A key to start to write shell

#!/bin/bash
APP_NAME=bonade-uaac-service-0.0.1-SNAPSHOT.jar
usage() {
echo "Usage: sh 执行脚本.sh [start|stop|restart|status]"
exit 1
}
is_exist(){
pid=`ps -ef|grep $APP_NAME|grep -v grep|awk '{print $2}' `
if [ -z "${pid}" ]; then
return 1
else
return 0
fi
}

start(){
is_exist
if [ $? -eq "0" ]; then
echo "${APP_NAME} is already running. pid=${pid} ."
else
nohup java -XX:InitialHeapSize=100m -XX:MaxHeapSize=300m -XX:+PrintGCDateStamps -XX:+PrintGCDetails -Xloggc:./logs/java_gc.log -XX:-HeapDumpOnOutOfMemoryError -XX:HeapDumpPath=./logs/ -Dfile.encoding=UTF-8 -Dsun.jnu.encoding=UTF-8 -jar /data/bonade-uaac-service/$APP_NAME --isJar=true --spring.profiles.active=fat &
fi
}

stop(){
is_exist
if [ $? -eq "0" ]; then
kill -9 $pid
else
echo "${APP_NAME} is not running"
fi
}

status(){
is_exist
if [ $? -eq "0" ]; then
echo "${APP_NAME} is running. Pid is ${pid}"
else
echo "${APP_NAME} is NOT running."
fi
}

# Restart
the restart () {
STOP
Start
}

case "$1" in
"start")
start
;;
"stop")
stop
;;
"status")
status
;;
"restart")
restart
;;
*)
usage
;;
esac
exit 0