The container 'Maven Dependencies' references non existing library - STS

So I get you are using Eclipse with the M2E plugin. Try to update your Maven configuration : In the Project Explorer, right-click on the project, Maven -> Update project.

If the problem still remains, try to clean your project: right-click on your pom.xml, Run as -> Maven build (the second one). Enter "clean package" in the Goals fields. Check the Skip Tests box. Click on the Run button.

Edit: For your new problem, you need to add Spring MVC to your pom.xml. Add something like the following:

<dependency>
    <groupId>org.springframework</groupId>
    <artifactId>spring-webmvc</artifactId>
    <version>4.0.0.RELEASE</version>
</dependency>

Maybe you have to change the version to match the version of your Spring framework. Take a look here:

http://mvnrepository.com/artifact/org.springframework/spring-webmvc

I finally found my maven repo mirror is down. I changed to another one, problem solved.

I got the same problem and this is how i solved. :

1. Right click your Spring MVC project, choose Run As -> Maven install. Observe the output console to see the installation progress. After the installation is finished, you can continue to the next step.

2. Right click your Spring MVC project, choose Maven -> Update Project.

3. Choose your project and click OK. Wait until update process is finished.
4. The error still yet, then do Project->Clean and then be sure you have selected our project directory and then do the follow Project->Build.