IntellijIDEA not recognizing classes specified in Maven dependencies

Question

I have a project in IntellijIDEA which was created with Maven. I then specified a set of dependencies and external repositories in the Pom.xml file.

The project builds

Answer 1

I have encountered this problem，idea cannot download all dependent jar packages using maven,i just tried the following operations:

mvn -U idea:idea

then all the dependent jar packages are download from the maven repository