Request

备注：该技术博客的内容是我根据技术视频整理与总结的（并非复制粘贴）。原视频源于黑马JavaWeb课程

一、Request原理

首先，我们要掌握request和response对象的原理

  1.  1.request和response对象是由服务器创建的。我们来使用他们呢
  2.  2.request对象是来获取请求消息，response对象是来设置响应消息

这样才能更好地指导这两个对象怎么去学习，他们是做什么的。我们通过画图的方式来讲解：
Request - 图1

  1. 首先，请求会携带请求消息找demo1资源，可以找到
  2. 因为我们在服务器端有一个Servlet配置的urlpatten是/demo1     (@WebServlet（“/demo1”）)
  3. 所以找到了这个类，然后Tomcat会自动执行service方法
  5. 我们聊聊这个过程：
  6. 1.Tomcat服务器会根据请求url中的资源路径（/demo1）去创建对应的SerlvetDemo1对象
  7. 2.Tomcat服务器会创建两个对象，分别是request和response对象。request对象中封装请求消息数据
  8. 3.tomcat将request和response两个对象传递service方法，并且去调用service方法
  9. 4.我们可以来操作通过request对象获取请求消息数据，可以通过response对象设置响应消息数据
  10. 5.服务器在给浏览器做出响应之前会从response对象中去拿程序员设置的响应消息数据

接下来，我们来学request对象获取请求消息
但是学习它之前我们先说一说request继承体系结构

二、Request继承体系结构

  1. ServletRequest                --接口
  2.         |    继承关系
  3. HttpServlet Request            --接口
  4.         |    实现关系
  5. org.apache.catalina.connector.RequestFacade

org.apache.catalina.connector.RequestFacade是一个类，实现了HTTPServlet接口。
这个类是Tomcat编写的，Tomcat将来通过这个类来创建Request对象，并且传递给service方法。

三、Request对象的功能

获取请求消息数据：

  1. 获取请求行数据
  1. 请求行：
  2. GET /day14/demo1?name=zhangsan HTTP/1.1
  4. 获取数据方法：
  5. 1.获取请求方式：GET
  6. String getMehtod()
  8. 2.获取虚拟目录(重点掌握)：/day14
  9. String getContextPath()
  11. 3.获取Servlet路径：/demo1
  12. String getServletPath()
  14. 4.获取get方式的请求参数：name=zhangsan
  15. String getQueryString()
  17. 5.获取请求的URI（重点掌握）：/day14/demo1
  18. String getRequestURI(): /day14/demo1
  19. StringBuffer getRequestURL(): http://localhost/day14/demo1
  21. URL：统一资源定位符    http://localhost/day14/demo1  （相当于中华人民共和国）
  22. URI：统一资源标识符    /day14/demo1    （相当于共和国）
  24. 6.获取协议及版本： HTTP/1.1
  25. String getProtocol()
  27. 7.获取客户机的IP地址:
  28. String getRemoteAddr()

代码演示：

  1. package cn.itcast.web.request;
  3. import javax.servlet.ServletException;
  4. import javax.servlet.annotation.WebServlet;
  5. import javax.servlet.http.HttpServlet;
  6. import javax.servlet.http.HttpServletRequest;
  7. import javax.servlet.http.HttpServletResponse;
  8. import javax.swing.*;
  9. import java.io.IOException;
  11. /**
  12.  * 演示Request对象获取请求行数据
  13.  */
  15. @WebServlet("/requestDemo1")
  16. public class RequestDemo1 extends HttpServlet {
  17.     protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
  19.     }
  21.     protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
  23.         //1.获取请求方式：
  24.         String method = request.getMethod();
  25.         System.out.println(method);
  26.         //2.获取虚拟目录(重点掌握)：
  27.         String contextPath = request.getContextPath();
  28.         System.out.println(contextPath);
  29.         //3.获取Servlet路径：
  30.         String servletPath = request.getServletPath();
  31.         System.out.println(servletPath);
  32.         //4.获取get方式的请求参数：
  33.         String queryString = request.getQueryString();
  34.         System.out.println(queryString);
  35.         //5.获取请求的URI（重点掌握）:
  36.         String requestURI = request.getRequestURI();
  37.         StringBuffer requestURL = request.getRequestURL();
  38.         System.out.println(requestURI);
  39.         System.out.println(requestURL);
  40.         //6.获取协议及版本：
  41.         String protocol = request.getProtocol();
  42.         System.out.println(protocol);
  43.         //7.获取客户机的IP地址:
  44.         String remoteAddr = request.getRemoteAddr();
  45.         System.out.println(remoteAddr);
  46.     }
  47. }

