Java EE开发第十二章：1.Servlet之Response相应(重定向、操作相应体、文件下载、随机验证码)

前言：前几篇讲解的关于Servlet的入门知识里有关于Response的简单介绍，今天我们就来给Response来个全面的介绍，介绍response的组成部分以及重定向、操作相应体、文件下载、验证码随机生成。

----Response作用----

简单的理解就是往浏览器上写东西。

----组成部分----

响应行 响应头 响应体

----操作响应行----

1、格式：协议/版本 状态码 状态码说明

2、状态码:
      1xx:已发送请求
      2xx:已完成响应
        200:正常响应
      3xx:还需浏览器进一步操作
        302:重定向 配合响应头:location
        304:读缓存
      4xx:用户操作错误
        404:用户操作错误.
        405:访问的方法不存在
      5xx:服务器错误
        500:内部异常

3、常用方法:setStatus(int 状态码):针对于 1 2 3 
了解 :sendError(int 状态码):针对于 4xx和5xx

----操作响应头----

格式:key/value(value可以是多个值)

常用的方法:

1.setHeader(String key,String value):设置字符串形式的响应头
2.了解:setIntHeader(String key,int value):设值整形的响应头
3.了解:setDateHeader(String key,long value):设值时间的响应头
4.addHeader(String key,String value):添加置字符串形式的响应头 之前设置过则追加,若没有设置过则设置
5.了解:addIntHeader(String key,int value):添加整形的响应头
6.了解:addDateHeader(String key,long value):添加时间的响应头

常用的响应头:

1.location:重定向

方式1:
        ★response.sendRedirect("/day10/loc2");
方式2:
	response.setStatus(302);
	respooen.setHeader("location","/day10/loc2");

2.refresh:定时刷新

方案1:设置头 refresh 
	respooen.setHeader("refresh","秒数;url=跳转的路径");
方案2:http的meta标签
	

3.content-type:设置文件的mime类型,设置响应流的编码及告诉浏览器用什么编码打开
4.content-disposition:文件下载

----操作响应体----

常用方法:

Writer getWriter():字符流
ServletOutputStream getOutputStream() :字节流

处理响应中文乱码:

方式1:
	response.setContentType("text/html;charset=utf-8");
方式2:理解
	response.setHeader("content-type", "text/html;charset=utf-8");

注意：两个流互斥，当响应完成之后,服务器会判断一下流是否已经关闭,若没有关闭,服务器会帮我们关闭.(底层使用的缓冲流)

-----重定向Demo-----

Loc1Servlet.java：

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

/**
 * 重定向
 * 
 * @author Fly
 *
 */
public class Loc1Servlet extends HttpServlet {

	protected void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		System.out.println("欢迎--->Loc1Servlet");
		
		//方式一
		//设置状态码302
//		response.setStatus(302);
		//设置相应头
//		response.setHeader("location", "/Day10/loc2");
		
		//方式二
		response.sendRedirect("/Day10/loc2");
	}

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

}

Loc2Servlet.java

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

/**
 * Servlet implementation class Loc2Servlet
 */
public class Loc2Servlet extends HttpServlet {

	protected void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		System.out.println("Loc2Servlet-->你现在已经到了loc2页面");
	}

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

}

配置文件：

/loc1

/loc2

----- 操作相应体Demo------

PrintSerlvet.java：

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;

/**
 * 操作相应体
 * @author Fly
 *
 */
public class PrintSerlvet extends HttpServlet {

	protected void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		// 处理相应中文的乱码
		// response.setContentType("text/html;charset=utf-8");
		response.setHeader("content-type", "text/html;charset=utf-8");
		// ServletOutputStream os = response.getOutputStream();

		// 打印表格
		// 获取字符流
		PrintWriter writer = response.getWriter();
		writer.print("");
		writer.print("");
		writer.print("");
		writer.print("");
		writer.print("");
		writer.print("
用户名
tom
密码
123
");

	}

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

	}

}

配置文件：

/print

----- 文件下载Demo-----

使用超链接下载：指定好文件路径即可下载。(注意文件放在WebContent下的download文件夹内)

