Request 和 Response 原理

2023-08-19 12:27:34

* Request 和 Response 原理：

   * request对象和response对象由服务器创建，我们只需要在service方法中使用这两个对象即可

   * 继承体系结构：
       ServletRequest <--继承-- HttpServletRequest <--实现--- RequestFacade

* Response：封装响应消息，设置响应消息
   * 设置响应行：HTTP/1.1 200 ok
       * setStatus(int code)：设置响应状态码
           * 演示重定向：302
               //简化版的重定向
               response.sendRedirect("http://192.168.1.66:8080/zxc/one");

               * 实现原理
               //1.设置响应状态码为 302
               response.setStatus(302);
               //2.设置响应头 location
               response.setHeader("location", "http://192.168.1.66:8080/zxc/one");

   * 设置响应头：
       * setHeader(String name,String value):
       * setDateHeader(String name, long date)
       * setIntHeader(String name, int value)

* 设置响应体：
       * getOutputStream():发送字节数据
           * 验证码：
               * 防止恶意注册

       * getWriter():发送字符数据
           * 发送中文数据时，需要在获取流之前设置编码方式，并且要告诉客户端浏览器，服务器使用的编码方式
               //简化版设置编码的方式
               response.setContentType("text/html;charset=utf-8");

 package Response;

 import java.io.IOException;

 import java.io.PrintWriter;

 import javax.servlet.ServletException;

 import javax.servlet.http.HttpServlet;

 import javax.servlet.http.HttpServletRequest;

 import javax.servlet.http.HttpServletResponse;

 public class ResponseTest extends HttpServlet {

     private static final long serialVersionUID = -3007244764565301466L;

     public void doGet(HttpServletRequest request, HttpServletResponse response)

             throws ServletException, IOException {

     /*

      * 设置响应消息体：

      *     getOutputStream():发送字节数据

      *     getWriter():发送字符数据

      */

         /*

         //设置流的编码方式

         response.setCharacterEncoding("utf-8");

         //告诉客户端，服务器使用的编码方式

         response.setHeader("content-type", "text/html;charset=utf-8");

         */

         //设置编码方式

         response.setContentType("text/html;charset=utf-8");

         //获取字符输出流

         PrintWriter pw = response.getWriter();//默认编码是 iso-8859-1

         //设置数据

         pw.write("<h3>你好啊 ！ response...</h3>");

         //刷新

         pw.flush();

     }

     public void doPost(HttpServletRequest request, HttpServletResponse response)

             throws ServletException, IOException {

         this.doGet(request, response);

     }

 }

* Request：封装请求消息，获取请求消息
   * 获取请求消息：
       * 获取请求行：GET /day08/req1?name=zs HTTP/1.1
           * getMethod():获取请求方式
           * getContextPath():获取虚拟目录

           * getRequestURI():获取URI(统一资源标识符)   /day07/one       /one
           * getRequestURL():获取URL(统一资源定位符)   http://localhost:8080/day07/one
           * getRemoteAddr():获取客户机的IP地址

           * getQueryString():get方式获取请求参数
       * 获取请求头：
           * String getHeader(String name)
           * long getDateHeader(String name)
           * int getIntHeader(String name)

 package Request;

 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 RequestTest2 extends HttpServlet {

     private static final long serialVersionUID = -5095708647887091449L;

     public void doGet(HttpServletRequest request, HttpServletResponse response)

             throws ServletException, IOException {

         //获取请求头

         String agent = request.getHeader("user-agent");

         System.out.println(agent);

         if(agent.contains("MSIE")){

             System.out.println("IE  来了...");

         }else if(agent.contains("Firefox")){

             System.out.println("火狐   来了...");

         }else if(agent.contains("Chrome")){

             System.out.println("谷歌    来了...");

         }else{

             System.out.println("其他浏览器  来了...");

         }

         System.err.println("..............................");

     }

     public void doPost(HttpServletRequest request, HttpServletResponse response)

             throws ServletException, IOException {

         this.doGet(request, response);

     }

 }

* 获取请求体：封装post请求参数数据
           * BufferedReader getReader():
           * ServletInputStream getInputStream():


           * 通用的获取请求参数的方式：
               * String getParameter(String name):根据键名获取值
               * String[] getParameterValues(String name):根据键名获取值的数组，一般用于复选框
               * Map<String,String[]> getParameterMap():获取所有参数的map集合
               * Enumeration getParameterNames():获取所有的键名枚举

 package Request;

 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 RequestTest extends HttpServlet {

     private static final long serialVersionUID = 4919849090529066482L;

     public void doGet(HttpServletRequest request, HttpServletResponse response)

             throws ServletException, IOException {

         //演示获取请求行数据

         System.out.println(request.getMethod());//获取请求发式

         System.out.println(request.getContextPath());//获取虚拟目录

         System.out.println(request.getRequestURI());//获取URI

         System.out.println(request.getRequestURL());//获取URL

         System.out.println(request.getRemoteAddr());//获取ip

         System.out.println(request.getQueryString());//获取请求参数

         System.out.println(request.getProtocol());//获取协议

         System.err.println("--------------------------");

         response.sendRedirect(request.getContextPath()+"/index.jsp");

     }

     public void doPost(HttpServletRequest request, HttpServletResponse response)

             throws ServletException, IOException {

         this.doGet(request, response);

     }

 }

* 请求参数中文乱码问题：
               1.通用：
                   //1.解码 iso
                   byte[] bytes = username.getBytes("iso-8859-1");
                   //2.编码 utf-8
                   username = new String(bytes, "utf-8");
               2.post专用
                   //设置输入流的编码为 utf-8
                   request.setCharacterEncoding("utf-8");

   * 域对象：代表一次请求

   * 请求转发：
       * 转发特点：
           1.地址栏不发生变化
           2.一次请求，一次响应
           3.不能转发外部站点

 package Request;

 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 RequestTest7 extends HttpServlet {

     private static final long serialVersionUID = 3744695995118989884L;

     public void doGet(HttpServletRequest request, HttpServletResponse response)

             throws ServletException, IOException {

         System.out.println("req7 被访问了。。。");

         //存储数据

         request.setAttribute("msg", "hehehe...");

         //转发至req

         request.getRequestDispatcher("/req").forward(request, response);

     }

     public void doPost(HttpServletRequest request, HttpServletResponse response)

             throws ServletException, IOException {

         this.doGet(request, response);

     }

 }

* 重定向的特点：
           1.地址栏发生变化
           2.两次请求，两次响应
           3.可以访问外部的站点

 package 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 ResponseTest2 extends HttpServlet {

     /**

      *

      */

     private static final long serialVersionUID = -449184946348811489L;

     public void doGet(HttpServletRequest request, HttpServletResponse response)

             throws ServletException, IOException {

         System.out.println("resp2 被访问了。。。");

         //演示重定向

         //1.设置相应状态码 302

         response.setStatus(302);

         //2.设置相应头  location

         //注意： http:// 不可以少

         //response.setHeader("location", "http://192.168.1.66:8080/zxc/resp");

         //简化版的重定向

         response.sendRedirect("http://192.168.1.66:8080/zxc/resp");

     }

     public void doPost(HttpServletRequest request, HttpServletResponse response)

             throws ServletException, IOException {

         this.doGet(request, response);

     }

 }

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