SpringMVC下獲取驗證碼

先說說登錄驗證碼的一些個人意見.

1. 用戶一開始登錄的時候, 不建議出現驗證碼, 這一點在很多網站上已經體現的很好了, 只有當用戶連續輸錯三次或者以上纔會要求用戶輸入驗證碼.
2. 記錄用戶輸錯次數最好不要使用 session 來記錄, 因爲 session 是跟客戶端瀏覽器會話有關的, 如果用重啓瀏覽器或者換新的瀏覽器再來登錄或者試錯, 就是新的回話了, 原來記錄的錯誤次數就失效了. 建議此處採用緩存機制來實現, 簡單處理就是採用 Map<用戶登錄id, 錯誤次數> 來實現, 如果有多臺服務器負載的話, 就需要採用另外的緩存機制, 比如採用 Redis.
3. 當用戶輸入完用戶名以後, 就需要用登錄名進行判斷, 是否需要進行驗證碼校驗.
4. 生成的驗證碼與 session 綁定, 是否需要校驗驗證碼, 要根據用戶規定時間內失敗的次數來判斷.

原生的 servlet 可以直接 write 圖片到客戶端. 但是剛用 springMVC 的童鞋可能不知道怎麼在此框架下返回圖片. 其實在本質上用 spring 返回圖片跟用 servlet 是一樣的。都是使用的 HttpServletResponse 來返回圖片.

springMVC 的 controller 裏獲取驗證碼的方法

/**
     * 生成驗證碼
     * @param request
     * @param response
     */
    @RequestMapping(value = "login/getVerifyCode")
	public void getVerifyCode(HttpServletRequest request,HttpServletResponse response){
        response.setHeader("Pragma","No-cache");
        response.setHeader("Cache-Control", "no-cache");
        response.setDateHeader("Expires", 0);
        response.setContentType("image/jpeg");

        //生成隨機字符串
        String verifyCode = VerifyCodeUtils.generateVerifyCode(4);
        //存入Session, 此處可以根據自己的需求
        HttpSession session = request.getSession();
        session.setAttribute("verifyCode",verifyCode);
        //生成圖片
        int w = 100, h = 35;
        try {
            //將圖片寫入到 response 的輸出流即可將圖片返回到客戶端了
            VerifyCodeUtils.outputImage(w, h , response.getOutputStream(), verifyCode);
        } catch (IOException e) {
            logger.error("生成驗證碼失敗, Cause by: {}", e.getMessage(), e);
        }
    }

生成驗證碼圖片的類

網上找到的一個, 還不錯.

import javax.imageio.ImageIO;
import java.awt.*;
import java.awt.geom.AffineTransform;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.util.Arrays;
import java.util.Random;

/**
 * 生成圖片流
 * @Description: Created by zcqshine on 2017/5/18.
 */
public class VerifyCodeUtils {
    private static final String VERIFY_CODES = "23456789ABCDEFGHJKLMNPQRSTUVWXYZ";
    private static Random random = new Random();

    /**
     * 使用系統默認字符源生成驗證碼
     * @param verifySize    驗證碼長度
     * @return
     */
    public static String generateVerifyCode(int verifySize){
        return generateVerifyCode(verifySize, VERIFY_CODES);
    }

    /**
     * 使用指定源生成驗證碼
     * @param verifySize    驗證碼長度
     * @param sources       驗證碼字符源
     * @return
     */
    public static String generateVerifyCode(int verifySize, String sources){
        if (sources == null || sources.trim().length() == 0){
            sources = VERIFY_CODES;
        }

        int codesLen = sources.length();
        Random rand = new Random(System.currentTimeMillis());
        StringBuilder verifyCode = new StringBuilder(verifySize);
        for (int i = 0; i < verifySize; i++){
            verifyCode.append(sources.charAt(rand.nextInt(codesLen -1 )));
        }
        return verifyCode.toString();
    }

    /**
     * 輸出隨機驗證碼圖片流, 並返回驗證碼值
     * @param w
     * @param h
     * @param outputFile
     * @param verifySize
     * @return
     */
    public static String outputVerifyImage(int w, int h, File outputFile, int verifySize) throws  IOException{
        String verifyCode = generateVerifyCode(verifySize);
        outputImage(w,h,outputFile,verifyCode);
        return verifyCode;
    }

