Servlet------>response

request代表了请求

response代表响应

HttpServletResponse

setStatus();----->发送状态码

setHeader();---->发送响应头

getWriter();和getOutputStream();------>发送数据

addHeader();---->添加一个头

containsHeader();--->包含几个头

 HttpServletResponse细节一-------》码表的对应设置charset=UTF-8

ResponseDemo1

如果不加：

response.setHeader("Content-type","text/html;charset=UTF-8");

浏览器读出涓球，默认国标读，不是utf-8

package cn.itcaste.web.servlet;

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

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


@WebServlet("/ResponseDemo1")
public class ResponseDemo1 extends HttpServlet {
    
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        
        // test2(response);
        
        //test1(response);
    }

    private void test2(HttpServletResponse response) throws IOException, UnsupportedEncodingException {
        //用html技术中的meta标签模拟http响应头,来控制浏览器的行为
        String data="中国";
        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 {
        //以什么编码发就用什么编码读
        response.setHeader("Content-type","text/html;charset=UTF-8");
        String data="中国";
        OutputStream out=response.getOutputStream();
        out.write(data.getBytes("UTF-8"));
    }

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

}

如下demo字符流输出：浏览器显示？？---------理由在下张图

	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		
		String data="中国";
		PrintWriter out=response.getWriter();
		out.write(data);
	}

先把中国写入respone，因为respone是外国人发明的，查找的是iso8859这个码表，查找不到所以显示？？

 如下代码可以改变所查码表和浏览器所读取时查询码表：

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//        response.setCharacterEncoding("UTF-8");//控制写入response时所查询的码表
//        response.setHeader("content-type", "text/html;charset=UTF-8");//控制浏览器输出时时所查询的码表
        response.setContentType("text/html;charset=UTF-8");//这句话可以代替上两句话
        String data="中国";
        PrintWriter out=response.getWriter();
        out.write(data);//writer流只能写字符串！
    }

 HttpServletResponse细节二-------》response实现（中文）文件下载

ResponseDemo3：

package cn.itcaste.web.servlet;

import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;

import javax.imageio.stream.FileCacheImageInputStream;
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 org.apache.taglibs.standard.tag.common.core.OutSupport;

/**
 * 文件下载案例
 */
@WebServlet("/ResponseDemo3")
public class ResponseDemo3 extends HttpServlet {
  
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		String path=this.getServletContext().getRealPath("/download/1.jpg");//获取绝对路径
		String filename=path.substring(path.lastIndexOf("\")+1);//获取文件名称
		response.setHeader("content-disposition", "attachment;filename="+filename );//设置成按下载方式读取的响应头
		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){//读取到缓冲区的总字节数，如果没有更多的数据，因为文件的结尾已经到达，则为-1
				out.write(buffer,0,len);//将该输入流中的len个字节数据读入一个字节数组
			}
		}
		finally {
			if (in!=null) {
				try {
					in.close();
				} catch (Exception e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				}
			}
		}
		
	}

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

}

 发布服务后浏览器显示：

下面我们来尝试中文：美女.jpg

demo

package cn.itcaste.web.servlet;

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

import javax.imageio.stream.FileCacheImageInputStream;
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 org.apache.taglibs.standard.tag.common.core.OutSupport;

/**
 * 文件下载案例
 */
@WebServlet("/ResponseDemo3")
public class ResponseDemo3 extends HttpServlet {
  
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		//如果下载名是中文，要经过url编码
		String path=this.getServletContext().getRealPath("/download/美女.jpg");//获取绝对路径
		String filename=path.substring(path.lastIndexOf("/")+1);//获取文件名称
		filename=URLEncoder.encode(filename, "UTF-8");//按理说这样就不会中文乱码，但是只有谷歌生效了，safari不行，我还在寻找办法
		System.out.println(filename);
		System.out.println(URLDecoder.decode(filename, "UTF-8"));
	//	response.setHeader("content-type", "charset=UTF-8");//控制浏览器输出时时所查询的码表
		response.setHeader("content-disposition", "attachment;filename="  +filename );  //设置成按下载方式读取的响应头
		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){//读取到缓冲区的总字节数，如果没有更多的数据，因为文件的结尾已经到达，则为-1
				out.write(buffer,0,len);//将该输入流中的len个字节数据读入一个字节数组
			}
		}
		finally {
			if (in!=null) {
				try {
					in.close();
				} catch (Exception e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				}
			}
		}
		
	}

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

}

浏览器显示：

  HttpServletResponse细节三-------》response实现输出随机图片

先来看效果：------》目的在于防止恶意注册

 demo：

package cn.itcaste.web.servlet;

