Hi Joan,
We did prepare a migration guide from Log4j 2 to Log4j Core 3:
https://logging.apache.org/log4j/3.x/migrate-from-log4j2.html
As Volkan mentioned, some features migrated to new modules, others were
deprecated.
On 25.01.2025 13:37, joan.balagu...@ventusproxy.com wrote:
2. My current maven looks like below now, where log4j2.version is '2.24.2'
<!-- disruptor -->
<dependency>
<groupId>com.lmax</groupId>
<artifactId>disruptor</artifactId>
<version>4.0.0</version>
</dependency>
<!-- log4j -->
<dependency>
<groupId>org.apache.logging.log4j</groupId>
<artifactId>log4j-core</artifactId>
<version>${log4j2.version}</version>
</dependency>
We strongly recommend the usage of the Bill-of-Materials (BOM):
<dependencyManagement>
<dependencies>
<dependency>
<groupId>org.apache.logging.log4j</groupId>
<artifactId>log4j-bom</artifactId>
<version>3.0.0-beta3</version>
<scope>import</scope>
<type>pom</type>
</dependency>
</dependencies>
</dependencyManagement>
There are multiple reasons behind that:
* If you don't use the BOM an unrelated direct dependency (e.g. Apache
POI) can pull a version of `log4j-api`, which is incompatible with
`log4j-core` version `3.0.0-beta3`.
* The `log4j-core` artifact version `3.0.0-beta3` requires `log4j-api`
version `2.24.x`. You don't have to remember that if you use the BOM.
We also recommend to put `log4j-core` in the `runtime` scope, since you
will not be referring to it from your code.
<dependency>
<groupId>org.apache.logging.log4j</groupId>
<artifactId>log4j-core</artifactId>
<scope>runtime</scope>
</dependency>
Regarding `com.lmax:disruptor`, you need to replace it with:
<dependency>
<groupId>org.apache.logging.log4j</groupId>
<artifactId>log4j-async-logger</artifactId>
<scope>runtime</scope>
</dependency>
LMAX Disruptor will still be a transitive dependency of your project,
but you don't need to upgrade it manually any more.
<dependency>
<groupId>org.apache.logging.log4j</groupId>
<artifactId>log4j-api</artifactId>
<version>${log4j2.version}</version>
</dependency>
As mentioned above, `log4j-core` 3.x will depend on `log4j-api` 2.x, so
you should use the BOM.
Also, if you don't use the Log4j API[1] in your code (because you use
another logging API like SLF4J for example), you can remove this
dependency. Don't get me wrong: we are happy if you use Log4j API and
there are a lot of advantages to use Log4j API over SLF4J[2], but we
understand if you use a different logging API. After all, logging APIs
are there to give you the freedom to choose whatever implementation you
want.
[1] https://logging.apache.org/log4j/3.x/manual/api.html
[2]
https://stackoverflow.com/questions/41498021/is-it-worth-to-use-slf4j-with-log4j2
<dependency>
<groupId>org.apache.logging.log4j</groupId>
<artifactId>log4j-jakarta-web</artifactId>
<version>${log4j2.version}</version>
</dependency>
As Volkan mentioned, `log4j-jakarta-web` will have its own lifecycle and
we didn't have the time to release a Beta version yet, sorry. It is on
our TODO list.
<dependency>
<groupId>org.apache.logging.log4j</groupId>
<artifactId>log4j-slf4j-impl</artifactId>
<version>${log4j2.version}</version>
</dependency>
The choice of the SLF4J-to-Log4j API bridge to use depends on the
version of SLF4J you use. For SLF4J 2.x you need to use
`log4j-slf4j2-impl` instead.
<dependency>
<groupId>org.apache.logging.log4j</groupId>
<artifactId>log4j-1.2-api</artifactId>
<version>${log4j2.version}</version>
</dependency>
This is a temporary artifact to help users upgrade from Log4j 1 to Log4j
2. In 2025 you probably don't want it. It is only required if:
* If you have dependencies that use Log4j 1 as logging API. Most
libraries migrated to Commons Logging or SLF4J by 2010, so no modern
library should require it.
* If you have an extensive user base that has custom `log4j.properties`
configuration files and you wish to allow them to keep using that format.
Piotr
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