servlet web之httpservletresponse

其他 2018-11-05 21:08:34 阅读次数: 0

 

向客户端输出中文数据

package cn.cast.response;

import java.io.IOException;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.io.UnsupportedEncodingException;

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

//在servlet中OutputStream输出中文的问题 
public class ResponseDemo1 extends HttpServlet {
	public void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		test4(response);
				
		
		
	}
	private void test4(HttpServletResponse response) throws IOException,
		UnsupportedEncodingException {
		OutputStream out = response.getOutputStream();
		//out.write(1);  //客户端显示的不是1
		out.write((1+"").getBytes());
	}
	private void test3(HttpServletResponse response) throws IOException,
		UnsupportedEncodingException {
		//分号写成逗号后会提示下载
		response.setHeader("content-type", "text/html,charset=utf-8");
		String data="你好！";
		OutputStream out = response.getOutputStream();
		out.write(data.getBytes("UTF-8"));
	}
	
	//用html技术中的meta标签模拟了一个http响应头，来控制浏览器的行为
	private void test2(HttpServletResponse response) throws IOException,
		UnsupportedEncodingException {
		String data="你好！";
		OutputStream out = response.getOutputStream();
		out.write("<meta http-equiv='content-type' content='text/html;charset=utf-8'>".getBytes());
		out.write(data.getBytes("UTF-8"));
		}
	private void test1(HttpServletResponse response) throws IOException,
			UnsupportedEncodingException {
		//告诉客户端控制浏览器使用什么码表打开。
		response.setHeader("content-type", "text/html;charset=utf-8");
		String data="你好！";
		OutputStream out = response.getOutputStream();
		//数据传输的方式时传输的数字，服务器以utf-8格式编码处处数据发送的时候，客户端接收的数字，也要用相应的编码来展示数据 
		out.write(data.getBytes("UTF-8"));
	}
	public void doPost(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		doGet(request, response);
	}

}

通过response的writer流输出数据的问题。

package cn.cast.response;

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

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


//通过response的writer流输出数据的问题。
public class ResponseDemo2 extends HttpServlet {


	public void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		test1(response);
	}
	private void test2(HttpServletResponse response) throws IOException {
		//设置response使用的码表，以控制response以什么码表向浏览器写出数据 
		//response.setCharacterEncoding("UTF-8");
		//指定浏览器以什么码表打开
		//response.setHeader("content-type", "text/html;charset=utf-8");
		
		//上面两句可合并为下面一句
		response.setContentType("text/html;charset=utf-8");
		
		String data = "你好！";
		PrintWriter  pw = response.getWriter();
		pw.write(data);
	}

	private void test1(HttpServletResponse response) throws IOException {
		//设置response使用的码表，以控制response以什么码表向浏览器写出数据 
		response.setCharacterEncoding("UTF-8");
		//指定浏览器以什么码表打开
		response.setHeader("content-type", "text/html;charset=utf-8");
		String data = "你好！";
		PrintWriter  pw = response.getWriter();
		pw.write(data);
	}

	public void doPost(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {

		doGet(request, response);
	}

}

文件下载和中文文件的下载

package cn.cast.response;

import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.net.URLEncoder;

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

public class responseDemo3 extends HttpServlet {
	public void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		String path = this.getServletContext().getRealPath("/img/图片.png");
		String filename = path.substring(path.lastIndexOf("\\")+1);
		//如果下载名为中文文件，则文件名需要经过url编码
		response.setHeader("content-disposition", "attachment;filename="+URLEncoder.encode(filename,"utf-8"));
		
		//response.setHeader("content-disposition", "attachment;filename="+filename);
		
		
		
		InputStream in = null;
		OutputStream out = null;
		try {
			in = new FileInputStream(path);
			int len = 0;
			byte buffer[] = new byte[1024];
			out = response.getOutputStream();
			while ((len=in.read(buffer))>0){
				out.write(buffer,0,len);
			}
		} finally {
			if (in !=null){
				try {
					in.close();
				} catch (Exception e) {
					// TODO: handle exception
				}
			}
		}
	}

	public void doPost(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		doGet(request, response);
	}
}

