Requset

request：后台服务器（Tomcat）会对HTTP请求中的数据进行解析，并把解析结果存入到request对象

Requset获取请求数据

请求行：GET /request-demo/req1?username=zhangsan HTTP/1.1
- String getMethod()获取请求方式：GET
- String getContextPath()获取虚拟目录（项目访问路径）：/request-demo
- String getRequestURI()获取URI（统一资源标识符）：/request-demo/req1
- StringBuffer getRequestURL()获取URL（同一资源定位符）：http://localhost:8080/request-demo/req1
- String getQueryString()获取请求参数（get方式）：username=zhangsan HTTP/1.1

请求头：

String getHeader(String name)

//获取浏览器的版本信息
String agent = request.getHeader("user-agent");

请求体（post方式）：
- 字节文件用：request.getInputStream()
- 纯文本用：request.getReader()

@WebServlet(value = "/Demo1")
public class Demo1Request extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //get请求
        System.out.println("请求方式 = " + request.getMethod());
        System.out.println("项目访问路径 = " + request.getContextPath());
        System.out.println("URI = " + request.getRequestURI());
        System.out.println("URL = " + request.getRequestURL());
        System.out.println("请求参数 = " + request.getQueryString());
        System.out.println("浏览器版本 = " + request.getHeader("user-agent"));
    }

    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //post请求
        //doGet(request, response);
        BufferedReader reader = request.getReader();
        String s = reader.readLine();
        System.out.println("POST请求参数 = " + s);
    }
}

//ufferedReader流是通过request对象来获取的，当请求完成后request对象就会被销毁，request对象被销毁后，BufferedReader流就会自动关闭，所以此处就不需要手动关闭流了

通用方式获取请求参数

GET 请求方式和 POST 请求方式区别主要在于获取请求参数的方式不一样，request对象已经将获取请求参数的方法进行了封装，将请求参数进行了分割，存入到Map<String,String[]>集合中

@WebServlet(value = "/Demo2")
public class Demo2Request extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //get请求
        //Tomcat8.0之后，已将GET请求乱码问题解决，设置默认的解码方式为UTF-8
        //POST的请求参数是通过request的getReader()来获取流中的数据，tomcat在获取流的时候采用的编码是ISO-8859-1，而该字符集是不支持中文的
        //需要解决POST请求中文乱码问题
        String method = request.getMethod();
        if (method.equalsIgnoreCase("post")) {
            request.setCharacterEncoding("UTF-8");
        }

        //获取单个参数对应的值
        String name = request.getParameter("username");
        System.out.println("username = " + name);
        //获取单个参数对应的数组
        String[] hobbies = request.getParameterValues("hobby");
        System.out.println("hobbies = " + Arrays.toString(hobbies));

        //获取所有参数的Map集合
        Map<String, String[]> map = request.getParameterMap();
        map.forEach((key, values) -> {
            System.out.println(key + ":" + Arrays.toString(values));
        });

    }

    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //post请求
        doGet(request, response);
    }
}

请求转发

请求转发（forward）：一种在==服务器内部==的资源跳转方式
- 浏览器只发出一次请求，URL不改变
- 只能转发到当前服务器内部的资源
- 可以在转发的资源间共享数据

//实现方式
request.getRequestDispatcher("资源B路径").forward(request,response);

//A资源
@WebServlet(value = "/a")
public class A_Servlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        //设置资源共享（要在转发前面）
        request.setAttribute("name","zhangsan");
        //请求转发
        request.getRequestDispatcher("b").forward(request,response);
    }

//B资源
@WebServlet(value = "/b")
public class B_Servlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        //接受共享的资源
        Object name = request.getAttribute("name");
        System.out.println("name = " + name);
    }

Response

常用方法

@WebServlet(value = "/Demo3")
public class Demo3Response extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        /**Response获取的字符输出流默认编码ISO-8859-1
         * 解决中文乱码问题：
         * 1.设置响应类型为：text/html
         * 2.设置编码格式：charset=utf-8
         */
        response.setContentType("text/html;charset=utf-8");

        //设置响应行
        response.setStatus(404);
        //设置响应头
        response.setHeader("content-type","text/html");

        //获取响应字符输出流
        PrintWriter writer = response.getWriter();
        //写数据
        writer.write("<h1 align='center'>你好 Demo4</h1>");
    }
    //该流不需要关闭，随着响应结束，response对象销毁，由服务器关闭

IOUtils工具类

导入坐标

<dependency>
  <groupId>commons-io</groupId>
  <artifactId>commons-io</artifactId>
  <version>2.11.0</version>
</dependency>

使用IOUtils工具类进行输出

@WebServlet(value = "/Demo5")
public class Demo5Servlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //get请求
        FileInputStream fis = new FileInputStream("F:\\java_code\\JavaSE182\\day12.03_Request_Response\\src\\main\\webapp\\imgs\\Desert.jpg");
        ServletOutputStream os = response.getOutputStream();

//        byte[] bytes = new byte[1024 * 8];
//        int len;
//        while ((len = fis.read(bytes)) != -1) {
//            os.write(bytes, 0, len);
//        }

        IOUtils.copy(fis,os);

        fis.close();
    }

Response重定向

重定向（redirect）：一种资源跳转方式
- 浏览器发出两次请求，URL发生改变
- 可以重定向到任意位置的资源（服务器内部、外部均可）
- 不能在资源间共享数据

//实现方式1
response.setStatus(302);
response.setHeader("location","资源B的路径");
//实现方式2
response.sendRedirect("资源B的路径");

路径问题

一般来说，在服务器内部进行跳转不需要添加"/"，一般只有使用@WebServlet("/demo")一定要添加"/"
从浏览器跳转需要添加"/"

登录&注册案例

@WebServlet(value = "/loginServlet")
public class LoginServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //get请求
        //解决中文报错
        request.setCharacterEncoding("utf-8");
        response.setContentType("text/html;charset=utf-8");
        //获取请求参数
        String username = request.getParameter("username");
        String password = request.getParameter("password");
        //调用Mapper查询用户信息
        SqlSession sqlSession = MyBatisUtils.openSqlSession();
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        User user = mapper.select(username, password);
        //输出登录信息
        PrintWriter writer = response.getWriter();
        if (user == null) {
            writer.write("登录失败，用户名或密码错误！");
        } else {
            writer.write("欢迎" + username + "登录成功！");
        }
        //释放资源
        sqlSession.close();
    }

@WebServlet(value = "/registerServlet")
public class RegisterServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //get请求
        //解决中文报错
        request.setCharacterEncoding("utf-8");
        response.setContentType("text/html;charset=utf-8");
        //获取请求参数
        String username = request.getParameter("username");
        String password = request.getParameter("password");
        //调用mapper进行判断
        SqlSession sqlSession = MyBatisUtils.openSqlSession();
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        User user = mapper.selectByName(username);
        PrintWriter writer = response.getWriter();
        if (user == null) {
            mapper.addUser(username,password);
            //【提交事务】
            sqlSession.commit();
            writer.write("恭喜"+username+"注册成功！");
        }else {
            writer.write("该用户名已经存在，请重新注册");
        }
        //释放资源
        sqlSession.close();
    }

public interface UserMapper {
    @Select("select * from tb_user where username=#{uname} and password=#{psw}")
    User select(@Param("uname") String username, @Param("psw") String password);

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

    @Insert("insert into tb_user values (null,#{username},#{password})")
    void addUser(@Param("username")String username, @Param("password")String password);
}

Day24-Request+Response

Requset

Requset获取请求数据

通用方式获取请求参数

请求转发

Response

Response重定向

路径问题

登录&注册案例

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