kmingulov / java-grpc-example

Simple example project demonstrating how to use gRPC in Java + Gradle environment.

java-grpc-example

java-grpc-example is a simple example project demonstarting use of gRPC in Java + Gradle environment.

The project consists of several modules:

• math-service-api, a common library with gRPC-generated classes and some additional helper classes;
• math-service-impl, a calculator-like micro-service which implements service APIs defined in math-service-api;
• math-service-client, a simple client able to connect to a micro-service implementing math-service-api and submit mathematical expressions.

Prerequisites

Only Java SDK is required (11 or higher).

Build & Run

Run ./gradlew clean build from the root of the project. Once the project is built, run the server:

$ java -jar math-service-impl/build/libs/server.jar
Starting the server...
Server started!

In a separate shell session, run:

$ java -jar math-service-client/build/libs/client.jar
>

You can submit mathematical expressions via the client to the server, which will queue and compute them. Currently, the supported operations are only +, -, *, / and the supported functions are sin, cos, tan, and prime:

> 1+2
3.0
> prime(10)
29.0

If another computation is currently in progress (all computations are done in one thread) or if computation takes too much time, the client will print PENDING... or RUNNING...:

> prime(20000)
PENDING...
PENDING...
RUNNING...
RUNNING...
224737.0

The client is also capable of subscribing to all server events via events:

$ java -jar math-service-client/build/libs/client.jar
> events
Listening to the server events. Type quit to terminate.
f0062b43-db95-4577-8793-f42a886b7d7e PENDING
f0062b43-db95-4577-8793-f42a886b7d7e RUNNING
f0062b43-db95-4577-8793-f42a886b7d7e COMPUTED 11.0
99255b04-b421-4a28-b573-156a911b8797 PENDING
99255b04-b421-4a28-b573-156a911b8797 RUNNING
99255b04-b421-4a28-b573-156a911b8797 COMPUTED 7919.0
a6153533-0b5c-42a9-8709-1736c92abed2 PENDING
a6153533-0b5c-42a9-8709-1736c92abed2 RUNNING
a6153533-0b5c-42a9-8709-1736c92abed2 ERROR Expected a positive integer number.

To emit events, run another instance of the client and submit an expression to the server.