使用Servlet3.0注解开发

首先建立servlet3.0 版的web.xml

因为servlet3.0支持注解开发

所以web.xml只保留个模板就好

也可以增加一个默认页的配置

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://java.sun.com/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" version="3.0" >
    <welcome-file-list>
        <welcome-file>login.jsp</welcome-file>
    </welcome-file-list>
</web-app>

我在这里定义了一个login.jsp的默认页

之后不需要在这配置servlet及映射，直接在类上打注解

@WebServlet(name="LoginServlet",value="/LoginServlet")
public class LoginServlet extends HttpServlet{
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        req.getRequestDispatcher("/login.jsp").forward(req,resp);
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        String username = req.getParameter("username");//获取表单用户名密码
        String password = req.getParameter("password");
        if (username.equals("SoDa") && password.equals("SoDa")){
            Double balance  = new Double("0.0");//判定成功初始化存储session
            HttpSession session = req.getSession();
            session.setAttribute("balance",balance);//把初始化的session放进去
            req.getRequestDispatcher("/index.jsp").forward(req,resp);
        }else{
            //验证失败放一个错误信息到前台显示
            req.setAttribute("error","Your Username or Password is wrong!!");
            req.getRequestDispatcher("/login.jsp").forward(req,resp);
        }

    }

效果等同于在web.xml中定义

  <servlet>
        <servlet-name>LoginServlet</servlet-name>
        <servlet-class>cn.edu.hyit.atm.web.LoginServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>LoginServlet</servlet-name>
        <url-pattern>/LoginServlet</url-pattern>
    </servlet-mapping>