发生了什么以及如何修复：无效的模块名称：“tomcat-embed-jasper-el”不是 Java 标识符

Question

I'm sort of reviving a project that was left in a broken state when I try to run the tests from IntelliJ, I get this error:

Information:java: Caused by: java.lang.module.FindException: Automatic-Module-Name: org.apache.tomcat-embed-jasper-el: Invalid module name: 'tomcat-embed-jasper-el' is not a Java identifier

When I try to run the tests from the command line, with mvn test I get a different error: What does this error mean Unsupported class file major version 56 and how do I fix it?

The error is clearly about Java Modules, but I'm still finding them a little bit puzzling. The project doesn't mention "tomcat" nor "jasper" anywhere.

The full backtrace is:

Information:java: An exception has occurred in the compiler (12.0.2). Please file a bug against the Java compiler via the Java bug reporting page (http://bugreport.java.com) after checking the Bug Database (http://bugs.java.com) for duplicates. Include your program and the following diagnostic in your report. Thank you.
Information:java: java.lang.module.FindException: Unable to derive module descriptor for C:\Users\pupeno\.m2\repository\org\apache\tomcat\embed\tomcat-embed-el\9.0.24\tomcat-embed-el-9.0.24.jar
Information:java:   at java.base/jdk.internal.module.ModulePath.readJar(ModulePath.java:646)
Information:java:   at java.base/jdk.internal.module.ModulePath.readModule(ModulePath.java:329)
Information:java:   at java.base/jdk.internal.module.ModulePath.scan(ModulePath.java:235)
Information:java:   at java.base/jdk.internal.module.ModulePath.scanNextEntry(ModulePath.java:188)
Information:java:   at java.base/jdk.internal.module.ModulePath.findAll(ModulePath.java:164)
Information:java:   at java.base/java.lang.module.Resolver.findAll(Resolver.java:842)
Information:java:   at java.base/java.lang.module.Resolver.bind(Resolver.java:223)
Information:java:   at java.base/java.lang.module.Configuration.resolveAndBind(Configuration.java:493)
Information:java:   at java.base/java.lang.module.Configuration.resolveAndBind(Configuration.java:299)
Information:java:   at jdk.compiler/com.sun.tools.javac.file.JavacFileManager.getServiceLoader(JavacFileManager.java:985)
Information:java:   at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
Information:java:   at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
Information:java:   at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
Information:java:   at java.base/java.lang.reflect.Method.invoke(Method.java:567)
Information:java:   at org.jetbrains.jps.javac.JavacMain$2.invoke(JavacMain.java:290)
Information:java:   at com.sun.proxy.$Proxy23.getServiceLoader(Unknown Source)
Information:java:   at com.sun.proxy.$Proxy24.getServiceLoader(Unknown Source)
Information:java:   at jdk.compiler/com.sun.tools.javac.processing.JavacProcessingEnvironment.initProcessorLoader(JavacProcessingEnvironment.java:266)
Information:java:   at jdk.compiler/com.sun.tools.javac.processing.JavacProcessingEnvironment.<init>(JavacProcessingEnvironment.java:237)
Information:java:   at jdk.compiler/com.sun.tools.javac.processing.JavacProcessingEnvironment.instance(JavacProcessingEnvironment.java:193)
Information:java:   at jdk.compiler/com.sun.tools.javac.main.JavaCompiler.initProcessAnnotations(JavaCompiler.java:1136)
Information:java:   at jdk.compiler/com.sun.tools.javac.main.JavaCompiler.compile(JavaCompiler.java:922)
Information:java:   at jdk.compiler/com.sun.tools.javac.api.JavacTaskImpl.lambda$doCall$0(JavacTaskImpl.java:104)
Information:java:   at jdk.compiler/com.sun.tools.javac.api.JavacTaskImpl.handleExceptions(JavacTaskImpl.java:147)
Information:java:   at jdk.compiler/com.sun.tools.javac.api.JavacTaskImpl.doCall(JavacTaskImpl.java:100)
