Create a repository folder under your project. Let's take
${project.basedir}/src/main/resources/repo
Then, install your custom jar to this repo:
mvn install:install-file -Dfile=[FILE_PATH] \
-DgroupId=[GROUP] -DartifactId=[ARTIFACT] -Dversion=[VERS] \
-Dpackaging=jar -DlocalRepositoryPath=[REPO_DIR]
Lastly, add the following repo and dependency definitions to the projects pom.xml:
project-repo
file://${project.basedir}/src/main/resources/repo
[GROUP]
[ARTIFACT]
[VERS]