Why Does Tomcat 10.0.4 Return 404 Errors for Servlets When Using Servlet 4.0 APIs?

Tomcat 10.0.4 Doesn't Load Servlets (WebServlet Classes) with 404 Error

In the provided code snippet, the issue arises due to the incompatibility between the Servlet APIs used in Tomcat 10.0.4 (Servlet 5.0) and your application (Servlet 4.0). This incompatibility stems from the package namespace change from javax.* to jakarta.* in Servlet 5.0.

Implications of the API Namespace Change:

• Compilation Errors: Servlet 4.0 code will fail to compile against Servlet 5.0 APIs.
• Runtime Errors: Servlet 4.0 applications using web.xml may encounter ClassNotFoundExceptions and fail to start.
• Annotation Recognition Issues: Servlets declared using @javax.servlet.WebServlet annotations will be ignored in Servlet 5.0, where @jakarta.servlet.WebServlet should be used instead.

Resolution:

To address this issue, it's necessary to ensure your application aligns with the API namespace change to Servlet 5.0. This can be achieved through the following approaches:

• Manual Migration: Manually update your code to use the jakarta.* packages for all Servlet API-related classes and annotations.
• Tomcat Migration Tool: Utilize the Tomcat Migration Tool for Jakarta EE, which automates the migration process and reduces the likelihood of errors.

Additional Note:

The official Tomcat download site clearly warns users about this API namespace change. Therefore, it's crucial for developers to be aware of this before upgrading to Tomcat 10.0.4 or later.

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