ppkarwasz opened a new issue, #4007:
URL: https://github.com/apache/logging-log4j2/issues/4007
This issue is a continuation of the long-running `-Werror -Xlint:all` saga.
When **all** of the following apply:
* the build uses **Gradle**,
* the compiler is **JDK 8 through 16**,
* compilation is run with `-Werror -Xlint:all`,
* the code references a Log4j API class annotated with a
`biz.aQute.bnd.annotation`
(for example
[`PropertiesUtil`](https://logging.apache.org/log4j/2.x/javadoc/log4j-api/org/apache/logging/log4j/util/PropertiesUtil.html)),
the build fails with a compiler warning promoted to an error.
The failure is caused by a **bytecode-level mismatch**: Log4j `2.25.3`
exposes `biz.aQute.bnd.annotation:7.1.0` via Gradle Module Metadata, but that
artifact is built for **Java 17 (class file version 61)** and is therefore
incompatible with JDK 8/11 compilers when `-Xlint:classfile` is enabled.
Example failure:
```text
> Task :compileJava FAILED
.../log4j-api-2.25.3.jar(org/apache/logging/log4j/util/ProviderUtil.class):
warning:
Cannot find annotation method 'value()' in type
'aQute.bnd.annotation.spi.ServiceConsumer':
bad class file:
.../biz.aQute.bnd.annotation-7.1.0.jar(aQute/bnd/annotation/spi/ServiceConsumer.class)
class வெளியாக has wrong version 61.0, should be 52.0
Please remove or make sure it appears in the correct subdirectory of the
classpath.
```
## Workarounds
Several workarounds are available:
1. **Use a newer JDK** to compile the project.
Even recent JDKs (including JDK 25) can still target Java 8 bytecode via
`--release`. The JDK used for compilation does not dictate the output bytecode
level.
2. **Disable the `classfile` lint category** by adding `-Xlint:-classfile`.
This category rarely provides actionable information and is the root
cause of the failure here. See
[https://github.com/apache/logging-log4j2/issues/3110#issuecomment-2423586754](https://github.com/apache/logging-log4j2/issues/3110#issuecomment-2423586754)
for additional context.
3. **Force a compatible annotation version** by adding
`biz.aQute.bnd.annotation:6.4.1` to the application’s `compileOnly`
configuration and enforcing that version in Gradle resolution.
## Planned fix
This will be addressed in a future Log4j API release by **downgrading the
exported `biz.aQute.bnd.annotation` version to `6.4.1` in the Gradle Module
Metadata** (via the Gradle Module Metadata Maven Plugin), ensuring
compatibility with Java 8 and Java 11 consumers.
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