web项目中验证码的实现步骤

1. 创建工具类：生成一个可成一张图片的工具类:代码如下(附录)可以直使用
2. 创建另一个工具类：随机生成数字字母的组合：
   1. 代码如下：

package com.bjsxt.lc.util;
import java.util.Random;
public class RandomString
{
public static String randomCode(int size)
{
//用来存储验证码
StringBuffer code = new StringBuffer();
String sourceStr = "123456789abcdefghijklmnopqrstuvwxyzABCDEFGHJKLMNOPQRSTUVWXYZ";

Random random = new Random();
for(int i=0; i<size; i++)
{
code.append(sourceStr.charAt(random.nextInt(30))+"");
}
return code.toString();
}
//测试方法
public static void main(String[] args)
{
for(int i=0; i<40; i++)
{
String code = randomCode(4);
System.out.println(code);
}
}
}

3 创建action其中调用两个工具类

outputImage(int w, int h, OutputStream os, String code)方法，

1. 参数说明：
   1. w：img的宽
   2. H：img的高
   3. os：img的输出流
   4. os:片上的验证码
2. 创建一个action(struts2框架)
   1. 将os输出流直接堆到response.getOutputStream()上，输出到网页，这时应当将返回值置为空，

代码

package com.bjsxt.lc.action;

import java.io.IOException;

import org.apache.catalina.deploy.ContextResource;
import org.apache.struts2.ServletActionContext;

import com.bjsxt.lc.action.BasicAction;
import com.bjsxt.lc.util.RandomString;
import com.bjsxt.lc.util.VerifyCodeUtils;

/**
 * 一些公共的Action
 * @author Administrator
 *
 */
public class CommonAction extends BasicAction
{
/**
 * 
 */
private static final long serialVersionUID = 1L;

/***
 * 生成验证验
 * @return
 */  
public String veritfCode()
{
//logger.info("--veritfCode--");
String code = RandomString.randomCode(4);
request.getSession().setAttribute("code", code);
try
{
VerifyCodeUtils.outputImage(120,80,response.getOutputStream(),code);
} catch (Exception e)
{
logger.info("-------------------------");
e.printStackTrace();
}
return null;
}
}

4、在jsp页面中<img src="${%home%}">引用：

<div class="form-group">
<label for="email" class="col-sm-2 control-label">验证码</label>
<div class="col-sm-8">
<div class="input-group">
<span class="input-group-addon"> <a href="#" tabindex="-1"
onclick="return refreshCode('imgCode');">
 <img id="imgCode" src="${pageContext.request.contextPath}/common_veritfCode.htm" onclick="" title="点击刷新验证码" width="75" height="20" />
</a>
</span> <input type="text" id="code" name="code" class="form-control"
placeholder="验证码">
</div>
</div>
</div>

5、添加js脚本，达到跟换验证码的效果：

function refreshCode(imgCode)
{
var dom = $("#"+imgCode);
dom.attr("src","/auth_mana1/common_veritfCode.htm?new="+new Date());
return false;
}

附录：生成随机验证图片的代码(从网上copy的)

1. package com.bjsxt.lc.util;
   
   import java.awt.Color;
   import java.awt.Font;
   import java.awt.Graphics;
   import java.awt.Graphics2D;
   import java.awt.LinearGradientPaint;
   import java.awt.Paint;
   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);
   }
   
   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) throws IOException
   {
   File dir = new File("F:/verifies");
   int w = 200, h = 80;
   for (int i = 0; i < 2; i++)
   {
   String verifyCode = generateVerifyCode(4);
   File file = new File(dir, verifyCode + ".jpg");
   outputImage(w, h, file, verifyCode);
   }
   }
   }