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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