1.用户一开始登录的时候, 不建议出现验证码, 这一点在很多网站上已经体现的很好了, 只有当用户连续输错三次或者以上才会要求用户输入验证码.
2.记录用户输错次数最好不要使用 session 来记录, 因为 session 是跟客户端浏览器会话有关的, 如果用重启浏览器或者换新的浏览器再来登录或者试错, 就是新的回话了, 原来记录的错误次数就失效了. 建议此处采用缓存机制来实现, 简单处理就是采用 Map用户登录id, 错误次数> 来实现, 如果有多台服务器负载的话, 就需要采用另外的缓存机制, 比如采用 Redis.
3.当用户输入完用户名以后, 就需要用登录名进行判断, 是否需要进行验证码校验.
4.生成的验证码与 session 绑定, 是否需要校验验证码, 要根据用户规定时间内失败的次数来判断.
原生的 servlet 可以直接 write 图片到客户端. 但是刚用 springMVC 的童鞋可能不知道怎么在此框架下返回图片. 其实在本质上用 spring 返回图片跟用 servlet 是一样的。都是使用的 HttpServletResponse 来返回图片.
/**
* 生成验证码
* @param request
* @param response
*/
@RequestMapping(value = "login/getVerifyCode")
public void getVerifyCode(HttpServletRequest request,HttpServletResponse response){
response.setHeader("Pragma","No-cache");
response.setHeader("Cache-Control", "no-cache");
response.setDateHeader("Expires", 0);
response.setContentType("image/jpeg");
//生成随机字符串
String verifyCode = VerifyCodeUtils.generateVerifyCode(4);
//存入Session, 此处可以根据自己的需求
HttpSession session = request.getSession();
session.setAttribute("verifyCode",verifyCode);
//生成图片
int w = 100, h = 35;
try {
//将图片写入到 response 的输出流即可将图片返回到客户端了
VerifyCodeUtils.outputImage(w, h , response.getOutputStream(), verifyCode);
} catch (IOException e) {
logger.error("生成验证码失败, Cause by: {}", e.getMessage(), e);
}
}
网上找到的一个, 还不错.
import javax.imageio.ImageIO;
import java.awt.*;
import java.awt.geom.AffineTransform;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.util.Arrays;
import java.util.Random;
/**
* 生成图片流
* @Description: Created by zcqshine on 2017/5/18.
*/
public class VerifyCodeUtils {
private static final String VERIFY_CODES = "23456789ABCDEFGHJKLMNPQRSTUVWXYZ";
private static Random random = new Random();
/**
* 使用系统默认字符源生成验证码
* @param verifySize 验证码长度
* @return
*/
public static String generateVerifyCode(int verifySize){
return generateVerifyCode(verifySize, VERIFY_CODES);
}
/**
* 使用指定源生成验证码
* @param verifySize 验证码长度
* @param sources 验证码字符源
* @return
*/
public static String generateVerifyCode(int verifySize, String sources){
if (sources == null || sources.trim().length() == 0){
sources = VERIFY_CODES;
}
int codesLen = sources.length();
Random rand = new Random(System.currentTimeMillis());
StringBuilder verifyCode = new StringBuilder(verifySize);
for (int i = 0; i verifySize; i++){
verifyCode.append(sources.charAt(rand.nextInt(codesLen -1 )));
}
return verifyCode.toString();
}
/**
* 输出随机验证码图片流, 并返回验证码值
* @param w
* @param h
* @param outputFile
* @param verifySize
* @return
*/
public static String outputVerifyImage(int w, int h, File outputFile, int verifySize) throws IOException{
String verifyCode = generateVerifyCode(verifySize);
outputImage(w,h,outputFile,verifyCode);
return verifyCode;
}
/**
* 生成指定验证码图像文件
* @param w
* @param h
* @param outputFile
* @param verifyCode
* @throws IOException
*/
public static void outputImage(int w, int h, File outputFile, String verifyCode) throws IOException{
if (outputFile == null){
return;
}
File dir = outputFile.getParentFile();
if(!dir.exists()){
dir.mkdirs();
}
try {
outputFile.createNewFile();
FileOutputStream fos = new FileOutputStream(outputFile);
outputImage(w, h, fos, verifyCode);
fos.close();
} catch (IOException e) {
throw e;
}
}
public static void outputImage(int w, int h, OutputStream os, String code) throws IOException{
int verifySize = code.length();
BufferedImage image = new BufferedImage(w,h, BufferedImage.TYPE_INT_RGB);
Random rand = new Random();
Graphics2D g2 = image.createGraphics();
