首頁 > 軟體

如何把MySQL及Tomcat打包到snap包中去

2020-06-16 17:34:27

Snap是一個在Ubuntu系統上一個新的技術.如果大家對這個技術還不是很理解的話,可以參閱文章"安裝snap應用到Ubuntu 16.4桌面系統".我們知道MySQLTomcat是在Java伺服器端常用的技術.那麼我們怎么來把它打包到我們的snap應用中去呢?很多人可能以為這個很簡單.我們可以直接在snapcraft.yaml中使用stage-package來安裝現有的debian包,不就可以了嗎?其實,由於在snap系統的安全性限制,在一個snap應用被成功安裝後,它自己所在的目錄是唯讀的,不可以寫入任何的資料.我們只有規定的部分目錄才是可以寫入的.我們以hello例程為例,我們有如下的目錄可以使用:

 

在上面,有兩個最重要的目錄:

 

  • SNAP_DATA
  • SNAP
在我們snap我們應用的時候,我們需要configure我們的應用盡量使用上面的兩個目錄,而不需要hard-code我們的目錄.特別是由於我們的應用不能向自己的安裝目錄SNAP寫入任何的資料(read-only),所以,我們必須把我們的資料庫及需要寫入資料的檔案設定到SNAP_DATA目錄中.另外必須注意的是,存取SNAP_DATA檔案目錄時需要root許可權.這對於一個daemon的應用來說,應該沒有問題,但是對於一般的應用來說,我們需要使用sudo來存取才可以存取到資料庫.

 

 

1)snap Tomcat

 
在我們的snapcraft中有一個例程叫做"tomcat-webapp-demo".它提供了一個很好的基礎.
 

snapcraft.yaml

name: tomcat-webapp-demo
version: 1.0
architectures:
 - amd64
summary: Demo of Tomcat-hosted Webapp
description: This is a demo snap of a Tomcat-hosted webapp produced by snapcraft with maven.
confinement: strict

apps:
 tomcat:
   command: bin/wrapper
   daemon: simple
   plugs: [network-bind]

parts:
    webapp:
        plugin: maven
        source: https://github.com/lool/snappy-mvn-demo.git
        source-type: git
    tomcat:
        plugin: dump
        source: https://archive.apache.org/dist/tomcat/tomcat-8/v8.0.29/bin/apache-tomcat-8.0.29.tar.gz
    local-files:
        plugin: make
        source: .
 
從上面我們可以看出來,它使用了dump plugin.這個plugin只有在snapcraft 2.14中才開始適使用,並最終代替copy plugin. 對於以前的版本我們可以使用tar-content來代替dump.從上面的程式碼中可以看出來,它知己從官網上下載所需要的版本,並做一個安裝.在啟動的時候,它使用bin/wrapper來啟動.wrapper的內容如下:
 

wrapper

#!/bin/sh

set -e
set -x

# installation pathes are based of CATALINA_HOME
export CATALINA_HOME="$SNAP"
# writable pathes are based of CATALINA_BASE
export CATALINA_BASE="$SNAP_DATA"

# create runtime data
mkdir -p "$CATALINA_BASE/logs"
mkdir -p "$CATALINA_BASE/temp"

if ! [ -d $CATALINA_BASE/conf ]; then
	echo "conf directory does not exist"
    cp -rd $CATALINA_HOME/tomcat-conf $CATALINA_BASE/conf
fi

if ! [ -d $CATALINA_BASE/webapps ]; then
	echo "webapps directory  does not exist"
    cp -rd $CATALINA_HOME/webapps $CATALINA_BASE/
    cp $CATALINA_HOME/war/*.war $CATALINA_BASE/webapps/
fi

$CATALINA_HOME/bin/catalina.sh run

從上面的程式碼中,我們可以看出來我們已經把我們所需要的目錄用SNAP及SNAP_DATA來代替了.
 
