源码解析

#!/bin/bash
#
#    .   ____          _            __ _ _
#   /\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
#  ( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
#   \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
#    '  |____| .__|_| |_|_| |_\__, | / / / /
#   =========|_|==============|___/=/_/_/_/
#   :: Spring Boot Startup Script ::
#

### BEGIN INIT INFO
# Provides:          {{initInfoProvides:spring-boot-application}}
# Required-Start:    {{initInfoRequiredStart:$remote_fs $syslog $network}}
# Required-Stop:     {{initInfoRequiredStop:$remote_fs $syslog $network}}
# Default-Start:     {{initInfoDefaultStart:2 3 4 5}}
# Default-Stop:      {{initInfoDefaultStop:0 1 6}}
# Short-Description: {{initInfoShortDescription:Spring Boot Application}}
# Description:       {{initInfoDescription:Spring Boot Application}}
# chkconfig:         {{initInfoChkconfig:2345 99 01}}
### END INIT INFO

# [ -z STRING ]   “STRING” 的长度为零则为真。
# [ -n STRING ]   “STRING” 的长度为非零 non-zero则为真。
# 判断是否开启 debug 模式。如果开启了 debug 模式，则通过 set -x 设置显示执行的命令
[[ -n "$DEBUG" ]] && set -x

# Initialize variables that cannot be provided by a .conf file
# 获取工作空间路径
WORKING_DIR="$(pwd)"
# shellcheck disable=SC2153
# 获取 jar 文件路径，并赋值
[[ -n "$JARFILE" ]] && jarfile="$JARFILE"
# 获取 APP 名字
[[ -n "$APP_NAME" ]] && identity="$APP_NAME"

# Follow symlinks to find the real jar and detect init.d script
cd "$(dirname "$0")" || exit 1
#  如果不存在 jarfile，则将 当路径/当前执行文件名赋值给 jarfile
[[ -z "$jarfile" ]] && jarfile=$(pwd)/$(basename "$0")
# 判断 jarfile 是否符号链接。-L 判断文件是否为符号链接
while [[ -L "$jarfile" ]]; do
    # 如果 jarfile 包含 “init.d” ,则将当前执行文件名赋值给 init_script
    [[ "$jarfile" =~ init\.d ]] && init_script=$(basename "$jarfile")
    # 获取符号链接所指向的位置
    jarfile=$(readlink "$jarfile")
    # 进入文件的真实目录
    cd "$(dirname "$jarfile")" || exit 1
    #  获取 jarfile 的绝对路径
    jarfile=$(pwd)/$(basename "$jarfile")
done

# 进入 jarfile 文件所在的目录，并获取文件绝对目录赋值给 jarfolder 。pwd -P 显示当前目录的绝对路径
jarfolder="$( (cd "$(dirname "$jarfile")" && pwd -P) )"
# 回到最初的工作空间
cd "$WORKING_DIR" || exit 1

# Source any config file
# 获取配置文件名称，从这里可以看出来，配置文件名和可执行文件名称除了后缀，其他的应该相同
configfile="$(basename "${jarfile%.*}.conf")"

# Initialize CONF_FOLDER location defaulting to jarfolder
# 如果  CONF_FOLDER 值为空，则通过 jarfolder 定义 CONF_FOLDER 的值
[[ -z "$CONF_FOLDER" ]] && CONF_FOLDER="{{confFolder:${jarfolder}}}"

# shellcheck source=/dev/null
# 如果配置文件存在，source 配置文件
[[ -r "${CONF_FOLDER}/${configfile}" ]] && source "${CONF_FOLDER}/${configfile}"

# Initialize PID/LOG locations if they weren't provided by the config file
#如果配置文件中未定义日志输出目录，pid 文件目录等，则初始化为默认值
[[ -z "$PID_FOLDER" ]] && PID_FOLDER="{{pidFolder:/var/run}}"
[[ -z "$LOG_FOLDER" ]] && LOG_FOLDER="{{logFolder:/var/log}}"
! [[ "$PID_FOLDER" == /* ]] && PID_FOLDER="$(dirname "$jarfile")"/"$PID_FOLDER"
! [[ "$LOG_FOLDER" == /* ]] && LOG_FOLDER="$(dirname "$jarfile")"/"$LOG_FOLDER"
# 是否可执行
! [[ -x "$PID_FOLDER" ]] && PID_FOLDER="/tmp"
! [[ -x "$LOG_FOLDER" ]] && LOG_FOLDER="/tmp"

