生成验证码

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package cn.itcast.estore.web;

import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.image.BufferedImage;
import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
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;

/**
* 生成验证码Servlet
*
*
*/
public class CheckImgServlet extends HttpServlet {

private List<String> words = new ArrayList<String>();

@Override
public void init() throws ServletException {
// 读取成语文件内容
try {
BufferedReader in = new BufferedReader(new InputStreamReader(new FileInputStream(this.getServletContext().getRealPath("/WEB-INF/new_words.txt")),"utf-8"));
String line;
while ((line = in.readLine()) != null) {
words.add(line);
}
in.close();
} catch (Exception e) {
e.printStackTrace();
}
}

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

int width = 120;
int height = 30;

// 步骤一 绘制一张内存中图片
BufferedImage bufferedImage = new BufferedImage(width, height,
BufferedImage.TYPE_INT_RGB);

// 步骤二 图片绘制背景颜色 ---通过绘图对象
Graphics graphics = bufferedImage.getGraphics();// 得到画图对象 --- 画笔
// 绘制任何图形之前 都必须指定一个颜色
graphics.setColor(getRandColor(200, 250));
graphics.fillRect(0, 0, width, height);

// 步骤三 绘制边框
graphics.setColor(Color.WHITE);
graphics.drawRect(0, 0, width - 1, height - 1);

// 步骤四 四个随机数字
Graphics2D graphics2d = (Graphics2D) graphics;
// 设置输出字体
graphics2d.setFont(new Font("宋体", Font.BOLD, 18));

Random random = new Random();// 生成随机数
int index = random.nextInt(wor
ds.size());
String checkcode = words.get(index);// 获得生成成员

// 定义x坐标
int x = 10;
for (int i = 0; i < checkcode.length(); i++) {
// 随机颜色
graphics2d.setColor(new Color(20 + random.nextInt(110), 20 + random
.nextInt(110), 20 + random.nextInt(110)));
// 旋转 -30 --- 30度
int jiaodu = random.nextInt(60) - 30;
// 换算弧度
double theta = jiaodu * Math.PI / 180;

// 获得字母数字
char c = checkcode.charAt(i);

// 将生成汉字 加入buffer

// 将c 输出到图片
graphics2d.rotate(theta, x, 20);
graphics2d.drawString(String.valueOf(c), x, 20);
graphics2d.rotate(-theta, x, 20);
x += 30;
}

// 将验证码内容保存session
request.getSession().setAttribute("checkcode_session", checkcode);

// 步骤五 绘制干扰线
graphics.setColor(getRandColor(160, 200));
int x1;
int x2;
int y1;
int y2;
for (int i = 0; i < 30; i++) {
x1 = random.nextInt(width);
x2 = random.nextInt(12);
y1 = random.nextInt(height);
y2 = random.nextInt(12);
graphics.drawLine(x1, y1, x1 + x2, x2 + y2);
}

// 将上面图片输出到浏览器 ImageIO
graphics.dispose();// 释放资源
ImageIO.write(bufferedImage, "jpg", response.getOutputStream());

}

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

/**
* 取其某一范围的color
*
* @param fc
* int 范围参数1
* @param bc
* int 范围参数2
* @return Color
*/
private Color getRandColor(int fc, int bc) {
// 取其随机颜色
Random random = new Random();
if (fc > 255) {
fc = 255;
}
if (bc > 255) {
bc = 255;
}
int r = fc + random.nextInt(bc - fc);
int g = fc + random.nextInt(bc - fc);
int b = fc + random.nextInt(bc - fc);
return new Color(r, g, b);
}

}

大家只要把红色部分替换掉就可以了,非常通用,若要点击更换图片则在页面的js中写一段js代码就可以了,如下:

<script type="text/javascript">
var n=0;
function change(img){
n++;
img.src="/myDemo/checkImg?"+n;
}
</script>

生成验证码

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原文地址：http://www.cnblogs.com/shaoyang/p/5631401.html