The following tools need to installed on the system before a GeoServer developer environment can be set up.
Developing with GeoServer requires a Java Development Kit (JDK), version 8, available from OpenJDK, AdoptOpenJDK for Windows and macOS installers, or provided by your OS distribution.
Due to subtle changes in Java class libraries we require development on Java 8 at this time (although the result is tested on Java 11).
GeoServer uses a tool known as Maven to build.
Maven tracks global settings in your home directory .m2/settings.xml. This file is used to control global options such as proxy settings or listing repository mirrors to download from.
GeoServer source code is stored and version in a git repository on github There are a variety of git clients available for a number of different platforms. Visit http://git-scm.com/ for more details.