[LOG4J2-3410] Log4j 1.2 bridge throws a ClassCastException when logging a Map with non-String keys

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 2.13.0, 2.17.1
• Fix Version/s: 2.17.2
• Component/s: Log4j 1.2 bridge

Environment

OS: Windows 10 Enterprise 64bit

Java version: zulu8.31.0.1-jdk8.0.181-win_x64{}

• Assignee: Gary D. Gregory
• Reporter: Barry Sham
• Created: 21/Feb/22 09:18
• Updated: 30/Mar/22 21:37
• Resolved: 21/Feb/22 16:34

Description

Our existing business logic contains a debug message which print out a org.apache.commons.collections.map.MultiKeyMap:

 

MultiKeyMap prnMap = MultiKeyMap.decorate(new LinkedMap());
prnMap.put("0", "1", "2");
logger.debug(prnMap);

 

in log4j-1.2-api 2.12.4, it can be print out properly:

 

{MultiKey[0, 1]=2}

 

However it becomes an ClassCastException since 2.13.0 (including the latest 2.17.1)

Exception in thread "main" java.lang.ClassCastException: org.apache.commons.collections.keyvalue.MultiKey cannot be cast to java.lang.String
    at org.apache.logging.log4j.util.SortedArrayStringMap.<init>(SortedArrayStringMap.java:154)
    at org.apache.logging.log4j.message.MapMessage.<init>(MapMessage.java:125)
    at org.apache.log4j.Category.maybeLog(Category.java:507)
    at org.apache.log4j.Category.debug(Category.java:243)
    at sideproject.sideproject.App.proeces(App.java:25)
    at sideproject.sideproject.App.main(App.java:17)

As the map can print out using System.out without issue, we are wondering if it is a bug in Apache Log4j 1.x Compatibility API

A GitHub Project is prepared for reference: shin779/log4j-multikeymap (github.com)

Issue Links

• links to: GitHub Pull Request #767