Protostuff RPC Service Example

In many cases we want to define messages and services in one place using one language. This example shows how to do it in a simple way.

Consider you have an input - proto file like this:

message SearchRequest {
    required string keyword = 1;
}

message SearchResponse {
    repeated string result = 1;
}

service SearchService {
    rpc search (SearchRequest) returns (SearchResponse);
}

The goal is to generate java code for messages and service interfaces.

Project structure

In this example we use protostuff-maven-plugin.

There are three main components:

1. search.proto - contains message and service definitions
2. service.java.stg - template for code generation (service only)
3. pom.xml - contains a configuration for protostuff-maven-plugin

Service definition

You should use same syntax as for protobuf compiler.

Example:

service SearchService {
    rpc search (SearchRequest) returns (SearchResponse);
    rpc extendedSearch (ExtendedSearchRequest) returns (SearchResponse);
}

Service code generation template

For basic protostuff code generation examples please check this.

In our example we want to generate service interface that:

1. Returns Guava's ListenableFuture<T> as a method return type, where T is a service response message.
2. Takes single argument U - the service request message.

Rule service_block specifies how to render service interface/class.

In the example we are using two service properties and some method properties:

Service properties:

Property	Description
name	Service name
rpcMethods	Collection of RpcMethod definitions of this service

Service method properties:

Property	Description
name	Service method name
returnType	Service method return type (message)
argType	Service method argument type (message)

This diagram shows all properties that are accessible in this block:

Maven plugin configuration

You can specify template for service code generation as an additional output for protostuff-maven-plugin:

<source>src/main/proto/search.proto</source>
<outputDir>target/generated-sources</outputDir>
<output>
    java_bean,
    src/main/st/service.java.stg
</output>

This way you can use

• any template for your messages
• custom template for services

Build instructions

As usually:

mvn clean install

After compilation you can go to target/generated-sources and examine generated code.

Generated service interface:

package io.protostuff.example.search;

import com.google.common.util.concurrent.ListenableFuture;

public interface SearchService {

  ListenableFuture<SearchResponse> search(SearchRequest request);

  ListenableFuture<SearchResponse> extendedSearch(ExtendedSearchRequest request);

}