输出结果如下：

  1. GET
  2. /day14
  3. /requestDemo1
  4. name=zhangsan
  5. /day14/requestDemo1
  6. http://localhost/day14/requestDemo1
  7. HTTP/1.1
  8. 0:0:0:0:0:0:0:1
  1. 获取请求头数据
  1. 获取方法：
  2. 1.(重点掌握)String getHeader(String name)：通过请求头的名称获取请求头的值
  3. 2.Enumeration<String> getHeaderNames()：获取所有的请求头名称

代码演示：

  1. package cn.itcast.web.request;
  3. import javax.servlet.ServletException;
  4. import javax.servlet.annotation.WebServlet;
  5. import javax.servlet.http.HttpServlet;
  6. import javax.servlet.http.HttpServletRequest;
  7. import javax.servlet.http.HttpServletResponse;
  8. import java.io.IOException;
  10. @WebServlet("/requestDemo4")
  11. public class RequestDemo4 extends HttpServlet {
  12.     protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
  14.     }
  16.     protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
  17.         //演示获取请求头数据:referer
  18.         String referer = request.getHeader("referer");
  19.         System.out.println(referer);//http://localhost/day14/login.html
  21.         //防盗链
  22.         if (referer != null){
  23.             if (referer.contains("/day14")){
  24.                 //正常访问
  25.                 System.out.println("播放电影...");
  26.             }else{
  27.                 //盗链
  28.                 System.out.println("想看电影吗？来优酷吧....");
  29.             }
  30.         }
  31.     }
  32. }
  1. 获取请求体数据
  1. 请求体：只有POST请求方式，才有请求体，在请求体中封装了POST请求的请求参数
  3. 获取请求体步骤：
  4. 1.获取流对象
  5. BufferedReader getReader():获取字符输入流，只能操作字符数据 （此博客演示这个方法）
  6. ServletInputSream getInputStream():获取字节输入流，可以操作任何类型数据（在文件上传知识点后讲解）
  8. 2.再从流对象中拿数据

代码展示：

  1. package cn.itcast.web.request;
  3. import javax.servlet.ServletException;
  4. import javax.servlet.annotation.WebServlet;
  5. import javax.servlet.http.HttpServlet;
  6. import javax.servlet.http.HttpServletRequest;
  7. import javax.servlet.http.HttpServletResponse;
  8. import java.io.BufferedReader;
  9. import java.io.IOException;
  11. @WebServlet("/requestDemo5")
  12. public class RequestDemo5 extends HttpServlet {
  13.     protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
  14.         //获取请求消息体--请求参数
  15.         //1.获取字符流
  16.         BufferedReader br = request.getReader();
  17.         //2.读取数据
  18.         String line = null;
  19.         while ((line = br.readLine()) != null){
  20.             System.out.println(line);
  21.         }
  22.     }
  24.     protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
  26.     }
  27. }

四、其他功能

  1. 获取请求参数通用方式：不论get还是post请求方式都可以使用下列方式方法来获取请求参数。
  1. 1.String getParameter(String name):根据参数名称获取参数值    (常用)
  2. 2.String[] getParameterValues(String name):根据参数名称获取数值的数组 
  3. 3.Enumeration<String> getParameterNames():获取所有请求的参数名称
  4. 4.Map<String,String[]> getParameterMap():获取所有参数的map集合    (常用)