 

2)snap MySQL

 
我們可以先看一下文章"Snapping Nextcloud: MySQL".從該文章中,我們可以看出來,直接通過stage-package的方式來snap MySQL是不可能的.我們可以直接編譯MySQL原始碼的方式來snap MySQL.
 

snapcraft.yaml

    # Download the boost headers for MySQL. Note that the version used may need to
    # be updated if the version of MySQL changes.
    boost:
        plugin: copy
        source: http://sourceforge.net/projects/boost/files/boost/1.59.0/boost_1_59_0.tar.gz
        files:
          '*': boost/
        snap:
          - -*
        
    mysql:
        plugin: cmake
        source: https://github.com/kyrofa/mysql-server.git
        source-type: git
        source-branch: feature/support_no_setpriority
        after: [boost]
        configflags:
          - -DWITH_BOOST=$SNAPCRAFT_STAGE/boost
          - -DWITH_INNODB_PAGE_CLEANER_PRIORITY=OFF
          - -DCMAKE_INSTALL_PREFIX=/
          - -DBUILD_CONFIG=mysql_release
          - -DWITH_UNIT_TESTS=OFF
          - -DWITH_EMBEDDED_SERVER=OFF
          - -DWITH_EMBEDDED_SHARED_LIBRARY=OFF
          - -DWITH_ARCHIVE_STORAGE_ENGINE=OFF
          - -DWITH_BLACKHOLE_STORAGE_ENGINE=OFF
          - -DWITH_FEDERATED_STORAGE_ENGINE=OFF
          - -DWITH_PARTITION_STORAGE_ENGINE=OFF
          - -DINSTALL_MYSQLTESTDIR=
        build-packages:
          - wget
          - g++
          - cmake
          - bison
          - libncurses5-dev
          - libaio-dev
        stage:
         # Remove scripts that we'll be replacing with our own
          - -support-files/mysql.server
        snap:
         # Remove scripts that we'll be replacing with our own
         - -support-files/mysql.server

         # Remove unused binaries that waste space
         - -bin/innochecksum
         - -bin/lz4_decompress
         - -bin/myisam*
         - -bin/mysqladmin
         - -bin/mysqlbinlog
         - -bin/mysql_client_test
         - -bin/mysql_config*
         - -bin/mysqld_multi
         - -bin/mysqldump*
         - -bin/mysqlimport
         - -bin/mysql_install_db
         - -bin/mysql_plugin
         - -bin/mysqlpump
         - -bin/mysql_secure_installation
         - -bin/mysqlshow
         - -bin/mysqlslap
         - -bin/mysql_ssl_rsa_setup
         - -bin/mysqltest
         - -bin/mysql_tzinfo_to_sql
         - -bin/perror
         - -bin/replace
         - -bin/resolveip
         - -bin/resolve_stack_dump
         - -bin/zlib_decompress

    # Copy over our MySQL scripts
    mysql-customizations:
        plugin: copy
        files:
           # This one is what creates the initial database and account for ownCloud.
           src/mysql/start_mysql: bin/
           src/mysql/my.cnf: my.cnf
           src/mysql/mysql.server: support-files/
           sample.war: war/sample.war
           mysql-connector-java-6.0.3.jar: lib/mysql-connector-java-6.0.3.jar

由於編譯MySQL時需要用到boost庫,所以直接把boost庫的原始碼下載下來,當然,在我們snap時,我們並不需要它,所以:
 
        snap:
          - -*
 
就想我們之前snap我們的tomcat時一樣,我們需要對MySQL的設定進行改變才可以:
 
 

src/mysql/my.cnf

 
[mysqld]
user=root
max_allowed_packet=100M
secure-file-priv=NULL
port=3306
bind-address=0.0.0.0
[client]
protocol=tcp
在這裡,我們設定了所需要的port號碼及使用的協定TCP.這樣我們的資料庫可以位於任何一個單獨的伺服器中(我們可以修改這裡的bind-address).在我們的設計中,MySQL的資料庫位於本機.這樣當我們的MySQL伺服器執行時,可以看到:
 
liuxg@liuxg:~$ netstat -lnp46 | grep -w 3306
(Not all processes could be identified, non-owned process info
 will not be shown, you would have to be root to see it all.)
tcp        0      0 0.0.0.0:3306            0.0.0.0:*               LISTEN      -               

src/mysql/mysql.server

這個檔案是我們在我們的下面的start_mysql的指令碼中被使用的:
 
$SNAP/support-files/mysql.server start

該指令碼的內容如下:
 
#!/bin/sh
# Copyright Abandoned 1996 TCX DataKonsult AB & Monty Program KB & Detron HB
# This file is public domain and comes with NO WARRANTY of any kind

# MySQL daemon start/stop script.

# Usually this is put in /etc/init.d (at least on machines SYSV R4 based
# systems) and linked to /etc/rc3.d/S99mysql and /etc/rc0.d/K01mysql.
# When this is done the mysql server will be started when the machine is
# started and shut down when the systems goes down.

