implementation="org.apache.servicecomb.samples.pojo.provider.PojoHelloImpl"/>
  </beans>
  

• Annotation configuration Mode: @RpcSchema is used to define schema during the API Hello implementation. The code is as follows:

  import org.apache.servicecomb.provider.pojo.RpcSchema;
  @RpcSchema(schemaId = "pojoHello")
  public class HelloImpl implements Hello {
     @Override
     public String sayHi(String name) {
       return "Hello " + name;
     }
  
     @Override
     public String sayHello(Person person) {
       return "Hello person " + person.getName();
     }
  }
  

  In the pojoHello.bean.xml file of resources/META-INF/spring directory, configure base-package that performs scanning. The content of the file is as follows:

  <?xml version="1.0" encoding="UTF-8"?>
  <beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xmlns:p="http://www.springframework.org/schema/p" xmlns:util="http://www.springframework.org/schema/util"
         xmlns:cse="http://www.huawei.com/schema/paas/cse/rpc"
         xmlns:context="http://www.springframework.org/schema/context"
         xsi:schemaLocation="http://www.springframework.org/schema/beans classpath:org/springframework/beans/factory/xml/spring-beans-3.0.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-3.0.xsd http://www.huawei.com/schema/paas/cse/rpc classpath:META-INF/spring/spring-paas-cse-rpc.xsd">
  
      <context:component-scan base-package="org.apache.servicecomb.samples.pojo.provider"/>
  </beans>
  

Note: THE PATH FOR RPC IS ClassName/MethodName, AND THE METHOD IS POST.

In this sample the Path of sayHi is /HelloImpl/sayHi, and the Path of sayHello is /HelloImpl/sayHello.

NOTE： Different from the Spring MVC and JAX-RS development modes, the transparent RPC development mode used @RpcSchema instead of @RestSchema.

• Step 5 Add service definition file:

  Add microservice.yaml file into resources folder of your project.

• Step 6 Add Main class:

   import org.apache.servicecomb.foundation.common.utils.BeanUtils;
   import org.apache.servicecomb.foundation.common.utils.Log4jUtils;
  
   public class Application {
     public static void main(String[] args) throws Exception {
        //initializing log, loading bean(including its parameters), and registering service, more detail can be found here : http://servicecomb.incubator.apache.org/users/application-boot-process/
        Log4jUtils.init();
        BeanUtils.init();
     }
   }