springboot1.3.5 version 升级到 springboot 2.0.5时候报错。错误信息如下：
Failure to transfer org.apache.logging.log4j:log4j-jul:jar:2.10.0 from https://repo.maven.apache.org/maven2 was cached in the local repository, resolution will not be reattempted until the update interval of central has elapsed or updates are forced. Original error: Could not transfer artifact org.apache.logging.log4j:log4j-jul:jar:2.10.0 from/to central (https://repo.maven.apache.org/maven2): The operation was cancelled.
org.eclipse.aether.transfer.ArtifactTransferException: Failure to transfer org.apache.logging.log4j:log4j-jul:jar:2.10.0 from https://repo.maven.apache.org/maven2 was cached in the local repository, resolution will not be reattempted until the update interval of central has elapsed or updates are forced. Original error: Could not transfer artifact org.apache.logging.log4j:log4j-jul:jar:2.10.0 from/to central (https://repo.maven.apache.org/maven2): The operation was cancelled.
at org.eclipse.aether.internal.impl.DefaultUpdateCheckManager.newException(DefaultUpdateCheckManager.java:240)
at org.eclipse.aether.internal.impl.DefaultUpdateCheckManager.checkArtifact(DefaultUpdateCheckManager.java:208)
at org.eclipse.aether.internal.impl.DefaultArtifactResolver.gatherDownloads(DefaultArtifactResolver.java:563)
at org.eclipse.aether.internal.impl.DefaultArtifactResolver.performDownloads(DefaultArtifactResolver.java:481)
at org.eclipse.aether.internal.impl.DefaultArtifactResolver.resolve(DefaultArtifactResolver.java:399)
at org.eclipse.aether.internal.impl.DefaultArtifactResolver.resolveArtifacts(DefaultArtifactResolver.java:224)
at org.eclipse.aether.internal.impl.DefaultRepositorySystem.resolveDependencies(DefaultRepositorySystem.java:338)
at org.apache.maven.project.DefaultProjectDependenciesResolver.resolve(DefaultProjectDependenciesResolver.java:202)
at org.apache.maven.project.DefaultProjectBuilder.resolveDependencies(DefaultProjectBuilder.java:212)
at org.apache.maven.project.DefaultProjectBuilder.build(DefaultProjectBuilder.java:185)
at org.apache.maven.project.DefaultProjectBuilder.build(DefaultProjectBuilder.java:116)
at org.eclipse.m2e.core.internal.embedder.MavenImpl.readMavenProject(MavenImpl.java:636)
at org.eclipse.m2e.core.internal.project.registry.DefaultMavenDependencyResolver.resolveProjectDependencies(DefaultMavenDependencyResolver.java:63)
at org.eclipse.m2e.core.internal.project.registry.ProjectRegistryManager.refreshPhase2(ProjectRegistryManager.java:530)
at org.eclipse.m2e.core.internal.project.registry.ProjectRegistryManager$3.call(ProjectRegistryManager.java:492)
at org.eclipse.m2e.core.internal.project.registry.ProjectRegistryManager$3.call(ProjectRegistryManager.java:1)
at org.eclipse.m2e.core.internal.embedder.MavenExecutionContext.executeBare(MavenExecutionContext.java:177)
at org.eclipse.m2e.core.internal.embedder.MavenExecutionContext.execute(MavenExecutionContext.java:151)
at org.eclipse.m2e.core.internal.project.registry.ProjectRegistryManager.refresh(ProjectRegistryManager.java:496)
at org.eclipse.m2e.core.internal.project.registry.ProjectRegistryManager.refresh(ProjectRegistryManager.java:351)
at org.eclipse.m2e.core.internal.project.registry.ProjectRegistryManager.refresh(ProjectRegistryManager.java:298)
at org.eclipse.m2e.core.internal.builder.MavenBuilder$BuildMethod.getProjectFacade(MavenBuilder.java:155)
at org.eclipse.m2e.core.internal.builder.MavenBuilder$BuildMethod$1.call(MavenBuilder.java:90)
at org.eclipse.m2e.core.internal.embedder.MavenExecutionContext.executeBare(MavenExecutionContext.java:177)
at org.eclipse.m2e.core.internal.embedder.MavenExecutionContext.execute(MavenExecutionContext.java:151)
at org.eclipse.m2e.core.internal.embedder.MavenExecutionContext.execute(MavenExecutionContext.java:99)
at org.eclipse.m2e.core.internal.builder.MavenBuilder$BuildMethod.execute(MavenBuilder.java:87)
at org.eclipse.m2e.core.internal.builder.MavenBuilder.build(MavenBuilder.java:201)
at org.eclipse.core.internal.events.BuildManager$2.run(BuildManager.java:798)
at org.eclipse.core.runtime.SafeRunner.run(SafeRunner.java:45)
at org.eclipse.core.internal.events.BuildManager.basicBuild(BuildManager.java:219)
at org.eclipse.core.internal.events.BuildManager.basicBuild(BuildManager.java:262)
at org.eclipse.core.internal.events.BuildManager$1.run(BuildManager.java:315)
at org.eclipse.core.runtime.SafeRunner.run(SafeRunner.java:45)
at org.eclipse.core.internal.events.BuildManager.basicBuild(BuildManager.java:318)
at org.eclipse.core.internal.events.BuildManager.basicBuildLoop(BuildManager.java:370)
at org.eclipse.core.internal.events.BuildManager.build(BuildManager.java:391)
at org.eclipse.core.internal.events.AutoBuildJob.doBuild(AutoBuildJob.java:145)
at org.eclipse.core.internal.events.AutoBuildJob.run(AutoBuildJob.java:235)
at org.eclipse.core.internal.jobs.Worker.run(Worker.java:63)
很明显，是缺少log4j-jul.jar包，它说从maven库中不会缓存到本地仓库！那么只有自动手动去download了
地址：https://mvnrepository.com/artifact/org.apache.logging.log4j/log4j-jul/2.10.0
重新编译，此问题解决！
下面是log4j2的日志导入：
<!-- https://mvnrepository.com/artifact/org.springframework.boot/spring-boot-starter-log4j2 -->
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-log4j2</artifactId>
<version>${spring-boot.version}</version>
<exclusions>
<exclusion>
<groupId>org.slf4j</groupId>
<artifactId>jcl-over-slf4j</artifactId>
</exclusion>
<exclusion>
<groupId>org.slf4j</groupId>
<artifactId>jul-to-slf4j</artifactId>
</exclusion>
</exclusions>
</dependency>
${spring-boot.version}为2.0.5.RELEASE