LoginServlet.java ~~~ package zyw.web; import zyw.bean.User; import zyw.service.UserService; import javax.servlet.ServletException; import javax.servlet.annotation.WebServlet; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import java.io.IOException; import java.sql.SQLException; @WebServlet(name = "LoginServlet",urlPatterns = "/login") public class LoginServlet extends HttpServlet { protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { String name = request.getParameter("name"); String password = request.getParameter("password"); UserService userService=new UserService(); User user=null; try { //调用service中登录方法 user = userService.login(name, password); } catch (SQLException e) { e.printStackTrace(); } if (user!=null){ //登录成功跳转生鲜种类列表界面 response.sendRedirect(request.getContextPath()+"/category-list.jsp"); }else { //登录失败提示 response.setContentType("text/html;charset=utf-8"); response.getWriter().write("用户登录失败"); } } protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { } } ~~~ UserService.java ~~~ package zyw.service; import zyw.bean.User; import zyw.dao.UserDao; import java.sql.SQLException; public class UserService { //1. 判断注册用户是否存在 public boolean register(String name,String password,String email) { boolean register=false; UserDao userDao = new UserDao(); boolean checkUser = userDao.checkUser(name); //2. 如果不存在就将用户信息添加到数据库 if (checkUser) { register = userDao.register(name,password,email); } return register; } public User login(String name, String password) throws SQLException { UserDao userDao=new UserDao(); User user = userDao.login(name, password); return user; } } ~~~ UserDao.java ~~~ package zyw.dao; import com.mchange.v2.c3p0.ComboPooledDataSource; import org.apache.commons.dbutils.QueryRunner; import org.apache.commons.dbutils.handlers.BeanHandler; import zyw.bean.User; import java.sql.SQLException; public class UserDao { /** * 检查用户是否存在 * @param name * @return */ public boolean checkUser(String name){ try { ComboPooledDataSource dataSource=new ComboPooledDataSource(); QueryRunner queryRunner=new QueryRunner(dataSource); String sql="select name from user where name=?"; User user = queryRunner.query(sql, new BeanHandler<User>(User.class),name); //如果没有查询到数据 说明这个用户名没有注册过 if (user==null) { return true; }else { return false; } } catch (SQLException e) { e.printStackTrace(); return false; } } /** * 用户注册 * @param * @return */ public boolean register(String name,String password,String email) { try { ComboPooledDataSource dataSource=new ComboPooledDataSource(); QueryRunner queryRunner=new QueryRunner(dataSource); String sql="insert into user values(null,?,?,?)"; int row = queryRunner.update(sql, name,password, email); //行数大于零说明注册成功 if (row>0) { return true; }else { return false; } } catch (SQLException e) { e.printStackTrace(); return false; } } /** * 用户登录 */ public User login(String name, String password) throws SQLException { ComboPooledDataSource dataSource=new ComboPooledDataSource(); QueryRunner queryRunner=new QueryRunner(dataSource); String sql="select * from user where name=? and password=?"; User user = queryRunner.query(sql, new BeanHandler<User>(User.class),name,password); return user; } } ~~~ 结果，如果账号密码正确，则跳转category-list.jsp页面，如果错误