Request和Response学习笔记2

Request 获取请求行数据

获取方法

String getMethod()
// 获取请求方式

String getContextPath()
// 获取虚拟目录

String getServletPath()
// 获取Servlet路径

String getRequestURI()
StringBuffer getRequestURL()
// 获取请求URI、URL

String getProtocol()
// 获取协议及版本

String getRemoteAddr()
// 获取客户机的IP地址

URI & URL 的说明：

URL：统一资源定位符
URI：统一资源标识符

如：

例子1
- http://localhost/stringbug/demo1 —— URL
- /stringbug/demo1 —— URI
例子2
- 中华人民共和国 —— URL
- 共和国 —— URI

创建一个类，继承HttpServlet类

package study.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("/study/request/demo01")
public class RequestDemo01 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp)
            throws ServletException, IOException {
    }
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp)
            throws ServletException, IOException {
    }
}

String getMethod() 方法

protected void doGet(HttpServletRequest req, HttpServletResponse resp)
        throws ServletException, IOException {
    // String getMethod() 获取请求方式
    System.out.println(req.getMethod());
}

String getContextPath() 方法

protected void doGet(HttpServletRequest req, HttpServletResponse resp)
        throws ServletException, IOException {
    // String getContextPath() 获取虚拟目录
    System.out.println(req.getContextPath());
}

String getServletPath() 方法

protected void doGet(HttpServletRequest req, HttpServletResponse resp)
        throws ServletException, IOException {
    // String getServletPath() 获取Servlet路径
    System.out.println(req.getServletPath());
}

String getRequestURI()、StringBuffer getRequestURL() 方法

protected void doGet(HttpServletRequest req, HttpServletResponse resp)
        throws ServletException, IOException {
    // String getRequestURI() 获取请求URI
    // StringBuffer getRequestURL() 获取请求URL
    System.out.println(req.getRequestURI());
    System.out.println(req.getRequestURL());
}

String getProtocol() 方法

protected void doGet(HttpServletRequest req, HttpServletResponse resp)
        throws ServletException, IOException {
    // String getProtocol() 获取协议及版本
    System.out.println(req.getProtocol());
}

String getRemoteAddr() 方法

protected void doGet(HttpServletRequest req, HttpServletResponse resp)
        throws ServletException, IOException {
    // String getRemoteAddr() 获取客户机的IP地址
    System.out.println(req.getRemoteAddr());
}

创建一个html文件

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Request Study</title>
</head>
<body>
    <form action="/RequestAndResponse_war_exploded/study/request/demo01" method="get">
        <input name="username">
        <input type="submit" value="get提交">
    </form>
</body>
</html>

开启服务器

用户访问：http://localhost:8080/RequestAndResponse_war_exploded/HelloRequest.html
随便输入点内容，提交，如输入：RequestTest

页面跳转到：http://localhost:8080/RequestAndResponse_war_exploded/study/request/demo01?username=RequestTest
- 获取请求方式：getMethod() 方法输出
```
GET
```
- 获取虚拟目录：getContextPath() 方法输出
```
/RequestAndResponse_war_exploded
```
- 获取Servlet路径：getServletPath() 方法输出
```
/study/request/demo01
```
- 获取请求URI：getRequestURI() 方法输出
```
/RequestAndResponse_war_exploded/study/request/demo01
```
- 获取请求URL：getRequestURL() 方法输出
```
http://localhost:8080/RequestAndResponse_war_exploded/study/request/demo01
```
- 获取协议及版本：getProtocol() 方法输出
```
HTTP/1.1
```
- 获取客户机的IP地址：getRemoteAddr() 方法输出
```
0:0:0:0:0:0:0:1
```

Request 获取请求头数据

获取方法

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

创建一个类(RequestDemo02.java)，使用这两个方法

package study.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("/study/request/demo02")
public class RequestDemo02 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp)
            throws ServletException, IOException {
        // 获取所有请求头名称
        Enumeration<String> headerNames = req.getHeaderNames();
        // Enumeration接口，功能由Iterator复制。
        while (headerNames.hasMoreElements()) {
            String headerName = headerNames.nextElement();
            // 根据请求头名称获取请求头名称的值
            String headerValue = req.getHeader(headerName);
            System.out.println(headerName + " : " + headerValue);
        }
    }
}

