在用户登录的时候，为了防止机器人攻击都会设置输入验证码，本篇文章就是介绍java如何生成验证码并使用在springMVC项目中的。
第一步：引入生成图片验证码的工具类
import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.RenderingHints;
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; import javax.imageio.ImageIO;
/**
* VerifyCodeUtils Description: (验证码生成)
*/
public class VerifyCodeUtils{ //使用到Algerian字体，系统里没有的话需要安装字体，字体只显示大写，去掉了1,0,i,o几个容易混淆的字符
public 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.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();
} /**
* 生成随机验证码文件,并返回验证码值
* @param w
* @param h
* @param outputFile
* @param verifySize
* @return
* @throws IOException
*/
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;
} /**
* 输出随机验证码图片流,并返回验证码值
* @param w
* @param h
* @param os
* @param verifySize
* @return
* @throws IOException
*/
public static String outputVerifyImage(int w, int h, OutputStream os, int verifySize) throws IOException{
String verifyCode = generateVerifyCode(verifySize);
outputImage(w, h, os, verifyCode);
return verifyCode;
} /**
* 生成指定验证码图像文件
* @param w
* @param h
* @param outputFile
* @param code
* @throws IOException
*/
public static void outputImage(int w, int h, File outputFile, String code) 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, code);
fos.close();
} catch(IOException e){
throw e;
}
} /**
* 输出指定验证码图片流
* @param w
* @param h
* @param os
* @param code
* @throws IOException
*/
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);
} } }
}
第二步：调用验证码的接口
/**
* 生成验证码
* @param response
*/
@RequestMapping(value="newVerify" ,method=RequestMethod.GET)
public void newVerify(HttpServletRequest request, HttpServletResponse response){
//生成随机字串
String verifyCode = VerifyCodeUtils.generateVerifyCode(4);
System.out.println(verifyCode);
System.out.println(request.getSession().getAttribute("verCode"));
//删除以前的
request.getSession().removeAttribute("verCode");
//进行更新
request.getSession().setAttribute("verCode", verifyCode.toLowerCase());
System.out.println(request.getSession().getAttribute("verCode"));
//生成图片
int w = 100, h = 30;
try {
VerifyCodeUtils.outputImage(w, h, response.getOutputStream(), verifyCode);
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
第三步：前台界面调用
<img id="img" src="router/newVerify" style="width: 200px;height: 50px"/>
没看错，就是这一句话即可，src里面填第二步设置的url即可，当然很多场景中都会遇到点击更换验证码的情况，则需要如下这段代码
<button id="changeimg">看不清，换一张</button><br/>
$("#changeimg").click(function(){
$("#img").attr("src", "router/newVerify?date="+new Date());
});
这里之所以后面会跟一个date参数是防止浏览器看到相同的url直接从缓存读取链接，并无任何实际意义、
第四步：后台校验验证码
String verCode = (String)request.getSession().getAttribute("verCode");
boolean flag = verCode.equals(yzm.toLowerCase());
flag为true则验证成功，false则验证码输入错误。
至此，结束。