@WebServlet(name = "ServletTest")
public class ServletTest extends HttpServlet {

  @Override
  public void init(ServletConfig config) throws ServletException {
    super.init(config);
  }

  @Override
  public void init() throws ServletException {
    super.init();
  }

  @Override
  public void service(ServletRequest req, ServletResponse res) throws ServletException, IOException {
    //super.service(req, res);
    String username=req.getParameter("username");
    String password=req.getParameter("password");
    System.out.println(username);
    System.out.println(password);

  }

  @Override
  public void destroy() {
    super.destroy();
  }

  @Override
  protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    super.doPost(req, resp);
  }

  @Override
  protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    super.doGet(req, resp);
  }
}

<form action="<%= request.getContextPath() %>/loginServlet" method="post">
  用户名：<input type="text" name="username"><br/>
  密码：<input type="password" name="password"><br/>
  <input type="submit" value="登录">
  <input type="reset" value="重置">
</form>

<servlet>
       <servlet-name>LoginServlet</servlet-name>
       <servlet-class>com.myServlet.ServletTest</servlet-class>
     </servlet>

     <servlet-mapping>
       <servlet-name>LoginServlet</servlet-name>
       <url-pattern>/loginServlet</url-pattern>
     </servlet-mapping>