Request 的学习

1. request对象和response对象的原理
   1. request和response对象是由服务器创建的。我们来使用它们
   2. request对象是来获取请求消息，response对象是来设置响应消息
   
   
2. request对象继承体系结构：   
   

   ServletRequest    --接口
       |    继承
   HttpServletRequest-- 接口
       |    实现
   org.apache.catalina.connector.RequestFacade 类(tomcat)

   ---

3. request功能
   1. 获取请求消息数据
   【1. 获取请求行数据
   

   * GET /day14/demo1?name=zhangsan HTTP/1.1（这是一个例子）
   * 方法：
       1. 获取请求方式 ：GET
           * String getMethod()  
       2. (*)获取虚拟目录：/day14
           * String getContextPath()
       3. 获取Servlet路径: /demo1
           * String getServletPath()
       4. 获取get方式请求参数：name=zhangsan
           * String getQueryString()
       5. (*)获取请求URI：/day14/demo1
           * String getRequestURI():        /day14/demo1
           * StringBuffer getRequestURL()  :http://localhost/day14/demo1
   
           * URL:统一资源定位符 ： http://localhost/day14/demo1    中华人民共和国
           * URI：统一资源标识符 :/day1/demo1        共和国
                       
       6. 获取协议及版本：HTTP/1.1
           * String getProtocol()
   
       7. 获取客户机的IP地址：
           * String getRemoteAddr()

   】
   
   【2.获取请求头数据
   * 方法：
                       * (*)String getHeader(String name):通过请求头的名称获取请求头的值
                       * Enumeration<String> getHeaderNames():获取所有的请求头名称
   】
   
   【3.获取请求体数据
   * 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
                   * 步骤：
                       1. 获取流对象
                           *  BufferedReader getReader()：获取字符输入流，只能操作字符数据
                           *  ServletInputStream getInputStream()：获取字节输入流，可以操作所有类型数据
                       2. 再从流对象中拿数据
   】
   

   ---

   
   
   
4. 其他功能
   
   【1.获取其他请求参数（通用方式）也就是兼容GET和POST方法
   1. String getParameter(String name):根据参数名称获取参数值
   2. String[] getParameterValues(String name):根据参数名称获取参数值的数组
   3. Enumeration<String> getParameterNames():获取所有请求的参数名称
   4. Map<String,String[]> getParameterMap():获取所有参数的map集合
   5.this.doPost(request,response);【在dopost中写代码，doget用此方法调用】
   
   * 中文乱码问题：
                       * get方式：tomcat 8 已经将get方式乱码问题解决了
                       * post方式：会乱码
                           * 解决：在获取参数前，设置request的编码request.setCharacterEncoding("utf-8");
   】
   
   【2.请求转发：一种在服务器内部的资源跳转方式
                   1.步骤：
                       1. 通过request对象获取请求转发器对象：RequestDispatcher getRequestDispatcher(String path)【资源路径/访问路径/也就是转发的地方】
                       2. 使用RequestDispatcher对象来进行转发：forward(ServletRequest request, ServletResponse response)
                           一般使用一行（写在doGet或doPost）【request.getRequestDispatcher("~~~~").forward(request,response);】
   
                   2. 特点：
                       1. 浏览器地址栏路径不发生变化
                       2. 只能转发到当前服务器内部资源中。
                       3. 转发是一次请求
   】
   
   【3.共享数据：
   * 域对象：一个有作用范围的对象，可以在范围内共享数据
                   * 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
                   * 方法：
                       1. void setAttribute(String name,Object obj):存储数据
                       2. Object getAttitude(String name):通过键获取值
                       3. void removeAttribute(String name):通过键移除键值对
   】
   
   【4.获取ServletContext
   * ServletContext getServletContext()
   】
   
   
   
5. 实操
   步骤：启动IDEA==》new Servlet==》修改注解配置==》在方法下编写
   

   获取请求行数据
   
   package cn.itcast.web.request;
   
   import javax.servlet.ServletException;
   import javax.servlet.annotation.WebServlet;
   import javax.servlet.http.HttpServlet;
   import javax.servlet.http.HttpServletRequest;
   import javax.servlet.http.HttpServletResponse;
   import java.io.IOException;
   
   /**
    * 演示Request对象获取请求行数据
    */
   
   @WebServlet("/requestDemo1")
   public class RequestDemo1 extends HttpServlet {
       protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
   
       }
   
       protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
           /*
               1. 获取请求方式 ：GET
                   * String getMethod()
               2. (*)获取虚拟目录：/day14
                   * String getContextPath()
               3. 获取Servlet路径: /requestDemo1
                   * String getServletPath()
               4. 获取get方式请求参数：name=zhangsan
                   * String getQueryString()
               5. (*)获取请求URI：/day14/demo1
                   * String getRequestURI():        /day14/requestDemo1
                   * StringBuffer getRequestURL()  :http://localhost/day14/requestDemo1
               6. 获取协议及版本：HTTP/1.1
                   * String getProtocol()
   
