Question

怎样用java实现验证码

Answer 1

package com.servlet;

import java.awt.*;
import java.awt.geom.*;
import java.awt.image.*;
import java.io.*;
import java.util.*;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import javax.imageio.ImageIO;

public class PictureCheckCode extends HttpServlet {

private static final long serialVersionUID = 1L;

public PictureCheckCode() {
super();
}

public void destroy() {
super.destroy();
}

public void init() throws ServletException {
super.init();
}
/*该方法主要作用是获得随机生成的颜色*/
public Color getRandColor(int s,int e){
Random random=new Random ();
if(s>255) s=255;
if(e>255) e=255;
int r,g,b;
r=s+random.nextInt(e-s); //随机生成RGB颜色中的r值
g=s+random.nextInt(e-s); //随机生成RGB颜色中的g值
b=s+random.nextInt(e-s); //随机生成RGB颜色中的b值
return new Color(r,g,b);
}

@Override
public void service(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
//设置不缓存图片
response.setHeader("Pragma", "No-cache");
response.setHeader("Cache-Control", "No-cache");
response.setDateHeader("Expires", 0);
//指定生成的响应图片,一定不能缺少这句话,否则错误.
response.setContentType("image/jpeg");
int width=86,height=22; //指定生成验证码的宽度和高度
BufferedImage image=new BufferedImage(width,height,BufferedImage.TYPE_INT_RGB); //创建BufferedImage对象,其作用相当于一图片
Graphics g=image.getGraphics(); //创建Graphics对象,其作用相当于画笔
Graphics2D g2d=(Graphics2D)g; //创建Grapchics2D对象
Random random=new Random();
Font mfont=new Font("楷体",Font.BOLD,16); //定义字体样式
g.setColor(getRandColor(200,250));
g.fillRect(0, 0, width, height); //绘制背景
g.setFont(mfont); //设置字体
g.setColor(getRandColor(180,200));

//绘制100条颜色和位置全部为随机产生的线条,该线条为2f
for(int i=0;i<100;i++){
int x=random.nextInt(width-1);
int y=random.nextInt(height-1);
int x1=random.nextInt(6)+1;
int y1=random.nextInt(12)+1;
BasicStroke bs=new BasicStroke(2f,BasicStroke.CAP_BUTT,BasicStroke.JOIN_BEVEL); //定制线条样式
Line2D line=new Line2D.Double(x,y,x+x1,y+y1);
g2d.setStroke(bs);
g2d.draw(line); //绘制直线
}
//输出由英文，数字，和中文随机组成的验证文字，具体的组合方式根据生成随机数确定。
String sRand="";
String ctmp="";
int itmp=0;
//制定输出的验证码为四位
for(int i=0;i<4;i++){
switch(random.nextInt(3)){
case 1: //生成A-Z的字母
itmp=random.nextInt(26)+65;
ctmp=String.valueOf((char)itmp);
break;
case 2: //生成汉字
String[] rBase={"0","1","2","3","4","5","6","7","8","9","a","b","c","d","e","f"};
//生成第一位区码
int r1=random.nextInt(3)+11;
String str_r1=rBase[r1];
//生成第二位区码
int r2;
if(r1==13){
r2=random.nextInt(7);
}else{
r2=random.nextInt(16);
}
String str_r2=rBase[r2];
//生成第一位位码
int r3=random.nextInt(6)+10;
String str_r3=rBase[r3];
//生成第二位位码
int r4;
if(r3==10){
r4=random.nextInt(15)+1;
}else if(r3==15){
r4=random.nextInt(15);
}else{
r4=random.nextInt(16);
}
String str_r4=rBase[r4];
//将生成的机内码转换为汉字
byte[] bytes=new byte[2];
//将生成的区码保存到字节数组的第一个元素中
String str_12=str_r1+str_r2;
int tempLow=Integer.parseInt(str_12, 16);
bytes[0]=(byte) tempLow;
//将生成的位码保存到字节数组的第二个元素中
String str_34=str_r3+str_r4;
int tempHigh=Integer.parseInt(str_34, 16);
bytes[1]=(byte)tempHigh;
ctmp=new String(bytes);
break;
default:
itmp=random.nextInt(10)+48;
ctmp=String.valueOf((char)itmp);
break;
}
sRand+=ctmp;
Color color=new Color(20+random.nextInt(110),20+random.nextInt(110),random.nextInt(110));
g.setColor(color);
//将生成的随机数进行随机缩放并旋转制定角度 PS.建议不要对文字进行缩放与旋转,因为这样图片可能不正常显示
/*将文字旋转制定角度*/
Graphics2D g2d_word=(Graphics2D)g;
AffineTransform trans=new AffineTransform();
trans.rotate((45)*3.14/180,15*i+8,7);
/*缩放文字*/
float scaleSize=random.nextFloat()+0.8f;
if(scaleSize>1f) scaleSize=1f;
trans.scale(scaleSize, scaleSize);
g2d_word.setTransform(trans);
g.drawString(ctmp, 15*i+18, 14);
}
HttpSession session=request.getSession(true);
session.setAttribute("randCheckCode", sRand);
g.dispose(); //释放g所占用的系统资源
ImageIO.write(image,"JPEG",response.getOutputStream()); //输出图片
}
}