后台生成验证码前台显示,防止前端绕过

转载至:后台生成验证码前台显示,防止前端绕过

后台通过代码生成验证码,保存在session中,用户登录的时候验证.

以下提供两种方式,都大同小异;

皆为参考他人文章,因时间较长,文章原文链接丢失,还请见谅!

第一种:

@RequestMapping(value = "authCode")
    public void getAuthCode(HttpServletRequest request, HttpServletResponse response,HttpSession session)
            throws IOException {
        int width = 63;
        int height = 37;
        Random random = new Random();
        //设置response头信息
        //禁止缓存
        response.setHeader("Pragma", "No-cache");
        response.setHeader("Cache-Control", "no-cache");
        response.setDateHeader("Expires", 0);
 
        //生成缓冲区image类
        BufferedImage image = new BufferedImage(width, height, 1);
        //产生image类的Graphics用于绘制操作
        Graphics g = image.getGraphics();
        //Graphics类的样式
        g.setColor(this.getRandColor(200, 250));
        g.setFont(new Font("Times New Roman",0,28));
        g.fillRect(0, 0, width, height);
        //绘制干扰线
        for(int i=0;i<40;i++){
            g.setColor(this.getRandColor(130, 200));
            int x = random.nextInt(width);
            int y = random.nextInt(height);
            int x1 = random.nextInt(12);
            int y1 = random.nextInt(12);
            g.drawLine(x, y, x + x1, y + y1);
        }
 
        //绘制字符
        String strCode = "";
        for(int i=0;i<4;i++){
            String rand = String.valueOf(random.nextInt(10));
            strCode = strCode + rand;
            g.setColor(new Color(20+random.nextInt(110),20+random.nextInt(110),20+random.nextInt(110)));
            g.drawString(rand, 13*i+6, 28);
        }
        //将字符保存到session中用于前端的验证
        session.setAttribute("strCode", strCode);
        g.dispose();
 
        ImageIO.write(image, "JPEG", response.getOutputStream());
        response.getOutputStream().flush();
 
    }
    
    
    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);
    }

 

调用方式:

<img src="authCode" id="codeImg"> <a href="javascript:;" onclick="chageCode()">看不清，换一张</a>
<script>
function chageCode(){
    $("#codeImg").attr('src','authCode?abc='+Math.random());
}
</script>

 

实现效果:

第二种:

@RequestMapping(value = "authCode")
    public void getAuthCode(HttpServletRequest request, HttpServletResponse response, HttpSession session)
            throws IOException {
        response.setContentType("image/jpeg");  
        response.setHeader("Pragma", "no-cache");  
        response.setHeader("Cache-Control", "no-cache");  
        response.setDateHeader("Expires", 0);  
        ValidateCode vCode = new ValidateCode(100,30,4,60);  
        session.removeAttribute("validateCode");  
        vCode.write(response.getOutputStream());  
        session.setAttribute("strCode", vCode.getCode());
        vCode.write(response.getOutputStream());  
}

 

ValidateCode类:

import java.awt.Color;
 
import java.awt.Font;
import java.awt.Graphics2D;
import java.awt.image.BufferedImage;
import java.io.ByteArrayInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.util.Random;
 
import javax.imageio.ImageIO;
 
/**
 * 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 = 50;
    // 验证码字符个数
    private int codeCount = 6;
    // 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 String getCode() {
        return code;
    }
 
}
class ImgFontByte {
    public Font getFont(int fontHeight){  
           try {  
               Font baseFont = Font.createFont(Font.ITALIC, new ByteArrayInputStream(hex2byte(getFontByteStr()))); 
               return baseFont.deriveFont(Font.PLAIN, fontHeight);  
           } catch (Exception e) {  
               return new Font("Consola",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(){ 
        return null;  
    }  
}

使用方式与第一种相同;

效果: