grpc-java requires Netty 4.1, which is still in flux. The version we need can be found in the lib/netty submodule, which requires Maven 3.2 or higher to build:
$ git submodule update --init
$ cd lib/netty
$ mvn install -pl codec-http2 -am -DskipTests=true
The codegen plugin is C++ code and requires protobuf 3.0.0-alpha-2.
If you are not changing the codegen plugin, nor any of the .proto files in
the source tree, you can skip this chapter and add grpc.skip.codegen=true
to $HOME/.gradle/gradle.properties. It will make the build script skip the
build and invocation of the codegen, and use generated code that has been
checked in.
For Linux, Mac and MinGW:
$ git clone https://github.com/google/protobuf.git
$ cd protobuf
$ git checkout v3.0.0-alpha-2
$ ./autogen.sh
$ ./configure
$ make
$ make check
$ sudo make install
If you are comfortable with C++ compilation and autotools, you can specify a
--prefix for Protobuf and use -I in CXXFLAGS, -L in
LDFLAGS, LD_LIBRARY_PATH, and PATH to reference it. The
environment variables will be used when building grpc-java.
Protobuf installs to /usr/local by default.
For Visual C++, please refer to the Protobuf README for how to compile Protobuf.
If /usr/local/lib is not in your library search path, you can add it by running:
$ sudo sh -c 'echo /usr/local/lib >> /etc/ld.so.conf'
$ sudo ldconfig
Some versions of Mac OS X (e.g., 10.10) doesn't have /usr/local in the
default search paths for header files and libraries. It will fail the build of
the codegen. To work around this, you will need to set environment variables:
$ export CXXFLAGS="-I/usr/local/include" LDFLAGS="-L/usr/local/lib"
On Linux, Mac or MinGW:
$ ./gradlew install
When building on Windows and VC++, you need to specify project properties for Gradle to find protobuf:
.\gradlew install ^
-Pvc.protobuf.include=C:\path\to\protobuf-3.0.0-alpha-2\src ^
-Pvc.protobuf.libs=C:\path\to\protobuf-3.0.0-alpha-2\vsprojects\Release
Since specifying those properties every build is bothersome, you can instead
create %HOMEDRIVE%%HOMEPATH%\.gradle\gradle.properties with contents like:
vc.protobuf.include=C:\\path\\to\\protobuf-3.0.0-alpha-2\\src
vc.protobuf.libs=C:\\path\\to\\protobuf-3.0.0-alpha-2\\vsprojects\\Release
The build script will build the codegen for the same architecture as the Java runtime installed on your system. If you are using 64-bit JVM, the codegen will be compiled for 64-bit, that means you must have compiled Protobuf in 64-bit.
If you have both MinGW and VC++ installed on Windows, VC++ will be used by
default. To override this default and use MinGW, add -Dvc.disable to your
Gradle command line.
Heres a quick readers guide to the code to help folks get started. At a high level there are three distinct layers to the library: stub, channel & transport.
The 'stub' layer is what is exposed to most developers and provides type-safe bindings to whatever datamodel/IDL/interface you are adapting. An example is provided of a binding to code generated by the protocol-buffers compiler but others should be trivial to add and are welcome.
The 'channel' layer is an abstraction over transport handling that is suitable for interception/decoration and exposes more behavior to the application than the stub layer. It is intended to be easy for application frameworks to use this layer to address cross-cutting concerns such as logging, monitoring, auth etc. Flow-control is also exposed at this layer to allow more sophisticated applications to interact with it directly.
The 'transport' layer does the heavy lifting of putting & taking bytes off the wire. The interfaces to it are abstract just enough to allow plugging in of different implementations. Transports are modeled as 'Stream' factories. The variation in interface between a server stream and a client stream exists to codify their differing semantics for cancellation and error reporting.
Tests showing how these layers are composed to execute calls using protobuf messages can be found here https://github.com/google/grpc-java/tree/master/integration-testing/src/main/java/io/grpc/testing/integration