输出随机图片

package cn.cast.response;

import java.awt.Color;
import java.awt.Font;
import java.awt.GradientPaint;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.Random;

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


//输出随机认证码图片 
//
public class ResponseDemo4 extends HttpServlet {
	
	private static final int Width = 120;
	private static final int Height = 30;
	
	public void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		md2(response);
	}

	private void md1(HttpServletResponse response) throws IOException {
		//1在内存中生成图像 
		BufferedImage image = new BufferedImage(Width, Height,BufferedImage.TYPE_INT_RGB);
		
		//2得到图像
		Graphics g = image.getGraphics();
		//3画背景 
		g.setColor(Color.WHITE);
		g.fillRect(0, 0, Width, Height);
		
		//4画边框
		g.setColor(Color.BLUE);
		g.drawRect(1, 1, Width-2, Height-2);
		
		//5画干扰线 
		g.setColor(Color.GREEN);
		for (int i=0;i<4;i++){
			int x1 = new Random().nextInt(Width);
			int y1 = new Random().nextInt(Height);
			int x2 = new Random().nextInt(Width);
			int y2 = new Random().nextInt(Height);
			g.drawLine(x1, y1, x2, y2);
		}
		
		//写文字   文字编码范围  [\u4e00-\u9fa5]
		g.setColor(Color.RED);
		g.setFont(new Font("宋体", Font.BOLD, 20));
		//常用汉字的unicode字符编码  
		String base ="\u7684\u4e00\u4e86\u662f\u6211\u4e0d\u5728\u4eba\u4eec\u6709\u6765\u4ed6\u8fd9\u4e0a\u7740\u4e2a\u5730\u5230\u5927\u91cc\u8bf4\u5c31\u53bb\u5b50\u5f97"+
				"\u4e5f\u548c\u90a3\u8981\u4e0b\u770b\u5929\u65f6\u8fc7\u51fa\u5c0f\u4e48\u8d77\u4f60\u90fd\u628a\u597d\u8fd8\u591a\u6ca1\u4e3a\u53c8\u53ef\u5bb6\u5b66"+
				"\u53ea\u4ee5\u4e3b\u4f1a\u6837\u5e74\u60f3\u751f\u540c\u8001\u4e2d\u5341\u4ece\u81ea\u9762\u524d\u5934\u9053\u5b83\u540e\u7136\u8d70\u5f88\u50cf\u89c1"+
				"\u4e24\u7528\u5979\u56fd\u52a8\u8fdb\u6210\u56de\u4ec0\u8fb9\u4f5c\u5bf9\u5f00\u800c\u5df1\u4e9b\u73b0\u5c71\u6c11\u5019\u7ecf\u53d1\u5de5\u5411\u4e8b"+
				"\u547d\u7ed9\u957f\u6c34\u51e0\u4e49\u4e09\u58f0\u4e8e\u9ad8\u624b\u77e5\u7406\u773c\u5fd7\u70b9\u5fc3\u6218\u4e8c\u95ee\u4f46\u8eab\u65b9\u5b9e"+
				"\u5403\u505a\u53eb\u5f53\u4f4f\u542c\u9769\u6253\u5462\u771f\u5168\u624d\u56db\u5df2\u6240\u654c\u4e4b\u6700\u5149\u4ea7\u60c5\u8def\u5206\u603b\u6761"+
