Servlet生成验证码图片

import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.util.Random;

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

import com.sun.image.codec.jpeg.JPEGCodec;
import com.sun.image.codec.jpeg.JPEGImageEncoder;

public class Image extends HttpServlet{
public void doGet(HttpServletRequestrequest,HttpServletResponseresponse)
throws ServletException,IOException{
response.setContentType( " image/jpeg " );
OutputStreamout = response.getOutputStream();
response.setHeader( " Pragma " , " No-cache " );
response.setHeader( " Cache-Control " , " no-cache " );
response.setDateHeader( " Expires " , 0 );
int width = 60 ,height = 20 ;
BufferedImageimage = new BufferedImage(width,height,
BufferedImage.TYPE_INT_RGB);
// 获取图形上下文
Graphicsg = image.getGraphics();
// 生成随机类
Randomrandom = new Random();
// 设定背景色
g.setColor(getRandColor( 200 , 250 ));
g.fillRect( 0 , 0 ,width,height);
// 设定字体
g.setFont( new Font( " TimesNewRoman " ,Font.PLAIN, 18 ));
// 随机产生155条干扰线，使图象中的认证码不易被其它程序探测到
g.setColor(getRandColor( 180 , 200 ));
for ( int i = 0 ;i < 155 ;i ++ ){
int x = random.nextInt(width);
int y = random.nextInt(height);
int xl = random.nextInt( 12 );
int yl = random.nextInt( 12 );
g.drawLine(x,y,x + xl,y + yl);
}
// 取随机产生的认证码(4位数字)
StringsRand = setRandValue(request);
if (sRand != null )
for ( int i = 0 ;i < sRand.length();i ++ ){
g.setColor( new Color( 20 + random.nextInt( 200 ), 20 + random
.nextInt( 200 ), 20 + random.nextInt( 200 )));
// 调用函数出来的颜色相同，可能是因为种子太接近，所以只能直接生成
g.drawString(sRand.charAt(i) + "" , 13 * i + 6 , 16 );
}

JPEGImageEncoderencoder = JPEGCodec.createJPEGEncoder(out);
encoder.encode(image);
// 图象生效
g.dispose();
// 输出图象到页面
// ImageIO.write(image,"JPG",response.getOutputStream());
out.flush();
out.close();
}

ColorgetRandColor( int fc, int bc){ // 给定范围获得随机颜色
Randomrandom = 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);
}
// 48-57对应0-9;65-90对应A-Z;97-122对应a-z;
StringsetRandValue(HttpServletRequestrequest){
Randomrandom = new Random();
StringsRand = "" ;
// 这里是生成验证码的位数
for ( int i = 0 ;i < 4 ;i ++ ){
char c = 0 ;
int k = random.nextInt( 3 );
switch (k){
case 0 :
c = ( char )(random.nextInt( 10 ) + 48 );
break ;
case 1 :
c = ( char )(random.nextInt( 26 ) + 65 );
break ;
case 2 :
c = ( char )(random.nextInt( 26 ) + 97 );
}
sRand += c;
}
request.getSession().setAttribute( " rands " ,sRand);
return sRand;
}
}