Tomcat 7 + Annotations in log4j-api-2.11.1.jar

Question

I get this exception from tomcat upon startup of the war file:

Unable to process Jar entry [META-INF/versions/9/module-info.class] from Jar [jar:file:/C:/tomcat/apache-tomcat-7.0.61/webapps/monitormonitor/WEB-INF/lib/log4j-api-2.11.1.jar!/] for annotations
org.apache.tomcat.util.bcel.classfile.ClassFormatException: Invalid byte tag in
constant pool: 19
    at org.apache.tomcat.util.bcel.classfile.Constant.readConstant(Constant.java:97)

I tried to switch the log4j to an older version in the pom.xml, but failed, it still scans log4j-api-2.11.1.jar. I added metadata-complete="true" to the tomcats web.xml but this didn't change the error.

I read other pages on stackoverflow, but it didn't resolve my problem:

Tomcat 7 and Java 8 compatibility issue

Invalid byte tag in constant pool: 19 error message

The latter seems to have a good answer, but I don't understand how to exclude files from annotation scanning, and I also do not know how excluding files affects the functionality of the web application.

Please find attached my pom.xml. It includes some of my attempts to fix this in a commented out version.

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.1.2.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.xxx</groupId>
    <artifactId>monitormonitor</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>monitormonitor</name>
    <description>Web Service Monitoring project for Spring Boot</description>

    <properties>
        <java.version>1.8</java.version>
    </properties>

    <packaging>war</packaging>

    <dependencies>
        <!-- added recent version of icu4j and log4j for invalid byte tag error -->
        <!-- https://mvnrepository.com/artifact/org.apache.logging.log4j/log4j-core -->
        <dependency>
            <groupId>org.apache.logging.log4j</groupId>
            <artifactId>log4j-core</artifactId>
            <!-- changed version vs. ClassFormatException: Invalid byte tag in constant pool: 19 -->
            <!--<version>2.11.1</version>-->
            <version>2.7</version>
            <!--<scope>provided</scope>-->
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-jdbc</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-mail</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
            <scope>provided</scope><!-- changed -->
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-devtools</artifactId>
            <scope>runtime</scope>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-context-support</artifactId>
        </dependency>
        <!-- duplicate
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-mail</artifactId>
        </dependency>
        -->
        <!--
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-tomcat</artifactId>
            <scope>provided</scope>
        </dependency>
        -->
        <!-- added recent version of icu4j and log4j for invalid byte tag error -->
        <!-- https://mvnrepository.com/artifact/com.ibm.icu/icu4j -->
        <!--<dependency>
            <groupId>com.ibm.icu</groupId>
            <artifactId>icu4j</artifactId>
            <version>63.1</version>
        </dependency>
        -->

        <!-- added this dependency vs. ClassFormatException: Invalid byte tag in constant pool: 19 -->
        <!-- https://mvnrepository.com/artifact/org.aspectj/aspectjtools -->
        <!--             <dependency>
                        <groupId>org.aspectj</groupId>
                        <artifactId>aspectjtools</artifactId>
                        <version>1.9.1</version>
                    </dependency>
        -->
                    <!-- https://mvnrepository.com/artifact/org.aspectj/aspectjweaver -->
        <!--         <dependency>
                        <groupId>org.aspectj</groupId>
                        <artifactId>aspectjweaver</artifactId>
                        <version>1.9.1</version>
                    </dependency>
        -->
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>

</project>

I would prefer a solution where I don't have to upgrade the tomcat. My tomcat version is apache-tomcat-7.0.61.

Answer 1

Downgrading the right log4j package seems to have solved the problem:

    <dependency>
        <groupId>org.apache.logging.log4j</groupId>
        <artifactId>log4j-api</artifactId>
        <!-- changed version vs. ClassFormatException: Invalid byte tag in constant pool: 19 -->
        <!--<version>2.11.1</version>-->
        <version>2.7</version>
        <!--<scope>provided</scope>-->
    </dependency>

The spring boot app still doesn't start up properly, but that is a different issue.