：tomcat/jsp/servlet对应版本和规范

http://tomcat.apache.org/whichversion.html

Apache Tomcat™ is an open source software implementation of the Java Servletand JavaServer Pages technologies. Different versions of Apache Tomcat areavailable for different versions of the Servlet and JSP specifications. Themapping between the specifications and the respective Apache Tomcat versions is:

Servlet Spec	JSP Spec	EL Spec	WebSocket Spec	Apache Tomcat version	Actual release revision	Support Java Versions
4.0	TBD (2.4?)	TBD (3.1?)	TBD (1.2?)	9.0.x	None	8 and later
3.1	2.3	3.0	1.1	8.0.x	8.0.23	7 and later
3.0	2.2	2.2	1.1	7.0.x	7.0.62	6 and later (WebSocket 1.1 requires 7 or later)
2.5	2.1	2.1	N/A	6.0.x	6.0.44	5 and later
2.4	2.0	N/A	N/A	5.5.x (archived)	5.5.36 (archived)	1.4 and later
2.3	1.2	N/A	N/A	4.1.x (archived)	4.1.40 (archived)	1.3 and later
2.2	1.1	N/A	N/A	3.3.x (archived)	3.3.2 (archived)	1.1 and later