How to pass system properties with spaces in Java within your Bash scripts

java.sh

#!/usr/bin/env bash

######################################################################################################################
# This script is a solution of when you want to pass Java options when they do come to the script as environment
# variable, or when you declare them inside a variable, using quotes. When you do so, you may obtain from the Java
# process an error that looks like this:
#
# $ ./java.sh
# Error: Could not find or load main class ...
#
# This usually means that your Bash environment split the arguments of your command by space, and this break the
# overall evaluation of the command to be execute. One possible solution can be the `eval`, although this brings
# with it also a security issue. So the other only option is to use Array notation.
# 
# This script will serve the purpose of using this last scenario ensuring you have no potential security issue in
# your script.
######################################################################################################################

add_java_options() {
  # Required to preserve the script integrity
  SAVEIFS=$IFS
  
  # Use a special character to split the string
  IFS="|"
  
  # Trim spaces around
  JAVA_OPTIONS=$(echo $JAVA_OPTIONS | xargs)
  
  # Ensure there is a space at the beginning so we don't need to check for - or not on each item later on
  in_options=" $JAVA_OPTIONS"
  
  # Split the string...
  in_options=${in_options//\ \-/\|}
  # ...and remove the first separator in order to not have a first item in array that is empty...
  in_options=${in_options#"|"}
  # ...finally dump the split items into an array
  array_options=($in_options)
  
  # Restore the IFS, we're done here
  IFS=$SAVEIFS

  # Add each item in the array inside of JAVA_CMD
  for (( i=0; i<${#array_options[@]}; i++ ))
  do
    _arg=$(echo "-${array_options[$i]}" | xargs)
    JAVA_CMD+=("$_arg")
  done
}

# Your custom options here
JAVA_OPTIONS="-Xms2G -Dprop=val -Danotherprop=\"a special value here that contains spaces, remember to use quotes around it\""

# The ONLY correct way to attach custom parameters to the java binary including system properties with spaces
JAVA_CMD=("java")
add_java_options

# Feel free to use any other parameter here to run your Java application, remember that for each "space" your would type in your terminal it correspongs to a new item in the array
JAVA_CMD+=("-jar")
JAVA_CMD+=("path/to/file.jar")

# Finally run the whole command inside the bash environment
exec "${JAVA_CMD[@]}"

If you want to test the script, this is a small Java application that you can build yourself:

import java.util.Properties;

public class PrintSystemProperties {
    public static void main(String[] args) {
        Properties properties = System.getProperties();
        properties.forEach((k, v) -> System.out.println(k + ":" + v));
    }
}

How to build:

#!/usr/bin/env bash
set -e

APP="PrintSystemProperties"

javac ${APP}.java
jar cfe ${APP}.jar ${APP} ${APP}.class

This was super helpful, thanks for publishing this.