grpc/Step_1.md

Step-1: Generate a service client.

In this step, we use protoc to generate the Java Stub classes. A Stub is the name gRPC uses for the code that initiates contact with a gRPC service running remotely via the internet.

If you did not install protoc on your system, you can skip this step and move onto the next one where we examine the generated code.

First, you'll need to build the protobuf plugin that generates the rpc classes. protoc uses other tools called plugins to add additional features to generated code.

The gRPC Java Stub classes are created using a gRPC Java plugin, but first the plugin must be built and installed.

To build the plugin:

$ pushd external/grpc_java
$ make java_plugin
$ popd

To use it to generate the code:

$ mkdir -p src/main/java
$ protoc -I . helloworld.proto --plugin=protoc-gen-grpc=external/grpc_java/bins/opt/java_plugin \
                               --grpc_out=src/main/java \
                               --java_out=src/main/java

Next, in Step - 2, we'll use the generated Stub implementation to write a client that uses the generated code to make a call to a service.