Javaweb Servlet核心接口学习记录(3)—HttpServletRequest接口

我们在创建Servlet时会覆盖service()方法，或doGet()/doPost(),这些方法都有两个参数，一个为代表请求的request和代表响应response。service方法中的request的类型是ServletRequest，而doGet/doPost方法的request的类型是HttpServletRequest，HttpServletRequest是ServletRequest的子接口。

javax.servlet.http.HttpServletRequest 接口的定义为：

public interface  HttpServletRequest  extends  ServletRequest

在 Servlet API 中， ServletRequest 接口被定义为用于封装请求的信息，ServletRequest 对象由 Servlet 容器在用户每次请求 Servlet 时创建并传入Servlet 的 service() 方法中
HttpServletRequest 接口继承了 ServletRequest 接口，是专用于 HTTP 协议的子接口，用于封装 HTTP 请求信息；
在 HttpServlet 类的 service() 方法中，传入的 ServletRequest 对象被强制转换为 HttpServletRequest 对象来进行 HTTP 请求信息的处理。
HttpServletRequest 接口提供了具有如下功能类型的方法：
1、获取请求报文信息（包括请求行、请求头、请求正文）的方法；
2、获取网络连接信息的方法；
3、存取请求域属性的方法。

HTTP 协议
POST请求报文信息格式样例
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1.获取请求行信息
HttpServletRequest接口对请求行各部分信息的获取方法

方法	方法描述
getMethod()	获取请求使用的HTTP方法，例如，GET、POST、PUT
getRequestURI()	获取请求行中的资源名部分
getProtocol()	获取使用的协议及版本号。例如，HTTP/1.1 、HTTP/1.0
getQueryString()	获取请求URL后面的查询字符串，只对GET有效
getServletPath()	获取Servlet所映射的路径
getContextPath()	获取请求资源所属于的Web应用的路径

演示：
创建RequestLineServlet

package com;

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * Servlet implementation class RequestLineServlet
 */
@WebServlet("/RequestLineServlet")
public class RequestLineServlet extends HttpServlet {
	private static final long serialVersionUID = 1L;

	/**
	 * @see HttpServlet#HttpServlet()
	 */
	public RequestLineServlet() {
		super();
		// TODO Auto-generated constructor stub
	}

	/**
	 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse
	 *      response)
	 */
	protected void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		// TODO Auto-generated method stub
		// 设置响应编码
		response.setContentType("text/html; charset=UTF-8");
		// 获取请求使用http的方法
		String method = request.getMethod();
		// 获取请求行的uri部分
		String uri = request.getRequestURI();
		// 获取使用的协议及版本
		String protcol = request.getProtocol();
		// 获取uri后面拼接的字符串（参数）
		String queryString = request.getQueryString();
		// 获取servlet映射路径
		String servletPath = request.getServletPath();
		// 获取应用的上下文路径
		String contextPath = request.getContextPath();

		PrintWriter out = response.getWriter();

		out.print("<p>请求使用http的方法:" + method + "</p>");
		out.print("<p>获取请求行的uri部分:" + uri + "</p>");
		out.print("<p>获取使用的协议及版本:" + protcol + "</p>");
		out.print("<p>获取uri后面拼接的字符串（参数）:" + queryString + "</p>");
		out.print("<p>获取servlet映射路径:" + servletPath + "</p>");
		out.print("<p>获取应用的上下文路径:" + contextPath + "</p>");

		out.flush();
		out.close();

	}

	/**
	 * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse
	 *      response)
	 */
	protected void doPost(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		// TODO Auto-generated method stub
		doGet(request, response);
	}

}

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2.获取请求正文

HTTP协议请求正文内容为POST请求参数名称和值所组成的一个字符串;而对于GET请求，其请求参数附属在请求行中，没有请求正文。
HTTP协议的POST请求，主要通过Form表单向Web服务器端程序提交数据请求的方式实现。
<form>表单元素的enctype属性用于指定浏览器使用哪种编码方式将表单中的数据传送给Web服务器，该属性有两种取值：

application/x-www form-urlencoded
multipart/form-data

enctype属性默认的值为“ application/x-www-form-urlencoded ”
使用"application/x-www-form-urlencoded“编码方式的请求正文，HttpServletRequest接口提供的获取方法如下：

方法	方法描述
String getParameter(String name)	返回由name指定的用户请求参数的值
Enumeration getParameterNames()	返回所有客户请求的参数名
String[] getParameterValues(String name)	返回由name指定的用户请求参数的值
Map getParameterMap()	返回一个请求参数的Map，Map中的键为参数的名称，值为参数名对应的参数值

演示：
创建register.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8"
	pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
</head>
<body>

	<form action="RegisterServlet" method="post">
		用户名：<input type="text" name="userName" /><br /> 密码：<input
			type="password" name="pwd" /><br /> 性别：<input type="radio"
			name="gender" value="1" checked="checked" />男 <input type="radio"
			name="gender" value="2" />女<br /> 爱好：<input type="checkbox"
			name="hobby" value="lq" checked="checked">篮球 <input
			type="checkbox" name="hobby" value="code">编程 <input
			type="checkbox" name="hobby" value="sing">唱歌<br /> 所在城市： <select
			name="city">
			<option>---请选择----</option>
			<option value="bj">北京</option>
			<option value="rg">广州</option>
			<option value="sh">上海</option>
		</select><br /> <input type="submit" value="注册">
	</form>
</body>
</html>