Information:java:   at jdk.compiler/com.sun.tools.javac.api.JavacTaskImpl.call(JavacTaskImpl.java:94)
Information:java:   at org.jetbrains.jps.javac.JavacMain.compile(JavacMain.java:195)
Information:java:   at org.jetbrains.jps.incremental.java.JavaBuilder.compileJava(JavaBuilder.java:460)
Information:java:   at org.jetbrains.jps.incremental.java.JavaBuilder.compile(JavaBuilder.java:330)
Information:java:   at org.jetbrains.jps.incremental.java.JavaBuilder.doBuild(JavaBuilder.java:255)
Information:java:   at org.jetbrains.jps.incremental.java.JavaBuilder.build(JavaBuilder.java:213)
Information:java:   at org.jetbrains.jps.incremental.IncProjectBuilder.runModuleLevelBuilders(IncProjectBuilder.java:1324)
Information:java:   at org.jetbrains.jps.incremental.IncProjectBuilder.runBuildersForChunk(IncProjectBuilder.java:1004)
Information:java:   at org.jetbrains.jps.incremental.IncProjectBuilder.buildTargetsChunk(IncProjectBuilder.java:1071)
Information:java:   at org.jetbrains.jps.incremental.IncProjectBuilder.buildChunkIfAffected(IncProjectBuilder.java:965)
Information:java:   at org.jetbrains.jps.incremental.IncProjectBuilder.buildChunks(IncProjectBuilder.java:794)
Information:java:   at org.jetbrains.jps.incremental.IncProjectBuilder.runBuild(IncProjectBuilder.java:376)
Information:java:   at org.jetbrains.jps.incremental.IncProjectBuilder.build(IncProjectBuilder.java:178)
Information:java:   at org.jetbrains.jps.cmdline.BuildRunner.runBuild(BuildRunner.java:139)
Information:java:   at org.jetbrains.jps.cmdline.BuildSession.runBuild(BuildSession.java:288)
Information:java:   at org.jetbrains.jps.cmdline.BuildSession.run(BuildSession.java:121)
Information:java:   at org.jetbrains.jps.cmdline.BuildMain$MyMessageHandler.lambda$channelRead0$0(BuildMain.java:228)
Information:java:   at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128)
Information:java:   at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628)
Information:java:   at java.base/java.lang.Thread.run(Thread.java:835)
Information:java: Caused by: java.lang.module.FindException: Automatic-Module-Name: org.apache.tomcat-embed-jasper-el: Invalid module name: 'tomcat-embed-jasper-el' is not a Java identifier
Information:java:   at java.base/jdk.internal.module.ModulePath.deriveModuleDescriptor(ModulePath.java:503)
Information:java:   at java.base/jdk.internal.module.ModulePath.readJar(ModulePath.java:642)
Information:java:   ... 49 more
Information:java: Errors occurred while compiling module 'projectxserver'
Information:javac 12.0.2 was used to compile java sources
Information:2019-09-24 18:12 - Build completed with 1 error and 0 warnings in 3 s 434 ms
Error:java: Compilation failed: internal java compiler error

Answer 1

Quickest of all the solution could be to upgrade to 9.0.26 of your dependency.

<dependency>
    <groupId>org.apache.tomcat.embed</groupId>
    <artifactId>tomcat-embed-el</artifactId>
    <version>9.0.26</version>
</dependency>

which shall then result in the derived automatic module name as:

org.apache.tomcat.embed.jasper.el@9.0.26 automatic

---

Additional Details

The issue in deriving the module name for the jar tomcat-embed-el-9.0.24.jar is that is includes the Automatic-Module-Name entry in its MANIFEST.MF which reads:

Automatic-Module-Name: org.apache.tomcat-embed-jasper-el

The naming convention doesn't bind by the java standards. On the other hand, the same value under the upgraded version reads:

Automatic-Module-Name: org.apache.tomcat.embed.jasper.el 

for which the automatic module name can be derived successfully.

This could be verified as well using the command line jar tool:

jar --file=<pathToJAR>\tomcat-embed-el-9.0.24.jar --describe-module