{"record":{"id":"e5e4e9452bab79d6","repo":"apache/maven","slug":"unable-to-load-the-mojo-mojodescriptor-getgoal","errorCode":null,"errorMessage":"Unable to load the mojo '${mojoDescriptor.getGoal()}' in the plugin '${pluginDescriptor.getId()}'. A required class is missing: ${cause.getMessage()}","messagePattern":"Unable to load the mojo '(.+?)' in the plugin '(.+?)'\\. A required class is missing: (.+?)","errorType":"exception","errorClass":"PluginContainerException","httpStatus":null,"severity":"error","filePath":"impl/maven-core/src/main/java/org/apache/maven/plugin/internal/DefaultMavenPluginManager.java","lineNumber":708,"sourceCode":" T mojo;\n\n try {\n mojo = container.lookup(mojoInterface, mojoDescriptor.getRoleHint());\n } catch (ComponentLookupException e) {\n Throwable cause = e.getCause();\n while (cause != null && !(cause instanceof LinkageError) && !(cause instanceof ClassNotFoundException)) {\n cause = cause.getCause();\n }\n\n if ((cause instanceof NoClassDefFoundError) || (cause instanceof ClassNotFoundException)) {\n ByteArrayOutputStream os = new ByteArrayOutputStream(1024);\n PrintStream ps = new PrintStream(os);\n ps.println(\"Unable to load the mojo '\" + mojoDescriptor.getGoal() + \"' in the plugin '\"\n + pluginDescriptor.getId() + \"'. A required class is missing: \"\n + cause.getMessage());\n pluginRealm.display(ps);\n\n throw new PluginContainerException(mojoDescriptor, pluginRealm, os.toString(), cause);\n } else if (cause instanceof LinkageError) {\n ByteArrayOutputStream os = new ByteArrayOutputStream(1024);\n PrintStream ps = new PrintStream(os);\n ps.println(\"Unable to load the mojo '\" + mojoDescriptor.getGoal() + \"' in the plugin '\"\n + pluginDescriptor.getId() + \"' due to an API incompatibility: \"\n + e.getClass().getName() + \": \" + cause.getMessage());\n pluginRealm.display(ps);\n\n throw new PluginContainerException(mojoDescriptor, pluginRealm, os.toString(), cause);\n }\n\n throw new PluginContainerException(\n mojoDescriptor,\n pluginRealm,\n \"Unable to load the mojo '\" + mojoDescriptor.getGoal()\n + \"' (or one of its required components) from the plugin '\"\n + pluginDescriptor.getId() + \"'\",\n e);","sourceCodeStart":690,"sourceCodeEnd":726,"githubUrl":"https://github.com/apache/maven/blob/e4093d4e120eac99d6bdce5ba67cace2f3085c97/impl/maven-core/src/main/java/org/apache/maven/plugin/internal/DefaultMavenPluginManager.java#L690-L726","documentation":"Maven built the plugin's class realm but could not load the mojo class because a class it references is absent from that realm. DefaultMavenPluginManager walks the cause chain to the first NoClassDefFoundError/ClassNotFoundException and throws PluginContainerException, appending a dump of every jar/URL in the plugin realm so you can see which artifact should have supplied the missing class. The class name after 'A required class is missing:' is the key diagnostic.","triggerScenarios":"Calling mojo execution (direct goal invocation, lifecycle phase, or embedder getConfiguredMojo) when the plugin realm lacks a jar: a blanket on the plugin or its dependency, dependency mediation dropping a transitive jar, an optional/provided dependency that is not present, or a corrupted/zero-byte jar in the local repository.","commonSituations":"Copy-pasted with groupId/artifactId wildcards in pluginManagement; interrupted downloads leaving broken jars in ~/.m2/repository; running with -o (offline) against a partially cached plugin; plugin version expecting a library that a pinned older dependency shadows.","solutions":["Read the realm dump in the message: find the class named after 'A required class is missing:' and check which artifact in the dump (or missing from it) should contain it.","Delete the suspect artifact directory under ~/.m2/repository and rebuild with mvn -U so it is re-downloaded and checksum-verified.","Remove or narrow declared on the plugin (or its parent pluginManagement) so the required transitive jar returns to the realm.","Pin the correct version of the missing library under if another plugin dependency pulls an incompatible subset.","Upgrade or downgrade the plugin to a version whose dependency set resolves cleanly in your environment."],"exampleFix":"// before: blanket exclusion strips a jar the mojo needs\n\n org.example\n example-maven-plugin\n 1.2.0\n \n \n org.example\n example-spi\n 1.4.0\n \n **\n \n \n \n\n\n// after: drop the wildcard exclusion so the missing class is back on the plugin classpath\n\n org.example\n example-maven-plugin\n 1.2.0\n","handlingStrategy":"try-catch","validationCode":"# pre-flight: force full plugin resolution and drop zero-byte stubs before the real build\nmvn -B dependency:resolve-plugins\nfind ~/.m2/repository -name '*.jar' -size -1b -print -delete\nmvn -U verify","typeGuard":"static boolean missingClassInMojoRealm(PluginContainerException e) {\n Throwable c = e.getCause();\n return c instanceof NoClassDefFoundError || c instanceof ClassNotFoundException;\n}","tryCatchPattern":"try {\n Object mojo = pluginManager.getConfiguredMojo(mojoDescriptor, pluginRealm, session, mojoExecution);\n} catch (PluginContainerException e) {\n Throwable c = e.getCause();\n if (c instanceof NoClassDefFoundError || c instanceof ClassNotFoundException) {\n // classpath hole: e.getMessage() already embeds the plugin realm dump\n reportPluginClasspathHole(e);\n }\n throw e;\n}","preventionTips":["Pin explicit versions for every plugin so the realm composition is reproducible.","Never use wildcard on plugin dependencies; exclude one artifact at a time.","Run CI builds against a pristine local repository so corrupt jars surface immediately.","After interrupted downloads, clean the affected group under ~/.m2/repository before the next build."],"tags":["maven","plugin","classpath","noclassdeffounderror","classnotfoundexception"],"backgroundTag":"missing-class-classpath","analyzedSha":"e4093d4e120eac99d6bdce5ba67cace2f3085c97","analyzedAt":"2026-08-21T22:58:24.034Z","schemaVersion":2},"datasetVersion":"2026-08-21T23:17:16.201Z"}