               7. 获取客户机的IP地址：
                   * String getRemoteAddr()
   
            */
           //1. 获取请求方式 ：GET
           String method = request.getMethod();
           System.out.println(method);
           //2.(*)获取虚拟目录：/day14
           String contextPath = request.getContextPath();
           System.out.println(contextPath);
           //3. 获取Servlet路径: /demo1
           String servletPath = request.getServletPath();
           System.out.println(servletPath);
           //4. 获取get方式请求参数：name=zhangsan
           String queryString = request.getQueryString();
           System.out.println(queryString);
           //5.(*)获取请求URI：/day14/demo1
           String requestURI = request.getRequestURI();
           StringBuffer requestURL = request.getRequestURL();
           System.out.println(requestURI);
           System.out.println(requestURL);
           //6. 获取协议及版本：HTTP/1.1
           String protocol = request.getProtocol();
           System.out.println(protocol);
           //7. 获取客户机的IP地址：
           String remoteAddr = request.getRemoteAddr();
           System.out.println(remoteAddr);
       }
   }

   获取请求头数据
   
   package cn.itcast.web.request;
   
   import javax.servlet.ServletException;
   import javax.servlet.annotation.WebServlet;
   import javax.servlet.http.HttpServlet;
   import javax.servlet.http.HttpServletRequest;
   import javax.servlet.http.HttpServletResponse;
   import java.io.IOException;
   import java.util.Enumeration;
   
   @WebServlet("/requestDemo2")
   public class RequestDemo2 extends HttpServlet {
       protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
   
       }
   
       protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
           //演示获取请求头数据
           
           //1.获取所有请求头名称
           Enumeration<String> headerNames = request.getHeaderNames();
           //2.遍历
           while(headerNames.hasMoreElements()){
               String name = headerNames.nextElement();
               //根据名称获取请求头的值
               String value = request.getHeader(name);
               System.out.println(name+"---"+value);
           }
   
       }
   }

   获取请求头数据2
   package cn.itcast.web.request;
   
   import javax.servlet.ServletException;
   import javax.servlet.annotation.WebServlet;
   import javax.servlet.http.HttpServlet;
   import javax.servlet.http.HttpServletRequest;
   import javax.servlet.http.HttpServletResponse;
   import java.io.IOException;
   import java.util.Enumeration;
   
   @WebServlet("/requestDemo3")
   public class RequestDemo3 extends HttpServlet {
       protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
   
       }
   
       protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
           //演示获取请求头数据:user-agent
   
           String agent = request.getHeader("user-agent");
           //判断agent的浏览器版本
           if(agent.contains("Chrome")){
               //谷歌
               System.out.println("谷歌来了...");
           }else if(agent.contains("Firefox")){
               //火狐
               System.out.println("火狐来了...");
           }
   
       }
   }

   获取请求头数据3
   package cn.itcast.web.request;
   
   import javax.servlet.ServletContext;
   import javax.servlet.ServletException;
   import javax.servlet.annotation.WebServlet;
   import javax.servlet.http.HttpServlet;
   import javax.servlet.http.HttpServletRequest;
   import javax.servlet.http.HttpServletResponse;
   import java.io.IOException;
   
   @WebServlet("/requestDemo4")
   public class RequestDemo4 extends HttpServlet {
       protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
   
       }
   
       protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
           //演示获取请求头数据:referer
   
           String referer = request.getHeader("referer");
           System.out.println(referer);//http://localhost/day14/login.html
   
           //防盗链
           if(referer != null ){
               if(referer.contains("/day14")){
                   //正常访问
                  // System.out.println("播放电影....");
                   response.setContentType("text/html;charset=utf-8");
                   response.getWriter().write("播放电影....");
               }else{
                   //盗链
                   //System.out.println("想看电影吗？来优酷吧...");
                   response.setContentType("text/html;charset=utf-8");
                   response.getWriter().write("想看电影吗？来优酷吧...");
               }
           }
   
       }
   }

   获取请求体数据
   package cn.itcast.web.request;
   
   import javax.servlet.ServletException;
   import javax.servlet.annotation.WebServlet;
   import javax.servlet.http.HttpServlet;
   import javax.servlet.http.HttpServletRequest;
   import javax.servlet.http.HttpServletResponse;
   import java.io.BufferedReader;
   import java.io.IOException;
   
   @WebServlet("/requestDemo5")
   public class RequestDemo5 extends HttpServlet {
       protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
           //获取请求消息体--请求参数
   
           //1.获取字符流
           BufferedReader br = request.getReader();
           //2.读取数据？？
           String line = null;
           while((line = br.readLine()) != null){
               System.out.println(line);
           }
   