				"\u767d\u8bdd\u4e1c\u5e2d\u6b21\u4eb2\u5982\u88ab\u82b1\u53e3\u653e\u513f\u5e38\u6c14\u4e94\u7b2c\u4f7f\u5199\u519b\u5427\u6587\u8fd0\u518d\u679c"+
				"\u600e\u5b9a\u8bb8\u5feb\u660e\u884c\u56e0\u522b\u98de\u5916\u6811\u7269\u6d3b\u90e8\u95e8\u65e0\u5f80\u8239\u671b\u65b0\u5e26\u961f\u5148\u529b"+
				"\u5b8c\u5374\u7ad9\u4ee3\u5458\u673a\u66f4\u4e5d\u60a8\u6bcf\u98ce\u7ea7\u8ddf\u7b11\u554a\u5b69\u4e07\u5c11\u76f4\u610f\u591c\u6bd4\u9636"+
				"\u8fde\u8f66\u91cd\u4fbf\u6597\u9a6c\u54ea\u5316\u592a\u6307\u53d8\u793e\u4f3c\u58eb\u8005\u5e72\u77f3\u6ee1\u65e5\u51b3\u767e\u539f\u62ff\u7fa4"+
				"\u7a76\u5404\u516d\u672c\u601d\u89e3\u7acb\u6cb3\u6751\u516b\u96be\u65e9\u8bba\u5417\u6839\u5171\u8ba9\u76f8\u7814\u4eca\u5176\u4e66\u5750"+
				"\u63a5\u5e94\u5173\u4fe1\u89c9\u6b65\u53cd\u5904\u8bb0\u5c06\u5343\u627e\u4e89\u9886\u6216\u5e08\u7ed3\u5757\u8dd1\u8c01\u8349\u8d8a\u5b57\u52a0\u811a\u7d27\u7231\u7b49\u4e60\u9635\u6015\u6708\u9752\u534a\u706b\u6cd5\u9898\u5efa\u8d76\u4f4d\u5531\u6d77\u4e03\u5973\u4efb\u4ef6\u611f"+
				"\u51c6\u5f20\u56e2\u5c4b\u79bb\u8272\u8138\u7247\u79d1\u5012\u775b\u5229\u4e16\u521a\u4e14\u7531\u9001\u5207\u661f\u5bfc\u665a\u8868\u591f\u6574\u8ba4\u54cd\u96ea\u6d41\u672a\u573a\u8be5\u5e76\u5e95\u6df1\u523b\u5e73\u4f1f\u5fd9\u63d0\u786e\u8fd1\u4eae\u8f7b\u8bb2\u519c\u53e4\u9ed1"+
				"\u544a\u754c\u62c9\u540d\u5440\u571f\u6e05\u9633\u7167\u529e\u53f2\u6539\u5386\u8f6c\u753b\u9020\u5634\u6b64\u6cbb\u5317\u5fc5\u670d"+
				"\u96e8\u7a7f\u5185\u8bc6\u9a8c\u4f20\u4e1a\u83dc\u722c\u7761\u5174\u5f62\u91cf\u54b1\u89c2\u82e6\u4f53\u4f17\u901a\u51b2\u5408\u7834"+
				"\u53cb\u5ea6\u672f\u996d\u516c\u65c1\u623f\u6781\u5357\u67aa\u8bfb\u6c99\u5c81\u7ebf\u91ce\u575a\u7a7a\u6536\u7b97\u81f3\u653f\u57ce"+
				"\u52b3\u843d\u94b1\u7279\u56f4\u5f1f\u80dc\u6559\u70ed\u5c55\u5305\u6b4c\u7c7b\u6e10\u5f3a\u6570\u4e61\u547c\u6027\u97f3\u7b54\u54e5"+
				"\u9645\u65e7\u795e\u5ea7\u7ae0\u5e2e\u5566\u53d7\u7cfb\u4ee4\u8df3\u975e\u4f55\u725b\u53d6\u5165\u5cb8\u6562\u6389\u5ffd\u79cd\u88c5"+
				"\u9876\u6025\u6797\u505c\u606f\u53e5\u533a\u8863\u822c\u62a5\u53f6\u538b\u6162\u53d4\u80cc\u7ec6";
		int x =10;
		for (int i=0;i<4;i++){
			String ch = base.charAt(new Random().nextInt(base.length())) + "";
			g.drawString(ch, x, 20);
			x +=30;
		}
		