2、编码下载：

DownloadServlet.java：

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

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

import org.apache.commons.io.IOUtils;

/**
 * 文件下载
 * 
 * @author Fly
 *
 */
public class DownloadServlet extends HttpServlet {

	protected void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		// 获取下载文件的名称
		String filename = request.getParameter("name");

		// 注意中文乱码
		filename = new String(filename.getBytes("iso8859-1"), "utf-8");

		ServletContext context = this.getServletContext();
		// 文件下载
		// 1设置文件下载的头信息
		String mimeType = context.getMimeType(filename);
		response.setContentType(mimeType);
		
		//2.设置下载的头信息
		//上午的
		//response.setHeader("content-dispostion", "attchment;filename=" + filename);
		
		// 常见的浏览器将文件名称使用utf-8 不推荐 不兼容火狐
		// response.setHeader("content-disposition", "attchment;filename="+URLEncoder.encode(filename, "utf-8"));
		
		//方式1:通过的方式 通过工具类编码
		//String _filename=DownLoadUtils.getName(request.getHeader("user-agent"), filename);
		//response.setHeader("content-disposition", "attachment;filename="+_filename);
		
		//方式2：网络上的方式
		response.setHeader("content-disposition", "attachment;filename="+new String(filename.getBytes("gbk"),"iso8859-1"));
		
		//3.对拷流
		//获取输入流
		InputStream is = context.getResourceAsStream("/download/"+filename);
		//获取输出流
		ServletOutputStream os = response.getOutputStream();
		
//		int len = -1;
//		byte[] b = new byte[1024];
//		while ((len=is.read(b)) != -1) {
//			os.write(b,0,len);
//		}
		IOUtils.copy(is, os);//扩展:使用commons-io工具类
		
		os.close();
		is.close();
	}

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

	}

}

配置文件：

/download

浏览器指定路径：(注意文件放在WebContent下的download文件夹内)

-----生成随机验证码----

CodeServlet.java：

import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.image.BufferedImage;
import java.io.IOException;
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;

public class CodeServlet extends HttpServlet {

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

		// 使用java图形界面技术绘制一张图片

		int charNum = 4;
		int width = 30 * 4;
		int height = 30;

		// 1. 创建一张内存图片
		BufferedImage bufferedImage = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);

		// 2.获得绘图对象
		Graphics graphics = bufferedImage.getGraphics();

		// 3、绘制背景颜色
		graphics.setColor(Color.YELLOW);
		graphics.fillRect(0, 0, width, height);

		// 4、绘制图片边框
		graphics.setColor(Color.BLUE);
		graphics.drawRect(0, 0, width - 1, height - 1);

		// 5、输出验证码内容
		graphics.setColor(Color.RED);
		graphics.setFont(new Font("宋体", Font.BOLD, 20));

		// 随机输出4个字符
		Graphics2D graphics2d = (Graphics2D) graphics;
		String s = "ABCDEFGHGKLMNPQRSTUVWXYZ23456789";
		Random random = new Random();
		// session中要用到
		String msg = "";
		int x = 5;
		for (int i = 0; i < 4; i++) {
			int index = random.nextInt(32);
			String content = String.valueOf(s.charAt(index));
			msg += content;
			double theta = random.nextInt(45) * Math.PI / 180;
			// 让字体扭曲
			graphics2d.rotate(theta, x, 18);
			graphics2d.drawString(content, x, 18);
			graphics2d.rotate(-theta, x, 18);
			x += 30;
		}

		// 6、绘制干扰线
		graphics.setColor(Color.GRAY);
		for (int i = 0; i < 5; i++) {
			int x1 = random.nextInt(width);
			int x2 = random.nextInt(width);

			int y1 = random.nextInt(height);
			int y2 = random.nextInt(height);
			graphics.drawLine(x1, y1, x2, y2);
		}

		// 释放资源
		graphics.dispose();

		// 图片输出 ImageIO
		ImageIO.write(bufferedImage, "jpg", response.getOutputStream());

	}

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

	}

}

配置文件：省略。

浏览器：

---------完------