【Java】Servlet中的Request对象

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<String> 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<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: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

<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Title</title>
</head>
<body>
<form action="/demo3" method="POST"> <!-- 这个表单不用点-->
<input name="username">
<input type="submit" value="提交">

</form>
<hr>

<a href="/day14/requestDemo4">demo4...</a> <!-- 点这个链接-->

</body>
</html>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

<!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>

## 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<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

* 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

<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>注册页面</title>
</head>
<body>
<form action="/day14/requestDemo7" 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>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<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);
}
}

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
防止中文乱码

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;
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);
}
}