JSP file not rendering in Spring Boot web application

Make sure that your pom.xml specifies the Tomcat JSP dependency as follows:

<dependency>
    <groupId>org.apache.tomcat.embed</groupId>
    <artifactId>tomcat-embed-jasper</artifactId>
    <scope>provided</scope>
</dependency>

It seems that embedded Tomcat treats the JSP rendering as optional.

As mentioned below, this JAR is sometimes necessary as well:

<dependency>
    <groupId>javax.servlet</groupId>
    <artifactId>jstl</artifactId>
    <scope>provided</scope>
</dependency>

(I added provided since this JAR should be included by the servlet container.