java生成图片验证码显示在页面上

java类：

import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics2D;
import java.awt.image.BufferedImage;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.util.Random;
import javax.imageio.ImageIO;
import java.io.ByteArrayInputStream;

/**
* 验证码生成器
*/
public class ValidateCode {

// 图片的宽度。
private int width = 160;
// 图片的高度。
private int height = 40;
// 验证码字符个数
private int codeCount = 5;
// 验证码干扰线数
private int lineCount = 150;
// 验证码
private static String code = null;
// 验证码图片Buffer
private BufferedImage buffImg=null;

private char[] codeSequence = { 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J','K', 'L',
'M', 'N',  'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W','X', 'Y',
'Z',  '1', '2', '3', '4', '5', '6', '7', '8', '9' };

public  ValidateCode() {
this.createCode();
}

/**
*
* @param width 图片宽
* @param height 图片高
*/
public  ValidateCode(int width,int height) {
this.width=width;
this.height=height;
this.createCode();
}

/**
*
* @param width 图片宽
* @param height 图片高
* @param codeCount 字符个数
* @param lineCount 干扰线条数
*/
public  ValidateCode(int width,int height,int codeCount,int lineCount) {
this.width=width;
this.height=height;
this.codeCount=codeCount;
this.lineCount=lineCount;
this.createCode();
}

public void createCode() {
int x = 0,fontHeight=0,codeY=0;
int red = 0, green = 0, blue = 0;

x = width / (codeCount +2);//每个字符的宽度
fontHeight = height - 2;//字体的高度
codeY = height - 4;

// 图像buffer
buffImg = new BufferedImage(width, height,BufferedImage.TYPE_INT_RGB);
Graphics2D g = buffImg.createGraphics();
// 生成随机数
Random random = new Random();
// 将图像填充为白色
g.setColor(Color.WHITE);
g.fillRect(0, 0, width, height);
// 创建字体
ImgFontByte imgFont=new ImgFontByte();
Font font =imgFont.getFont(fontHeight);
g.setFont(font);

for (int i = 0; i < lineCount; i++) {
int xs = random.nextInt(width);
int ys = random.nextInt(height);
int xe = xs+random.nextInt(width/8);
int ye = ys+random.nextInt(height/8);
red = random.nextInt(255);
green = random.nextInt(255);
blue = random.nextInt(255);
g.setColor(new Color(red, green, blue));
g.drawLine(xs, ys, xe, ye);
}

// randomCode记录随机产生的验证码
StringBuffer randomCode = new StringBuffer();
// 随机产生codeCount个字符的验证码。
for (int i = 0; i < codeCount; i++) {
String strRand = String.valueOf(codeSequence[random.nextInt(codeSequence.length)]);
// 产生随机的颜色值，让输出的每个字符的颜色值都将不同。
red = random.nextInt(255);
green = random.nextInt(255);
blue = random.nextInt(255);
g.setColor(new Color(red, green, blue));
g.drawString(strRand, (i + 1) * x, codeY);
// 将产生的四个随机数组合在一起。
randomCode.append(strRand);
}
// 将四位数字的验证码保存到Session中。
code = randomCode.toString();
}

public void write(String path) throws IOException {
OutputStream sos = new FileOutputStream(path);
this.write(sos);
}

public void write(OutputStream sos) throws IOException {
ImageIO.write(buffImg, "png", sos);
sos.close();
}

public BufferedImage getBuffImg() {
return buffImg;
}

public static String getCode() {
return code;
}

}

写一个servlet:

import java.io.IOException;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

import com.maijinjie.web.ValidateCode;

public class ValidateCodeServlet extends HttpServlet {
private static final long serialVersionUID = 1L;

public ValidateCodeServlet() {
super();
}
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {

response.setContentType("image/jpeg");
response.setHeader("Pragma", "no-cache");
response.setHeader("Cache-Control", "no-cache");
response.setDateHeader("Expires", 0);
ValidateCode vCode = new ValidateCode(100,30,4,5);
System.out.println(vCode.getCode());
HttpSession session = request.getSession();
session.removeAttribute("validateCode");
vCode.write(response.getOutputStream());
session.setAttribute("validateCode", vCode.getCode());
vCode.write(response.getOutputStream());
}

public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {

this.doGet(request, response);
}

}

类ImgFontByte:

import java.io.ByteArrayInputStream;  import java.awt.*;  /**  * ttf字体文件  * @author dsna  *  */  public class ImgFontByte {      public Font getFont(int fontHeight){          try {              Font baseFont = Font.createFont(Font.TRUETYPE_FONT, new ByteArrayInputStream(hex2byte(getFontByteStr())));              return baseFont.deriveFont(Font.PLAIN, fontHeight);          } catch (Exception e) {              return new Font("Arial",Font.PLAIN, fontHeight);          }      }            private  byte[] hex2byte(String str) {           if (str == null)              return null;          str = str.trim();          int len = str.length();          if (len == 0 || len % 2 == 1)              return null;            byte[] b = new byte[len / 2];          try {              for (int i = 0; i < str.length(); i += 2) {                  b[i / 2] = (byte) Integer                          .decode("0x" + str.substring(i, i + 2)).intValue();              }              return b;          } catch (Exception e) {              return null;          }      } /**   * ttf字体文件的十六进制字符串   * @return   */   private String getFontByteStr(){<span style="white-space:pre">	</span> return null;  }  }

生成验证码只需要访问此servlet即可，如果要放在页面某个位置。可以使用：<img alt="" id="yzm" src="${pageContext.request.contextPath}/ValidateCodeServlet" width="100" height="30">src中为访问servlet的地址。剩下就是判断输入的验证码与图片中验证码是否一致的问题了。src中url后面需要加上一个生成随机数的参数，否则src以为每次都一样就不加载了。