tomcat - Unable to process file module-info.class within a Java9 project results in ClassFormatException

Question

Trying to Run Vaadin 8.1 app under Java 9 prerelease in IntelliJ 2017.2.2 I was able to build a vaadinjavanine.war using a fresh project and host the same using Jetty Server.

I ended up trying to deploy the generated war to a tomcat server. But, during the startup of the tomcat server, I am getting the following exception:

21-Aug-2017 22:53:38.830 SEVERE [localhost-startStop-1] org.apache.catalina.startup.ContextConfig.processAnnotationsFile Unable to process file [/Library/Tomcat/apache-tomcat-8.0.22/webapps/vaadinjavanine/WEB-INF/classes/module-info.class] 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)
    at org.apache.tomcat.util.bcel.classfile.ConstantPool.<init>(ConstantPool.java:55)
    at org.apache.tomcat.util.bcel.classfile.ClassParser.readConstantPool(ClassParser.java:177)
    at org.apache.tomcat.util.bcel.classfile.ClassParser.parse(ClassParser.java:85)
    at org.apache.catalina.startup.ContextConfig.processAnnotationsStream(ContextConfig.java:2011)
    at org.apache.catalina.startup.ContextConfig.processAnnotationsFile(ContextConfig.java:1994)
    at org.apache.catalina.startup.ContextConfig.processAnnotationsFile(ContextConfig.java:1988)
    at org.apache.catalina.startup.ContextConfig.processAnnotationsUrl(ContextConfig.java:1939)
    at org.apache.catalina.startup.ContextConfig.processAnnotations(ContextConfig.java:1897)
    at org.apache.catalina.startup.ContextConfig.webConfig(ContextConfig.java:1149)
    at org.apache.catalina.startup.ContextConfig.configureStart(ContextConfig.java:771)
    at org.apache.catalina.startup.ContextConfig.lifecycleEvent(ContextConfig.java:305)
    at org.apache.catalina.util.LifecycleSupport.fireLifecycleEvent(LifecycleSupport.java:117)
    at org.apache.catalina.util.LifecycleBase.fireLifecycleEvent(LifecycleBase.java:90)
    at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5066)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
    at org.apache.catalina.core.ContainerBase.addChildInternal(ContainerBase.java:725)
    at org.apache.catalina.core.ContainerBase.addChild(ContainerBase.java:701)
    at org.apache.catalina.core.StandardHost.addChild(StandardHost.java:717)
    at org.apache.catalina.startup.HostConfig.deployWAR(HostConfig.java:945)
    at org.apache.catalina.startup.HostConfig$DeployWar.run(HostConfig.java:1768)
    at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
    at java.util.concurrent.FutureTask.run(FutureTask.java:266)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
    at java.lang.Thread.run(Thread.java:745)

21-Aug-2017 22:53:38.980 SEVERE [localhost-startStop-1] org.apache.catalina.core.ContainerBase.addChildInternal ContainerBase.addChild: start: 
 org.apache.catalina.LifecycleException: Failed to start component [StandardEngine[Catalina].StandardHost[localhost].StandardContext[/vaadinjavanine]]
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:154)
    at org.apache.catalina.core.ContainerBase.addChildInternal(ContainerBase.java:725)
    at org.apache.catalina.core.ContainerBase.addChild(ContainerBase.java:701)
    at org.apache.catalina.core.StandardHost.addChild(StandardHost.java:717)
    at org.apache.catalina.startup.HostConfig.deployWAR(HostConfig.java:945)
    at org.apache.catalina.startup.HostConfig$DeployWar.run(HostConfig.java:1768)
    at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
    at java.util.concurrent.FutureTask.run(FutureTask.java:266)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
    at java.lang.Thread.run(Thread.java:745)
Caused by: java.lang.UnsupportedClassVersionError: nullpointer/MyUI$MyUIServlet has been compiled by a more recent version of the Java Runtime (class file version 53.0), this version of the Java Runtime only recognizes class file versions up to 52.0 (unable to load class nullpointer.MyUI$MyUIServlet)
    at org.apache.catalina.loader.WebappClassLoaderBase.findClassInternal(WebappClassLoaderBase.java:2476)
    at org.apache.catalina.loader.WebappClassLoaderBase.findClass(WebappClassLoaderBase.java:854)
    at org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1274)
    at org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1157)
    at org.atmosphere.util.IOUtils.isAtmosphere(IOUtils.java:381)
    at org.atmosphere.cpr.ContainerInitializer.onStartup(ContainerInitializer.java:58)
    at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5156)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
    ... 10 more

21-Aug-2017 22:53:38.981 SEVERE [localhost-startStop-1] org.apache.catalina.startup.HostConfig.deployWAR Error deploying web application archive /Library/Tomcat/apache-tomcat-8.0.22/webapps/vaadinjavanine.war
 java.lang.IllegalStateException: ContainerBase.addChild: start: org.apache.catalina.LifecycleException: Failed to start component [StandardEngine[Catalina].StandardHost[localhost].StandardContext[/vaadinjavanine]]
    at org.apache.catalina.core.ContainerBase.addChildInternal(ContainerBase.java:728)
    at org.apache.catalina.core.ContainerBase.addChild(ContainerBase.java:701)
    at org.apache.catalina.core.StandardHost.addChild(StandardHost.java:717)
    at org.apache.catalina.startup.HostConfig.deployWAR(HostConfig.java:945)
    at org.apache.catalina.startup.HostConfig$DeployWar.run(HostConfig.java:1768)
    at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
    at java.util.concurrent.FutureTask.run(FutureTask.java:266)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
    at java.lang.Thread.run(Thread.java:745)

The exception states unable to process the module-info.class, which is generated from Java9's module-info.java. Is there a way to resolve this? Or does this actually means tomcat is not ready for java9 modules yet?

Note: Being novice to Tomcat, I have not customised any of the settings. Let me know, if something else can be shared for further information.

Answer 1

I'm not a Tomcat expert, but it looks like the module descriptor is not the most severe problem. The nexted exception contains this block:

Caused by: java.lang.UnsupportedClassVersionError: nullpointer/MyUI$MyUIServlet has been compiled by a more recent version of the Java Runtime (class file version 53.0), this version of the Java Runtime only recognizes class file versions up to 52.0 (unable to load class nullpointer.MyUI$MyUIServlet)

This makes it look like you're running Tomcat on Java 8 (class file version 52), whereas your code is compiled with Java 9 (class file version 53).

Make sure to run Tomcat on Java 9. Furthermore you might want to try an early access build of Tomcat 9, which is required for Java 9 compatibility.