异常问题 谢谢!!

Question

package com.itheima.b_login;import java.io.IOException;import javax.servlet.ServletException;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import sun.security.util.Password;/** * Servlet implementation class UserServlet */public class UserServlet extends HttpServlet {    private static final long serialVersionUID = 1L;    protected void doGet(HttpServletRequest request, HttpServletResponse response)            throws ServletException, IOException {        try {            String username = request.getParameter("username");            String password = request.getParameter("password");            User user = new User();            user.setUsername(username);            user.setUsername(password);            UserService userService = new UserService();            User existUser = userService.login(user);        } catch (Exception e) {            e.printStackTrace();        }    }    protected void doPost(HttpServletRequest request, HttpServletResponse response)            throws ServletException, IOException {        doGet(request, response);    }}请问代码中的异常已经抛出了 为神恶魔还要try catch;它俩有什么不同,以及什么时候用, 什么时候一起用?

Answer 1

他声明的异常只是servlet 和io 异常，但你看他通过try catch 捕捉的是所有异常！