原因:是因为项目中没有引入jsp的包
解决方法:(在pom中添加依赖)
<!-- https://mvnrepository.com/artifact/javax.servlet/jsp-api -->
<dependency>
<groupId>javax.servlet</groupId>
<artifactId>jsp-api</artifactId>
<version>2.0</version>
<scope>provided</scope>
</dependency>