class org.apache.logging.slf4j.Log4jLogger cannot be cast to class ch.qos.logback.classic.Logger

[notxndy]

This bug(?) appears in later versions of ch.qos.logback: classic > 1.2.12

I am using the below code in a unit test class with the following imports and declarations

`
import ch.qos.logback.classic.Logger;
import ch.qos.logback.classic.spi.ILoggingEvent;
import ch.qos.logback.core.read.ListAppender;
import org.slf4j.LoggerFactory;

private final Logger logger = (Logger) LoggerFactory.getLogger(MyClass.class);
private final ListAppender listAppender = new ListAppender<>();

@BeforeEach
public void setUp() {
    listAppender.start();
    logger.addAppender(listAppender);

}
`

I am using org.slf4j:api version 2.0.9 and logback-classic version 1.2.12 as that's the last version that doesn't break the casting.

Hoping I can get an answer or a guide to this issue.

[ceki]

SLF4J 2.x requires logback 1.3 or later.

[notxndy]

Right but 1.3 and above breaks the casting.

[ceki]

It should not. What is the exception?

[notxndy]

As the title reads: java.lang.ClassCastException: class org.apache.logging.slf4j.Log4jLogger cannot be cast to class ch.qos.logback.classic.Logger

Edit: With the following in my maven pom file dependencymanagement:

    <dependency>
        <groupId>org.slf4j</groupId>
        <artifactId>slf4j-api</artifactId>
        <version>2.0.9</version>
    </dependency>

    <dependency>
        <groupId>ch.qos.logback</groupId>
        <artifactId>logback-classic</artifactId>
        <version>1.3.0</version>
        <scope>test</scope>
    </dependency>

[ceki]

org.apache.logging.slf4j.Log4jLogger ships with log4j-slf4j-impl module, part of log4j 2.x project. Thus, you surely have log4j-slf4j-impl.jar in your class path which is causing the cast exception.

[notxndy]

I see such a jar is compiled under the following dependency

`[INFO] - org.springframework.boot:spring-boot-starter-log4j2:jar:2.7.11:compile

[INFO] +- org.apache.logging.log4j:log4j-slf4j-impl:jar:2.18.0:compile`

Will exclude it and post results.

[notxndy]

For some reason I wasn't able to exclude from the dependency tree. But I'm sure this is still an acceptable answer.

[ceki]

qos-ch/slf4j#415 (comment) is closely related.