How to read properties file in Install4j - example appreciated

Question

I have a properties file that basically looks like this:

version.major=2
version.minor=1
version.revision=3

And am trying to read in all 3 pieces of information using the "Read a properties file" action. The information area says the following of the variable:

The name of the variable that will be set with an instance of java.util.Map.

There is no "map" variable type in Install4j. Are we supposed to declare a single variable of type "array" like "string array" and then loop through it and set 3 discrete variables? Is there a way to leverage the array as a map throughout the installer so as to avoid helper variables like this (simply look up each key/value pair as needed)? I feel like I'm missing something.

Here's the script I'm currently using. I have read the properties into a string array called BUILD and use this to set the "major" variable (which I repeat for "minor" and "revision").

final String key = "version.major";
String[] arr = (String[])context.getVariable("BUILD");

for (int i = 0; i < arr.length; i++) {
    if (arr[i].startsWith(key)) {
        return arr[i].substring(arr[i].indexOf('=') + 1).trim();
    }
}

return null;

Answer 1

1 - Create your own Properties class extension: (optional)

public class ConfigProperties extends Properties 
{       
    private static final long serialVersionUID = 1L;
    public Integer readMandatoryInteger(String key) throws IOException
    {
       String value = getProperty(key);
       if (value == null || value.isEmpty())
          throw new IOException(String.format("Insert missing config: %s.",key));
        
       return Integer.parseInt(value);
    }       

    //readMandatoryString, and so on....

    public String getKey(String prefix, String key)
    {
        String value = key;
        if (prefix != null && !prefix.isEmpty())
            value = prefix + "." + key;
        return value;
    }
}

This is the simplest example I could get, you can add a function for reading Longs, Strings, Booleans, or whatever.

2- Initialize your properties entity and read the file:

ConfigProperties props = new ConfigProperties();
props.load(new FileInputStream(propertiesFile));

3- Read from your properties instance:

You can just retrieve the values by key.

int majorv = props.readMandatoryInteger("version.major"); 

System.out.print(majorv); // 2

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You can also print/show key and values, just:

• list(PrintStream out)

Prints this property list out to the specified output stream.

props.list(System.out);

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Or you could get an Enumeration of the keys, in order to be retrieved by the first shown read operation:

• propertyNames()

Returns an enumeration of all the keys in this property list, including distinct keys in the default property list if a key of the same name has not already been found from the main properties list.**

 nameEnums = props.propertyNames(); 

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Create a getter method in your extended Properties class

You could use your extended Properties class and create a method that returns a HashMap, or desired structure, that stores your property file keys and values.