[logback-dev] [qos-ch/logback] f27b6d: prevent access to LoggingEvent's CACHED_NULL_MAP

[Ceki Gulcu]

  Branch: refs/heads/master
  Home:   https://github.com/qos-ch/logback
  Commit: f27b6dc3cf92e1f6225d89eae47529812e4972fa
      https://github.com/qos-ch/logback/commit/f27b6dc3cf92e1f6225d89eae47529812e4972fa
  Author: Ceki Gulcu <ceki at qos.ch>
  Date:   2015-03-25 (Wed, 25 Mar 2015)

  Changed paths:
    M logback-classic/src/main/java/ch/qos/logback/classic/spi/LoggingEvent.java
    M logback-classic/src/test/java/ch/qos/logback/classic/log4j/XMLLayoutTest.java

  Log Message:
  -----------
  prevent access to LoggingEvent's CACHED_NULL_MAP

This prevents developers from attempting to modify event's mdc map. For example by invoking

event.getMDCPropertyMap().put("k", "v");

This fixes LOGBACK-1063 by ricochet.