I accidentally removed Maven Dependencies yesterday. A pain in the ass...!
1: Find the previous version of the project
2: Replace your .classpath file directly
3: Find the project-right click-Maven-Update Project... Alt+F5
4: Find the project - right click - Build Path - Configure Build Path... Have you seen Maven Dependencies in the LiBraries list?
If your project has no previous version
1: Open the .classpath file
Just add the blue background part above to your .classpath file
The line numbers are added in front of the above code because Sina Blog directly displays the code to avoid this problem.