Servlet-SrpingMVC 生成验证码

在SpringMVC中配置生成验证码：

 import org.springframework.stereotype.Controller;
 import org.springframework.web.bind.annotation.RequestMapping;

 import java.awt.Color;
 import java.awt.Graphics;
 import java.awt.image.BufferedImage;
 import java.io.IOException;
 import java.io.PrintWriter;
 import java.util.Random;

 import javax.imageio.ImageIO;
 import javax.servlet.ServletException;
 import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletResponse;

 @Controller
 public class RegisterController {

     // 图片高度
     private static final int IMG_HEIGHT = 100;
     // 图片宽度
     private static final int IMG_WIDTH = 30;
     // 验证码长度
     private static final int CODE_LEN = 4;

     @RequestMapping(value = "/getCode.action")
     public void getCode(HttpServletRequest req, HttpServletResponse resp)
             throws ServletException, IOException {
         // 用于绘制图片，设置图片的长宽和图片类型（RGB)
         BufferedImage bi = new BufferedImage(IMG_HEIGHT, IMG_WIDTH, BufferedImage.TYPE_INT_RGB);
         // 获取绘图工具
         Graphics graphics = bi.getGraphics();
         graphics.setColor(new Color(100, 230, 200)); // 使用RGB设置背景颜色
         graphics.fillRect(0, 0, 100, 30); // 填充矩形区域

         // 验证码中所使用到的字符
         char[] codeChar = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456".toCharArray();
         String captcha = ""; // 存放生成的验证码
         Random random = new Random();
         for(int i = 0; i < CODE_LEN; i++) { // 循环将每个验证码字符绘制到图片上
             int index = random.nextInt(codeChar.length);
             // 随机生成验证码颜色
             graphics.setColor(new Color(random.nextInt(150), random.nextInt(200), random.nextInt(255)));
             // 将一个字符绘制到图片上，并制定位置（设置x,y坐标）
             graphics.drawString(codeChar[index] + "", (i * 20) + 15, 20);
             captcha += codeChar[index];
         }
         // 将生成的验证码code放入sessoin中
         req.getSession().setAttribute("code", captcha);

         //设置响应头部
         response.setContentType("image/jpeg");

         // 通过ImageIO将图片输出
         ImageIO.write(bi, "JPG", resp.getOutputStream());

     }

 }