Eclipse add Tomcat 7 blank server name 【无法输入server name】

I was trying to add Tomcat 7 in my Eclipse in Ubuntu. When I click "Add new server" in Eclipse and select "Tomcat v7.0 Server", the field "Server Name" is blank and I cannot type in anything in that textbox as shown below:

What I did before is I deleted a Tomcat 7 server from Eclipse and I was trying to reinstall Tomcat 7. But it doesn't allow me to type anything in that textbox and I cannot proceed to the "Next" button. My environment is Ubuntu Linux and Eclipse for JavaEE.

Here is the workaround that worked for me:

1. Close Eclipse
2. In {workspace-directory}/.metadata/.plugins/org.eclipse.core.runtime/.settings
3. delete the following two files: 
   • org.eclipse.wst.server.core.prefs
   • org.eclipse.jst.server.tomcat.core.prefs
4. Restart Eclipse
5. original blog link:http://www.xuebuyuan.com/1361033.html