Grails Goodness: Creating A Fully Executable JAR

With Grails 3 we can create a so-called fat jar or war file. To run our application, we only have to use java -jar followed by our archive file name, and the application starts. Another option is to create a fully executable jar or war file, which adds a shell script in front of the jar or war file so we can immediately run the jar or war file. We don't have to use java -jar to run our Grails application any longer. The fully executable JAR file can only run on Unix-like systems and it is ready to be used as service using init.d or systemd.

To create a fully executable jar file for our Grails application we must add the following lines to our build.gradle file:

// File: build.gradle
...
// Disable war plugin to create a jar file
// otherwise a fully executable war file
// is created.
//apply plugin: 'war'

...
springBoot {
    // Enable the creation of a fully
    // executable archive file.
    executable = true
}

Next we execute the Gradle assemble task to create the fully executable archive:

grails> assemble
...
:compileGroovyPages
:jar
:bootRepackage
:assemble

BUILD SUCCESSFUL

Total time: 5.619 secs
| Built application to build/libs using environment: production
grails>

We can find the executable archive file in the build/libs directory. Suppose our Grails application is called grails-full-executable-jar and has version 0.1 - we can execute the jar file grails-full-executable-jar-0.1.jar:

$ cd build/libs
$ ./grails-full-executable-jar-0.1.jar
Grails application running at http://localhost:8080 in environment: production

The launch script that is prepended to the archive file can be changed by defining a new launch script with the springBoot property embeddedLaunchScript. The default launch script that is used has some variable placeholders we can change using the embeddedLaunchScriptProperties property. For example, the launch script can determine if the script is used to run the application standalone or as a Linux/Unix service, and it will act accordingly. We can also set the mode property to service so it will always act like a Linux/Unix service. Furthermore, we can set some meta information for the launch script with several properties. To learn more about the different options see the Spring Boot documentation.

// File: build.gradle
...
springBoot {
    // Enable the creation of a fully
    // executable archive file.
    executable = true

    // Set values for variable placeholders
    // in the default launch script.
    embeddedLaunchScriptProperties =
        [initInfoDescription: project.description,
         initInfoShortDescription: project.name,
         initInfoProvides: jar.baseName,
         mode: 'service']
}

After we have recreated the archive file we can check the launch script that is created:

$ head -n 55 build/libs/grails-full-executable-jar-0.1.jar
#!/bin/bash
#
#    .   ____          _            __ _ _
#   /\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
#  ( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
#   \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
#    '  |____| .__|_| |_|_| |_\__, | / / / /
#   =========|_|==============|___/=/_/_/_/
#   :: Spring Boot Startup Script ::
#

### BEGIN INIT INFO
# Provides:          grails-full-executable-jar
# Required-Start:    $remote_fs $syslog $network
# Required-Stop:     $remote_fs $syslog $network
# Default-Start:     2 3 4 5
# Default-Stop:      0 1 6
# Short-Description: grails-full-executable-jar
# Description:       Sample Grails Application
# chkconfig:         2345 99 01
### END INIT INFO

[[ -n "$DEBUG" ]] && set -x

# Initialize variables that cannot be provided by a .conf file
WORKING_DIR="$(pwd)"
# shellcheck disable=SC2153
[[ -n "$JARFILE" ]] && jarfile="$JARFILE"
[[ -n "$APP_NAME" ]] && identity="$APP_NAME"

# Follow symlinks to find the real jar and detect init.d script
cd "$(dirname "$0")" || exit 1
[[ -z "$jarfile" ]] && jarfile=$(pwd)/$(basename "$0")
while [[ -L "$jarfile" ]]; do
[[ "$jarfile" =~ init\.d ]] && init_script=$(basename "$jarfile")
jarfile=$(readlink "$jarfile")
cd "$(dirname "$jarfile")" || exit 1
jarfile=$(pwd)/$(basename "$jarfile")
done
jarfolder="$(dirname "$jarfile")"
cd "$WORKING_DIR" || exit 1

# Source any config file
configfile="$(basename "${jarfile%.*}.conf")"
# shellcheck source=/dev/null
[[ -r "${jarfolder}/${configfile}" ]] && source "${jarfolder}/${configfile}"

# Initialize PID/LOG locations if they weren't provided by the config file
[[ -z "$PID_FOLDER" ]] && PID_FOLDER="/var/run"
[[ -z "$LOG_FOLDER" ]] && LOG_FOLDER="/var/log"
! [[ -x "$PID_FOLDER" ]] && PID_FOLDER="/tmp"
! [[ -x "$LOG_FOLDER" ]] && LOG_FOLDER="/tmp"

# Set up defaults
[[ -z "$MODE" ]] && MODE="service" # modes are "auto", "service" or "run"
$ cd build/libs
$ ./grails-full-executable-jar.0.1.jar
Usage: ./grails-full-executable-jar-0.1.jar {start|stop|restart|force-reload|status|run}
$

Written with Grails 3.1.8.