pom.xml中总是提示Missing artifact org.slf4j:slf4j-log4j12:jar: 1.76

照着老师代码敲得

但是pom.xml中总是提示Missing artifact org.slf4j:slf4j-log4j12:jar:1.76

执行mvn jetty:run 时报错

[ERROR] Failed to execute goal on project spring-blog: Could not resolve dependencies for project rd-arthur:spring-blog:jar:1.0-SNAPSHOT: Failure to find org.slf4j:slf4j-log4j12:jar:1.76 in http://maven.aliyun.com/nexus/content/groups/public/ was cached in the local repository, resolution will not be reattempted until the update interval of alimaven has elapsed or updates are forced -> [Help 1]

是不是有什么步骤漏了没讲？