报错
但是其实javax.servlet存在，且能正常运行，但是提示这个信息也特别让人难受。
解决方法
在pom.xml文件中添加
<dependencies>
<dependency>
<groupId>org.apache.geronimo.specs</groupId>
<artifactId>geronimo-servlet_2.4_spec</artifactId>
<version>1.1.1</version>
<scope>provided</scope>
</dependency>
</dependencies>
完整的pom.xml
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>Test2</groupId>
<artifactId>Test2</artifactId>
<version>1.0-SNAPSHOT</version>
<dependencies>
<dependency>
<groupId>org.apache.geronimo.specs</groupId>
<artifactId>geronimo-servlet_2.4_spec</artifactId>
<version>1.1.1</version>
<scope>provided</scope>
</dependency>
</dependencies>
</project>
原文：https://www.cnblogs.com/hahayixiao/p/14543674.html