    /**
     * 生成指定驗證碼圖像文件
     * @param w
     * @param h
     * @param outputFile
     * @param verifyCode
     * @throws IOException
     */
    public static void outputImage(int w, int h, File outputFile, String verifyCode) throws IOException{
        if (outputFile == null){
            return;
        }
        File dir = outputFile.getParentFile();
        if(!dir.exists()){
            dir.mkdirs();
        }

        try {
            outputFile.createNewFile();
            FileOutputStream fos = new FileOutputStream(outputFile);
            outputImage(w, h, fos, verifyCode);
            fos.close();
        } catch (IOException e) {
            throw e;
        }
    }

    public static void outputImage(int w, int h, OutputStream os, String code) throws IOException{
        int verifySize = code.length();
        BufferedImage image = new BufferedImage(w,h, BufferedImage.TYPE_INT_RGB);
        Random rand = new Random();
        Graphics2D g2 = image.createGraphics();
        g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,RenderingHints.VALUE_ANTIALIAS_ON);
        Color[] colors = new Color[5];
        Color[] colorSpaces = new Color[]{Color.WHITE, Color.CYAN, Color.GRAY,
                Color.LIGHT_GRAY, Color.MAGENTA, Color.ORANGE,
                Color.PINK, Color.YELLOW};
        float[] fractions = new float[colors.length];
        for (int i = 0; i < colors.length; i++){
            colors[i] = colorSpaces[rand.nextInt(colorSpaces.length)];
            fractions[i] = rand.nextFloat();
        }
        Arrays.sort(fractions);

        g2.setColor(Color.GRAY);    //設置邊框色
        g2.fillRect(0,0, w, h);

        Color c = getRandColor(200, 250);
        g2.setColor(c); //設置背景色
        g2.fillRect(0, 2, w, h-4);

        //繪製干擾線
        Random random = new Random();
        g2.setColor(getRandColor(160, 200));// 設置線條的顏色
        for (int i = 0; i < 20; i++) {
            int x = random.nextInt(w - 1);
            int y = random.nextInt(h - 1);
            int xl = random.nextInt(6) + 1;
            int yl = random.nextInt(12) + 1;
            g2.drawLine(x, y, x + xl + 40, y + yl + 20);
        }

        // 添加噪點
        float yawpRate = 0.05f;// 噪聲率
        int area = (int) (yawpRate * w * h);
        for (int i = 0; i < area; i++) {
            int x = random.nextInt(w);
            int y = random.nextInt(h);
            int rgb = getRandomIntColor();
            image.setRGB(x, y, rgb);
        }

        shear(g2, w, h, c);// 使圖片扭曲

        g2.setColor(getRandColor(100, 160));
        int fontSize = h-4;
        Font font = new Font("Algerian", Font.ITALIC, fontSize);
        g2.setFont(font);
        char[] chars = code.toCharArray();
        for(int i = 0; i < verifySize; i++){
            AffineTransform affine = new AffineTransform();
            affine.setToRotation(Math.PI / 4 * rand.nextDouble() * (rand.nextBoolean() ? 1 : -1), (w / verifySize) * i + fontSize/2, h/2);
            g2.setTransform(affine);
            g2.drawChars(chars, i, 1, ((w-10) / verifySize) * i + 5, h/2 + fontSize/2 - 10);
        }

        g2.dispose();
        ImageIO.write(image, "jpg", os);

    }

    private static Color getRandColor(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);
    }

    private static int getRandomIntColor() {
        int[] rgb = getRandomRgb();
        int color = 0;
        for (int c : rgb) {
            color = color << 8;
            color = color | c;
        }
        return color;
    }

    private static int[] getRandomRgb() {
        int[] rgb = new int[3];
        for (int i = 0; i < 3; i++) {
            rgb[i] = random.nextInt(255);
        }
        return rgb;
    }

    private static void shear(Graphics g, int w1, int h1, Color color) {
        shearX(g, w1, h1, color);
        shearY(g, w1, h1, color);
    }

    private static void shearX(Graphics g, int w1, int h1, Color color) {

        int period = random.nextInt(2);

        boolean borderGap = true;
        int frames = 1;
        int phase = random.nextInt(2);

        for (int i = 0; i < h1; i++) {
            double d = (double) (period >> 1)
                    * Math.sin((double) i / (double) period
                    + (6.2831853071795862D * (double) phase)
                    / (double) frames);
            g.copyArea(0, i, w1, 1, (int) d, 0);
            if (borderGap) {
                g.setColor(color);
                g.drawLine((int) d, i, 0, i);
                g.drawLine((int) d + w1, i, w1, i);
            }
        }

    }

    private static void shearY(Graphics g, int w1, int h1, Color color) {

        int period = random.nextInt(40) + 10; // 50;

        boolean borderGap = true;
        int frames = 20;
        int phase = 7;
        for (int i = 0; i < w1; i++) {
            double d = (double) (period >> 1)
                    * Math.sin((double) i / (double) period
                    + (6.2831853071795862D * (double) phase)
                    / (double) frames);
            g.copyArea(i, 0, 1, h1, 0, (int) d);
            if (borderGap) {
                g.setColor(color);
                g.drawLine(i, (int) d, i, 0);
                g.drawLine(i, (int) d + h1, i, h1);
            }
        }
    }

public static void main(String[] args) {
        File dir = new File("/Users/zcqshine/Downloads/test");
        int w = 200, h= 80;
        for (int i = 0; i< 50; i++){
            String verifyCode = generateVerifyCode(4);
            File file = new File(dir, verifyCode + ".jpg");
            try {
                outputImage(w, h, file, verifyCode);
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}