       }
   
       protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
       }
   }

   获取其他请求参数（通用方式）
   package cn.itcast.web.request;
   
   import javax.servlet.ServletException;
   import javax.servlet.annotation.WebServlet;
   import javax.servlet.http.HttpServlet;
   import javax.servlet.http.HttpServletRequest;
   import javax.servlet.http.HttpServletResponse;
   import java.io.BufferedReader;
   import java.io.IOException;
   import java.util.Enumeration;
   import java.util.Map;
   import java.util.Set;
   
   @WebServlet("/requestDemo6")
   public class RequestDemo6 extends HttpServlet {
       protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
           //post 获取请求参数
   
           //根据参数名称获取参数值
           String username = request.getParameter("username");
          /* System.out.println("post");
           System.out.println(username);*/
   
          //根据参数名称获取参数值的数组
           String[] hobbies = request.getParameterValues("hobby");
           /*for (String hobby : hobbies) {
               System.out.println(hobby);
           }*/
   
           //获取所有请求的参数名称
   
           Enumeration<String> parameterNames = request.getParameterNames();
           /*while(parameterNames.hasMoreElements()){
               String name = parameterNames.nextElement();
               System.out.println(name);
               String value = request.getParameter(name);
               System.out.println(value);
               System.out.println("----------------");
           }*/
   
           // 获取所有参数的map集合
           Map<String, String[]> parameterMap = request.getParameterMap();
           //遍历
           Set<String> keyset = parameterMap.keySet();
           for (String name : keyset) {
               
               //获取键获取值
               String[] values = parameterMap.get(name);
               System.out.println(name);
               for (String value : values) {
                   System.out.println(value);
               }
   
               System.out.println("-----------------");
           }
   
   
       }
   
       protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
           //get 获取请求参数
   /*
           //根据参数名称获取参数值
           String username = request.getParameter("username");
           System.out.println("get");
           System.out.println(username);*/
   
           this.doPost(request,response);
       }
   }

   中文乱码问题
   package cn.itcast.web.request;
   
   import javax.servlet.ServletException;
   import javax.servlet.annotation.WebServlet;
   import javax.servlet.http.HttpServlet;
   import javax.servlet.http.HttpServletRequest;
   import javax.servlet.http.HttpServletResponse;
   import java.io.IOException;
   import java.util.Enumeration;
   import java.util.Map;
   import java.util.Set;
   
   @WebServlet("/requestDemo7")
   public class RequestDemo7 extends HttpServlet {
       protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
           //1.设置流的编码
           request.setCharacterEncoding("utf-8");
   
           //获取请求参数username
           String username = request.getParameter("username");
   
           System.out.println(username);
       }
   
       protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
   
           this.doPost(request,response);
       }
   }

   请求转发/共享数据
   package cn.itcast.web.request;
   
   import javax.servlet.RequestDispatcher;
   import javax.servlet.ServletException;
   import javax.servlet.annotation.WebServlet;
   import javax.servlet.http.HttpServlet;
   import javax.servlet.http.HttpServletRequest;
   import javax.servlet.http.HttpServletResponse;
   import java.io.IOException;
   
   @WebServlet("/requestDemo8")
   public class RequestDemo8 extends HttpServlet {
       protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
           System.out.println("demo8888被访问了。。。");
           //转发到demo9资源
   /*
           RequestDispatcher requestDispatcher = request.getRequestDispatcher("/requestDemo9");
           requestDispatcher.forward(request,response);
           */
   
           //存储数据到request域中
           request.setAttribute("msg","hello");
   
           request.getRequestDispatcher("/requestDemo9").forward(request,response);
           //request.getRequestDispatcher("http://www.itcast.cn").forward(request,response);
   
       }
   
       protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
   
           this.doPost(request,response);
       }
   }
   
   
   package cn.itcast.web.request;
   
   import javax.servlet.ServletException;
   import javax.servlet.annotation.WebServlet;
   import javax.servlet.http.HttpServlet;
   import javax.servlet.http.HttpServletRequest;
   import javax.servlet.http.HttpServletResponse;
   import java.io.IOException;
   
   @WebServlet("/requestDemo9")
   public class RequestDemo9 extends HttpServlet {
       protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
   
           //获取数据
           Object msg = request.getAttribute("msg");
           System.out.println(msg);
   
           System.out.println("demo9999被访问了。。。");
   
       }
   
       protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
   
           this.doPost(request,response);
       }
   }
   
   
   

   获取ServletContext
   package cn.itcast.web.request;
   
   import javax.servlet.ServletContext;
   import javax.servlet.ServletException;
   import javax.servlet.annotation.WebServlet;
   import javax.servlet.http.HttpServlet;
   import javax.servlet.http.HttpServletRequest;
   import javax.servlet.http.HttpServletResponse;
   import java.io.IOException;
   
   @WebServlet("/requestDemo10")
   public class RequestDemo10 extends HttpServlet {
       protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
   
   
           ServletContext servletContext = request.getServletContext();
   
           System.out.println(servletContext);
   
       }
   
       protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
   
           this.doPost(request,response);
       }
   }