不施用Java插件来生成Java验证码

不使用Java插件来生成Java验证码
代码如：

import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.util.Random;
import javax.imageio.ImageIO;
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 org.mortbay.log.Log;
  
@SuppressWarnings("serial")
public class RegisterCaptcha1 extends HttpServlet {
  public void doPost(HttpServletRequest request, HttpServletResponse response) 
      throws ServletException, IOException {
       doGet(request, response);
  }
    
  public void doGet(HttpServletRequest request, HttpServletResponse response) 
      throws ServletException, IOException {
    //设置页面不缓存
    response.setHeader("Pragma","No-cache");
    response.setHeader("Cache-Control","no-cache");
    response.setDateHeader("Expires", 0);
  
    // 设置图片的长宽
   /* int width = Integer.parseInt(request.getParameter("width")); 
    int height = Integer.parseInt(request.getParameter("height"));*/
     int width=120, height=30;
    
    // 备选字符集
    // String[] set = {"a","b","c","d","e","f","g","h","i","j","k","l","m","n","o","p","q","r","s","t","u","v","y","z","0","1","2","3","4","5","6","7","8","9"};
    String[] set = {"0","1","2","3","4","5","6","7","8","9"};
    
    // 备选字体
    String[] fontTypes = {"\u5b8b\u4f53","\u65b0\u5b8b\u4f53","\u9ed1\u4f53","\u6977\u4f53","\u96b6\u4e66"};
      
    // 创建内存图像
    BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
    
    // 获取图形上下文
    Graphics graphics = image.getGraphics();
    
    // 设定图像背景色(设置为白色)
    graphics.setColor(Color.WHITE);
    graphics.fillRect(0, 0, width, height);
    
    //创建随机类的实例
    Random random = new Random();

    //在图片背景上增加噪点
    graphics.setColor(getRandColor(random,160,200));
    graphics.setFont(new Font("Times New Roman",Font.PLAIN,14));
    for (int i=0;i<6;i++) {
      graphics.drawString("*********************************************",0,5*(i+2));
    }

    // 生成随机数(6个字母)
    String  sRand="";
    int len=4;//四位
    for (int i=0;i<len;i++) {
      int nRand = random.nextInt(set.length);
      String subRand= set[nRand];
      sRand += subRand;

      // 设置字体的随机颜色
      graphics.setColor(getRandColor(random,10,150));

      // 设置随机字体及大小
      graphics.setFont(new Font(fontTypes[random.nextInt(fontTypes.length)],Font.BOLD,18 + random.nextInt(6)));

      // 将此字母画到图片上
      graphics.drawString(subRand, 17*i, 18);
    }

    // 将认证码存入session
    HttpSession session = request.getSession();
    session.setAttribute("rand",sRand);
    
    Log.debug("生成的验证码为：" + (String)session.getAttribute("rand"));
    
    // 输出图象到页面
    graphics.dispose();
    ImageIO.write(image, "JPEG", response.getOutputStream());
    response.getOutputStream().flush();
    response.getOutputStream().close();
  }
  
  public Color getRandColor(Random random,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);
  }

 }

    然后在web.xml中配置这个servlet，就可以在页面需要显示验证码的地方访问这个servlet来显示验证码。
    由于这个深成验证码的思路是，首先用Java的Random随机类来生成随机产生的字符串保存在Session中，然后把这个字符串用awt的画图类把字符串输入到图片上，并且加上干扰。因此在前台把用户输入的验证码传到后台与Session中拿到验证码字符串对比进行验证。