Improve openjdk::install_openjdk_via_jvm_common_buildpack (#181)

Author: Malax

CHANGELOG.md

@@ -6,6 +6,9 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/).
 
 ## [Unreleased]
 
+### Changed
+
+* Improve OpenJDK installation via jvm-common buildpack to prevent function overrides and fix environment variable handling ([#181](https://github.com/heroku/heroku-buildpack-gradle/pull/181))
 
 ## [v48] - 2025-09-17
 

lib/openjdk.sh

@@ -5,10 +5,10 @@
 set -euo pipefail
 
 function openjdk::install_openjdk_via_jvm_common_buildpack() {
-	local build_directory="${1}"
+	local build_dir="${1}"
 	# The install_openjdk function from the JVM common buildpack requires the path to the host buildpack to write to the
 	# export script so that OpenJDK can be found by subsequent buildpacks.
-	local host_buildpack_directory="${2}"
+	local host_buildpack_dir="${2}"
 
 	# Legacy behaviour for customers and testing code can override the download location of the heroku/jvm buildpack
 	# with JVM_COMMON_BUILDPACK for testing and debugging purposes.
@@ -17,22 +17,42 @@ function openjdk::install_openjdk_via_jvm_common_buildpack() {
 	local jvm_common_buildpack_tarball_path
 	jvm_common_buildpack_tarball_path=$(mktemp)
 
-	local jvm_common_buildpack_directory
-	jvm_common_buildpack_directory=$(mktemp -d)
+	local jvm_common_buildpack_dir
+	jvm_common_buildpack_dir=$(mktemp -d)
 
-	curl --silent --show-error --fail --retry 3 --retry-connrefused --connect-timeout 5 --location "${jvm_common_buildpack_tarball_url}" -o "${jvm_common_buildpack_tarball_path}"
-	tar -xzm --directory "${jvm_common_buildpack_directory}" --strip-components=1 -f "${jvm_common_buildpack_tarball_path}"
+	curl \
+		--connect-timeout 3 \
+		--max-time 60 \
+		--retry 5 \
+		--retry-connrefused \
+		--no-progress-meter \
+		--fail \
+		--location \
+		"${jvm_common_buildpack_tarball_url}" \
+		-o "${jvm_common_buildpack_tarball_path}"
+
+	tar -xzm --directory "${jvm_common_buildpack_dir}" --strip-components=1 -f "${jvm_common_buildpack_tarball_path}"
 
 	# This script translates non-JDBC compliant DATABASE_URL (and similar) environment variables into their
 	# JDBC compatible counterparts and writes them to "JDBC_" prefixed environment variables. We source this script
 	# here to allow customers to connect to their databases via JDBC during the build. If no database environment
 	# variables are present, this script does nothing.
 	# shellcheck source=/dev/null
-	source "${jvm_common_buildpack_directory}/opt/jdbc.sh"
+	source "${jvm_common_buildpack_dir}/opt/jdbc.sh"
 
-	# shellcheck source=/dev/null
-	source "${jvm_common_buildpack_directory}/bin/java"
+	# Run the main installation in a sub-shell to avoid it overriding library functions and global
+	# variables in the host buildpack.
+	(
+		# shellcheck source=/dev/null
+		source "${jvm_common_buildpack_dir}/bin/java"
 
-	# See: https://github.com/heroku/heroku-buildpack-jvm-common/blob/main/bin/java
-	install_openjdk "${build_directory}" "${host_buildpack_directory}"
+		# See: https://github.com/heroku/heroku-buildpack-jvm-common/blob/main/bin/java
+		install_openjdk "${build_dir}" "${host_buildpack_dir}"
+	)
+
+	# Since we run install_openjdk in a sub-shell, any environment variables set by it will not be available in this
+	# (parent) shell. As documented in the jvm buildpack, we can source the modified export script from this (host)
+	# buildpack to get the necessary changes.
+	# shellcheck source=/dev/null
+	source "${host_buildpack_dir}/export"
 }