java实现验证码功能

通过java代码实现验证码功能的一般思路：

一、通过java代码生成一张验证码的图片，将验证码的图片保存到项目中的指定文件中去，代码如下：

package com.util;

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;

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);

}

/**

* 通过数值获取颜色

* @param fc

* @param bc

* @return

*/

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);

}

/**

* 获取一个随机的颜色

* @return

*/

private static int getRandomIntColor() {

int[] rgb = getRandomRgb();

int color = 0;

for (int c : rgb) {

color = color << 8;

color = color | c;

}

return color;

}

/**

* 获取一个随机的三位数的颜色值

* @return

*/

private static int[] getRandomRgb() {

int[] rgb = new int[3];

for (int i = 0; i < 3; i++) {

rgb[i] = random.nextInt(255);

}

return rgb;

}

/**

* 使图片扭曲

* @param g

* @param w1

* @param h1

* @param color

*/

private static void shear(Graphics g, int w1, int h1, Color color) {

shearX(g, w1, h1, color);

shearY(g, w1, h1, color);

}

/**

* 使图片X方向扭曲

* @param g

* @param w1

* @param h1

* @param 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);

}

}

}

/**

* 使图片Y方向扭曲

* @param g

* @param w1

* @param h1

* @param color

*/

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);

}

}

}

//生成一张验证码图片，并保存到项目的verifyCodeImg文件夹下

public static String createOneCodeImage(){

String imgName = "";

try {

File dir = new File("./verifyCodeImg");

int w = 100, h = 30;

String verifyCode = generateVerifyCode(4);

File file = new File(dir, verifyCode + ".jpg");

outputImage(w, h, file, verifyCode);

imgName = verifyCode;

} catch (IOException e) {

imgName = "";

e.printStackTrace();

}finally{

return imgName;

}

}

public static void main(String[] args) throws IOException {

String codeImage = VerifyCodeUtils.createOneCodeImage();

System.out.println(codeImage);

}

}

二、将项目中指定文件夹中刚刚生成的验证码图片的路径在登录页面显示出来，并将生成验证码返回的字符串保存在一个字符串变量中，假设保存在变量A中；

三、在用户登录时，通过登录中的输入框获取用户输入的验证码值，保存在一个字符串类型的变量中，假设保存在变量B中；

四、将变量A与变量B通过equals()方法进行比较，如果A.equals(B)那么用户输入的验证码正确，否则输入的验证码不正确；