6.后台验证码-session作用域

首先要有生成验证码图片和验证码文字的逻辑

package cn.bingou.util;

import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics2D;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.OutputStream;
import java.util.Random;
import javax.imageio.ImageIO;
/**
 * 动态生成图片
 */
public class VerifyCode {
    // {"宋体", "华文楷体", "黑体", "华文新魏", "华文隶书", "微软雅黑", "楷体_GB2312"}
    private static String[] fontNames = { "宋体", "华文楷体", "黑体", "微软雅黑",  "楷体_GB2312" };
    // 可选字符
    //"23456789abcdefghjkmnopqrstuvwxyzABCDEFGHJKMNPQRSTUVWXYZ";
    private static String codes = "23456789abcdefghjkmnopqrstuvwxyzABCDEFGHJKMNPQRSTUVWXYZ";
    // 背景色
    private Color bgColor = new Color(255, 255, 255);
    // 基数(一个文字所占的空间大小)
    private int base = 30;
    // 图像宽度
    private int width = base * 4;
    // 图像高度
    private int height = base;
    // 文字个数
    private int len = 4;
    // 设置字体大小
    private int fontSize = 22;
    // 验证码上的文本
    private String text;

    private BufferedImage img = null;
    private Graphics2D g2 = null;

    /**
     * 生成验证码图片
     */
    public void drawImage(OutputStream outputStream) {
        // 1.创建图片缓冲区对象, 并设置宽高和图像类型
        img = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
        // 2.得到绘制环境
        g2 = (Graphics2D) img.getGraphics();
        // 3.开始画图
        // 设置背景色
        g2.setColor(bgColor);
        g2.fillRect(0, 0, width, height);

        StringBuffer sb = new StringBuffer();// 用来装载验证码上的文本

        for (int i = 0; i < len; i++) {
            // 设置画笔颜色 -- 随机
            // g2.setColor(new Color(255, 0, 0));
            g2.setColor(new Color(getRandom(0, 150), getRandom(0, 150),getRandom(0, 150)));

            // 设置字体
            g2.setFont(new Font(fontNames[getRandom(0, fontNames.length)], Font.BOLD, fontSize));

            // 旋转文字(-45~+45)
            int theta = getRandom(-45, 45);
            g2.rotate(theta * Math.PI / 180, 7 + i * base, height - 8);

            // 写字
            String code = codes.charAt(getRandom(0, codes.length())) + "";
            g2.drawString(code, 7 + i * base, height - 8);
            sb.append(code);
            g2.rotate(-theta * Math.PI / 180, 7 + i * base, height - 8);
        }

        this.text = sb.toString();

        // 画干扰线
        for (int i = 0; i < len + 2; i++) {
            // 设置画笔颜色 -- 随机
            // g2.setColor(new Color(255, 0, 0));
            g2.setColor(new Color(getRandom(0, 150), getRandom(0, 150),
                    getRandom(0, 150)));
            g2.drawLine(getRandom(0, 120), getRandom(0, 30), getRandom(0, 120),
                    getRandom(0, 30));
        }
        /**
         * 绘制边框
         */
        // 设置边框的颜色
        g2.setColor(Color.GRAY);
        // 绘制边框
        g2.drawRect(0, 0, width-1, height-1);
        
        // 4.保存图片到指定的输出流
        try {
             ImageIO.write(this.img, "JPEG", outputStream);
        } catch (Exception e) {
            e.printStackTrace();
            throw new RuntimeException(e);
        }finally{
            // 5.释放资源
            g2.dispose();
        }
    }
    
    /**
     * 获取验证码字符串
     * @return
     */
    public String getCode() {
        return this.text;
    }

    /*
     * 生成随机数的方法
     */
    private static int getRandom(int start, int end) {
        Random random = new Random();
        return random.nextInt(end - start) + start;
    }
    
    public static void main(String[] args) throws Exception {
        VerifyCode vc = new VerifyCode();
        vc.drawImage(new FileOutputStream("d:/vc.jpg"));
        System.out.println("执行成功~!");
    }
}

VerifyCode