# Set up defaults
[[ -z "$MODE" ]] && MODE="{{mode:auto}}" # modes are "auto", "service" or "run"
[[ -z "$USE_START_STOP_DAEMON" ]] && USE_START_STOP_DAEMON="{{useStartStopDaemon:true}}"

# Create an identity for log/pid files
# 给日志文件，进程ID文件创建一个唯一的标识
if [[ -z "$identity" ]]; then
  if [[ -n "$init_script" ]]; then
    identity="${init_script}"
  else
    identity=$(basename "${jarfile%.*}")_${jarfolder//\//}
  fi
fi

# Initialize log file name if not provided by the config file
#日志文件名录
[[ -z "$LOG_FILENAME" ]] && LOG_FILENAME="{{logFilename:${identity}.log}}"

# Initialize stop wait time if not provided by the config file
[[ -z "$STOP_WAIT_TIME" ]] && STOP_WAIT_TIME="{{stopWaitTime:60}}"

# ANSI Colors
echoRed() { echo $'\e[0;31m'"$1"$'\e[0m'; }
echoGreen() { echo $'\e[0;32m'"$1"$'\e[0m'; }
echoYellow() { echo $'\e[0;33m'"$1"$'\e[0m'; }

# Utility functions
# &> /dev/null ：把标准错误重新定向到文件  /dev/null
checkPermissions() {
  touch "$pid_file" &> /dev/null || { echoRed "Operation not permitted (cannot access pid file)"; return 4; }
  touch "$log_file" &> /dev/null || { echoRed "Operation not permitted (cannot access log file)"; return 4; }
}

isRunning() {
  ps -p "$1" &> /dev/null
}

await_file() {
  end=$(date +%s)
  let "end+=10"
  while [[ ! -s "$1" ]]
  do
    now=$(date +%s)
    if [[ $now -ge $end ]]; then
      break
    fi
    sleep 1
  done
}

# Determine the script mode
action="run"
if [[ "$MODE" == "auto" && -n "$init_script" ]] || [[ "$MODE" == "service" ]]; then
  action="$1"
  shift
fi

# Build the pid and log filenames
PID_FOLDER="$PID_FOLDER/${identity}"
pid_file="$PID_FOLDER/{{pidFilename:${identity}.pid}}"
log_file="$LOG_FOLDER/$LOG_FILENAME"

# Determine the user to run as if we are root
# shellcheck disable=SC2012
# id -u 获取当前用户 uid 的值 ，$(ls -ld "$jarfile" | awk '{print $3}')获取用户名
[[ $(id -u) == "0" ]] && run_user=$(ls -ld "$jarfile" | awk '{print $3}')

# Find Java
# 查找 Java 
# type命令用来显示指定命令的类型，判断给出的指令是内部指令还是外部指令。
# -t：输出“file”、“alias”或者“builtin”，分别表示给定的指令为“外部指令”、“命令别名”或者“内部指令”；
# -p：如果给出的指令为外部指令，则显示其绝对路径； 
# -a：在环境变量“PATH”指定的路径中，显示给定指令的信息，包括命令别名。
# "Unable to find Java" 问题的根本所在
if [[ -n "$JAVA_HOME" ]] && [[ -x "$JAVA_HOME/bin/java" ]]; then
    javaexe="$JAVA_HOME/bin/java"
elif type -p java > /dev/null 2>&1; then
    javaexe=$(type -p java)
elif [[ -x "/usr/bin/java" ]];  then
    javaexe="/usr/bin/java"
else
    echo "Unable to find Java"
    exit 1
fi

# Java 虚拟机参数配置 ，数组
arguments=(-Dsun.misc.URLClassPath.disableJarChecking=true $JAVA_OPTS -jar "$jarfile" $RUN_ARGS "$@")

# Action functions
start() {
  if [[ -f "$pid_file" ]]; then
    pid=$(cat "$pid_file")
    isRunning "$pid" && { echoYellow "Already running [$pid]"; return 0; }
  fi
  do_start "$@"
}

