Request继承体系 

Request 获取请求数据

getContextPath() 会用的比较多 

请求体中方法代码：

BufferedReader br =req.getReader();

String line =br.readline();

sout(line);

就可以得到请求体了

 Servlet模板可以在file settings  editer  files and template  点other 下拉到web  找到使用注解创建Servlet的那个模板就可以修改了

Request 请求转发 

response

 

 

 用resp.sendRedirect()就是简化了前面的两步

路径问题

 

 

 

用户登录案例

loginServlet:

@WebServlet("/loginServlet")
public class LoginServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //接收用户名和密码
        String username = request.getParameter("username");
        String password = request.getParameter("password");
        //调用mybatis完成查询
        //加载核心配置文件 获取sqlSessionFactory对象
        String resource = "mybatis_config.xml";
        InputStream inputStream = Resources.getResourceAsStream(resource);
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        //获取sqlSession对象
        SqlSession sqlSession = sqlSessionFactory.openSession();
        //获取brandMapper接口的代理对象 执行语句
        UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
        User user =userMapper.select(username,password);
        //释放资源
        sqlSession.close();

        //获取字符输出流，并设置content type
         response.setContentType("text/html;charset=utf-8");
        PrintWriter writer = response.getWriter();
        //判断user是否为null
        if (user!=null){
            writer.write("登陆成功");
        }else {
            writer.write("登录失败");
        }


    }

    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
this.doGet(request,response);
    }
}

简易HTML

    
    



  
登录
  
输入用户名
 
    
输入密码


    


没有账号？点击注册

 用户注册

注册的servlet:

@WebServlet("/registerServlet")
public class RegisterServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //接收用户名和密码
        String username = request.getParameter("username");
        String password = request.getParameter("password");

        User user = new User();
        user.setUsername(username);
        user.setPassword(password);
        //调用mybatis完成查询
        //加载核心配置文件 获取sqlSessionFactory对象
        String resource = "mybatis_config.xml";
        InputStream inputStream = Resources.getResourceAsStream(resource);
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        //获取sqlSession对象
        SqlSession sqlSession = sqlSessionFactory.openSession();
        //获取brandMapper接口的代理对象 执行语句
        UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
        User user1 =userMapper.selectByUsername(username);

        //获取字符输出流，并设置content type
         response.setContentType("text/html;charset=utf-8");
        PrintWriter writer = response.getWriter();
        //判断user是否为null
        if (user1==null){
            //用户名不存在，添加数据
            userMapper.add(user);
            writer.write("注册成功");
            //提交事务
            sqlSession.commit();

            //释放资源
            sqlSession.close();
        }else {
            writer.write("用户名已存在");
        }


    }

    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
this.doGet(request,response);
    }
}

UserMapper:

public interface UserMapper {
    //根据用户名跟密码查询对象
    @Select("select * from tb_user where username=#{username} and password=#{password}")
    User select(@Param("username") String username, @Param("password")String password);

    @Select("select * from tb_user where username=#{username}")
    User selectByUsername(@Param("username") String username);

    @Insert("insert into tb_user (username, password) values (#{username},#{password})")
    void add(User user);
}

简易html：

    
    



  
登录
  
输入用户名
 
  
输入密码

  
  


已有账号？点击登录

代码优化

 也就是将这三行，包装成一个工具类，因为只创建一次，所以就使用静态代码块

静态代码块无法抛出异常，我们可以用try catch

代码：创建工厂对象

public class SqlSessionFactoryUtils {

    private static final SqlSessionFactory sqlSessionFactory;
    //静态代码块随着类的加载自动执行，且只执行一次
    static {
        String resource = "mybatis_config.xml";
        InputStream inputStream = null;
        try {
            inputStream = Resources.getResourceAsStream(resource);
        } catch (IOException e) {
            throw new RuntimeException(e);
        }
         sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
    }

    public static SqlSessionFactory getSqlSessionFactory() {
        return sqlSessionFactory;
    }
}

后续要使用的时候，直接用 SqlSessionFactoryUtils.getSqlSessionFactory就可以了