错误处理程序Servlet:如何获取异常原因

import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

@WebServlet("/errorHandler")
public class ErrorHandlerServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // 获取异常原因
        Throwable throwable = (Throwable) request.getAttribute("javax.servlet.error.exception");
        Integer statusCode = (Integer) request.getAttribute("javax.servlet.error.status_code");
        String servletName = (String) request.getAttribute("javax.servlet.error.servlet_name");
        String requestUri = (String) request.getAttribute("javax.servlet.error.request_uri");

        // 处理异常
        // ...
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doPost(request, response);
    }
}

   <exception-type>java.lang.Throwable</exception-type>
   <location>/errorHandler</location>
</error-page>