Using Log4j 1.2 Bridge with Log4j 2 API

Q

How can I run my application with both Apache Log4j 2 API and Log4j 1.2 API? My program has two parts, one part uses the new Log4j 2 API, but the other part uses the old Log4j 1.2 API.

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A

The Apache Log4j 2 package comes with the Log4j 1.2 Bridge module to allow you run programs that use both Log4j 2 API and Log4j 1.2 API.

When you run your program, you need to include these JAR files in the classpath:

  • log4j-api-2.x.jar - Provides the Log4j 2 API.
  • log4j-core-2.x.jar - Provides the implementation of Log4j 2 API.
  • log4j-1.2-api-2.x.jar - Provides the bridge converting Log4j 1.2 API to Log4j 2 API.

Warning, you should not include log4j-1.2.x.jar in the classpath. Log4j 1.2 API calls will be handled by log4j-1.2-api-2.x.jar.

The picture belows shows you the JAR dependency diagram of your application and Log4j JAR files.

Using Log4j 1.2 Bridge with Log4j 2 API
Using Log4j 1.2 Bridge with Log4j 2 API

 

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2022-01-12, 8075👍, 1💬