代码演示这四个方法：

  1. 第一个方法：
  3. @WebServlet("/requestDemo6")
  4. public class RequestDemo6 extends HttpServlet {
  5.     protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
  6.         //post 获取请求参数
  7.         //根据参数名称获取参数值
  8.         String username = request.getParameter("username");
  9.         System.out.println("post");
  10.         System.out.println(username);
  11.     }
  13.     protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
  14.         //get 获取请求参数
  15.         /*//根据参数名称获取参数值
  16.         String username = request.getParameter("username");
  17.         System.out.println("get");
  18.         System.out.println(username);*/
  19.         this.doPost(request,response);
  20.     }
  21. }
  24. ================================================================================
  25. 第二个方法：
  27. @WebServlet("/requestDemo6")
  28. public class RequestDemo6 extends HttpServlet {
  29.     protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
  30.         //post 获取请求参数
  31.         //根据参数名称获取参数值
  32.         String username = request.getParameter("username");
  33.        /*System.out.println("post");
  34.         System.out.println(username);*/
  36.         //根据参数获取参数值的数组
  37.         String[] hobbies = request.getParameterValues("hobby");
  38.         for (String hobby : hobbies) {
  39.             System.out.println(hobby);
  40.         }
  41.     }
  43.     protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
  44.         //get 获取请求参数
  45.         /*//根据参数名称获取参数值
  46.         String username = request.getParameter("username");
  47.         System.out.println("get");
  48.         System.out.println(username);*/
  49.         this.doPost(request,response);
  50.     }
  51. }
  54. ================================================================================
  55. 第三个方法：
  57. @WebServlet("/requestDemo6")
  58. public class RequestDemo6 extends HttpServlet {
  59.     protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
  60.         //post 获取请求参数
  61.         //根据参数名称获取参数值
  62.         String username = request.getParameter("username");
  63.        /*System.out.println("post");
  64.         System.out.println(username);*/
  66.         //根据参数获取参数值的数组
  67.         String[] hobbies = request.getParameterValues("hobby");
  68.         /*for (String hobby : hobbies) {
  69.             System.out.println(hobby);
  70.         }*/
  72.         //获取所有请求的参数名称
  73.         Enumeration<String> parameterNames = request.getParameterNames();
  74.         while (parameterNames.hasMoreElements()){
  75.             String name = parameterNames.nextElement();
  76.             System.out.println(name);
  77.             String value = request.getParameter(name);
  78.             System.out.println(value);
  79.             System.out.println("------------------------------------");
  80.         }
  81.     }
  83.     protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
  84.         //get 获取请求参数
  85.         /*//根据参数名称获取参数值
  86.         String username = request.getParameter("username");
  87.         System.out.println("get");
  88.         System.out.println(username);*/
  89.         this.doPost(request,response);
  90.     }
  91. }
  94. ================================================================================
  95. 第四个方法：
  97. @WebServlet("/requestDemo6")
  98. public class RequestDemo6 extends HttpServlet {
  99.     protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
  100.         //post 获取请求参数
  101.         //根据参数名称获取参数值
  102.         String username = request.getParameter("username");
  103.        /*System.out.println("post");
  104.         System.out.println(username);*/
  106.         //根据参数获取参数值的数组
  107.         String[] hobbies = request.getParameterValues("hobby");
  108.         /*for (String hobby : hobbies) {
  109.             System.out.println(hobby);
  110.         }*/
  112.         //获取所有请求的参数名称
  113.         Enumeration<String> parameterNames = request.getParameterNames();
  114.         /*while (parameterNames.hasMoreElements()){
  115.             String name = parameterNames.nextElement();
  116.             System.out.println(name);
  117.             String value = request.getParameter(name);
  118.             System.out.println(value);
  119.             System.out.println("------------------------------------");*/
  121.         //获取所有参数的map集合
  122.         Map<String, String[]> parameterMap = request.getParameterMap();
  123.         //遍历
  124.         Set<String> keyset = parameterMap.keySet();
  125.         for (String name : keyset) {
  126.             //根据键获取值
  127.             String[] values = parameterMap.get(name);
  128.             System.out.println(name);
  129.             for (String value : values) {
  130.                 System.out.println(value);
  131.             }
  132.             System.out.println("-----------------------");
  133.         }
  134.     }
  137.     protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
  138.         //get 获取请求参数
  139.         /*//根据参数名称获取参数值
  140.         String username = request.getParameter("username");
  141.         System.out.println("get");
  142.         System.out.println(username);*/
  143.         this.doPost(request,response);
  144.     }
  145. }
  1. 请求转发：一种在服务器内部的资源跳转方式
  1. 1.步骤：
  2.     1.通过request对象来获取请求转发器对象：RequestDispatcher getRequestDispatcher(String path)
  3.     2.使用RequestDispatcher对象来进行转发：forward(ServletRequest request,ServletResponse response)
  5. 2.特点：
  6.     1.浏览器地址栏路径不发生变化
  7.     2.只能转发到当前的服务器内部资源中
  8.     3.转发是一次请求

