Does log4j support JSON format?

Question

Is it possible to let log4j output its logging in JSON format by only altering the log4j.properties.xml configuration file?
I make use of an old application tha

Answer 1

just use buildin PatternLayout is ok:

log4j.appender.stdout=org.apache.log4j.ConsoleAppender
log4j.appender.stdout.encoding=UTF-8
log4j.appender.stdout.layout=org.apache.log4j.PatternLayout
log4j.appender.stdout.layout.ConversionPattern={"debug_level":"%p","debug_timestamp":"%d{ISO8601}","debug_thread":"%t","debug_file":"%F", "debug_line":"%L","debug_message":"%m"}%n

will out put like:

{
    "debug_level" : "INFO",
    "debug_timestamp" : "2016-05-26 16:37:08,938",
    "debug_thread" : "main",
    "debug_file" : "TestLogOutPut.java",
    "debug_line" : "316",
    "debug_message" : "hello i am a log message"
}

Answer 2

this is official JSON layout

https://github.com/logstash/log4j-jsonevent-layout

1) Add maven dependency https://mvnrepository.com/artifact/net.logstash.log4j/jsonevent-layout

<dependency>
    <groupId>net.logstash.log4j</groupId>
    <artifactId>jsonevent-layout</artifactId>
    <version>1.7</version>  
</dependency>

2) Add configuration to your log4j.properties file

 log4j.rootCategory=WARN, RollingLog
 log4j.appender.RollingLog=org.apache.log4j.DailyRollingFileAppender
 log4j.appender.RollingLog.Threshold=TRACE
 log4j.appender.RollingLog.File=api.log
 log4j.appender.RollingLog.DatePattern=.yyyy-MM-dd
 log4j.appender.RollingLog.layout=net.logstash.log4j.JSONEventLayoutV1

Answer 3

I used logback.xml with below pattern

<appender name="Console"
          class="ch.qos.logback.core.ConsoleAppender">
    <layout class="ch.qos.logback.classic.PatternLayout">
        <Pattern>
            {"level":"%p","timestamp":"%d{ISO8601}","thread":"%t","file":"%F", "line":"%L","message":"%m"}%n
        </Pattern>
    </layout>
</appender>

and it generates logs in json format. I am using log4j which comes with springboot dependencies.

{"level":"INFO","timestamp":"2020-09-22 15:26:38,354","thread":"main","file":"StartupInfoLogger.java", "line":"55","correlationId":"","message":"Starting Application on XX with PID 88794 (/Users/Documents/target/classes started by xxx in /Users/Documents)"}

Answer 4

Yes It is possible. Take a look at this link It can generate

{
   "timestamp":1352412458890,
   "date":"Nov 8, 2012 10:07:38 PM",
   "hostname":"michael1",
   "username":"michael",
   "level":"INFO",
   "thread":"main",
   "classname":"uk.me.mjt.log4jjson.SimpleJsonLayoutTest",
   "filename":"SimpleJsonLayoutTest.java",
   "linenumber":25,
   "methodname":"testDemonstration",
   "message":"Example of some logging"
 }