ThreadContext.remove("key1");
ThreadContext.remove("key2");
this.root.error("finished mdc pattern test", new NullPointerException("test"));
appender.stop();
final List<String> list = appender.getMessages();
// System.out.println(list);
// [[, {, "logger":"root",, "timestamp":"1376676700199",, "level":"DEBUG",, "thread":"main",,