代码演示：

  1. //RequestDemo8类
  2. @WebServlet("/requestDemo8")
  3. public class RequestDemo8 extends HttpServlet {
  4.     protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
  5.         System.out.println("demo8888被访问了...");
  6.         //转发到demo9资源
  7.         /*RequestDispatcher requestDispatcher = request.getRequestDispatcher("/requestDemo9");
  8.         requestDispatcher.forward(request,response);*/
  10.         request.getRequestDispatcher("/requestDemo9").forward(request,response);
  11.     }
  14.     protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
  16.         this.doPost(request,response);
  17.     }
  18. }
  19. =========================================================================================
  20. //RequestDemo9类
  21. @WebServlet("/requestDemo9")
  22. public class RequestDemo9 extends HttpServlet {
  23.     protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
  24.         System.out.println("demo9999被访问了...");
  25.     }
  28.     protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
  30.         this.doPost(request,response);
  31.     }
  32. }
  1. 共享数据：
  1. 域对象：一个有作用范围的对象，可以在范围内共享数据。
  2. request域：代表一次请求的范围，一般用于请求转发的多个资源中共享数据
  4. 方法：
  5.     1.void setAttribute(String name,Object obj):存储数据
  6.     2.Object getAttribute(String name):通过键获取值
  7.     3.void remove Attribute(String name):通过键移除键值对
  9. 1234567

代码演示：

  1. //RequestDemo8类
  2. @WebServlet("/requestDemo8")
  3. public class RequestDemo8 extends HttpServlet {
  4.     protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
  5.         System.out.println("demo8888被访问了...");
  6.         //转发到demo9资源
  7.         /*RequestDispatcher requestDispatcher = request.getRequestDispatcher("/requestDemo9");
  8.         requestDispatcher.forward(request,response);*/
  10.         //存储数据到request域中
  11.         request.setAttribute("msg","hello");
  13.         request.getRequestDispatcher("/requestDemo9").forward(request,response);
  14.         /*request.getRequestDispatcher("http://www.itcast.cn").forward(request,response);*/
  15.     }
  18.     protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
  20.         this.doPost(request,response);
  21.     }
  22. }
  23. =========================================================================================
  24. //RequestDemo9类
  25. @WebServlet("/requestDemo9")
  26. public class RequestDemo9 extends HttpServlet {
  27.     protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
  29.         //获取数据
  30.         Object msg = request.getAttribute("msg");
  31.         System.out.println(msg);
  33.         System.out.println("demo9999被访问了...");
  34.     }
  37.     protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
  39.         this.doPost(request,response);
  40.     }
  41. }
  1. 获取ServletContext对象(有个印象即可)
  1. 1.ServletContext getServletContext()
  3. 1

代码如下：

  1. @WebServlet("/requestDemo10")
  2. public class RequestDemo10 extends HttpServlet {
  3.     protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
  5.         ServletContext servletContext = request.getServletContext();
  6.         System.out.println(servletContext);
  7.     }
  10.     protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
  12.         this.doPost(request,response);
  13.     }
  14. }

五、解决中文乱码问题：

  1. get方式：tomcat8以上的版本已经将get方式乱码问题解决了
  3. post方式：会乱码
  4. 解决：在获取参数前，设置request的编码        request.setCharacterEncoding("urf-8");

代码演示如下：

  1. @WebServlet("/requestDemo7")
  2. public class RequestDemo7 extends HttpServlet {
  3.     protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
  4.         //1.设置流的编码
  5.         request.setCharacterEncoding("utf-8");
  8.         //获取请求参数username
  9.         String username = request.getParameter("username");
  10.         System.out.println(username);
  12.     }
  15.     protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
  17.         this.doPost(request,response);
  18.     }
  19. }