开启服务器

访问：http://localhost:8080/RequestAndResponse_war_exploded/study/request/demo02

控制台输出：

自己根据请求头名字获取请求头

user-agent

获取用户访问资源链接时使用的浏览器。

package study.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("/study/request/demo02")
public class RequestDemo02 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp)
            throws ServletException, IOException {
        // 演示获取请求头数据：user-agent
        String userAgentValue = req.getHeader("user-agent");
        // 判断用户使用什么浏览器发出的请求
        if (userAgentValue.contains("Chrome")) {
            System.out.println("来自谷歌浏览器的访问！！！");
        } else if (userAgentValue.contains("Firefox")) {
            System.out.println("来自火狐浏览器的访问！！！");
        } else if (userAgentValue.contains("XXX")) {
            System.out.println("来自 XXX 浏览器的访问！！！");
        }
    }
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp)
            throws ServletException, IOException {

    }
}

谷歌浏览器访问：http://localhost:8080/RequestAndResponse_war_exploded/study/request/demo02

控制台输出：

来自谷歌浏览器的访问！！！

referer

获取用户跳转到目的页面之前的那个页面的URL

package study.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("/study/request/demo02")
public class RequestDemo02 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp)
            throws ServletException, IOException {
        // 演示获取请求头数据：referer
        String refererValue = req.getHeader("referer");
        System.out.println(refererValue);
        if (refererValue.contains("/RequestAndResponse_war_exploded")) {
            System.out.println("可以正常访问");
        } else {
            System.out.println("不可以正常访问");
        }
    }
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp)
            throws ServletException, IOException {

    }
}

浏览器访问：http://localhost:8080/RequestAndResponse_war_exploded/HelloRequest02.html

点击看电影，页面跳转到：http://localhost:8080/RequestAndResponse_war_exploded/study/request/demo02?View+Name=唐人街探案3

控制台输出：

http://localhost:8080/RequestAndResponse_war_exploded/HelloRequest02.html
可以正常访问

假如不是从 /RequestAndResponse_war_exploded 资源链接中跳转过来的话，那么，控制台会输出：不可以正常访问

也可以更改上例中的部分内容，是的部分输出在页面上：

// 将这部分内容修改
System.out.println("可以正常访问");

System.out.println("不可以正常访问");

// 修改为
System.out.println("可以正常访问");
resp.setContentType("text/html;charset=utf-8");
resp.getWriter().write("你可以看电影～～～");

System.out.println("不可以正常访问");
resp.setContentType("text/html;charset=utf-8");
resp.getWriter().write("你不可以看电影～～～");

从 /RequestAndResponse_war_exploded 资源链接中跳转过来，控制台输出：
```
http://localhost:8080/RequestAndResponse_war_exploded/HelloRequest02.html
可以正常访问
```
点击看电影，页面跳转到：http://localhost:8080/RequestAndResponse_war_exploded/study/request/demo02?View+Name=唐人街探案3

页面内容如下：

Request 获取请求体的数据

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

简单实现

创建一个demo.java：RequestDemo03.java

package study.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("/study/request/demo03")
public class RequestDemo03 extends HttpServlet {
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp)
            throws ServletException, IOException {
        // 获取请求消息体
        // 1. 获取字符流
        BufferedReader reqReader = req.getReader();
        String line;
        while ((line = reqReader.readLine()) != null) {
            System.out.println(line);
        }
    }
}

创建一个html文件：login.html

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>用户登录</title>
</head>
<body>
    <form action="/RequestAndResponse_war_exploded/study/request/demo03" method="post">
        <input type="email" name="userEmail" placeholder="请输入您的邮箱"><br>
        <input type="password" name="userPassword" placeholder="请输入您的密码"><br>
        <input type="submit" value="登录">
    </form>
</body>
</html>

启动服务器，浏览器访问：http://localhost:8080/RequestAndResponse_war_exploded/login.html
点击登录，页面跳转到：http://localhost:8080/RequestAndResponse_war_exploded/study/request/demo03

控制台输出：
```
userEmail=stringbug%40icloud.com&userPassword=123456
```
浏览器页面内容：

参考文献

HttpServletRequest获取客户端所有参数
[JavaEE-HttpServletRequest总结](

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原文地址：https://www.cnblogs.com/liyihua/p/14477433.html