Request 的学习

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（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
】

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()
】

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);
    }
}