HTTP&Request学习笔记
1）HTTP 概念
- 概念：Hyper Text Transfer Protocol 超文本传输协议
- *传输协议：定义了，客户端和服务器端通信时，发送数据的格式
- 特点：
1. 基于TCP/IP的高级协议【也是安全协议】
2. 默认端口号:80
3. 基于请求/响应模型的:一次请求对应一次响应【响应和请求是一一对应的】
4. 无状态的：每次请求之间相互独立，不能交互数据 - 历史版本：
* 1.0：每一次请求响应都会建立新的连接
* 1.1：复用连接
2）Request [请求消息]数据格式
请求行
请求方式 请求url 请求协议/版本 ---->> GET /login.html HTTP/1.1
* 请求方式：
* HTTP协议有7中请求方式，常用的有2种
* GET：
1. 请求参数在请求行中，在url后。
2. 请求的url长度有限制的
3. 不太安全
* POST：
1. 请求参数在请求体中
2. 请求的url长度没有限制的
3. 相对安全
请求头
请求头：客户端浏览器告诉服务器一些信息；
请求头名称： 请求头值；
常见的请求头：
1. User-Agent
User-Agent：浏览器告诉服务器，我访问你使用的浏览器版本信息；
可以在服务器端获取该头的信息，解决浏览器的兼容性问题
【在服务器端获取请求头信息，根据不同的浏览器版本相应不同的信息，使用户通过不同的浏览器访问同一个资源看到相同的响应布局和结果，以此来解决浏览器的兼容性问题】
2. Referer
http://localhost/login.html
告诉服务器，我(当前请求)从哪里来？
服务器知道从哪里来的作用：
1. 防盗链：【防止盗取超链接，只有请求头从“优酷首页”才可以正常播放】
2. 统计工作：【300W广告费，统计流量来源来判断哪里做广告效果好】
请求空行
空行，就是用于分割POST请求的请求头和请求体的
请求体(正文)
封装POST请求消息的请求参数的
字符串格式：
POST /login.html HTTP/1.1
Host: localhost
User-Agent: Mozilla/5.0 (Windows NT 6.1; Win64; x64; rv:60.0) Gecko/20100101 Firefox/60.0
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
Accept-Language: zh-CN,zh;q=0.8,zh-TW;q=0.7,zh-HK;q=0.5,en-US;q=0.3,en;q=0.2
Accept-Encoding: gzip, deflate
Referer: http://localhost/login.html
Connection: keep-alive
Upgrade-Insecure-Requests: 1
3）Request [请求消息] 原理
调用过程如下图：
注意事项：
- request和response对象是由服务器创建的。我们来使用它们；
- request对象是来获取请求消息，response对象是来设置响应消息
4）Request [请求消息] 体系结构
ServletRequest – 接口
| 继承
HttpServletRequest – 接口
| 实现
org.apache.catalina.connector.RequestFacade – 类(tomcat)
5）Request [请求消息] 功能
5.1 获取请求消息数据
5.1.1 获取请求行数据
GET /day14/demo1?name=zhangsan HTTP/1.1
方法如下：
- 获取请求方式 ：GET
String getMethod() - 【重要】获取虚拟目录：/day14
String getContextPath() - 获取Servlet路径: /demo1
String getServletPath() - 获取get方式请求参数：name=zhangsan
String getQueryString() - 【重要】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 - 获取协议及版本：HTTP/1.1
String getProtocol() - 获取客户机的IP地址：
String getRemoteAddr()
代码展示：
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 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: /requestDemo1
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/requestDemo1
String requestURI = request.getRequestURI();
StringBuffer requestURL = request.getRequestURL();
System.out.println(requestURI); // /day14/requestDemo1
System.out.println(requestURL); // http://localhost/day14/requestDemo1
//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); // 0:0:0:0:0:0:0:1
}
}
输出：
5.1.2 获取请求头数据
方法如下：
- 【重要】通过请求头的名称获取请求头的值
String getHeader(String name) - 获取所有的请求头名称
Enumeration getHeaderNames()
代码展示1：演示获取请求头数据
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);
}
}
}
输出：
代码展示2：演示获取请求头数据:user-agent【浏览器兼容问题解决方案】
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...");
}
}
}
输出：
代码展示3：演示获取请求头数据:referer【防盗链】 RequestDemo4.java
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...");
}
}
}
}
login.html
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Title</title>
</head>
<body>
<form action="/demo3" method="POST">
<input name="username">
<input type="submit" value="提交">
</form>
<hr>
<a href="/day14/requestDemo4">demo4...</a>
</body>
</html>
5.1.3 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：
- 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 - 再从流对象中拿数据
代码展示：获取请求消息体–请求参数 RequestDemo5.java
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 {
}
}
regist.html