# Comments to support chkconfig on RedHat Linux
# chkconfig: 2345 64 36
# description: A very fast and reliable SQL database engine.

# Comments to support LSB init script conventions
### BEGIN INIT INFO
# Provides: mysql
# Required-Start: $local_fs $network $remote_fs
# Should-Start: ypbind nscd ldap ntpd xntpd
# Required-Stop: $local_fs $network $remote_fs
# Default-Start:  2 3 4 5
# Default-Stop: 0 1 6
# Short-Description: start and stop MySQL
# Description: MySQL is a very fast and reliable SQL database engine.
### END INIT INFO
 
# If you install MySQL on some other places than /, then you
# have to do one of the following things for this script to work:
#
# - Run this script from within the MySQL installation directory
# - Create a /etc/my.cnf file with the following information:
#   [mysqld]
#   basedir=<path-to-mysql-installation-directory>
# - Add the above to any other configuration file (for example ~/.my.ini)
#   and copy my_print_defaults to /usr/bin
# - Add the path to the mysql-installation-directory to the basedir variable
#   below.
#
# If you want to affect other MySQL variables, you should make your changes
# in the /etc/my.cnf, ~/.my.cnf or other MySQL configuration files.

# If you change base dir, you must also change datadir. These may get
# overwritten by settings in the MySQL configuration files.

basedir=$SNAP
datadir=$SNAP_DATA/mysql

# Default value, in seconds, afterwhich the script should timeout waiting
# for server start. 
# Value here is overriden by value in my.cnf. 
# 0 means don't wait at all
# Negative numbers mean to wait indefinitely
service_startup_timeout=900

# Lock directory for RedHat / SUSE.
lockdir="$SNAP_DATA/mysql/lock"
lock_file_path="$lockdir/mysql"

# The following variables are only set for letting mysql.server find things.

# Set some defaults
mysqld_pid_file_path=
if test -z "$basedir"
then
  basedir=/
  bindir=//bin
  if test -z "$datadir"
  then
    datadir=//data
  fi
  sbindir=//bin
  libexecdir=//bin
else
  bindir="$basedir/bin"
  if test -z "$datadir"
  then
    datadir="$basedir/data"
  fi
  sbindir="$basedir/sbin"
  libexecdir="$basedir/libexec"
fi

# datadir_set is used to determine if datadir was set (and so should be
# *not* set inside of the --basedir= handler.)
datadir_set=

#
# Use LSB init script functions for printing messages, if possible
#
lsb_functions="/lib/lsb/init-functions"
if test -f $lsb_functions ; then
  . $lsb_functions
else
  log_success_msg()
  {
    echo " SUCCESS! $@"
  }
  log_failure_msg()
  {
    echo " ERROR! $@"
  }
fi

PATH="/sbin:/usr/sbin:/bin:/usr/bin:$basedir/bin"
export PATH

mode=$1    # start or stop

[ $# -ge 1 ] && shift


other_args="$*"   # uncommon, but needed when called from an RPM upgrade action
           # Expected: "--skip-networking --skip-grant-tables"
           # They are not checked here, intentionally, as it is the resposibility
           # of the "spec" file author to give correct arguments only.

case `echo "testingc"`,`echo -n testing` in
    *c*,-n*) echo_n=   echo_c=     ;;
    *c*,*)   echo_n=-n echo_c=     ;;
    *)       echo_n=   echo_c='c' ;;
esac

parse_server_arguments() {
  for arg do
    case "$arg" in
      --basedir=*)  basedir=`echo "$arg" | sed -e 's/^[^=]*=//'`
                    bindir="$basedir/bin"
		    if test -z "$datadir_set"; then
		      datadir="$basedir/data"
		    fi
		    sbindir="$basedir/sbin"
		    libexecdir="$basedir/libexec"
        ;;
      --datadir=*)  datadir=`echo "$arg" | sed -e 's/^[^=]*=//'`
		    datadir_set=1
	;;
      --pid-file=*) mysqld_pid_file_path=`echo "$arg" | sed -e 's/^[^=]*=//'` ;;
      --service-startup-timeout=*) service_startup_timeout=`echo "$arg" | sed -e 's/^[^=]*=//'` ;;
    esac
  done
}

wait_for_pid () {
  verb="$1"           # created | removed
  pid="$2"            # process ID of the program operating on the pid-file
  pid_file_path="$3" # path to the PID file.

