生成的登錄驗證碼Java類RandomCodeRender

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.ServletOutputStream;
import javax.servlet.http.Cookie;
import com.jfinal.render.Render;
import com.wangxiaowang.common.util.StringUtil;

public class RandomCodeRender extends Render {

private static final String[] strArr = {"3", "4", "5", "6", "7", "8", "9", "A", "B", "C", "D", "E", "F", "G", "H", "J", "K", "M", "N", "P", "Q", "R", "S", "T", "U", "V", "W", "X", "Y"};
static final int WIDTH = 85, HEIGHT = 20;

private String randomCodeKey;

public RandomCodeRender(String randomCodeKey) {
    if (StringUtil.isBlank(randomCodeKey))
        throw new IllegalArgumentException("randomCodeKey can not be blank");
    this.randomCodeKey = randomCodeKey;
}

public void render() {
    BufferedImage image = new BufferedImage(WIDTH, HEIGHT, BufferedImage.TYPE_INT_RGB);
    String vCode = drawGraphic(image);
    vCode = RandomCodeService.encode(vCode);
    Cookie cookie = new Cookie(randomCodeKey, vCode);
    cookie.setMaxAge(-1);
    cookie.setPath("/");
    response.addCookie(cookie);
    response.setHeader("Pragma","no-cache");
    response.setHeader("Cache-Control","no-cache");
    response.setDateHeader("Expires", 0);
    response.setContentType("image/jpeg");

    ServletOutputStream sos = null;
    try {
        sos = response.getOutputStream();
        ImageIO.write(image, "jpeg",sos);
    } catch (Exception e) {
        throw new RuntimeException(e);
    }
    finally {
        try {sos.close();} catch (IOException e) {e.printStackTrace();}
    }
}

private String drawGraphic(BufferedImage image){
    // 獲取圖形上下文
    Graphics g = image.createGraphics();
    // 生成隨機類
    Random random = new Random();
    // 設定背景色
    g.setColor(getRandColor(200, 250));
    g.fillRect(0, 0, WIDTH, HEIGHT);
    // 設定字體
    g.setFont(new Font("Times New Roman", Font.PLAIN, 18));

    // 隨機產生155條干擾線，使圖象中的認證碼不易被其它程序探測到
    g.setColor(getRandColor(160, 200));
    for (int i = 0; i < 155; i++) {
        int x = random.nextInt(WIDTH);
        int y = random.nextInt(HEIGHT);
        int xl = random.nextInt(12);
        int yl = random.nextInt(12);
        g.drawLine(x, y, x + xl, y + yl);
    }

    // 取隨機產生的認證碼(6位數字)
    String sRand = "";
    for (int i = 0; i < 6; i++) {
        String rand = String.valueOf(strArr[random.nextInt(strArr.length)]);
        sRand += rand;
        // 將認證碼顯示到圖象中
        g.setColor(new Color(20 + random.nextInt(110), 20 + random.nextInt(110), 20 + random.nextInt(110)));
        // 調用函數出來的顏色相同，可能是因為種子太接近，所以只能直接生成
        g.drawString(rand, 13 * i + 6, 16);
    }

    // 圖象生效
    g.dispose();

    return sRand;
}

/*
 * 給定范圍獲得隨機顏色
 */
private Color getRandColor(int fc, int bc) {
    Random random = new Random();
    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);
}

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