Log4j2 add to layout if user logged in

I wish to add or append to a PatternLayout in log4j2 depending if the user is authenticated or not.

If the user is not authenticated the log would look like this:

{
  "value1": "Here is our values",
  "map": {
    "key1": "value1",
    "key2": "value2"
  },
  "something": "something else"
}

And if the user is authenticated I would get something like this:

{
  "value1": "Here is our values",
  "map": {
    "key1": "value1",
    "key2": "value2"
  },
  "user": {
    "name": "name",
    "client": "some value"
  },
  "something": "something else"
}

Is there some way of achieving this?

One way to achieve this is to use a PatternSelector with Log4j2. Currently Log4j 2 supports a LevelPatternSelector, MarkerPatternSelector, and ScriptPatternSelector. More than likely you would really like something like a ThreadContextPatternSelector that could select a pattern based on the presence of a key in the ThreadContext. However, until someone requests that you could implement the same thing using the ScriptPatternSelector doing something like:

<PatternLayout>
  <ScriptPatternSelector defaultPattern="[%-5level] %c{1.} %C{1.}.%M.%L %msg%n">
    <Script name="BeanShellSelector" language="bsh"><![CDATA[
      if (logEvent.getContextMap().containsKey("client")) {
        return "Client";
      } 
      return null;
     ]]>
     </Script>
     <PatternMatch key="Client" pattern="{ ... \"user\": { \"name\": \"${mdc:name}\", \"client\": \"${mdc:client}\"}, ..."/>
  </ScriptPatternSelector>
</PatternLayout>

If you are obtaining the client information from an OAuth token you could create a custom PatternSelector that gets it from the Spring SecurityContext and returns the key of the pattern to apply or null to use the default pattern. To create a custom plugin you can look at either the LevelPatternSelector or the MarkerPatternSelector as examples.