Linkage error when deploying DXA web application to Tomcat

Question

Getting following error when deploying to Tomcat container. Only thing which I have changed is that I have removed default ROOT.war in webapps, renamed by dxawebapp to ROOT.war as I wanted the conext root not to be the WAR name

type Exception report

message java.lang.LinkageError: loader constraint violation: when resolving method "org.apache.jasper.runtime.InstanceManagerFactory.getInstanceManager(Ljavax/servlet/ServletConfig;)Lorg/apache/tomcat/InstanceManager;" the class loader (instance of org/apache/jasper/servlet/JasperLoader) of the current class, org/apache/jsp/WEB_002dINF/Views/Core/Page/GeneralPage_jsp, and the class loader (instance of java/net/URLClassLoader) for the method's defining class, org/apache/jasper/runtime/InstanceManagerFactory, have different Class objects for the type org/apache/tomcat/InstanceManager used in the signature

description The server encountered an internal error that prevented it from fulfilling this request.

exception

javax.servlet.ServletException: java.lang.LinkageError: loader constraint violation: when resolving method "org.apache.jasper.runtime.InstanceManagerFactory.getInstanceManager(Ljavax/servlet/ServletConfig;)Lorg/apache/tomcat/InstanceManager;" the class loader (instance of org/apache/jasper/servlet/JasperLoader) of the current class, org/apache/jsp/WEB_002dINF/Views/Core/Page/GeneralPage_jsp, and the class loader (instance of java/net/URLClassLoader) for the method's defining class, org/apache/jasper/runtime/InstanceManagerFactory, have different Class objects for the type org/apache/tomcat/InstanceManager used in the signature
    org.apache.jasper.servlet.JspServlet.service(JspServlet.java:349)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:725)
    org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)

MY POM

    <!-- Dependencies -->
<dependencies>
    <!-- SDL Digital Experience Accelerator -->
    <dependency>
        <groupId>com.sdl.dxa</groupId>
        <artifactId>dxa-common-api</artifactId>
    </dependency>
    <dependency>
        <groupId>com.sdl.dxa</groupId>
        <artifactId>dxa-common-impl</artifactId>
    </dependency>

    <dependency>
        <groupId>com.sdl.dxa</groupId>
        <artifactId>dxa-web8-provider</artifactId>
    </dependency>


    <dependency>
        <groupId>org.slf4j</groupId>
        <artifactId>slf4j-api</artifactId>
    </dependency>
    <dependency>
        <groupId>javax.servlet</groupId>
        <artifactId>javax.servlet-api</artifactId>
    </dependency>

    <!-- Testing -->
    <dependency>
        <groupId>junit</groupId>
        <artifactId>junit</artifactId>
    </dependency>
    <dependency>
        <groupId>org.mockito</groupId>
        <artifactId>mockito-all</artifactId>
    </dependency>
</dependencies>

Answer 1

Fixed this Issue by Excluding the Tomcat embedded Jars, so the issue was that tomcat embedded jars were included as a transitive dependency in

<artifactId>dxa-web8-provider</artifactId>

and when deploying to a tomcat container there was a classloader issue, where classloader was finding 2 versions of the same class.

Fixed this error by excluding the tomcat-embed-jasper jar.In your dependency section add the exclusion tag.

<dependency>
            <groupId>com.sdl.dxa</groupId>
            <artifactId>dxa-web8-provider</artifactId>
            <exclusions>
                <exclusion>
                    <groupId>org.apache.tomcat.embed</groupId>
                    <artifactId>tomcat-embed-jasper</artifactId>
                </exclusion>
            </exclusions>
        </dependency>