log4j 2 migration bridge log4j-1.2-api.jar missing classes

Question

I'm upgrading the version of log4j in our application from log4j 1.2.16 to log4j 2.5. We have many dependencies, so I'm using the log4j 1.x bridge (log4j-1.2-api.jar) that is described in the migration documentation. It describes replacing the old log4j-1.2.16.jar with log4j-1.2-api.jar. Now, however, when a specific dependency is referenced at application start up, I'm getting this message:

java.lang.ClassNotFoundException: org.apache.log4j.SimpleLayout

I see this class in the log4j-1.2.16.jar but not in log4j-1.2-api.jar.

How would I resolve this problem? Here is a portion of my pom for reference:

    <dependency>
        <groupId>org.slf4j</groupId>
        <artifactId>slf4j-log4j12</artifactId>
        <version>1.6.1</version>
        <exclusions>
            <exclusion>
                <artifactId>log4j</artifactId>
                <groupId>log4j</groupId>
            </exclusion>
        </exclusions>
    </dependency>
    <dependency>
        <groupId>org.apache.logging.log4j</groupId>
        <artifactId>log4j-slf4j-impl</artifactId>
        <version>2.5</version>
    </dependency>
    <dependency>
        <groupId>org.apache.logging.log4j</groupId>
        <artifactId>log4j-api</artifactId>
        <version>2.5</version>
    </dependency>
    <dependency>
        <groupId>org.apache.logging.log4j</groupId>
        <artifactId>log4j-web</artifactId>
        <version>2.5</version>
        <scope>runtime</scope>
    </dependency>
    <dependency>
        <groupId>org.apache.logging.log4j</groupId>
        <artifactId>log4j-core</artifactId>
        <version>2.5</version>
    </dependency>
    <dependency>
        <groupId>org.apache.logging.log4j</groupId>
        <artifactId>log4j-1.2-api</artifactId>
        <version>2.5</version>
    </dependency>

Answer 1

Can you post the stack trace? Something is referring to a Log4j 1.x specific Layout that won't work in Log4j 2. More than likely something is modifying the logging configuration programmatically. That code will have to be converted to use Log4j 2 configuration and/or APIs.