Introduction

MultiBit is a Simplified Payment Verification (SPV) Bitcoin desktop client.

MultiBit relies on the following technologies:

• Maven as the build system, so the usual Maven processes apply. If you're not familiar with Maven then download it first and follow their installation instructions.
• ZXing ("Zebra Crossing") for QR codes
• Bitcoinj for access to the Bitcoin network
• IzPack for creating installers for Windows, Mac, Linux
• Bitcoinj Enforcer Rules to prevent dependency chain attacks
• XChange for access to several Bitcoin exchanges

A note on the Bitcoinj dependency

MultiBit depends on a special fork of Bitcoinj for its Bitcoin support. This is due to legacy wallet serialization issues and the MultiBit team are working towards a complete integration. To build MultiBit you will need to clone this fork from here:

https://code.google.com/r/jimburton618-bitcoinj-coinbase-tx/source/checkout

The branch you should use for the MultiBit develop code is: bcj-0.10.2-mb-alice

Once cloned, you should then install the custom Bitcoinj library using

mvn clean install

Branching strategy

This follows the master-develop pattern.

There are 2 main branches: master and develop. The master branch is exclusively for releases, while the develop is exclusively for release candidates. The develop branch always has a Maven version of develop-SNAPSHOT.

Every GitHub Issue gets a branch off develop. When it is complete and code reviewed it is merged into develop.

When sufficient Issues are merged into develop to justify a release, a new branch off develop is created with the release number (e.g. release-1.2.3). The Maven pom.xml is updated to reflect the snapshot version (e.g. 1.2.3-SNAPSHOT).

Once the release has been tested and is ready to go live, the final act is to update the pom.xml to remove the SNAPSHOT suffix and merge it into master.

The master branch is then tagged with the release number. Tags are in the format v1.2.3 to distinguish them from branch names.

An announcement is made on the MultiBit website to alert everyone that a new version is available.

Maven build targets

The important targets are:

mvn clean package

which will package the MultiBit project into multibit-x.y.z.jar where x.y.z is the current version number. This is suitable for local development work.

If you want to generate a complete set of multi-platform installers (Windows, Mac and Linux) you use the following command

maven clean install

After some processing, you will have the following artifacts in the target directory:

• an executable jar = multibit-exe.jar
• a Mac application bundle = MultiBit.app
• a Mac DMG file = multibit-x.y.z.dmg
• an installer for Windows = multibit-x.y.z-windows.exe
• an installer for Linux = multibit-x.y.z-linux.jar

To run MultiBit from these artifacts you can follow the instructions provided on the main MultiBit website

MultiBit contains cut down JREs so is a large clone

The MultiBit installers contain cut down JREs so the project clone is quite large. (100 to 200 MB).

Custom configuration

MultiBit is quite flexible and has several features only accessible to power users through the configuration file. This is discussed in more detail in configuration.md

Contributing

MultiBit is a very active project and if you would like to contribute please feel free to get in touch using jim@multibit.org. We are particularly looking for developers with the following skills to contribute:

• Experienced Java programmers
• Web designers for the website
• Translators using the Crowdin site
• Beta testers for checking the latest pre-release

All contributors must be OK with releasing their work under the MIT license.