Maven / Spring项目中缺少工件的问题

I'm trying to learn REST with a Spring/Maven context and so I'm going through a Pankaj Kumar (JournalDev) tutorial. I set up a Spring project in STS (Spring Tool Suite), and according to the tutorial, I will need to include the following dependencies: jackson-databind, jackson-core, and jackson-annotations. I declared them in the pom.xml editor in STS.I'm trying to learn REST with a Spring/Maven co