When the Log4j LogEvent context data contains non string values e.g string arrays or java maps, the resulting attributes are incorrect.

Create a class extending ObjectThreadContextMap and set it as the default using the log4j system property log4j2.threadContextMap

Add the following code:

public class MyObjectContextMap implements ReadOnlyThreadContextMap, ObjectThreadContextMap {
//Implementation methods
}

In the logging code add the following

MyObjectContextMap map = (MyObjectContextMap)ThreadContext.getThreadContextMap();
map.putValue("numbers", new String[]{"one", "two", "three"});
HashMap testmap = new HashMap();
testmap.put("fn", "firstname");
testmap.put("ln", "lastname");
testmap.put(age, 25);
map.put("testmap", testmap);

logger.log(Level.TRACE, "test message");

What did you expect to see?
I would expect that the nested value and the array value would be included in attributes properly.

What did you see instead?
I saw the .toString() representations of the array and map. So numbers showed as an attribute with value [Ljava.lang.String and testmap showed up as a single value with the map values as {fn=firstname, ln=lastname}.

What version are you using?
1.23.0-alpha
Log4j: 2.17.1