Answers:
Servlet API version 3.0 is fully backward compatible with versions 2.3, 2.4,
and 2.5, so all existing servlets should work without modification or
recompilation.
此外,Apache Tomcat 7文档中指出,Tomcat 7特别实现了Servlet API版本3:
Apache Tomcat version 7.0 implements the Servlet 3.0 and JavaServer Pages 2.2
specifications from the Java Community Process...
因此,我建议您使用Servlet API的版本3。