Overview

Here is a sample gRPC Java based implementation. This implemetation is basically for supporting REST to gRPC scenario using wso2 microgateway's java interceptors.

There is a gRPC server and client implementation for the "order" Resource. The proto file is as follows.

syntax = "proto3";
package org.mgw_demo.order_service_lib;

service OrderService {
    rpc order (OrderRequest) returns (OrderResponse);
}

message OrderRequest {
    string item = 1;
    int32 quantity = 2;
    string location = 3;
}

message OrderResponse {
    Status status = 1;
    int32 price = 2;
    string description = 3;
}

enum Status {
    SUCCESSFUL = 0;
    FAILED = 1;
}

gRPC server do not perform any authentication. The server will execute a simple logic.

• if quantity < 5, order client will receive success with price is set to 10 * quantity
• else it will set the status to failed saying out of stock

How to execute

• Install Java and Maven and update the PATH variables accordingly.

• Build the project using Maven.

mvn clean install

• To run the gRPC server, (server will use the port 50001)

java -jar serverImpl/target/serverImpl-1.0-SNAPSHOT.jar

• To run the gRPC client, (for testing purpose. The request object in this case is hard coded.)

java -jar clientImpl/target/clientImpl-1.0-SNAPSHOT.jar

• To invoke the gRPC service using a REST client using microgateway

  • Copy the orderService.yaml to < Microgateway_Project > /api_definitions directory.

  • Copy the following jar files to the < Microgateway_Project > /lib directory

    • mgwGrpcInterceptor/target/mgwGrpcInterceptor-1.0-SNAPSHOT.jar
    • clientImpl/target/clientImpl-1.0-SNAPSHOT.jar
    • all the jars inside clientImpl/target/lib directory

  • build and run the microgateway.

  • invoke the gateway with the following url.

    • curl http://localhost:9090/retailStore/order -X POST -d '{"item":"Cake", "quantity":3, "location":"Colombo"}' -H "Content-Type: application/json" -H "Authorization: Bearer $TOKEN"