运行
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后端，创建RegisterServlet

package com;

import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * Servlet implementation class RegisterServlet
 */
@WebServlet("/RegisterServlet")
public class RegisterServlet extends HttpServlet {
	private static final long serialVersionUID = 1L;

	/**
	 * @see HttpServlet#HttpServlet()
	 */
	public RegisterServlet() {
		super();
		// TODO Auto-generated constructor stub
	}

	/**
	 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse
	 *      response)
	 */
	protected void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		request.setCharacterEncoding("UTF-8");
		response.setContentType("text/html;charset=utf-8");

		String name = request.getParameter("userName");
		String pwd = request.getParameter("pwd");
		String gender = request.getParameter("gender");

		String[] hobbys = request.getParameterValues("hobby");

		String city = request.getParameter("city");

		System.out.println("姓名为：" + name);
		System.out.println("密码为：" + pwd);
		if (gender != null && gender.equals("1")) {
			System.out.println("姓名为：男");
		} else if (gender != null && gender.equals("2")) {
			System.out.println("姓名为：女");
		} else {
			System.out.println("请选择性别");
		}

		System.out.print("兴趣爱好：");
		for (String hobby : hobbys) {
			System.out.print(hobby + "\t");
		}
		System.out.println();

		System.out.println("所在城市：" + city);
	}

	/**
	 * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse
	 *      response)
	 */
	protected void doPost(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		// TODO Auto-generated method stub
		doGet(request, response);
	}

}

运行
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查看控制台获取数据

enctype属性只有在<form>表单向服务器上传文件时才会设置值为“multipart/form-data”，并且此属性值只适用于POST请求方式。

<form action="服务器端程序地址”method= "post" enctype= ”multipart/form-data">
<input name=”文件城名称”type="file">
<input type= submit" value=" 提交">
</form>

演示：
创建upLoad.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
</head>
<body>
	<form action="UploadServlet" method="post" enctype="multipart/form-data"><br/>
		文件名称：<input type="text" name = "fileName"><br/>
		上传文件:   <input type="file" name="uploadFile"><br/>
		<input type="submit" value="提交">
	</form>
</body>
</html>

运行
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创建UploadServlet

package com;

import java.io.IOException;
import java.io.InputStream;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * Servlet implementation class UploadServlet
 */
@WebServlet("/UploadServlet")
public class UploadServlet extends HttpServlet {
	private static final long serialVersionUID = 1L;

	/**
	 * @see HttpServlet#HttpServlet()
	 */
	public UploadServlet() {
		super();
		// TODO Auto-generated constructor stub
	}

	/**
	 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse
	 *      response)
	 */
	protected void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		request.setCharacterEncoding("utf-8");
		InputStream in = request.getInputStream();
		byte[] b = new byte[1024];
		in.read(b);
		System.out.println(new String(b));
	}

	/**
	 * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse
	 *      response)
	 */
	protected void doPost(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		// TODO Auto-generated method stub
		doGet(request, response);
	}

}

运行
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查看控制台输出

3.存取请求域属性

存储在 HttpServletRequest 对象中的对象称之为请求域属性，属于同一个请求的多个处理组件之间可以通过请求域属性来传递对象数据。
HttpServletRequest 接口提供了如下与请求域属性相关的方法:

方法	方法描述
void setAtrribute(String name,Object value)	设定name属性的值为value,保存在request范围内
Object getAttribute(String name)	从request范围内获取name属性的值
void removeAttribute(String name)	从request范围内移除name属性的值
Enumeration getAttributeNames()	获取所有request范围的属性

创建RequestScopeAttrServlet

package com;

import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * Servlet implementation class RequestScopeAttrServlet
 */
@WebServlet("/RequestScopeAttrServlet")
public class RequestScopeAttrServlet extends HttpServlet {
	private static final long serialVersionUID = 1L;

	/**
	 * @see HttpServlet#HttpServlet()
	 */
	public RequestScopeAttrServlet() {
		super();
		// TODO Auto-generated constructor stub
	}

	/**
	 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse
	 *      response)
	 */
	protected void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {

		request.setAttribute("msg1", "request域中的value值1");
		request.setAttribute("msg2", "request域中的value值2");
		request.getRequestDispatcher("/ResultServlet").forward(request, response);
	}

	/**
	 * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse
	 *      response)
	 */
	protected void doPost(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		// TODO Auto-generated method stub
		doGet(request, response);
	}

}

创建ResultServlet

package com;

import java.io.IOException;
import java.io.PrintWriter;
import java.util.Enumeration;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * Servlet implementation class ResultServlet
 */
@WebServlet("/ResultServlet")
public class ResultServlet extends HttpServlet {
	private static final long serialVersionUID = 1L;

	/**
	 * @see HttpServlet#HttpServlet()
	 */
	public ResultServlet() {
		super();
		// TODO Auto-generated constructor stub
	}

	/**
	 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse
	 *      response)
	 */
	protected void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		request.setCharacterEncoding("utf-8");
		response.setContentType("text/html;charset=utf-8");

		String value01 = (String) request.getAttribute("msg1");
		String value02 = (String) request.getAttribute("msg2");

		PrintWriter out = response.getWriter();
		out.print("<p>参数1:" + value01);
		out.print("<p>参数2:" + value02 + "<br/>");

		Enumeration<String> names = request.getAttributeNames();
		while (names.hasMoreElements()) {
			out.print(names.nextElement() + "==");
		}
	}

	/**
	 * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse
	 *      response)
	 */
	protected void doPost(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		// TODO Auto-generated method stub
		doGet(request, response);
	}

}

运行
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原文链接：https://blog.csdn.net/asdfghjkl_zth/article/details/104642208