COMPILING.md

Building gRPC-Java
==================

Building is only necessary if you are making changes to gRPC-Java.

Building requires JDK 8, as our tests use TLS.

grpc-java has a C++ code generation plugin for protoc. Since many Java
developers don't have C compilers installed and don't need to modify the
codegen, the build can skip it. To skip, create the file
`<project-root>/gradle.properties` and add `skipCodegen=true`.

Then, to build, run:
```
$ ./gradlew build
```

To install the artifacts to your Maven local repository for use in your own
project, run:
```
$ ./gradlew install
```

How to Build Code Generation Plugin
-----------------------------------
This section is only necessary if you are making changes to the code
generation. Most users only need to use `skipCodegen=true` as discussed above.

### Build Protobuf
The codegen plugin is C++ code and requires protobuf 3.0.0 or later.

For Linux, Mac and MinGW:
```
$ git clone https://github.com/google/protobuf.git
$ cd protobuf
$ git checkout v3.5.1
$ ./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](https://github.com/google/protobuf/blob/master/cmake/README.md)
for how to compile Protobuf. gRPC-java assumes a Release build.

#### Linux and MinGW
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
```

#### Mac
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"
```

### Notes for Visual C++

When building on Windows and VC++, you need to specify project properties for
Gradle to find protobuf:
```
.\gradlew install ^
    -PvcProtobufInclude=C:\path\to\protobuf-3.5.1\src ^
    -PvcProtobufLibs=C:\path\to\protobuf-3.5.1\vsprojects\Release ^
    -PtargetArch=x86_32
```

Since specifying those properties every build is bothersome, you can instead
create ``<project-root>\gradle.properties`` with contents like:
```
vcProtobufInclude=C:\\path\\to\\protobuf-3.5.1\\src
vcProtobufLibs=C:\\path\\to\\protobuf-3.5.1\\vsprojects\\Release
targetArch=x86_32
```

By default, 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. Since Protobuf is only built for 32-bit by
default, the `targetArch=x86_32` is necessary.

### Notes for MinGW on Windows
If you have both MinGW and VC++ installed on Windows, VC++ will be used by
default. To override this default and use MinGW, add ``-PvcDisable=true``
to your Gradle command line or add ``vcDisable=true`` to your
``<project-root>\gradle.properties``.

### Notes for Unsupported Operating Systems
The build script pulls pre-compiled ``protoc`` from Maven Central by default.
We have built ``protoc`` binaries for popular systems, but they may not work
for your system. If ``protoc`` cannot be downloaded or would not run, you can
use the one that has been built by your own, by adding this property to
``<project-root>/gradle.properties``:
```
protoc=/path/to/protoc
```