Jsp生成图片验证码

package cn.z.servlet;

import java.awt.Color;import java.awt.Graphics;
import java.awt.image.BufferedImage;
import java.io.IOException;
import javax.imageio.ImageIO;
import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse; import java.awt.Font;

public class GenerateCheckCodeServlet extends HttpServlet {

// 生成的验证码的宽与高
int WIDTH = 80, HEIGHT = 30;

public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.setDateHeader("Expires", 0);
response.setHeader("Cache-control", "no-cache");
response.setHeader("Pragma", "no-cache");

ServletOutputStream out = response.getOutputStream();
// 得到随机的验证码
char[] rands = generateCheckCode();

BufferedImage image = new BufferedImage(WIDTH, HEIGHT,
BufferedImage.TYPE_INT_RGB);
Graphics g = image.getGraphics();
// 先画背景
drawBackground(g);
// 再画验证码
drawCheckCode(g, rands);

g.dispose();
// 设置响应头为image/jpeg
response.setContentType("image/jpeg");

// 把验证码也放到session里，以便和用户手工输入的进行对比
request.getSession().setAttribute("check-code", new String(rands));
System.out.println(new String(rands));

// 输出图片
ImageIO.write(image, "JPEG", out);

//一定要的

out.clear();
out = pageContext.pushBody();

out.flush();
out.close();
}

// 生成4位随机验证码的函数
private char[] generateCheckCode() {
// 这个是用ASCII的方法，
char[] rands = new char[4];
int rand = -1;
for (int i = 0; i < rands.length; i++) {
while (rand < 48 || (rand > 57 && rand < 65)
|| (rand > 90 && rand < 97) || rand > 122) {

rand = (int) (Math.random() * 127);
// System.out.print(rand + "/t");
}
rands[i] = (char) rand;
}
return rands;
}

// 第二种生成验证码的方法
private char[] generateCheckCode2() {
// 这个是随机取出字符串中的字符.
String chars = "abcdefghijklmnopqrstuvwxyz123456789";
char[] rands = new char[4];
int rand = -1;
for (int i = 0; i < rands.length; i++) {

rand = (int) (Math.random() * chars.length());
rands[i] = chars.charAt(rand);
}
return rands;
}

private void drawCheckCode(Graphics g, char[] rands) {
// 在不同的高度画验证码的每一个字符
g.setColor(Color.BLACK);
g.setFont(new Font(null, Font.ITALIC | Font.BOLD, 18));
g.drawString("" + rands[0], 11, 25);
g.drawString("" + rands[1], 26, 15);
g.drawString("" + rands[2], 41, 23);
g.drawString("" + rands[3], 56, 18);
}

private void drawBackground(Graphics g) {
// 画背景
g.setColor(new Color(0xdcdcdc));
g.fillRect(0, 0, WIDTH, HEIGHT);

for (int i = 0; i < 500; i++) {
// 随机生成500个位置随机，颜色随机的干扰点，并画在背景上

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, 2, 0);
}
}
}