In Java Servlets, exception handling is an important concept to ensure that your application is robust and can handle unexpected errors gracefully. Servlets use the standard Java exception handling mechanism, which involves catching exceptions and handling them appropriately.

Here is an example of how to handle exceptions in a Servlet:

import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.*;

public class MyServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        try {
            // Code that may throw an exception
        } catch (MyException e) {
            // Handle the exception
            response.sendError(HttpServletResponse.SC_INTERNAL_SERVER_ERROR, "An error occurred: " + e.getMessage());
        } catch (Exception e) {
            // Handle all other exceptions
            response.sendError(HttpServletResponse.SC_INTERNAL_SERVER_ERROR, "An unexpected error occurred: " + e.getMessage());
        }
    }
}

In the above code, the doGet() method throws an exception of type MyException, which is caught and handled appropriately. Any other exceptions that are not MyException are caught by the catch (Exception e) block. In both cases, an HTTP response with an error code and a message is sent back to the client.

It's also a good practice to log exceptions that occur in your application. This can help with debugging and troubleshooting issues. Here's an example of how to log exceptions in a Servlet:

import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.*;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

public class MyServlet extends HttpServlet {
    private static final Logger logger = LoggerFactory.getLogger(MyServlet.class);

    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        try {
            // Code that may throw an exception
        } catch (Exception e) {
            // Handle the exception
            logger.error("An unexpected error occurred", e);
            response.sendError(HttpServletResponse.SC_INTERNAL_SERVER_ERROR, "An unexpected error occurred");
        }
    }
}

In the above code, we are using the SLF4J logging library to log exceptions. The Logger instance is created using the getLogger() method, which takes the name of the class that the logger is being used in. When an exception occurs, the error() method is called on the logger instance, which logs the exception with the message "An unexpected error occurred". This log message can then be viewed in a log file or a logging service like Logstash or ELK.