生成验证码

验证码的生成方案（本文供小白入门参考，技术大牛请自动忽略）

前台jsp页面：

生成验证码的位置：

<li class="fix"><input type="text" id="captcha" name="captcha" autocomplete="off" class="input fl" placeholder="请输入验证码" style="width:4.6rem;"/>    <a href="javascript:void(0);" class="fl"><img id="imgVerCode" src="${basePath}/captcha" style="height: 0.8rem; margin-left: 0.22rem;" onclick="changeCode();"/></a></li>

对应的js代码：

function changeCode() {    $("#imgVerCode").attr("src", "${basePath}/captcha?gf=" + new Date().getTime());}

说明：第一次加载页面时，根据路径映射后台为captcha的方法，初次生成验证码；点击验证码，调用changeCode()方法，再次映射后台为captcha对应的方法（也就是imageCaptha），更换验证码。

后台对应的代码：

@RequestMapping("/captcha")public void imageCaptcha(HttpServletRequest request,                         HttpServletResponse response) throws IOException {    Map<String, BufferedImage> map = ImageUtil.createImage();    String code = map.keySet().iterator().next(); // 得到所有的map的key值进行遍历(就是验证码)    BufferedImage image = map.get(code);    request.getSession().setAttribute("verCode", code);    byte[] imgBytes = ImageUtil.getInputStream(image); // 读入图片    response.setDateHeader("Expires", 0);    // Set standard HTTP/1.1 no-cache headers.    response.setHeader("Cache-Control",            "no-store, no-cache, must-revalidate");    // Set IE extended HTTP/1.1 no-cache headers (use addHeader).    response.addHeader("Cache-Control", "post-check=0, pre-check=0");    // Set standard HTTP/1.0 no-cache header.    response.setHeader("Pragma", "no-cache");    // return a jpeg    response.setContentType("image/jpeg");    ServletOutputStream os = response.getOutputStream();    os.write(imgBytes);    os.flush();    os.close();}

其中用到的工具类代码如下：

package com.huadingts.salesrecord.module.utils;

import com.sun.image.codec.jpeg.JPEGCodec;
import com.sun.image.codec.jpeg.JPEGImageEncoder;

import java.awt.*;
import java.awt.image.BufferedImage;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.util.HashMap;
import java.util.Map;
import java.util.Random;

/**
* 验证码工具类
*
* @author 
* @version
*/
public final class ImageUtil {

private static final String[] chars = { "1", "3", "4", "5", "6", "7", "8",
"9", "A", "B", "C", "D", "E", "F", "G", "H", "J", "K", "Q", "W",
"R", "T", "Y", "U", "X", "V", "N", "M" };

private static final int SIZE = 4;

private static final int LINES = 2;

private static final int WIDTH = 200;

private static final int HEIGHT = 100;

private static final int FONT_SIZE = 60;

public static Map<String, BufferedImage> createImage() {
StringBuffer sb = new StringBuffer();
BufferedImage image = new BufferedImage(WIDTH, HEIGHT,
BufferedImage.TYPE_INT_RGB);
Graphics graphic = image.getGraphics();
// graphic.setColor(Color.LIGHT_GRAY); // 底色
graphic.fillRect(0, 0, WIDTH, HEIGHT);
Random ran = new Random();
// 画随机字符
for (int i = 1; i <= SIZE; i++) {
int r = ran.nextInt(chars.length);
graphic.setColor(getRandomColor());
graphic.setFont(new Font(null, Font.BOLD + Font.ITALIC, FONT_SIZE));
graphic.drawString(chars[r], (i - 1) * WIDTH / SIZE,
(HEIGHT / 2) + 20);
sb.append(chars[r]);// 将字符保存，存入Session
}
// 画干扰线
for (int i = 1; i <= LINES; i++) {
graphic.setColor(getRandomColor());
graphic.drawLine(ran.nextInt(WIDTH), ran.nextInt(HEIGHT),
ran.nextInt(WIDTH), ran.nextInt(HEIGHT));
}
Map<String, BufferedImage> map = new HashMap<String, BufferedImage>();
map.put(sb.toString(), image);
return map;
}

public static Color getRandomColor() {
Random ran = new Random();
Color color = new Color(ran.nextInt(256), ran.nextInt(256),
ran.nextInt(256));
return color;
}

public static byte[] getInputStream(BufferedImage image) throws IOException {
ByteArrayOutputStream bos = new ByteArrayOutputStream();
JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(bos);
encoder.encode(image);
byte[] imgBytes = bos.toByteArray();
bos.close();
return imgBytes;
}

}