The LiquiBase migrator is designed to require no dependencies to run and be easy to integrate into various build and deployment processes.
The primary worker class for LiquiBase is liquibase.migrator.Migrator. All the various ways of interacting with LiquiBase (command line, Ant, etc.) are thin wrappers around the Migrator class.
Each database refactoring/change is implemented by a class in the liquibase.change package. As the LiquiBase migrator runs, it uses a SAX XML parser to parse the change logs, instantiate the necessary change class, and run or save the corresponding SQL.
If you have additional questions about LiquiBase's architecture, please contact us via the mailing list.