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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

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)

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			* 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 : /day14/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()

示例代码

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.(*重点)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.(*重点)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);    }}

2. 获取请求头数据			* 方法：				* (*重点)String getHeader(String name):通过请求头的名称获取请求头的值				* Enumeration
   
     getHeaderNames():获取所有的请求头名称
   

获取所有请求头名称

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
   
     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:user-agent

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...");        }    }}

防止盗链示例代码

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...");            }        }    }}

防止盗链前端代码

    
           
   
  
            
            
        
   
   
demo4...  
   

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						* 在文件上传知识点后讲解				2. 再从流对象中拿数据

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 {
       }}

前端代码

## request其他功能（重点掌握）

2. 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法来获取请求参数			1. String getParameter(String name):根据参数名称获取参数值    username=zs&password=123			2. String[] getParameterValues(String name):根据参数名称获取参数值的数组  hobby=xx&hobby=game			3. Enumeration
   
     getParameterNames():获取所有请求的参数名称			4. Map
    
      getParameterMap():获取所有参数的map集合			* 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");
    
   

demo6与demo7的前端代码

    
           
   
        
    
    
        
    
    
        
    游戏        
    学习        
    
        
        
   

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");   //只能获取到1个参数       /* 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");   //获取前端标签name为hobby的值，一般为复选框        /*for (String hobby : hobbies) {            System.out.println(hobby);        }*/        //获取所有请求的参数名称        Enumeration
   
     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
    
      parameterMap = request.getParameterMap();        //遍历        Set
     
       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);    }}
     
    
   

注意对于复选框，getParameter只能获得一个参数，前端的标签name=hobby有两个选项，一个为game，一个对study。但getParameter方法只获得第一个

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);    }}

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)				2. 使用RequestDispatcher对象来进行转发：forward(ServletRequest request, ServletResponse 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

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);    }}

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);    }}

4. 获取ServletContext：			* ServletContext getServletContext()

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);    }}

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