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>注册页面</title>
</head>
<body>
<form action="/day14/requestDemo5" method="post">
<input type="text" placeholder="请输入用户名" name="username"><br>
<input type="text" placeholder="请输入密码" name="password"><br>
<input type="submit" value="注册">
</form>
</body>
</html>
输出：
5.2 其他功能
5.2.1 获取请求参数通用方式
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
- 根据参数名称获取参数值 ---- username=zs&password=123
String getParameter(String name) - 根据参数名称获取参数值的数组 ---- hobby=xx&hobby=game
String[] getParameterValues(String name) - 获取所有请求的参数名称
Enumeration getParameterNames() - 获取所有参数的map集合
Map<String,String[]> getParameterMap()
代码展示：演示获取请求参数 RequestDemo6.java
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) {
//根据键获取值
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);
}
}
regist2.html
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>注册页面</title>
</head>
<body>
<form action="/day14/requestDemo6" method="post">
<input type="text" placeholder="请输入用户名" name="username"><br>
<input type="text" placeholder="请输入密码" name="password"><br>
<input type="checkbox" name="hobby" value="game">游戏
<input type="checkbox" name="hobby" value="study">学习
<br>
<input type="submit" value="注册">
</form>
</body>
</html>
输出：
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”)
代码展示：演示中文乱码 RequestDemo7.java
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);
}
}
输出：
5.2.2 请求转发
请求转发：一种在服务器内部的资源跳转方式
步骤：
- 通过request对象获取请求转发器对象 — RequestDispatcher
getRequestDispatcher(String path) - 使用RequestDispatcher对象来进行转发
forward(ServletRequest request, ServletResponse response)
特点：
- 浏览器地址栏路径不发生变化；
- 只能转发到当前服务器内部资源中；
- 转发是一次请求
代码展示：演示请求转发 RequestDemo8.java
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);
一般将上面两句合并为下面的 getRequestDispatcher("/requestDemo9").forward(request,response)
*/
request.getRequestDispatcher("/requestDemo9").forward(request,response);
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
this.doPost(request,response);
}
}
RequestDemo9.java
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 {
System.out.println("demo9999被访问了。。。");
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
this.doPost(request,response);
}
}
输出：
5.2.3 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：
- 存储数据
void setAttribute(String name,Object obj) - 通过键获取值
Object getAttitude(String name) - 通过键移除键值对
void removeAttribute(String name)
代码展示：演示共享数据 RequestDemo8.java
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。。。");
//存储数据到request域中
request.setAttribute("msg","hello");
request.getRequestDispatcher("/requestDemo9").forward(request,response);
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
this.doPost(request,response);
}
}
RequestDemo9.java
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);
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
this.doPost(request,response);
}
}
输出：
5.2.4 获取ServletContext
ServletContext getServletContext()
代码展示：获取ServletContext RequestDemo10.java
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 {
// 获取ServletContext
ServletContext servletContext = request.getServletContext();
System.out.println(servletContext);
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
this.doPost(request,response);
}
}
输出：
————————————————————————————————————————————
内容来源：《学习传智播客的课程《JavaWeb+黑马旅游网》》
关注公众号，回复 【算法】，获取高清算法书！
扫一扫
被折叠的 条评论
为什么被折叠?
到【灌水乐园】发言
