JDK Manager

README.md

JDK Manager

The jdk-manager.sh script automates managing JDK versions on macOS using Homebrew and jenv. It can install or remove JDK 17, 21, and 25 (or a subset you specify), link them so /usr/libexec/java_home can detect them, and register them with jenv for version switching. It also cleans up stale jenv entries and old Homebrew versions, ensuring only the latest patch of each JDK is kept.

jdk-manager.sh

#!/usr/bin/env bash
set -euo pipefail

BREW_PREFIX="${BREW_PREFIX:-/opt/homebrew}"
DEFAULT_VERSIONS=(17 21 25)

usage() {
  cat <<EOF
Usage:
  $(basename "$0") install [versions...]
  $(basename "$0") remove [versions...]

Examples:
  $(basename "$0") install
  $(basename "$0") install 17 21
  $(basename "$0") remove
  $(basename "$0") remove 25

If no versions are provided, defaults to: ${DEFAULT_VERSIONS[*]}

Behavior:
  install
    - installs the requested JDKs with Homebrew
    - links them into /Library/Java/JavaVirtualMachines for java_home
    - removes stale jenv entries for those major versions
    - adds the current JDK homes to jenv
    - runs brew cleanup for the requested formulas

  remove
    - removes matching jenv entries for those major versions
    - removes the java_home symlinks
    - uninstalls the requested Homebrew formulas
    - runs brew cleanup for the requested formulas
EOF
  exit 1
}

log() {
  printf '\n==> %s\n' "$*"
}

die() {
  echo "Error: $*" >&2
  exit 1
}

require_cmd() {
  command -v "$1" >/dev/null 2>&1 || die "required command not found: $1"
}

brew_formula() {
  case "$1" in
    17|21) echo "openjdk@$1" ;;
    25) echo "openjdk" ;;
    *) die "unsupported JDK version: $1 (supported: 17, 21, 25)" ;;
  esac
}

jdk_opt_path() {
  echo "$BREW_PREFIX/opt/$(brew_formula "$1")"
}

jdk_bundle() {
  echo "$(jdk_opt_path "$1")/libexec/openjdk.jdk"
}

jdk_home() {
  echo "$(jdk_bundle "$1")/Contents/Home"
}

jdk_link() {
  echo "/Library/Java/JavaVirtualMachines/openjdk-$1.jdk"
}

ensure_jenv() {
  if ! command -v jenv >/dev/null 2>&1; then
    log "Installing jenv"
    brew install jenv
  fi

  export PATH="$HOME/.jenv/bin:$PATH"
  command -v jenv >/dev/null 2>&1 || die "jenv is not available on PATH"

  # Do not run: eval "$(jenv init -)"
  # The script only needs the jenv executable, not the interactive shell hooks.
}

set_versions() {
  if [[ $# -eq 0 ]]; then
    log "No JDK versions provided. Defaulting to: ${DEFAULT_VERSIONS[*]}"
    VERSIONS=("${DEFAULT_VERSIONS[@]}")
  else
    VERSIONS=("$@")
  fi
}

validate_versions() {
  local v
  for v in "$@"; do
    case "$v" in
      17|21|25) ;;
      *) die "unsupported JDK version: $v (supported: 17, 21, 25)" ;;
    esac
  done
}

cleanup_jenv_version() {
  local version="$1"
  local entries=()

  while IFS= read -r entry; do
    [[ -n "$entry" ]] && entries+=("$entry")
  done < <(jenv versions --bare 2>/dev/null | grep -E "^(openjdk64-${version}\.|${version}(\.|$))" || true)

  [[ ${#entries[@]} -eq 0 ]] && return 0

  log "Removing stale jenv entries for JDK $version"
  local entry
  for entry in "${entries[@]}"; do
    jenv remove -f "$entry" >/dev/null 2>&1 || jenv remove "$entry" >/dev/null 2>&1 || true
  done
}

brew_cleanup_versions() {
  local formulas=()
  local v

  for v in "$@"; do
    formulas+=("$(brew_formula "$v")")
  done

  log "Running brew cleanup"
  brew cleanup "${formulas[@]}" || true
}

install_versions() {
  local versions=("$@")
  local v formula bundle home link

  ensure_jenv

  for v in "${versions[@]}"; do
    formula="$(brew_formula "$v")"

    log "Installing $formula"
    brew install "$formula"

    bundle="$(jdk_bundle "$v")"
    home="$(jdk_home "$v")"
    link="$(jdk_link "$v")"

    [[ -d "$bundle" ]] || die "missing JDK bundle: $bundle"
    [[ -d "$home" ]] || die "missing JDK home: $home"

    log "Linking JDK $v for java_home"
    sudo mkdir -p /Library/Java/JavaVirtualMachines
    sudo ln -sfn "$bundle" "$link"

    cleanup_jenv_version "$v"

    log "Adding JDK $v to jenv"
    jenv add "$home"
  done

  log "Enabling jenv export plugin"
  jenv enable-plugin export || true
  jenv rehash

  brew_cleanup_versions "${versions[@]}"

  log "Done. Verify:"
  /usr/libexec/java_home -V || true
  jenv versions
}

remove_versions() {
  local versions=("$@")
  local v formula link

  ensure_jenv

  for v in "${versions[@]}"; do
    formula="$(brew_formula "$v")"
    link="$(jdk_link "$v")"

    cleanup_jenv_version "$v"

    log "Removing java_home link for JDK $v"
    sudo rm -f "$link"

    if brew list --versions "$formula" >/dev/null 2>&1; then
      log "Uninstalling $formula"
      brew uninstall "$formula" || true
    else
      log "$formula is not installed"
    fi
  done

  jenv rehash
  brew_cleanup_versions "${versions[@]}"

  log "Done. Remaining:"
  /usr/libexec/java_home -V || true
  jenv versions
}

main() {
  require_cmd brew
  require_cmd sudo

  [[ $# -eq 0 ]] && usage

  local cmd="$1"
  shift

  VERSIONS=()
  set_versions "$@"
  validate_versions "${VERSIONS[@]}"

  case "$cmd" in
    install) install_versions "${VERSIONS[@]}" ;;
    remove) remove_versions "${VERSIONS[@]}" ;;
    *) usage ;;
  esac
}

main "$@"