package net.loyin.util;
import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.image.BufferedImage;
import java.io.ByteArrayOutputStream;
import java.util.Random;
import javax.imageio.ImageIO;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpSession;
/**
* 随机生成四位验证码,并输出图像
*/
@SuppressWarnings("serial")
public class ValidateCode extends HttpServlet {
private static final int WIDTH = 150;
private static final int HEIGHT = 50;
private static final String chars = "23456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghjkmnpqrstuvwxyz";
@Override
public void service(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("image/jpeg");
// 防止浏览器缓冲
response.setHeader("Pragma", "No-cache");
response.setHeader("Cache-Control", "no-cache");
response.setDateHeader("Expires", 0);
HttpSession session = request.getSession();
BufferedImage image = new BufferedImage(WIDTH, HEIGHT,BufferedImage.TYPE_INT_RGB);
Graphics g = image.getGraphics();
char[] rands = getCode(4);
drawBackground(g);
drawRands(g, rands);
g.dispose();
ServletOutputStream out = response.getOutputStream();
ByteArrayOutputStream bos = new ByteArrayOutputStream();
ImageIO.write(image, "PNG", bos);
byte[] buf = bos.toByteArray();
response.setContentLength(buf.length);
out.write(buf);
bos.close();
out.close();
session.setAttribute("check", new String(rands).toLowerCase());
}
/**
* 产生随机数
*
* @return
*/
private char[] getCode(int length) {
char[] rands = new char[length];
for (int i = 0; i < length; i++) {
int rand = (int) (Math.random() * chars.length());
rands[i] = chars.charAt(rand);
}
return rands;
}
/**
* 绘制背景
*
* @param g
*/
private void drawBackground(Graphics g) {
g.setColor(new Color(0xDCeeee));
g.fillRect(0, 0, WIDTH, HEIGHT);
Random random=new Random();
int len=0;
while(len<=5){
len=random.nextInt(15);
}
for (int i = 0; i < len; i++) {
int x = (int) (random.nextInt(WIDTH));
int y = (int) (random.nextInt(HEIGHT) );
int red = (int) (255-random.nextInt(200));
int green = (int) (255-random.nextInt(200) );
int blue = (int) (255-random.nextInt(200) );
g.setColor(new Color(red, green, blue));
// g.drawLine(x, y, random.nextInt(WIDTH)-x, random.nextInt(HEIGHT)-y);
g.drawOval(x, y, 2, 2);
}
}
/**
* 绘制验证码
*
* @param g
* @param rands
*/
private void drawRands(Graphics g, char[] rands) {
Random random=new Random();
g.setFont(new Font("黑体", Font.ITALIC | Font.BOLD, 45));
for(int i=0;i<rands.length;i++){
int red = (int) (random.nextInt(255));
int green = (int) (random.nextInt(255) );
int blue = (int) (random.nextInt(255) );
g.setColor(new Color(red, green, blue));
g.drawString("" + rands[i], i*40, 40);
}
}
@Override
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
service(request, response);
}
}