  i=0
  avoid_race_condition="by checking again"

  while test $i -ne $service_startup_timeout ; do

    case "$verb" in
      'created')
        # wait for a PID-file to pop into existence.
        test -s "$pid_file_path" && i='' && break
        ;;
      'removed')
        # wait for this PID-file to disappear
        test ! -s "$pid_file_path" && i='' && break
        ;;
      *)
        echo "wait_for_pid () usage: wait_for_pid created|removed pid pid_file_path"
        exit 1
        ;;
    esac

    # if server isn't running, then pid-file will never be updated
    if test -n "$pid"; then
      if kill -0 "$pid" 2>/dev/null; then
        :  # the server still runs
      else
        # The server may have exited between the last pid-file check and now.  
        if test -n "$avoid_race_condition"; then
          avoid_race_condition=""
          continue  # Check again.
        fi

        # there's nothing that will affect the file.
        log_failure_msg "The server quit without updating PID file ($pid_file_path)."
        return 1  # not waiting any more.
      fi
    fi

    echo $echo_n ".$echo_c"
    i=`expr $i + 1`
    sleep 1

  done

  if test -z "$i" ; then
    log_success_msg
    return 0
  else
    log_failure_msg
    return 1
  fi
}

# Get arguments from the my.cnf file,
# the only group, which is read from now on is [mysqld]
if test -x ./bin/my_print_defaults
then
  print_defaults="./bin/my_print_defaults"
elif test -x $bindir/my_print_defaults
then
  print_defaults="$bindir/my_print_defaults"
elif test -x $bindir/mysql_print_defaults
then
  print_defaults="$bindir/mysql_print_defaults"
else
  # Try to find basedir in /etc/my.cnf
  conf=/etc/my.cnf
  print_defaults=
  if test -r $conf
  then
    subpat='^[^=]*basedir[^=]*=(.*)$'
    dirs=`sed -e "/$subpat/!d" -e 's//1/' $conf`
    for d in $dirs
    do
      d=`echo $d | sed -e 's/[ 	]//g'`
      if test -x "$d/bin/my_print_defaults"
      then
        print_defaults="$d/bin/my_print_defaults"
        break
      fi
      if test -x "$d/bin/mysql_print_defaults"
      then
        print_defaults="$d/bin/mysql_print_defaults"
        break
      fi
    done
  fi

  # Hope it's in the PATH ... but I doubt it
  test -z "$print_defaults" && print_defaults="my_print_defaults"
fi

#
# Read defaults file from 'basedir'.   If there is no defaults file there
# check if it's in the old (depricated) place (datadir) and read it from there
#

extra_args=""
if test -r "$basedir/my.cnf"
then
  extra_args="-e $basedir/my.cnf"
else
  if test -r "$datadir/my.cnf"
  then
    extra_args="-e $datadir/my.cnf"
  fi
fi

parse_server_arguments `$print_defaults $extra_args mysqld server mysql_server mysql.server`

#
# Set pid file if not given
#
if test -z "$mysqld_pid_file_path"
then
  mysqld_pid_file_path=$datadir/`hostname`.pid
else
  case "$mysqld_pid_file_path" in
    /* ) ;;
    * )  mysqld_pid_file_path="$datadir/$mysqld_pid_file_path" ;;
  esac
fi

case "$mode" in
  'start')
    # Start daemon

    # Safeguard (relative paths, core dumps..)
    cd $basedir

    echo $echo_n "Starting MySQL"
    if test -x $bindir/mysqld_safe
    then
      # Give extra arguments to mysqld with the my.cnf file. This script
      # may be overwritten at next upgrade.
      $bindir/mysqld_safe --datadir="$datadir" --pid-file="$mysqld_pid_file_path" --lc-messages-dir="$SNAP/share" $other_args >/dev/null 2>&1 &
      wait_for_pid created "$!" "$mysqld_pid_file_path"; return_value=$?

