request与response

作用:   往浏览器写东西

组成部分:  响应行 响应头 响应体

操作响应行 
        格式: 协议/版本 状态码 状态码说明

状态码:
    1xx:已发送请求
    2xx:已完成响应
        200:正常响应
    3xx:还需浏览器进一步操作
        302:重定向 配合响应头:location
        304:读缓存
    4xx:用户操作错误
        404:用户操作错误.
        405:访问的方法不存在
    5xx:服务器错误
        500:内部异常

常用方法:
    setStatus(int 状态码):针对于 1xx  2xx  3xx 

了解 :sendError(int 状态码):针对于 4xx和5xx

常用的方法:
    setHeader(String key,String value):设置字符串形式的响应头
    了解:setIntHeader(String key,int value):设值整形的响应头
    了解:setDateHeader(String key,long value):设值时间的响应头
            
    addHeader(String key,String value):添加字符串形式的响应头 之前设置过则追加,若没有设置过则设置
    了解:addIntHeader(String key,int value):添加整形的响应头
    了解:addDateHeader(String key,long value):添加时间的响应头

常用的响应头:
    location:重定向
    refresh:定时刷新
    content-type:设置文件的mime类型,设置响应流的编码及告诉浏览器用什么编码打开
    content-disposition:文件下载

重定向:    
    方式1:
        ★response.sendRedirect("/day10/loc2");
    方式2:
        response.setStatus(302);
        respooen.setHeader("location","/day10/loc2");

<servlet>
      <servlet-name>SHServlet1</servlet-name>
      <servlet-class>com.hjh.request_response.SHServlet1</servlet-class>
  </servlet>
  <servlet-mapping>
      <servlet-name>SHServlet1</servlet-name>
      <url-pattern>/servlet1</url-pattern>
  </servlet-mapping>

<servlet>
    <servlet-name>SHServlet2</servlet-name>
    <servlet-class>com.hjh.request_response.SHServlet2</servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>SHServlet2</servlet-name>
    <url-pattern>/servlet2</url-pattern>
  </servlet-mapping>

package com.hjh.request_response;

import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class SHServlet1 extends HttpServlet {
    private static final long serialVersionUID = 1L;

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
            //重定向方式一
        //1.设置状态码
        response.setStatus(302);
        //2.设置响应头
        //response.setHeader("location", "/Servlet/servlet2");
        
        
        //重定向方式二：设置响应头
        response.sendRedirect("/Servlet/servlet2");
        
    }

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

package com.hjh.request_response;

import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class SHServlet2 extends HttpServlet {
    private static final long serialVersionUID = 1L;

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        response.setContentType("text/html;charset=utf-8");
        response.getWriter().print("跳转到这里啦，哈哈哈");
    }

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

定时刷新:
    方案1:设置头 refresh 
        respooen.setHeader("refresh","秒数;url=跳转的路径");
    方案2:http的meta标签
        <meta http-equiv="refresh" content="3;url=/day10/refresh2.html">