Merge properties into a ResourceBundle from System.getProperties()

Hello honorable forum,

I'm building a ResourceBundle from a file, this bundle holds < String, String> values.

InputStream in = getClass().getResourceAsStream("SQL.properties");
properties = new PropertyResourceBundle(in);
in.close();

I would like to add/replace on this bundle some properties that I'm passing from the command line using -Dsome.option.val.NAME1=HiEarth

I don't care dumping the old bundle and creating a new one instead.

Could you please tip?

I think that what I need to do is :

1. Create from the bundle a HashMap< String, String>
2. Replace values.
3. Transform the HashMap into a InputStream. //This is the complicated part...
4. Build the new bundle from that.

From stackoverflow

• This might not be the best way to do it but it's the best I can think of: implement a subclass of ResourceBundle that stores the properties you want to add/replace, then set the parent of that bundle to be the PropertyResourceBundle you load from the input stream.

  InputStream in = getClass().getResourceAsStream("SQL.properties");
  properties = new PropertyResourceBundle(in);
  in.close();
  MyCLIResourceBundle b = new MyCLIResourceBundle(properties);
  // use b as your bundle
  

  where the implementation would be something like

  public class MyCLIResourceBundle extends ResourceBundle {
      public MyCLIResourceBundle(ResourceBundle parent) {
          super();
          this.setParent(parent);
          // go on and load your chosen properties from System.getProperties() or wherever
      }
  }
  

• This does some of what you want (converts the System.properties to a ResourceBundle). Better error handling is left up to you :-)

      
      public static ResourceBundle createBundle()
      {
          final ResourceBundle  bundle;
          final Properties      properties;
          final CharArrayWriter charWriter;
          final PrintWriter     printWriter;
          final CharArrayReader charReader;
  
          charWriter = new CharArrayWriter();
          printWriter = new PrintWriter(charWriter);
  
          properties = System.getProperties();
          properties.list(printWriter);
  
          charReader = new CharArrayReader(charWriter.toCharArray());
  
          try
          {
              bundle = new PropertyResourceBundle(charReader);
  
              return (bundle);
          }
          catch(final IOException ex)
          {
              // cannot happen
              ex.printStackTrace();
          }
  
          throw new Error();
      }