      # Make lock for RedHat / SuSE
      if test -w "$lockdir"
      then
        touch "$lock_file_path"
      fi

      exit $return_value
    else
      log_failure_msg "Couldn't find MySQL server ($bindir/mysqld_safe)"
    fi
    ;;

  'stop')
    # Stop daemon. We use a signal here to avoid having to know the
    # root password.

    if test -s "$mysqld_pid_file_path"
    then
      # signal mysqld_safe that it needs to stop
      touch "$mysqld_pid_file_path.shutdown"

      mysqld_pid=`cat "$mysqld_pid_file_path"`

      if (kill -0 $mysqld_pid 2>/dev/null)
      then
        echo $echo_n "Shutting down MySQL"
        kill $mysqld_pid
        # mysqld should remove the pid file when it exits, so wait for it.
        wait_for_pid removed "$mysqld_pid" "$mysqld_pid_file_path"; return_value=$?
      else
        log_failure_msg "MySQL server process #$mysqld_pid is not running!"
        rm "$mysqld_pid_file_path"
      fi

      # Delete lock for RedHat / SuSE
      if test -f "$lock_file_path"
      then
        rm -f "$lock_file_path"
      fi
      exit $return_value
    else
      log_failure_msg "MySQL server PID file could not be found!"
    fi
    ;;

  'restart')
    # Stop the service and regardless of whether it was
    # running or not, start it again.
    if $0 stop  $other_args; then
      $0 start $other_args
    else
      log_failure_msg "Failed to stop running server, so refusing to try to start."
      exit 1
    fi
    ;;

  'reload'|'force-reload')
    if test -s "$mysqld_pid_file_path" ; then
      read mysqld_pid <  "$mysqld_pid_file_path"
      kill -HUP $mysqld_pid && log_success_msg "Reloading service MySQL"
      touch "$mysqld_pid_file_path"
    else
      log_failure_msg "MySQL PID file could not be found!"
      exit 1
    fi
    ;;
  'status')
    # First, check to see if pid file exists
    if test -s "$mysqld_pid_file_path" ; then 
      read mysqld_pid < "$mysqld_pid_file_path"
      if kill -0 $mysqld_pid 2>/dev/null ; then 
        log_success_msg "MySQL running ($mysqld_pid)"
        exit 0
      else
        log_failure_msg "MySQL is not running, but PID file exists"
        exit 1
      fi
    else
      # Try to find appropriate mysqld process
      mysqld_pid=`pidof $libexecdir/mysqld`

      # test if multiple pids exist
      pid_count=`echo $mysqld_pid | wc -w`
      if test $pid_count -gt 1 ; then
        log_failure_msg "Multiple MySQL running but PID file could not be found ($mysqld_pid)"
        exit 5
      elif test -z $mysqld_pid ; then 
        if test -f "$lock_file_path" ; then 
          log_failure_msg "MySQL is not running, but lock file ($lock_file_path) exists"
          exit 2
        fi 
        log_failure_msg "MySQL is not running"
        exit 3
      else
        log_failure_msg "MySQL is running but PID file could not be found"
        exit 4
      fi
    fi
    ;;
    *)
      # usage
      basename=`basename "$0"`
      echo "Usage: $basename  {start|stop|restart|reload|force-reload|status}  [ MySQL server options ]"
      exit 1
    ;;
esac

exit 0

這個指令碼的內容其實和標準的從MySQL編譯後的指令碼沒有什麼大的差別.除了如下的地方發生改變:
 
basedir=$SNAP
datadir=$SNAP_DATA/mysql
 
這個地方的改變是為了提供我們執行檔案的參考目錄位置及資料庫的檔案位置.
 

src/mysql/start_mysql

 
 
這是一個我們需要的指令碼來真正啟動我們的MySQL伺服器:
 
 mysql:
   command: start_mysql
   stop-command: support-files/mysql.server stop
   daemon: simple
   plugs: [network, network-bind]
 
顯然這是一個daemon應用.它的內容如下:
 