		//图形写给浏览器 ：
		response.setContentType("image/jpeg");
		ImageIO.write(image, "jpg", response.getOutputStream());
	}
	
	//生成旋转的字 
	private void md2(HttpServletResponse response) throws IOException {
		//1在内存中生成图像 
		BufferedImage image = new BufferedImage(Width, Height,BufferedImage.TYPE_INT_RGB);
		
		//2得到图像
		Graphics g = image.getGraphics();
		//3画背景 
		g.setColor(Color.WHITE);
		g.fillRect(0, 0, Width, Height);
		
		//4画边框
		g.setColor(Color.BLUE);
		g.drawRect(1, 1, Width-2, Height-2);
		
		//5画干扰线 
		g.setColor(Color.GREEN);
		for (int i=0;i<4;i++){
			int x1 = new Random().nextInt(Width);
			int y1 = new Random().nextInt(Height);
			int x2 = new Random().nextInt(Width);
			int y2 = new Random().nextInt(Height);
			g.drawLine(x1, y1, x2, y2);
		}
		
		drawString((Graphics2D) g);
		
		//图形写给浏览器 ：
		response.setContentType("image/jpeg");
		
		//发头控制浏览器不要缓存 
		response.setDateHeader("Expires", -1);
		response.setHeader("Cache-Control","no-cache");
		response.setHeader("Pragma","no-cache");
		ImageIO.write(image, "jpg", response.getOutputStream());
	}

