Building J2ObjC


  • Apple Mac OS X system
  • Latest version of Xcode
  • JDK JDK 11 installed
  • Apache Maven
  • (Recommended but not required) Google Protocol Buffer source

Mac Setup

  • Install Xcode command line tools by running:
sudo xcode-select --install
  • Add to your .bash_profile:
export JAVA_HOME=`/usr/libexec/java_home -v 11`

Create a Fork of the J2ObjC project

To fork the J2ObjC project, open its main page and click the Fork button:


Select your GitHub account name, and the fork will be created in a few seconds.

Next, clone a copy of your fork to your local system for development. First, click the [Clone or download button], then click the Copy to Clipboard button:


Then clone into a local directory:

git clone (Command-V)  # Paste the copied URL

Install protobuf

You need to have protobuf C++ installed before you can build J2ObjC.

To install the protobuf binary package, use Homebrew:

brew install protobuf

You need to set PROTOBUF_ROOT_DIR to the root where protobuf is installed. Normally, that's the Homebrew default /usr/local. Add the following to your .bash_profile:

export PROTOBUF_ROOT_DIR=/usr/local # or your custom Homebrew dir

To verify, run $PROTOBUF_ROOT_DIR/bin/protoc --version.

Building J2ObjC

To build from a command-line in a Terminal window, run:

# Build just the translator and libraries
make dist

# Build the full distribution (including frameworks)
make frameworks

# Build the protocol buffer compiler and runtime for J2ObjC
make protobuf_dist

# Build everything that is included in the project's distribution bundles
make all_dist

Optional Setup for Protocol Buffers

The J2ObjC Protocol Buffers compiler and runtime requires that Protocol Buffers (at least 3.21.3) be installed:

  • Download the source code from the Protocol Buffers 3.21.7 release.
  • Follow the C++ installation instructions from the README. Pay attention to the --prefix option to specify your install location.
  • Define the PROTOBUF_ROOT_DIR environment variable to point to your Protocol Buffers install location.

Post Java 8 language features.

See announcement. In addition to the steps in the previous section, a JRE module needs to be built with the JDK 11:

JAVA_HOME=`/usr/libexec/java_home -v 11` \
make -C jre_emul/ -f emul_module_dist

Testing J2ObjC

To test from a command-line in a Terminal window, run:

# Run translator and library unit tests
make test

# Run all unit tests, including for protocol buffers
make test_all

Cleaning/Resetting a Build

# Remove all files generated by the build
make clean

Parallel Builds

The J2ObjC build supports parallel builds, which are specified using the -j<n> flag, where n is the maximum number of concurrent tasks. The maximum depends on how fast/powerful your system is; we suggest starting with -j4. Increase the number to shorten build times if your system can handle it, and decrease it if make fails with system errors.

Building Processor Architectures

As of j2objc release 2.3, 32-bit iOS architectures ("iphone" and "simulator") are not included in the public distribution. You can build j2objc with these by first specifying the J2OBJC_ARCHS environment variable:

$ export J2OBJC_ARCHS="iphone simulator macosx iphone64 watchv7k watch64 watchsimulator simulator64"
$ make -j8 all_dist

This can also be used to speed up the build, by only specifying the architectures your app needs. To only build the 64-bit iOS ("iphone64") and its associated simulator ("simulator64"), for example, define J2OBJC_ARCHS="iphone64 simulator64" before running make.