#!/bin/sh

root_option_file="$SNAP_DATA/mysql/root.ini"
demouser_password_file="$SNAP_DATA/mysql/demouser_password"
mysqld_pid_file_path=$SNAP_DATA/mysql/`hostname`.pid
#mysql_socket_file_path=$SNAP_DATA/mysql/mysql.sock
new_install=false

# Make sure the database is initialized (this is safe to run if already
# initialized)
mysqld --initialize-insecure --basedir="$SNAP" --datadir="$SNAP_DATA/mysql" --lc-messages-dir="$SNAP/share"

# If the above command succeeded, it means this is a new installation.
if [ $? -eq 0 ]; then
	echo "it is new install"
	new_install=true
fi

# Start mysql
$SNAP/support-files/mysql.server start

# Initialize new installation if necessary.
if [ $new_install = true ]; then
	# Generate a password for the root mysql user.
	echo -n "Generating root mysql password... "
	root_password="123"
	echo "done."

	# Generate a password for the owncloud mysql user.
	echo -n "Generating owncloud mysql password... "
	demouser_password="123"
	echo "done."

	# Save root user information
	echo "writing client"
	echo "[client]" >> $root_option_file
	echo "writing user=root"
	echo "user=root" >> $root_option_file
	chmod 600 $root_option_file
	
	echo "dump the root option file"
	cat $root_option_file

	# Now set everything up in one step:
	# 1) Set the root user's password
	# 2) Create the 'demouser' user
	# 3) Create the 'demodb' database
	# 4) Grant the 'demodb' user privileges on the 'demodb' database
	echo -n "Setting up users and owncloud database... "
	mysql --defaults-file=$root_option_file <<SQL
ALTER USER 'root'@'localhost' IDENTIFIED BY '$root_password';
CREATE USER 'demouser'@'localhost' IDENTIFIED BY '$demouser_password';
CREATE DATABASE demodb;
GRANT ALL PRIVILEGES ON demodb.* TO 'demouser'@'localhost' IDENTIFIED BY '$demouser_password';
USE demodb;
create table Employees
    (
     id int not null,
     age int not null,
     first varchar (255),
     last varchar (255)
    );
INSERT INTO Employees VALUES (100, 18, 'Zara', 'Ali');
INSERT INTO Employees VALUES (101, 25, 'Mahnaz', 'Fatma');    
INSERT INTO Employees VALUES (102, 30, 'Zaid', 'Khan');
INSERT INTO Employees VALUES (103, 28, 'Sumit', 'Mittal');
SQL
	if [ $? -eq 0 ]; then
		echo "done."
	else
		echo "Failed to initialize-- reverting..."
		$SNAP/support-files/mysql.server stop
		rm -rf $SNAP_DATA/mysql/*
	fi

	# Now the root mysql user has a password. Save that as well.
	echo "writing root password"
	echo "password=$root_password" >> $root_option_file
fi

# Wait here until mysql is running
echo "Waiting for server..."
#while [ ! -f "$mysqld_pid_file_path" -o ! -S "$mysql_socket_file_path" ]; do
while [ ! -f "$mysqld_pid_file_path" -o ]; do
	sleep 1
done

# Check and upgrade mysql tables if necessary. This will return 0 if the upgrade
# succeeded, in which case we need to restart mysql.
echo "Checking/upgrading mysql tables if necessary..."
mysql_upgrade --defaults-file=$root_option_file
if [ $? -eq 0 ]; then
	echo "Restarting mysql server after upgrade..."
	$SNAP/support-files/mysql.server restart

	echo "Waiting for server to come back after upgrade..."
#	while [ ! -f "$mysqld_pid_file_path" -o ! -S "$mysql_socket_file_path" ]; do
	while [ ! -f "$mysqld_pid_file_path" -o ]; do
        	sleep 1
	done
fi

# If this was a new installation, wait until the server is all up and running
# before saving off the owncloud user's password. This way the presence of the
# file can be used as a signal that mysql is ready to be used.
if [ $new_install = true ]; then
	echo "$demouser_password" > $demouser_password_file
fi

# Wait here until mysql exits (turn a forking service into simple). This is
# only needed for Ubuntu Core 15.04, as 16.04 supports forking services.
mysqld_pid=$(cat "$mysqld_pid_file_path")
while kill -0 $mysqld_pid 2>/dev/null; do
	sleep 1
done
 
