学习笔记，javaWeb中的Request

最新推荐文章于 2025-04-14 14:58:01 发布

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最新推荐文章于 2025-04-14 14:58:01 发布

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分类专栏： javaWeb 文章标签： request javaweb

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本文介绍Servlet中如何处理客户端请求，包括获取请求信息、解决乱码问题、实现请求转发及页面包含，并演示了防盗链技术。

1. 获取请求信息

package request;

import java.io.IOException;
import java.io.InputStream;
import java.util.Enumeration;
import java.util.Map;

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

import org.apache.commons.beanutils.BeanUtils;

import request.bean.User;
/**
 * request基本功能，获取请求数据
 */
public class RequestDemo extends HttpServlet{
	@Override
	protected void doGet(HttpServletRequest req, HttpServletResponse resp)
			throws ServletException, IOException {
		//1. 获取基本请求信息
		requestGetMethods(req);
		//2.获取用户提交的请求数据
		requestGetMethods2(req);
	}
	//request的常用获取信息方法
	private void requestGetMethods(HttpServletRequest req) {
		//客户端请求地址部分URI 和 客户端请求地址URL
		System.out.println("URI = "+req.getRequestURI());
		System.out.println("URL = "+req.getRequestURL());
		//请求的参数部分
		System.out.println("GetParameters = "+req.getQueryString());
		//获得客户端IP、完整主机名(DNS注册的名称)、网络端口号
		System.out.println("Client IP = "+req.getRemoteAddr());
		System.out.println("Client Name = "+req.getRemoteHost());
		System.out.println("Client Port = "+req.getRemotePort());
		//获得Web服务器的IP、
		System.out.println("Server IP = "+req.getLocalAddr());
		System.out.println("Server Name = "+req.getLocalName());
		System.out.println("Server Port = "+req.getLocalPort());
		//获取请求方式
		System.out.println("Request Method = "+req.getMethod());
	}
	//request获取请求数据
	private void requestGetMethods2(HttpServletRequest req) {
		//方法五，获取request的流对象，然后打印，注意这个不能在用了request.getParameter()、request.getParameterNames()、request.getParameterValues()后使用
		System.out.println("------第五次-------");
		try {
			InputStream in = req.getInputStream();
			int len = 0;
			byte[] buf = new byte[1024];
			while((len=in.read(buf))!=-1){
				System.out.println(new String(buf,0,len));
			}
		} catch (IOException e1) {
			e1.printStackTrace();
		}
		//方法一，直接获取用户名
		System.out.println("------第一次-------");
		String username = req.getParameter("username");
		System.out.println("username = "+username);
		
		//方法二，获取所有请求数据，例子中在使用了req.getInputStream()后调用，是取不到值的
		System.out.println("------第二次-------");
		Enumeration<String> e = req.getParameterNames();
		while(e.hasMoreElements()){
			String name = e.nextElement();
			String value = req.getParameter(name);
			System.out.println(name+" = "+value);
		}
		//方法三，获得同一个参数的所有的值，例子中在使用了req.getInputStream()后调用，是取不到值的
		System.out.println("------第三次-------");
		String[] s = req.getParameterValues("username");
		if(s!=null&&s.length>0){
			for(String value:s){
				System.out.println("username = "+value);
			}
		}
//		//方法四，获取参数map对象，然后使用beanUtils封装到userBean中（需要提前创建好userBean，保证封装所有的请求数据）
		System.out.println("------第四次-------");
		//以map形式获取请求数据
		Map map = req.getParameterMap();
		User user = new User();
		try {
			//判断取到的map是否为空，如果为空在调用下面的方法会报空指针异常
			if(map!=null&&map.size()>0){
				//将map对象存入userBean中
				BeanUtils.populate(user, map);
			}
			System.out.println(user);
		} catch (Exception e1) {
			e1.printStackTrace();
		}
		
		
	}
	
	@Override
	protected void doPost(HttpServletRequest req, HttpServletResponse resp)
			throws ServletException, IOException {
		doGet(req, resp);
	}
}

提交数据请求页面部分代码，login.jsp

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>传数据给RequestDemo</title>
</head>
<body>	
	<a href="/javaWeb/RequestDemo?username=AAA">发送请求</a>
	<form action="/javaWeb/RequestDemo" method="post">
		用户名：<input type="text" name="username"><br />
		密码：<input type="password" name="password"><br />
		<input type="hidden" name="username" value="default">
		性别：<input type="radio" name="gender" value="male">男<input type="radio" name="gender" value="female">女<br />
		城市：
			<select name="city">
				<option value="bj">北京</option>
				<option value="sh">上海</option>
				<option value="gz">广州</option>
			</select>
			<br />
		爱好：
			<input type="checkbox" name="like" value="sing">唱歌
			<input type="checkbox" name="like" value="dance">跳舞
			<input type="checkbox" name="like" value="basketball">篮球
			<input type="checkbox" name="like" value="football">足球	
			<br />
		备注：<textarea rows="5" cols="45" name="description"></textarea><br />
		头像：<input type="file" name="image">
		<input type="submit" value="提交">
	</form>
</body>
</html>

2. 获取的数据乱码问题

package request;

import java.io.IOException;
import java.io.UnsupportedEncodingException;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
/**
 * request获取中文数据乱码问题
 */
public class RequestDemo2 extends HttpServlet{

	@Override
	protected void doGet(HttpServletRequest req, HttpServletResponse resp)
			throws ServletException, IOException {
		//解决post方式乱码问题
		charsetPost(req);
		//解决get方式乱码问题
		charsetGet(req);
		
