Test for null parameter in .properties file for MessageFormat

Question

Is it possible, with resource bundles and MessageFormat to have the following result?

• when I call getBundle("message.07", "test") to get "Group test"
• when I call getBundle("message.07", null) to get "No group selected"

Every example I found on the Internet is with planets, with files on the disk and so on.

I only need to check if one parameter is null (or doesn't exist) in the resource bundle's properties file. I hope to find a special format for the null parameter something like {0,choice,null#No group selected|notnull#Group {0}}.

The method I use to get the bundles is:

public String getBundle(String key, Object... params) {
  try {
    String message = resourceBundle.getString(key);
    if (params.length == 0) {
      return message;
    } else {
      return MessageFormat.format(message, params);
    }
  } catch (Exception e) {
    return "???";
  }
}

I also call this method for other bundles, like

• getBundle("message.08", 1, 2) => "Page 1 of 2" (always parameters, no need to check for null)
• getBundle("message.09") => "Open file" (no parameters, no need to check for null)

What should I write in my .properties file for message.07 to have the result described?
What I have now is:

message.07=Group {0} 
message.08=Page {0} of {1}    # message with parameters where I always send them
message.09=Open file          # message without parameters

Answer 1

Your .properties file,

message.07=Group {0} 
message.08=Page {0} of {1}
message.09=Open file
message.null = No group selected

And then you need to change your code to put an explicit check params for null. And if null then you can do something like resourceBundle.getString(NULL_MSG). Where NULL_MSG will be this,

private static final String NULL_MSG = "message.null";

So, now your original method would become something like this.

public String getBundle(String key, Object... params) {
  String message = null;
  try {
    if (params == null) {
      message = resourceBundle.getString(NULL_MSG);
    } else {
      message = MessageFormat.format(resourceBundle.getString(key), params);
    }
  } catch (Exception e) {
    e.printStackTrace();
  }
  return message;
}

Calling my method like below,

getBundle("message.07", "test") // returning 'Group test'
getBundle("message.07", null) // returning 'No group selected'
getBundle("message.08", 1, 2) // returning 'Page 1 of 2'
getBundle("message.08", null) // returning 'No group selected'
getBundle("message.09", new Object[0]) // returning 'Open file'
getBundle("message.09", null) // returning 'No group selected'

Now tell me where is the problem?

Answer 2

I'll recommend not trying to change the bundle functionality (even if you have a getBundle method encapsulating it).

Simply do in your code:

getBundle(param == null? "message.07.null": "message.07", param)

Or make another method:

getBundleOrNull("message.07", param, "message.07.null")

that does

public String getBundleOrNull(String key, value, nullKey) {
   return getBundle(value == null? nullKey: key: value);
}