4. 这里我们主要关注web层，基于servlet去实现登录和注册
   db中已经创建了user表，插入一行数据即可

登录功能实现

其实就是简单的CRUD实现

需要注意的是

1. 我们通过request.getParameter获取请求数据
2. PrintWriter writer = response.getWriter();返回响应数据
3. Mapper的实现方便我们直接定义sql语句
4. 通过 User user = userMapper.select(username, password);返回值进行业务逻辑判断

/*** 登录*/
@WebServlet("/loginServlet")
public class LoginServlet extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {//1. 接收用户名和密码String username = request.getParameter("username");String password = request.getParameter("password");//2. 调用MyBatis完成查询//2.1 获取SqlSessionFactory对象/* String resource = "mybatis-config.xml";InputStream inputStream = Resources.getResourceAsStream(resource);SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);*/SqlSessionFactory sqlSessionFactory = SqlSessionFactoryUtils.getSqlSessionFactory();//2.2 获取SqlSession对象SqlSession sqlSession = sqlSessionFactory.openSession();//2.3 获取MapperUserMapper userMapper = sqlSession.getMapper(UserMapper.class);//2.4 调用方法User user = userMapper.select(username, password);//2.5 释放资源sqlSession.close();//获取字符输出流，并设置content typeresponse.setContentType("text/html;charset=utf-8");PrintWriter writer = response.getWriter();//3. 判断user释放为nullif(user != null){// 登陆成功writer.write("登陆成功");}else {// 登陆失败writer.write("登陆失败");}}@Overrideprotected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {this.doGet(request, response);}
}

注册功能实现

/*** 注册* 观察log功能，我们其实可以发现，sqlfactory这一工具类频繁被创建和释放* 手动操作太多，同时累赘得重复代码并不优雅* 这个可以通过装饰器、工厂等设计模式来实现** 所以Spring框架应运而生*/
@WebServlet("/registerServlet")
public class RegisterServlet extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {//1. 接收用户数据String username = request.getParameter("username");String password = request.getParameter("password");//封装用户对象User user = new User();user.setUsername(username);user.setPassword(password);//2. 调用mapper 根据用户名查询用户对象//2.1 获取SqlSessionFactory对象/* String resource = "mybatis-config.xml";InputStream inputStream = Resources.getResourceAsStream(resource);SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);*/SqlSessionFactory sqlSessionFactory = SqlSessionFactoryUtils.getSqlSessionFactory();//2.2 获取SqlSession对象SqlSession sqlSession = sqlSessionFactory.openSession();//2.3 获取MapperUserMapper userMapper = sqlSession.getMapper(UserMapper.class);//2.4 调用方法User u = userMapper.selectByUsername(username);//3. 判断用户对象释放为nullif( u == null){// 用户名不存在，添加用户userMapper.add(user);// 提交事务sqlSession.commit();// 释放资源sqlSession.close();}else {// 用户名存在，给出提示信息response.setContentType("text/html;charset=utf-8");response.getWriter().write("用户名已存在");}}@Overrideprotected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {this.doGet(request, response);}
}

5. 结果展示
   

总结

这里是基本的CRUD功能展示，需要注意的就是表单的创建和提交

    
LOGIN IN
Username:
Password:
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