Metaspace is at a premium in the application server environment, and the number one consumer is presently generated log classes.

Introduce a leaner variation on generated classes with the following requirements:

• The generated class must be final
• The generated class must contain no message strings
• The generated class must accept both a Logger and a Locale, and load its resources from a file based on that information
• The usage of Java 8's locale lookup functionality should be considered, to support language tags etc.; a helper utility could be introduced into jboss-logging for this

Here are some implementation ideas:

• Option 1: The resource files contain only messages, one per line, loaded directly into a String[] instance field in the implementation class; each logging method uses a hard-coded array index to access its message
  • A key advantage is that the implementation class is very small, and consumes very little metaspace; also, it is fast, requiring only an array lookup to acquire the string
  • A disadvantage is, any change to the message set invalidates all the locale files, which must then be regenerated
  • Also, each locale file must contain all messages, unless a fallback mechanism is used (e.g. an empty line signifies that the string should come from the parent locale)
• Option 2: The resource files contain key-value pairs, with the key being equal to the method name
  • Advantage: the file is not invalidated if a key is added, and sub-locales can inherit more easily from parent locales
  • Disadvantage: the added overhead of mapping lines to methods (for example, using a switch statement to map method names to fixed indexes, or loading the messages into a hash table e.g. HashMap) will fill metaspace or impact performance, or both