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

/**
 * Servlet implementation class ResponseDemo4
 */
@WebServlet("/ResponseDemo4")
public class ResponseDemo4 extends HttpServlet {
   public static final int WIDTH=120;
   public static final int HEIGHT=35;   
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //BufferedImage.TYPE_INT_RGB图像类型
		BufferedImage image=new BufferedImage(WIDTH, HEIGHT,BufferedImage.TYPE_INT_RGB);//在内存中构建出一幅图像
		Graphics g=image.getGraphics();//得到图形！Graphics类是所有图形上下文的抽象基类，允许应用程序绘制在各种设备上实现的组件以及屏幕外图像。
		
		//1.设置背景色
		setBackGround(g);
		
		//2.设置边框
		setBorder(g);
	
		//3.画干扰线
		drawRandomLine(g);
		
		//4.画随机数
		drawRandomNum((Graphics2D)g);
		
		//5.图形写给随机数
		response.setContentType("image/jpeg");
		//发头控制浏览器不要缓存
		response.setDateHeader("expries", -1);
		response.setHeader("Cache-Control", "no-cache");
		response.setHeader("Pragma ","no-cache" );
		ImageIO.write(image, "jpg",  response.getOutputStream());
		
		
	}
	/**
	 * @param g
	 * 设置背景色
	 */
	private void setBackGround(Graphics g) {
		g.setColor(Color.WHITE);
		g.fillRect(0, 0, WIDTH, HEIGHT);
		
		
	}
	/**
	 * @param g
	 * 设置边框
	 */
	private void setBorder(Graphics g) {
		g.setColor(Color.RED);
		g.drawRect(0, 0, WIDTH-2, HEIGHT-2);
		
	}
	/**
	 * @param g
	 * 画干扰线
	 */
	private void drawRandomLine(Graphics g) {
		g.setColor(Color.GREEN);
		for(int i=0;i<5;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);
		}
	}
	/**
	 * @param g
	 * 画随机数
	 */
	private void drawRandomNum(Graphics2D g) {
		g.setColor(Color.BLACK);
		String c1 = null;
		g.setFont(new Font("宋体", Font.BOLD, 18));
		for(int i=0;i<4;i++){
			int d=new Random().nextInt()%30;
			char c=(char) (0x4e00+(int)(Math.random()*(0x9fa5-0x4e00+1)));
			c1 = String.valueOf(c);
			g.rotate((d*3.14)/180,( WIDTH-(30*i)-30),(HEIGHT-20));
			g.drawString(c1,( WIDTH-(30*i)-30), (HEIGHT-15));
			g.rotate((-1*d*3.14)/180,( WIDTH-(30*i)-30),(HEIGHT-20));
		
		}
	}







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

}

 点击图片换一张js：

HttpServletResponse细节二-------》response实现 refresh定时刷新页面以及特定情景

/**
 * Servlet implementation class ResponseDemo5
 */
@WebServlet("/ResponseDemo5")
public class ResponseDemo5 extends HttpServlet {
	//控制浏览器定时刷新
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		//假设这是一个用于处理登录的servlet
		
		
		//假设程序运行到此，用户等录成功
		
		
		//test1(response);
		response.setCharacterEncoding("UTF-8");
		response.setContentType("text/html;charset=UTF-8 ");
		response.getWriter().write("登录成功，三秒后将跳转到首页，如果没有，请点击<a href='/day04/ResponseDemo4'>超链接</a>");
		response.setHeader("refresh", "3;url='/day04/ResponseDemo4'");//每隔三秒拿一次数据 
	}

	private void test1(HttpServletResponse response) throws IOException {
		response.setHeader("refresh", "3");//每隔三秒拿一次数据 
		String data=new Random().nextInt(10000)+"";
		response.getWriter().write(data);
	}

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

}

 浏览器先看到如下，不点击超链接则3秒后自动跳转，点击则立刻跳转：

HttpServletResponse细节三-------》控制浏览器要缓存

/**
 * 控制浏览器要缓存
 */
@WebServlet("/ResponsDemo6")
public class ResponseDemo6 extends HttpServlet {
	
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		response.setDateHeader("expires", System.currentTimeMillis()+1000*3600);//设置缓存时间，当前时间加一秒乘3600=一天
		String data="aaaaaaaaa";
		response.getWriter().write(data);
	}

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

}

 HttpServletResponse细节四-------》重定向

/**
 * 实现请求重定向
 * 地址栏会发生变化：适用于登录跳转首页，购物
 */
@WebServlet("/ResponseDemo7")
public class ResponseDemo7 extends HttpServlet {

	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		
//	 response.setStatus(302);
//	 response.setHeader("location", "/day04/1.jsp");
		response.sendRedirect("/day04/1.jsp");//这句可以代替上面两句，重定向等于发送两次请求
	}

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

}

  HttpServletResponse细节五-------》 

       response.getOutputStream();
        response.getWriter();

不能同时调用