	private void drawString(Graphics2D g) {
		//写文字   文字编码范围  [\u4e00-\u9fa5]
		g.setColor(Color.RED);
		g.setFont(new Font("宋体", Font.BOLD, 20));
		//常用汉字的unicode字符编码  
		String base ="\u7684\u4e00\u4e86\u662f\u6211\u4e0d\u5728\u4eba\u4eec\u6709\u6765\u4ed6\u8fd9\u4e0a\u7740\u4e2a\u5730\u5230\u5927\u91cc\u8bf4\u5c31\u53bb\u5b50\u5f97"+
				"\u4e5f\u548c\u90a3\u8981\u4e0b\u770b\u5929\u65f6\u8fc7\u51fa\u5c0f\u4e48\u8d77\u4f60\u90fd\u628a\u597d\u8fd8\u591a\u6ca1\u4e3a\u53c8\u53ef\u5bb6\u5b66"+
				"\u53ea\u4ee5\u4e3b\u4f1a\u6837\u5e74\u60f3\u751f\u540c\u8001\u4e2d\u5341\u4ece\u81ea\u9762\u524d\u5934\u9053\u5b83\u540e\u7136\u8d70\u5f88\u50cf\u89c1"+
				"\u4e24\u7528\u5979\u56fd\u52a8\u8fdb\u6210\u56de\u4ec0\u8fb9\u4f5c\u5bf9\u5f00\u800c\u5df1\u4e9b\u73b0\u5c71\u6c11\u5019\u7ecf\u53d1\u5de5\u5411\u4e8b"+
				"\u547d\u7ed9\u957f\u6c34\u51e0\u4e49\u4e09\u58f0\u4e8e\u9ad8\u624b\u77e5\u7406\u773c\u5fd7\u70b9\u5fc3\u6218\u4e8c\u95ee\u4f46\u8eab\u65b9\u5b9e"+
				"\u5403\u505a\u53eb\u5f53\u4f4f\u542c\u9769\u6253\u5462\u771f\u5168\u624d\u56db\u5df2\u6240\u654c\u4e4b\u6700\u5149\u4ea7\u60c5\u8def\u5206\u603b\u6761"+
				"\u767d\u8bdd\u4e1c\u5e2d\u6b21\u4eb2\u5982\u88ab\u82b1\u53e3\u653e\u513f\u5e38\u6c14\u4e94\u7b2c\u4f7f\u5199\u519b\u5427\u6587\u8fd0\u518d\u679c"+
				"\u600e\u5b9a\u8bb8\u5feb\u660e\u884c\u56e0\u522b\u98de\u5916\u6811\u7269\u6d3b\u90e8\u95e8\u65e0\u5f80\u8239\u671b\u65b0\u5e26\u961f\u5148\u529b"+
				"\u5b8c\u5374\u7ad9\u4ee3\u5458\u673a\u66f4\u4e5d\u60a8\u6bcf\u98ce\u7ea7\u8ddf\u7b11\u554a\u5b69\u4e07\u5c11\u76f4\u610f\u591c\u6bd4\u9636"+
				"\u8fde\u8f66\u91cd\u4fbf\u6597\u9a6c\u54ea\u5316\u592a\u6307\u53d8\u793e\u4f3c\u58eb\u8005\u5e72\u77f3\u6ee1\u65e5\u51b3\u767e\u539f\u62ff\u7fa4"+
				"\u7a76\u5404\u516d\u672c\u601d\u89e3\u7acb\u6cb3\u6751\u516b\u96be\u65e9\u8bba\u5417\u6839\u5171\u8ba9\u76f8\u7814\u4eca\u5176\u4e66\u5750"+
				"\u63a5\u5e94\u5173\u4fe1\u89c9\u6b65\u53cd\u5904\u8bb0\u5c06\u5343\u627e\u4e89\u9886\u6216\u5e08\u7ed3\u5757\u8dd1\u8c01\u8349\u8d8a\u5b57\u52a0\u811a\u7d27\u7231\u7b49\u4e60\u9635\u6015\u6708\u9752\u534a\u706b\u6cd5\u9898\u5efa\u8d76\u4f4d\u5531\u6d77\u4e03\u5973\u4efb\u4ef6\u611f"+
				"\u51c6\u5f20\u56e2\u5c4b\u79bb\u8272\u8138\u7247\u79d1\u5012\u775b\u5229\u4e16\u521a\u4e14\u7531\u9001\u5207\u661f\u5bfc\u665a\u8868\u591f\u6574\u8ba4\u54cd\u96ea\u6d41\u672a\u573a\u8be5\u5e76\u5e95\u6df1\u523b\u5e73\u4f1f\u5fd9\u63d0\u786e\u8fd1\u4eae\u8f7b\u8bb2\u519c\u53e4\u9ed1"+
				"\u544a\u754c\u62c9\u540d\u5440\u571f\u6e05\u9633\u7167\u529e\u53f2\u6539\u5386\u8f6c\u753b\u9020\u5634\u6b64\u6cbb\u5317\u5fc5\u670d"+
				"\u96e8\u7a7f\u5185\u8bc6\u9a8c\u4f20\u4e1a\u83dc\u722c\u7761\u5174\u5f62\u91cf\u54b1\u89c2\u82e6\u4f53\u4f17\u901a\u51b2\u5408\u7834"+
				"\u53cb\u5ea6\u672f\u996d\u516c\u65c1\u623f\u6781\u5357\u67aa\u8bfb\u6c99\u5c81\u7ebf\u91ce\u575a\u7a7a\u6536\u7b97\u81f3\u653f\u57ce"+
				"\u52b3\u843d\u94b1\u7279\u56f4\u5f1f\u80dc\u6559\u70ed\u5c55\u5305\u6b4c\u7c7b\u6e10\u5f3a\u6570\u4e61\u547c\u6027\u97f3\u7b54\u54e5"+
				"\u9645\u65e7\u795e\u5ea7\u7ae0\u5e2e\u5566\u53d7\u7cfb\u4ee4\u8df3\u975e\u4f55\u725b\u53d6\u5165\u5cb8\u6562\u6389\u5ffd\u79cd\u88c5"+
				"\u9876\u6025\u6797\u505c\u606f\u53e5\u533a\u8863\u822c\u62a5\u53f6\u538b\u6162\u53d4\u80cc\u7ec6";
		int x =10;
		for (int i=0;i<4;i++){
			//生成0-30的随机数 度数 
			int degree = new Random().nextInt()%30;  //-30 -30
			
