Why do I get an HTTP Status 404 (requested resource [servlet] is not available) in Tomcat but not in Glassfish with the exact same configuration?

Question

The following config/code works in glassfish 6 but not Tomcat 8, why is that?

web.xml:

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="https://jakarta.ee/xml/ns/jakartaee"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="https://jakarta.ee/xml/ns/jakartaee https://jakarta.ee/xml/ns/jakartaee/web-app_5_0.xsd"
         version="5.0">
</web-app>

Servlet:

@WebServlet(name = "abcServlet", urlPatterns = {"/abcServlet"})
public class abcServlet extends HttpServlet {...

JSP:

<a href="abcServlet">ABC</a>

Answer 1

Solved it by upgrading to Tomcat 10 and adding the following dependencies in the pom.xml:

<!-- https://mvnrepository.com/artifact/jakarta.servlet.jsp/jakarta.servlet.jsp-api -->
        <dependency>
            <groupId>jakarta.servlet.jsp</groupId>
            <artifactId>jakarta.servlet.jsp-api</artifactId>
            <version>3.0.0</version>
            <scope>provided</scope>
        </dependency>
        <!-- https://mvnrepository.com/artifact/jakarta.servlet.jsp.jstl/jakarta.servlet.jsp.jstl-api -->
        <dependency>
            <groupId>jakarta.servlet.jsp.jstl</groupId>
            <artifactId>jakarta.servlet.jsp.jstl-api</artifactId>
            <version>3.0.0</version>
        </dependency>
        <!-- https://mvnrepository.com/artifact/org.glassfish.web/jakarta.servlet.jsp.jstl -->
        <dependency>
            <groupId>org.glassfish.web</groupId>
            <artifactId>jakarta.servlet.jsp.jstl</artifactId>
            <version>2.0.0</version>
        </dependency>

Answer 2

That's not enough information to answer exactly. Basically Glassfish 6 uses Jakarta EE and Tomcat 8 uses Java EE. Try to use Tomcat 9 or edit your XML namespaces accordingly.