g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,RenderingHints.VALUE_ANTIALIAS_ON);
Color[] colors = new Color[5];
Color[] colorSpaces = new Color[]{Color.WHITE, Color.CYAN, Color.GRAY,
Color.LIGHT_GRAY, Color.MAGENTA, Color.ORANGE,
Color.PINK, Color.YELLOW};
float[] fractions = new float[colors.length];
for (int i = 0; i colors.length; i++){
colors[i] = colorSpaces[rand.nextInt(colorSpaces.length)];
fractions[i] = rand.nextFloat();
}
Arrays.sort(fractions);
g2.setColor(Color.GRAY); //设置边框色
g2.fillRect(0,0, w, h);
Color c = getRandColor(200, 250);
g2.setColor(c); //设置背景色
g2.fillRect(0, 2, w, h-4);
//绘制干扰线
Random random = new Random();
g2.setColor(getRandColor(160, 200));// 设置线条的颜色
for (int i = 0; i 20; i++) {
int x = random.nextInt(w - 1);
int y = random.nextInt(h - 1);
int xl = random.nextInt(6) + 1;
int yl = random.nextInt(12) + 1;
g2.drawLine(x, y, x + xl + 40, y + yl + 20);
}
// 添加噪点
float yawpRate = 0.05f;// 噪声率
int area = (int) (yawpRate * w * h);
for (int i = 0; i area; i++) {
int x = random.nextInt(w);
int y = random.nextInt(h);
int rgb = getRandomIntColor();
image.setRGB(x, y, rgb);
}
shear(g2, w, h, c);// 使图片扭曲
g2.setColor(getRandColor(100, 160));
int fontSize = h-4;
Font font = new Font("Algerian", Font.ITALIC, fontSize);
g2.setFont(font);
char[] chars = code.toCharArray();
for(int i = 0; i verifySize; i++){
AffineTransform affine = new AffineTransform();
affine.setToRotation(Math.PI / 4 * rand.nextDouble() * (rand.nextBoolean() ? 1 : -1), (w / verifySize) * i + fontSize/2, h/2);
g2.setTransform(affine);
g2.drawChars(chars, i, 1, ((w-10) / verifySize) * i + 5, h/2 + fontSize/2 - 10);
}
g2.dispose();
ImageIO.write(image, "jpg", os);
}
private static Color getRandColor(int fc, int bc) {
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 int getRandomIntColor() {
int[] rgb = getRandomRgb();
int color = 0;
for (int c : rgb) {
color = color 8;
color = color | c;
}
return color;
}
private static int[] getRandomRgb() {
int[] rgb = new int[3];
for (int i = 0; i 3; i++) {
rgb[i] = random.nextInt(255);
}
return rgb;
}
private static void shear(Graphics g, int w1, int h1, Color color) {
shearX(g, w1, h1, color);
shearY(g, w1, h1, color);
}
private static void shearX(Graphics g, int w1, int h1, Color color) {
int period = random.nextInt(2);
boolean borderGap = true;
int frames = 1;
int phase = random.nextInt(2);
for (int i = 0; i h1; i++) {
double d = (double) (period >> 1)
* Math.sin((double) i / (double) period
+ (6.2831853071795862D * (double) phase)
/ (double) frames);
g.copyArea(0, i, w1, 1, (int) d, 0);
if (borderGap) {
g.setColor(color);
g.drawLine((int) d, i, 0, i);
g.drawLine((int) d + w1, i, w1, i);
}
}
}
private static void shearY(Graphics g, int w1, int h1, Color color) {
int period = random.nextInt(40) + 10; // 50;
boolean borderGap = true;
int frames = 20;
int phase = 7;
for (int i = 0; i w1; i++) {
double d = (double) (period >> 1)
* Math.sin((double) i / (double) period
+ (6.2831853071795862D * (double) phase)
/ (double) frames);
g.copyArea(i, 0, 1, h1, 0, (int) d);
if (borderGap) {
g.setColor(color);
g.drawLine(i, (int) d, i, 0);
g.drawLine(i, (int) d + h1, i, h1);
}
}
}
public static void main(String[] args) {
File dir = new File("/Users/zcqshine/Downloads/test");
int w = 200, h= 80;
for (int i = 0; i 50; i++){
String verifyCode = generateVerifyCode(4);
File file = new File(dir, verifyCode + ".jpg");
try {
outputImage(w, h, file, verifyCode);
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