# ${arguments[@]} : 数组使用@ 或 * 可以获取数组中的所有元素
do_start() {
  working_dir=$(dirname "$jarfile")
  pushd "$working_dir" > /dev/null
  mkdir -p "$PID_FOLDER" &> /dev/null
  if [[ -n "$run_user" ]]; then
    checkPermissions || return $?
    chown "$run_user" "$PID_FOLDER"
    chown "$run_user" "$pid_file"
    chown "$run_user" "$log_file"
    if [ $USE_START_STOP_DAEMON = true ] && type start-stop-daemon > /dev/null 2>&1; then
      start-stop-daemon --start --quiet \
        --chuid "$run_user" \
        --name "$identity" \
        --make-pidfile --pidfile "$pid_file" \
        --background --no-close \
        --startas "$javaexe" \
        --chdir "$working_dir" \
        -- "${arguments[@]}" \ 
        >> "$log_file" 2>&1
      await_file "$pid_file"
    else
      su -s /bin/sh -c "$javaexe $(printf "\"%s\" " "${arguments[@]}") >> \"$log_file\" 2>&1 & echo \$!" "$run_user" > "$pid_file"
    fi
    pid=$(cat "$pid_file")
  else
    checkPermissions || return $?
    "$javaexe" "${arguments[@]}" >> "$log_file" 2>&1 &
    pid=$!
    disown $pid
    echo "$pid" > "$pid_file"
  fi
  [[ -z $pid ]] && { echoRed "Failed to start"; return 1; }
  echoGreen "Started [$pid]"
}

stop() {
  working_dir=$(dirname "$jarfile")
  pushd "$working_dir" > /dev/null
  [[ -f $pid_file ]] || { echoYellow "Not running (pidfile not found)"; return 0; }
  pid=$(cat "$pid_file")
  isRunning "$pid" || { echoYellow "Not running (process ${pid}). Removing stale pid file."; rm -f "$pid_file"; return 0; }
  do_stop "$pid" "$pid_file"
}

do_stop() {
  kill "$1" &> /dev/null || { echoRed "Unable to kill process $1"; return 1; }
  for i in $(seq 1 $STOP_WAIT_TIME); do
    isRunning "$1" || { echoGreen "Stopped [$1]"; rm -f "$2"; return 0; }
    [[ $i -eq STOP_WAIT_TIME/2 ]] && kill "$1" &> /dev/null
    sleep 1
  done
  echoRed "Unable to kill process $1";
  return 1;
}

force_stop() {
  [[ -f $pid_file ]] || { echoYellow "Not running (pidfile not found)"; return 0; }
  pid=$(cat "$pid_file")
  isRunning "$pid" || { echoYellow "Not running (process ${pid}). Removing stale pid file."; rm -f "$pid_file"; return 0; }
  do_force_stop "$pid" "$pid_file"
}

do_force_stop() {
  kill -9 "$1" &> /dev/null || { echoRed "Unable to kill process $1"; return 1; }
  for i in $(seq 1 $STOP_WAIT_TIME); do
    isRunning "$1" || { echoGreen "Stopped [$1]"; rm -f "$2"; return 0; }
    [[ $i -eq STOP_WAIT_TIME/2 ]] && kill -9 "$1" &> /dev/null
    sleep 1
  done
  echoRed "Unable to kill process $1";
  return 1;
}

restart() {
  stop && start
}

force_reload() {
  working_dir=$(dirname "$jarfile")
  pushd "$working_dir" > /dev/null
  [[ -f $pid_file ]] || { echoRed "Not running (pidfile not found)"; return 7; }
  pid=$(cat "$pid_file")
  rm -f "$pid_file"
  isRunning "$pid" || { echoRed "Not running (process ${pid} not found)"; return 7; }
  do_stop "$pid" "$pid_file"
  do_start
}

status() {
  working_dir=$(dirname "$jarfile")
  pushd "$working_dir" > /dev/null
  [[ -f "$pid_file" ]] || { echoRed "Not running"; return 3; }
  pid=$(cat "$pid_file")
  isRunning "$pid" || { echoRed "Not running (process ${pid} not found)"; return 1; }
  echoGreen "Running [$pid]"
  return 0
}

run() {
  pushd "$(dirname "$jarfile")" > /dev/null
  "$javaexe" "${arguments[@]}"
  result=$?
  popd > /dev/null
  return "$result"
}

# Call the appropriate action function
case "$action" in
start)
  start "$@"; exit $?;;
stop)
  stop "$@"; exit $?;;
force-stop)
  force_stop "$@"; exit $?;;
restart)
  restart "$@"; exit $?;;
force-reload)
  force_reload "$@"; exit $?;;
status)
  status "$@"; exit $?;;
run)
  run "$@"; exit $?;;
*)
  echo "Usage: $0 {start|stop|force-stop|restart|force-reload|status|run}"; exit 1;
esac

exit 0

References:

spring-boot