SpringMVC下获取验证码实例详解

springmvc下获取验证码实例详解

前言：

1.用户一开始登录的时候, 不建议出现验证码, 这一点在很多网站上已经体现的很好了, 只有当用户连续输错三次或者以上才会要求用户输入验证码.

2.记录用户输错次数最好不要使用 session 来记录, 因为 session 是跟客户端浏览器会话有关的, 如果用重启浏览器或者换新的浏览器再来登录或者试错, 就是新的回话了, 原来记录的错误次数就失效了. 建议此处采用缓存机制来实现, 简单处理就是采用 map<用户登录id, 错误次数> 来实现, 如果有多台服务器负载的话, 就需要采用另外的缓存机制, 比如采用 redis.

3.当用户输入完用户名以后, 就需要用登录名进行判断, 是否需要进行验证码校验.

4.生成的验证码与 session 绑定, 是否需要校验验证码, 要根据用户规定时间内失败的次数来判断.

原生的 servlet 可以直接 write 图片到客户端. 但是刚用 springmvc 的童鞋可能不知道怎么在此框架下返回图片. 其实在本质上用 spring 返回图片跟用 servlet 是一样的。都是使用的 httpservletresponse 来返回图片.

springmvc 的 controller 里获取验证码的方法

/**
   * 生成验证码
   * @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");

    //生成随机字符串
    string verifycode = verifycodeutils.generateverifycode(4);
    //存入session, 此处可以根据自己的需求
    httpsession session = request.getsession();
    session.setattribute("verifycode",verifycode);
    //生成图片
    int w = 100, h = 35;
    try {
      //将图片写入到 response 的输出流即可将图片返回到客户端了
      verifycodeutils.outputimage(w, h , response.getoutputstream(), verifycode);
    } catch (ioexception e) {
      logger.error("生成验证码失败, cause by: {}", e.getmessage(), e);
    }
  }

生成验证码图片的类

网上找到的一个, 还不错.

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;

/**
 * 生成图片流
 * @description: created by zcqshine on 2017/5/18.
 */
public class verifycodeutils {
  private static final string verify_codes = "23456789abcdefghjklmnpqrstuvwxyz";
  private static random random = new random();

  /**
   * 使用系统默认字符源生成验证码
   * @param verifysize  验证码长度
   * @return
   */
  public static string generateverifycode(int verifysize){
    return generateverifycode(verifysize, verify_codes);
  }

  /**
   * 使用指定源生成验证码
   * @param verifysize  验证码长度
   * @param sources    验证码字符源
   * @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();
  }

  /**
   * 输出随机验证码图片流, 并返回验证码值
   * @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;
  }

  /**
   * 生成指定验证码图像文件
   * @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);  //设置边框色
    g2.fillrect(0,0, w, h);

    color c = getrandcolor(200, 250);
    g2.setcolor(c); //设置背景色
    g2.fillrect(0, 2, w, h-4);

    //绘制干扰线
    random random = new random();
    g2.setcolor(getrandcolor(160, 200));// 设置线条的颜色
    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);
    }

    // 添加噪点
    float yawprate = 0.05f;// 噪声率
    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);// 使图片扭曲

    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();
      }
    }
  }
}

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