Request

Request继承体系

Request获取请求数据

获取请求数据

通用方式获取请求参数

@WebServlet("/req1")
public class req1 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //System.out.println("get...");
        // 获取所有参数的Map集合
        Map<String, String[]> parameterMap = req.getParameterMap();
        for (String s : parameterMap.keySet()) {
            System.out.print(s+":");
            String[] strings = parameterMap.get(s);
            for (String string : strings) {
                System.out.print(string+" ");
            }
            System.out.println();
        }
        // 根据key获取参数值。数组
        System.out.println("----------------");
        String[] hobbies = req.getParameterValues("hobby");
        for (String hobby : hobbies) {
            System.out.println(hobby);
        }
        // 根据key获取单个参数值
        System.out.println("-------------------");
        String username = req.getParameter("username");
        String password = req.getParameter("password");
        System.out.println(username);
        System.out.println(password);
    }

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

请求参数中文乱码

@WebServlet("/req2")
public class req2 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        String username = request.getParameter("username");
        username = new String(username.getBytes(StandardCharsets.ISO_8859_1),StandardCharsets.UTF_8);
        System.out.println(username);
    }

    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        request.setCharacterEncoding("UTF-8");
        this.doGet(request, response);
    }
}

Request请求转发

Response

Response设置响应数据功能介绍

Response完成重定向

目录问题

动态获取虚拟目录：

Response响应字符数据

@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    // 设置解析方式,和字符集
    //response.setHeader("content-type","text/html");
    response.setContentType("text/html;charset=utf-8");
    // 获取流
    PrintWriter writer = response.getWriter();
    writer.write("<h1>侯一鸣</h1>");
}

Response响应字节数据

    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        // 读取文件
        FileInputStream fis = new FileInputStream("d://桌面/1.png");

        // 获取response的输出流
        ServletOutputStream os = response.getOutputStream();

        // 完成流的拷贝
//        byte[] bytes = new byte[1024];
//        int len = 0;
//        while ((len = fis.read(bytes)) != -1){
//            os.write(bytes,0,len);
//        }
        IOUtils.copy(fis,os);
        fis.close();
    }

案例

用户登录

编写LoginServlet方法

@WebServlet("/loginServlet")
public class loginServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        String username = request.getParameter("username");
        String password = request.getParameter("password");

        //调用maybatis查询
        String resource = "mybatis-config.xml";
        InputStream inputStream = Resources.getResourceAsStream(resource);
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);

        SqlSession sqlSession = sqlSessionFactory.openSession();
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        User user = mapper.select(username, password);
        sqlSession.close();

        // 判断
        response.setContentType("text/html;charset=utf-8");
        PrintWriter writer = response.getWriter();
        if(user != null){
            writer.write("登陆成功");
        }else{
            writer.write("登陆失败");
        }
    }

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

用户注册

registerServlet

@WebServlet("/registerServlet")
public class registerServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        String username = request.getParameter("username");
        String password = request.getParameter("password");

        User user = new User();
        user.setUsername(username);
        user.setPassword(password);

        String resource = "mybatis-config.xml";
        InputStream inputStream = Resources.getResourceAsStream(resource);
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        SqlSession sqlSession = sqlSessionFactory.openSession();
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);

        User u = mapper.selectByUsername(username);
        response.setContentType("text/html;charset=utf-8");
        PrintWriter writer = response.getWriter();
        if (u == null){
            mapper.add(user);
            sqlSession.commit();// 增删改需要提交事务
            sqlSession.close();
            writer.write("注册成功");
        }else{
            writer.write("用户名已存在");
        }
    }

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

SqlSessionFactory工具类抽取

package com.houyiming.util;

import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;

import java.io.IOException;
import java.io.InputStream;

public class SqlSessionFactoryUtils {

    private static SqlSessionFactory sqlSessionFactory;

    static {
        // 静态代码块会随着类的加载自动执行，且只执行一次
        try {
            String resource = "mybatis-config.xml";
            InputStream inputStream = Resources.getResourceAsStream(resource);
            sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

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

可以用一行代码代替原来的三行

// 原来的三行
String resource = "mybatis-config.xml";
InputStream inputStream = Resources.getResourceAsStream(resource);
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);


// 新的一行
SqlSessionFactory sqlSessionFactory = SqlSessionFactoryUtils.getSqlSessionFactory();
= "mybatis-config.xml";
InputStream inputStream = Resources.getResourceAsStream(resource);
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);


// 新的一行
SqlSessionFactory sqlSessionFactory = SqlSessionFactoryUtils.getSqlSessionFactory();