第一种方法：
在xxxControl 控制器下面新建返回验证码的方法：
public void captcha() {
renderCaptcha();
}
在前台页面中这样调用：
<img title="点击刷新" class="captcha" src="/login/captcha" onclick="updateCaptcha();">
<script>
function updateCaptcha() {
$(".captcha").attr("src", "/login/captcha?v=" + Math.random());
$("#captchaInput").val("");
}
</script>
后台验证验证码是否正确：
boolean result = validateCaptcha("inputRandomCode");//inputRandomCode是用户提交过来的验证码
第二种方法，自己新建一个类来实现：
import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.security.MessageDigest;
import java.util.Random;
import javax.imageio.ImageIO;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.Cookie;
import com.jfinal.core.Controller;
import com.jfinal.kit.StrKit;
import com.jfinal.render.Render;
/**
* @Author www.hiai.top
* @Email goodsking@163.com
* 图形验证类
*/
public class MyCaptchaRender extends Render{
@SuppressWarnings("unused")
private static final long serialVersionUID = -7599510915228560611L;
private static final String[] strArr = {"3", "4", "5", "6", "7", "8", "9", "A", "B", "C", "D", "E", "F", "G", "H", "J", "K", "M", "N", "P", "Q", "R", "S", "T", "U", "V", "W", "X", "Y"};
private static String randomCodeKey = "JFINAL_JLHHWH_Key";
private static boolean caseInsensitive = true;
private int img_width = 85;
private int img_height = 20;
private int img_randNumber = 6;
public MyCaptchaRender() {
}
public MyCaptchaRender(String randomKey) {
if (StrKit.isBlank(randomKey))
throw new IllegalArgumentException("randomKey can not be blank");
randomCodeKey = randomKey;
}
public MyCaptchaRender(int width, int height, int count, boolean isCaseInsensitive) {
if(width <=0 || height <=0 || count <=0)
{
throw new IllegalArgumentException("Image width or height or count must be > 0");
}
this.img_width = width;
this.img_height = height;
this.img_randNumber = count;
caseInsensitive = isCaseInsensitive;
}
public MyCaptchaRender(String randomKey,int width, int height, int count, boolean isCaseInsensitive) {
if (StrKit.isBlank(randomKey))
throw new IllegalArgumentException("randomKey can not be blank");
randomCodeKey = randomKey;
if(width <=0 || height <=0 || count <=0)
{
throw new IllegalArgumentException("Image width or height or count must be > 0");
}
this.img_width = width;
this.img_height = height;
this.img_randNumber = count;
caseInsensitive = isCaseInsensitive;
}
public void render() {
BufferedImage image = new BufferedImage(img_width, img_height, BufferedImage.TYPE_INT_RGB);
String vCode = drawGraphic(image);
vCode = encrypt(vCode);
Cookie cookie = new Cookie(randomCodeKey, vCode);
cookie.setMaxAge(-1);
cookie.setPath("/");
response.addCookie(cookie);
response.setHeader("Pragma","no-cache");
response.setHeader("Cache-Control","no-cache");
response.setDateHeader("Expires", 0);
response.setContentType("image/jpeg");
ServletOutputStream sos = null;
try {
sos = response.getOutputStream();
ImageIO.write(image, "jpeg",sos);
} catch (Exception e) {
throw new RuntimeException(e);
}
finally {
if (sos != null)
try {sos.close();} catch (IOException e) {e.printStackTrace();}
}
}
private String drawGraphic(BufferedImage image){
// 获取图形上下文
Graphics g = image.createGraphics();
// 生成随机类
Random random = new Random();
// 设定背景色
g.setColor(getRandColor(200, 250));
g.fillRect(0, 0, img_width, img_height);
// 设定字体
g.setFont(new Font("Times New Roman", Font.PLAIN, 18));
// 随机产生155条干扰线，使图象中的认证码不易被其它程序探测到
g.setColor(getRandColor(160, 200));
for (int i = 0; i < 155; i++) {
int x = random.nextInt(img_width);
int y = random.nextInt(img_height);
int xl = random.nextInt(12);
int yl = random.nextInt(12);
g.drawLine(x, y, x + xl, y + yl);
}
// 取随机产生的认证码(img_randNumber位数字)
String sRand = "";
for (int i = 0; i < img_randNumber; i++) {
String rand = String.valueOf(strArr[random.nextInt(strArr.length)]);
sRand += rand;
// 将认证码显示到图象中
g.setColor(new Color(20 + random.nextInt(110), 20 + random.nextInt(110), 20 + random.nextInt(110)));
// 调用函数出来的颜色相同，可能是因为种子太接近，所以只能直接生成
g.drawString(rand, 13 * i + 6, 23);
}
// 图象生效
g.dispose();
return sRand;
}
/*
* 给定范围获得随机颜色
*/
private Color getRandColor(int fc, int bc) {
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);
}
private static final String encrypt(String srcStr) {
try {
String result = "";
MessageDigest md = MessageDigest.getInstance("MD5");
byte[] bytes = md.digest(srcStr.getBytes("utf-8"));
for(byte b:bytes){
String hex = Integer.toHexString(b&0xFF).toUpperCase();
result += ((hex.length() ==1 ) ? "0" : "") + hex;
}
return result;
} catch (Exception e) {
throw new RuntimeException(e);
}
}
public static boolean validate(Controller controller, String inputRandomCode) {
if (StrKit.isBlank(inputRandomCode))
return false;
try {
if(caseInsensitive)
inputRandomCode = inputRandomCode.toUpperCase();
inputRandomCode = encrypt(inputRandomCode);
return inputRandomCode.equals(controller.getCookie(randomCodeKey));
} catch (Exception e) {
e.printStackTrace();
return false;
}
}
}
后台这样验证验证码是否正确：
boolean validate = MyCaptchaRender.validate(this, inputRandomCode);//inputRandomCode是用户提交过来的验证码
前台的调用同上面的使用方法
第二种方法控制验证的大小，以及验证中间的字体显示的位置，在代码的第115行中，显示的是坐标：
// 调用函数出来的颜色相同，可能是因为种子太接近，所以只能直接生成
g.drawString(rand, 13 * i + 6, 23);
