This error occurs when the required servlet JAR files are not present in the classpath of your project. Here are some steps you can follow to try and solve the issue:
1. Check if the required servlet JAR files are present in your project's build path. To do this, right-click on your project in Eclipse, select "Build Path" and then "Configure Build Path". Click on the "Libraries" tab and ensure that the "javax.servlet" library is included in the list.
2. If the required JAR files are not present in your project, you can add them manually. To do this, right-click on your project in Eclipse, select "Build Path" and then "Configure Build Path". Click on the "Libraries" tab and then click the "Add External JARs" button to add the required JAR files.
3. Ensure that you are using the correct version of Tomcat that is compatible with your servlet version. For example, if you are using servlet version 4.0, make sure that you are using Tomcat version 9 or later.
4. If you have tried the above steps and still cannot resolve the issue, try deleting and recreating your project in Eclipse. This may help to refresh any build path issues that may be causing the problem.
Hopefully, one of these steps will help you to resolve the issue. If you are still having trouble, feel free to provide more details or ask for further assistance.
