java基础入门源码

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package cn.itcast.chapter06.session.example02;

import java.io.*;

import javax.servlet.*;

import javax.servlet.http.*;

import java.awt.*;

import java.awt.image.*;

import javax.imageio.ImageIO;

public class CheckServlet extends HttpServlet

{

private static int WIDTH = 60; //验证码图片宽度

private static int HEIGHT = 20; //验证码图片高度

public void doGet(HttpServletRequest request,HttpServletResponse java基础入门源码 response)

throws ServletException,IOException

{

HttpSession session = request.getSession();

response.setContentType("image/jpeg");

ServletOutputStream sos = response.getOutputStream();

//设置浏览器不要缓存此图片

response.setHeader("Pragma","No-cache");

response.setHeader("Cache-Control","no-cache");

response.setDateHeader("Expires", 0);

//创建内存图象并获得其图形上下文

BufferedImage image =

new BufferedImage(WIDTH, HEIGHT, BufferedImage.TYPE_INT_RGB);

Graphics g = image.getGraphics();

//产生随机的认证码

char [] rands = generateCheckCode();

//产生图像

drawBackground(g);

drawRands(g,rands);

//结束图像的绘制过程，完成图像

g.dispose();

//将图像输出到客户端

ByteArrayOutputStream bos = new ByteArrayOutputStream();

ImageIO.write(image, "JPEG", bos);

byte [] buf = bos.toByteArray();

response.setContentLength(buf.length);

//下面的语句也可写成：bos.writeTo(sos);

sos.write(buf);

bos.close();

sos.close();

//将当前验证码存入到Session中

session.setAttribute("check_code",new String(rands));

//直接使用下面的代码将有问题，Session对象必须在提交响应前获得

//request.getSession().setAttribute("check_code",new String(rands));

}

//生成一个4字符的验证码

private char [] generateCheckCode()

{

//定义验证码的字符表

String chars = "0abcdefghijklmnopqrstuvwxyz";

char [] rands = new char[4];

for(int i=0; i<4; i++)

{

int rand = (int)(Math.random() * 36);

rands[i] = chars.charAt(rand);

}

return rands;

}

private void drawRands(Graphics g , char [] rands)

{

g.setColor(Color.BLACK);

g.setFont(new Font(null,Font.ITALIC|Font.BOLD,18));

//在不同的高度上输出验证码的每个字符

g.drawString("" + rands[0],1,17);

g.drawString("" + rands[1],16,15);

g.drawString("" + rands[2],31,18);

g.drawString("" + rands[3],46,16);

System.out.println(rands);

}

private void drawBackground(Graphics g)

{

//画背景

g.setColor(new Color(0xDCDCDC));

g.fillRect(0, 0, WIDTH, HEIGHT);

//随机产生120个干扰点

for(int i=0; i<120; i++)

{

int x = (int)(Math.random() * WIDTH);

int y = (int)(Math.random() * HEIGHT);

int red = (int)(Math.random() * 255);

int green = (int)(Math.random() * 255);

int blue = (int)(Math.random() * 255);

g.setColor(new Color(red,green,blue));

g.drawOval(x,y,1,0);

}

java基础入门源码

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