我在系统中安装了nexus存储库管理器3。我配置了maven2代理存储库，当我尝试使用"mvn clean"命令清理pom.xml文件时，出现以下错误。
[INFO] Scanning for projects...
[INFO]
[INFO] ------------------< com.sample.app:nexus-proxy-test >-------------------
[INFO] Building nexus-proxy-test 1.0-SNAPSHOT
[INFO] --------------------------------[ jar ]---------------------------------
Downloading from nexus: http://localhost:8081/repository/maven-proxy-test/org/apache/maven/plugins/maven-clean-plugin/2.5/maven-clean-plugin-2.5.pom
[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 0.377 s
[INFO] Finished at: 2019-10-03T19:04:32+05:30
[INFO] ------------------------------------------------------------------------
[ERROR] Plugin org.apache.maven.plugins:maven-clean-plugin:2.5 or one of its dependencies could not be resolved: Failed to read artifact descriptor for org.apache.maven.plugins:maven-clean-plugin:jar:2.5: Could not transfer artifact org.apache.maven.plugins:maven-clean-plugin:pom:2.5 from/to nexus (http://localhost:8081/repository/maven-proxy-test/): Not authorized -> [Help 1]
[ERROR]
[ERROR] To see the full stack trace of the errors, re-run Maven with the -e switch.
[ERROR] Re-run Maven using the -X switch to enable full debug logging.
[ERROR]
[ERROR] For more information about the errors and possible solutions, please read the following articles:
[ERROR] [Help 1] http://cwiki.apache.org/confluence/display/MAVEN/PluginResolutionException
错误堆栈跟踪如下所示。
Caused by: org.apache.maven.wagon.authorization.AuthorizationException: Not authorized
at org.apache.maven.wagon.providers.http.wagon.shared.AbstractHttpClientWagon.resourceExists (AbstractHttpClientWagon.java:838)
at org.apache.maven.wagon.providers.http.wagon.shared.AbstractHttpClientWagon.resourceExists (AbstractHttpClientWagon.java:809)
at org.eclipse.aether.transport.wagon.WagonTransporter$PeekTaskRunner.run (WagonTransporter.java:512)
at org.eclipse.aether.transport.wagon.WagonTransporter.execute (WagonTransporter.java:435)
at org.eclipse.aether.transport.wagon.WagonTransporter.peek (WagonTransporter.java:406)
at org.eclipse.aether.connector.basic.BasicRepositoryConnector$PeekTaskRunner.runTask (BasicRepositoryConnector.java:390)
at org.eclipse.aether.connector.basic.BasicRepositoryConnector$TaskRunner.run (BasicRepositoryConnector.java:364)
at org.eclipse.aether.util.concurrency.RunnableErrorForwarder$1.run (RunnableErrorForwarder.java:75)
at org.eclipse.aether.connector.basic.BasicRepositoryConnector$DirectExecutor.execute (BasicRepositoryConnector.java:644)
at org.eclipse.aether.connector.basic.BasicRepositoryConnector.get (BasicRepositoryConnector.java:262)
at org.eclipse.aether.internal.impl.DefaultArtifactResolver.performDownloads (DefaultArtifactResolver.java:499)
at org.eclipse.aether.internal.impl.DefaultArtifactResolver.resolve (DefaultArtifactResolver.java:401)
at org.eclipse.aether.internal.impl.DefaultArtifactResolver.resolveArtifacts (DefaultArtifactResolver.java:229)
at org.eclipse.aether.internal.impl.DefaultArtifactResolver.resolveArtifact (DefaultArtifactResolver.java:207)
at org.apache.maven.repository.internal.DefaultArtifactDescriptorReader.loadPom (DefaultArtifactDescriptorReader.java:240)
at org.apache.maven.repository.internal.DefaultArtifactDescriptorReader.readArtifactDescriptor (DefaultArtifactDescriptorReader.java:171)
at org.eclipse.aether.internal.impl.DefaultRepositorySystem.readArtifactDescriptor (DefaultRepositorySystem.java:255)
at org.apache.maven.plugin.internal.DefaultPluginDependenciesResolver.resolve (DefaultPluginDependenciesResolver.java:106)
at org.apache.maven.plugin.internal.DefaultMavenPluginManager.getPluginDescriptor (DefaultMavenPluginManager.java:182)
at org.apache.maven.plugin.internal.DefaultMavenPluginManager.getMojoDescriptor (DefaultMavenPluginManager.java:286)
at org.apache.maven.plugin.DefaultBuildPluginManager.getMojoDescriptor (DefaultBuildPluginManager.java:244)
at org.apache.maven.lifecycle.internal.DefaultLifecycleExecutionPlanCalculator.setupMojoExecution (DefaultLifecycleExecutionPlanCalculator.java:169)
at org.apache.maven.lifecycle.internal.DefaultLifecycleExecutionPlanCalculator.setupMojoExecutions (DefaultLifecycleExecutionPlanCalculator.java:154)
at org.apache.maven.lifecycle.internal.DefaultLifecycleExecutionPlanCalculator.calculateExecutionPlan (DefaultLifecycleExecutionPlanCalculator.java:130)
at org.apache.maven.lifecycle.internal.DefaultLifecycleExecutionPlanCalculator.calculateExecutionPlan (DefaultLifecycleExecutionPlanCalculator.java:144)
at org.apache.maven.lifecycle.internal.builder.BuilderCommon.resolveBuildPlan (BuilderCommon.java:97)
at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject (LifecycleModuleBuilder.java:111)
at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject (LifecycleModuleBuilder.java:81)
at org.apache.maven.lifecycle.internal.builder.singlethreaded.SingleThreadedBuilder.build (SingleThreadedBuilder.java:56)
at org.apache.maven.lifecycle.internal.LifecycleStarter.execute (LifecycleStarter.java:128)
at org.apache.maven.DefaultMaven.doExecute (DefaultMaven.java:305)
at org.apache.maven.DefaultMaven.doExecute (DefaultMaven.java:192)
at org.apache.maven.DefaultMaven.execute (DefaultMaven.java:105)
at org.apache.maven.cli.MavenCli.execute (MavenCli.java:956)
at org.apache.maven.cli.MavenCli.doMain (MavenCli.java:288)
at org.apache.maven.cli.MavenCli.main (MavenCli.java:192)
at sun.reflect.NativeMethodAccessorImpl.invoke0 (Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke (NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke (DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke (Method.java:498)
at org.codehaus.plexus.classworlds.launcher.Launcher.launchEnhanced (Launcher.java:282)
at org.codehaus.plexus.classworlds.launcher.Launcher.launch (Launcher.java:225)
at org.codehaus.plexus.classworlds.launcher.Launcher.mainWithExitCode (Launcher.java:406)
at org.codehaus.plexus.classworlds.launcher.Launcher.main (Launcher.java:347)
参考 https://help.sonatype.com/learning/repository-manager-3/first-time-installation-and-setup/lesson-2%3A-proxy-and-hosted-maven-repositories
这是授权问题。从安装了 maven 的文件夹中打开 settings.xml 文件，然后更正用户 ID 和密码。它应该解决你的问题。
由于密码不正确，无法下载 Jar。
如果您已确保您的设置.xml文件具有正确的用户名和密码，但它仍然不起作用，请确保您指向正确的 Maven 版本。我遇到了这个错误，结果我的IDE默认为不同版本的Maven，一个没有更正设置.xml文件的版本。