第一个异常：

 Servlet should have a mapping less... (Ctrl+F1) 

Checks if all servlets have mappings

第二个异常：Cannot resolve Servlet 'ListServlet' less... (Ctrl+F1) 

This inspection lets you spot the following problems that might occur in descriptors that are used to deploy your Web Module to a server:

References to the non-instantiable classes

References to the classes that do not extend required class

References to classes with inappropriate scope

Empty tag and attribute values

Tag and attribute values that do not match required pattern (e.g. Java Identifiers)

Tags that do not include required children tags or attributes

Tags that define objects with duplicate names