我們在table中也建立了幾個記錄.在這裡也請大家注意,我hard-code了資料庫的密碼"123".這個密碼在我們以後的資料庫存取中需要用到.注意我們在這裡已經建立了兩個使用者,一個叫做root,另外一個叫做demouser
 
	mysql --defaults-file=$root_option_file <<SQL
ALTER USER 'root'@'localhost' IDENTIFIED BY '$root_password';
CREATE USER 'demouser'@'localhost' IDENTIFIED BY '$demouser_password';
CREATE DATABASE demodb;
GRANT ALL PRIVILEGES ON demodb.* TO 'demouser'@'localhost' IDENTIFIED BY '$demouser_password';
USE demodb;
create table Employees
    (
     id int not null,
     age int not null,
     first varchar (255),
     last varchar (255)
    );
INSERT INTO Employees VALUES (100, 18, 'Zara', 'Ali');
INSERT INTO Employees VALUES (101, 25, 'Mahnaz', 'Fatma');    
INSERT INTO Employees VALUES (102, 30, 'Zaid', 'Khan');
INSERT INTO Employees VALUES (103, 28, 'Sumit', 'Mittal');
SQL
 

如何呼叫MySQL命令列

 
我們在snapcraft.yaml文件中,定義了如下的command:
 
 mysql-client:
   command: mysql --defaults-file=$SNAP_DATA/mysql/root.ini --protocol=TCP
   plugs: [network, network-bind]
 
由於在MySQL的命令列中需要存取到資料庫,需要root許可權.我們可以通過su命令進入到root使用者:
 
 
我們可以通過執行我們定???的命令來啟動MySQL用戶端.通過這個命令,我們可以建立我們的資料等操作.
 

3)JSP 資料庫存取

 
最後,我們需要一個JSP的程式來存取我們的資料庫.我們的設計如下:
 

index.jsp

<%@ page import="java.sql.*"%>
<html>
<head>
<title>JDBC Connection example</title>
</head>

<body>
<h1>JDBC Connection example</h1>

<%
  String user = "demouser";
  String password = "123";
  
  try {
    java.sql.Connection con;
    Class.forName("com.mysql.jdbc.Driver");
    con = DriverManager.getConnection("jdbc:mysql://localhost:3306/demodb", user, password);
    out.println (user + " account opens database successfully opened.");
    
    String query="select * from Employees";
    Statement stmt=con.createStatement();
	ResultSet rs=stmt.executeQuery(query);
%>	   
    <br />
    <h3>The data read from database is:</h3>
    <br />
    
	<table border="2">
	<tr>
		<td>Id</td>
		<td>Age</td>
		<td>First</td>
		<td>Last</td>
	</tr>
<%
	while(rs.next())
	{
%>
	<tr>
		<td><%=rs.getInt("id")%></td>
		<td><%=rs.getInt("age")%></td>
		<td><%=rs.getString("first")%></td>
		<td><%=rs.getString("last")%></td>
	</tr>
<%
	}
%>
	</table>
	
<%
    // close the connection
    rs.close();
    stmt.close();
    con.close();
  }
  catch(SQLException e) {
    out.println("SQLException caught: " +e.getMessage());
  }
%>

</body>
</html>
 
最終打包我們的應用,並部署我們的應用.我們可以看到最終的結果為:
 
 
 
在實際的使用中,我們也可以把我們已經開發好的war包放入到我們的tomcat的目錄中:
 
    mysql-customizations:
        plugin: copy
        files:
           # This one is what creates the initial database and account for ownCloud.
           src/mysql/start_mysql: bin/
           src/mysql/my.cnf: my.cnf
           src/mysql/mysql.server: support-files/
           sample.war: war/sample.war
           mysql-connector-java-6.0.3.jar: lib/mysql-connector-java-6.0.3.jar
 
比如上面的sample.war,我們可以通過如下的方式來執行該應用:
 


 
更多關於snap的介紹,可以參閱文章"安裝snap應用到Ubuntu 16.4桌面系統

本文永久更新連結地址http://www.linuxidc.com/Linux/2016-08/134680.htm


IT145.com E-mail:sddin#qq.com