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 : https://docs.servicecomb.io/java-chassis/zh_CN/build-provider/bootup.html
      Log4jUtils.init();
      BeanUtils.init();
   }
 }