	}
	private void charsetPost(HttpServletRequest req)
			throws UnsupportedEncodingException {
		//解决post方式提交的中文乱码,需要在使用request获取数据前设置。（注：通过设置解码只能解决post方式提交的中文数据）
		req.setCharacterEncoding("UTF-8");
		String username2 = req.getParameter("username2");
		System.out.println("POST:"+username2);
		
	}
	
	private void charsetGet(HttpServletRequest req)
			throws UnsupportedEncodingException {

		String username = req.getParameter("username1");
		//解决get方式提交的中文乱码，将获取的数据转码
		if(username!=null){
			//浏览器默认的是iso8859-1编码，通过get方式取到数据后，再次转换成utf-8
			username = new String(username.getBytes("iso8859-1"),"utf-8");
		}
		System.out.println("GET:"+username);
		
	}
	@Override
	protected void doPost(HttpServletRequest req, HttpServletResponse resp)
			throws ServletException, IOException {
		doGet(req, resp);
	}
}

乱码问题请求页面部分代码，login.jsp

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<title>request中文乱码问题</title>
<meta http-equiv="content-type" content="text/html;charset=UTF-8">
</head>
<body>
<form action="/javaWeb/RequestDemo2" method="get">
	GET:用户名1<input type="text" name="username1">
	<input type="submit" value="提交">
</form>
<form action="/javaWeb/RequestDemo2" method="post">
	POST:用户名2<input type="text" name="username2">
	<input type="submit" value="提交">
</form>
</body>
</html>

3. 请求转发和页面包含

package request;

import java.io.IOException;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
/**
 * request请求转发，以及使用request域对象把数据带给转发资源
 * 
 * request实现页面包含
 */
public class RequestDemo3 extends HttpServlet{
	@Override
	protected void doGet(HttpServletRequest req, HttpServletResponse resp)
			throws ServletException, IOException {
		//请求转发
//		dispatcher(req, resp);
		//包含页面
		include(req, resp);
		
	}
	//页面包含
	private void include(HttpServletRequest req, HttpServletResponse resp)
			throws ServletException, IOException {
		
		//手动添加页面头
		resp.getOutputStream().write("<!DOCTYPE><html><head><title>组合页面</title></head><body>".getBytes());
		
		//将多个页面组成一个页面，为了组成后为格式良好的页面，内容页面部分应该去头去尾
		req.getRequestDispatcher("/part1.html").include(req, resp);
		resp.getOutputStream().write("被包含的内容<br />".getBytes());
		req.getRequestDispatcher("/part2.html").include(req, resp);
		
		//手动添加页面尾
		resp.getOutputStream().write("</body></html>".getBytes());
	}
	//页面转发
	private void dispatcher(HttpServletRequest req, HttpServletResponse resp)
			throws ServletException, IOException {
		String data = "要转发的数据";
		req.setAttribute("data", data);
		//request也可以实现转发
		
		/*
		 * 注意:servlet中只能有一个跳转
		 * 不能再有第二个跳转request.getRequestDispatcher("/dispatcher.jsp").forward(req, resp);
		 * 同时，也不能使用response.getOutputStream().close()，而且response.getOutputStream().write()中的数据会被清空
		 * 否则会有异常 java.lang.IllegalStateException: Cannot forward after response has been committed
		 * 如：下面注释掉的代码就会报错
		 */
//		resp.getOutputStream().write("AAA".getBytes());
//		resp.getOutputStream().close();
//		req.getRequestDispatcher("/index.jsp").forward(req, resp);
		
		req.getRequestDispatcher("/dispatcher.jsp").forward(req, resp);
	}
	@Override
	protected void doPost(HttpServletRequest req, HttpServletResponse resp)
			throws ServletException, IOException {
		doGet(req, resp);
	}
}

请求转发页面部分代码，dispatcher.jsp

<%@ page language="java" contentType="text/html; charset=utf-8"
    pageEncoding="utf-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>request请求转发</title>
</head>
<body>
中国
${data }
<%
	String data = (String)request.getAttribute("data");
	out.write("data = "+data);
 %>
</body>
</html>

请求转发页面部分代码

part1.html

第一部分，开始<br />

part2.html

最后部分，结束<br />

4. 防盗链演示

package request;

import java.io.IOException;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
/**
 * request防盗链
 *
 */
public class RequestDemo4 extends HttpServlet {

	@Override
	protected void doGet(HttpServletRequest req, HttpServletResponse resp)
			throws ServletException, IOException {
		
		resp.setCharacterEncoding("UTF-8");
		resp.setContentType("text/html;charset=UTF-8");
		
		//防盗链就是检查访问地址，是不是被直接访问，如果是跳转到首页，如果不是给出正确页面
		String referer = req.getHeader("referer");
		//如果是通过复制地址的方式访问的，那么referer会为空
		if(referer==null||!referer.startsWith("http://localhost")){
			//如果是盗链访问，那么就先看广告
			resp.sendRedirect("ad.jsp");
		}
		this.getServletContext().setAttribute("message", "精彩的页面");
				
	}
	@Override
	protected void doPost(HttpServletRequest req, HttpServletResponse resp)
			throws ServletException, IOException {
		doGet(req, resp);
	}
}

防盗链演示的页面部分代码，ad.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<meta http-equiv="refresh" content="3;url=/javaWeb/message.jsp">
<title>广告</title>
</head>
<body>
	先看广告，页面3秒后跳转，如果没有跳转<a href="/javaWeb/message.jsp">请点击超链接进行跳转</a>

</body>
</html>