			String ch = base.charAt(new Random().nextInt(base.length())) + "";
			g.rotate(degree*Math.PI/180, x, 20);  //设置旋转角度 
			g.drawString(ch, x, 20);
			g.rotate(-degree*Math.PI/180, x, 20);
			x +=30;
		}
	}

	public void doPost(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		doGet(request, response);
	}

}

发送浏览器头控制浏览器定时刷新

package cn.cast.response;

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

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


//控制浏览器定时刷新 
public class ResponseDemo5 extends HttpServlet {

	public void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		test3(request, response);
	}
	
	
	//实用的自动跳转技术  
	private void test3(HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException {
		//假设这是一个用于处理登录的servlet
		String data = "<meta http-equiv='refresh' content='3;url=/web1/index.jsp'>恭喜你登录成功，浏览器将在3s后跳转，否则请点击<a href=''>超链接</a>";
		this.getServletContext().setAttribute("data", data);
		this.getServletContext().getRequestDispatcher("/message.jsp").forward(request, response);
	}

	private void test2(HttpServletResponse response) throws IOException {
		//假设这是一个用于处理登录的servlet
		
		
		//程序运行到此，用户登录成功  
		response.setCharacterEncoding("UTF-8");
		response.setContentType("/text/html;charset=utf-8");
		response.setHeader("refresh", "3;url=/web1/index.jsp");
		response.getWriter().write("恭喜你登录成功，浏览器将在3s后跳转，否则请点击<a href=''>超链接</a>");
	}

	private void test1(HttpServletResponse response) throws IOException {
		String data = new Random().nextInt(10000) + "";
		response.setHeader("refresh", "3");
		response.getWriter().write(data);
	}

	public void doPost(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		doGet(request, response);
	}
}

发送http头部，控制浏览器缓存。

jsp

<%@ page language="java" import="java.util.*" pageEncoding="ISO-8859-1"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    <base href="<%=basePath%>">
    
    <title>My JSP 'index.jsp' starting page</title>
  </head>
  
  <body>
    <a href="/web1/servlet/ResponseDemo6">aaa</a>
  </body>
</html>
package cn.cast.response;

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

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


//控制浏览器缓存 
public class ResponseDemo6 extends HttpServlet {

	public void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		response.setHeader("Expires", System.currentTimeMillis()+"1000*60");
		String data ="xxxxxxxxyyyyy";
		response.getWriter().write(data);
		

	}


	public void doPost(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		doGet(request, response);
	}

}

访问index.html可看到页面没有重复发送请求，使用httpwatch。

通过response实现请求重定向

package cn.cast.response;

import java.io.IOException;

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

//实现请求重定向 
//1.浏览器向服务器发送两次请求，意味着有2个request\response
//2.用重定向技术，浏览器地址栏会发生变化  
//3.登录和购物车功能。
public class ResponseDemo7 extends HttpServlet {

	public void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		
		//服务器发送了两次请求 ，尽量不用重定向，因为发送了2次请求，增加服务器的压力。  一般在登录界面使用请求重定向。购物也使用了重定向功能。
			response.setStatus(302);
			response.setHeader("location", "/web1/index.jsp");
			
			//上面两句代码 等价于
			//response.sendRedirect("/web/index.jsp");

		}


		public void doPost(HttpServletRequest request, HttpServletResponse response)
				throws ServletException, IOException {
			doGet(request, response);
		}

	}

同时调用response.getOutputStream(); response.getWriter();会报错：

exception

java.lang.IllegalStateException: getOutputStream() has already been called for this response
	org.apache.catalina.connector.Response.getWriter(Response.java:564)

 

 

 

 

 

 

 

 

 

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