Tomcat版本与jdk版本不匹配导致的。
我这是jdk9和Tomcat7组合启动造成的。
以下是Tomcat官方提供的版本对应关系：
|
Servlet Spec
|
JSP Spec
|
EL Spec
|
WebSocket Spec
|
JASPIC Spec
|
Apache Tomcat Version
|
Latest Released Version
|
Supported Java Versions
|
|
4.0
|
2.3
|
3.0
|
1.1
|
1.1
|
9.0.x
|
9.0.6
|
8 and later
|
|
3.1
|
2.3
|
3.0
|
1.1
|
1.1
|
8.5.x
|
8.5.29
|
7 and later
|
|
3.1
|
2.3
|
3.0
|
1.1
|
N/A
|
8.0.x (superseded)
|
8.0.50 (superseded)
|
7 and later
|
|
3.0
|
2.2
|
2.2
|
1.1
|
N/A
|
7.0.x
|
7.0.85
|
6 and later
(7 and later for WebSocket)
|
|
2.5
|
2.1
|
2.1
|
N/A
|
N/A
|
6.0.x (archived)
|
6.0.53 (archived)
|
5 and later
|
|
2.4
|
2.0
|
N/A
|
N/A
|
N/A
|
5.5.x (archived)
|
5.5.36 (archived)
|
1.4 and later
|
|
2.3
|
1.2
|
N/A
|
N/A
|
N/A
|
4.1.x (archived)
|
4.1.40 (archived)
|
1.3 and later
|
|
2.2
|
1.1
|
N/A
|
N/A
|
N/A
|
3.3.x (archived)
|
3.3.2 (archived)
|
1.1 and later
|
参考：https://blog.csdn.net/wsm0712syb/article/details/52495034