qmvn

#!/usr/bin/env bash

# Maven wrapper script to accelerate the build of multi-module projects
# This script detects which modules have been modified since the last build, and executes maven in `-amd -pl ...` mode.
# See this page for details of how these flags accelerate the build:
#   http://blog.sonatype.com/2009/10/maven-tips-and-tricks-advanced-reactor-options/
#
# USAGE:
#  ./qmvn <goal>, e.g. ./qmvn install
#

set -euo pipefail
#set -x

# All modules in the project. This could be detected automatically...
MODULES=(. core modules/jdbc modules/mysql modules/postgresql modules/selenium modules/nginx)
# Array to collect which modules have changed
CHANGED_MODULES=()
# We need to known when the maven command (args to this script) were last run
COMMAND_HASH=$(echo $@ | md5)
# JVM options to make maven run more quickly
export MAVEN_OPTS="-XX:+TieredCompilation -XX:TieredStopAtLevel=1"

# Iterate over all the modules to detect changes
for MODULE in ${MODULES[@]}; do

    GUARDFILE="${MODULE}/target/.lastchange.${COMMAND_HASH}"

    if [[ ! -f ${GUARDFILE} ]]; then
        mkdir -p ${GUARDFILE} && rm -rf ${GUARDFILE}
        touch -t "$(date -r 0 +%Y%m%d%H%M.%S)" ${GUARDFILE}
    fi

    # Specifically ignore changes the to target and src/generated directories
    CHANGES=$(find ${MODULE} -newer ${GUARDFILE} -not -path "${MODULE}/target/*" -not -path "${MODULE}/src/generated/*" | wc -l | xargs)

    if [[ $CHANGES > 0 ]]; then
        echo "$MODULE has changes since the last invocation of mvn $@"
        CHANGED_MODULES+=($MODULE)
    fi
done

# Exit right away if nothing has changed
if [[ ${#CHANGED_MODULES[@]} == 0 ]]; then
    echo "No changes"
    exit 0
fi

function join { local IFS="$1"; shift; echo "$*"; }

PL_LIST=$(join "," ${CHANGED_MODULES[@]})

# Execute maven such that just the changed modules, and modules that depend on them, get built
mvn $@ -pl ${PL_LIST} -amd

# Finally, assuming successful invocation of maven, update our guardfiles so that future changes are detected from now onwards
for MODULE in ${MODULES[@]}; do
    GUARDFILE="${MODULE}/target/.lastchange.${COMMAND_HASH}"
    touch ${GUARDFILE}
done