servlet中的方法实现代码：
import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics2D;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.Random;
import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
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 IdentityServlet extends HttpServlet {
public static final char[] CHARS={‘2‘,‘3‘,‘4‘,‘5‘,‘6‘,‘7‘,‘8‘,‘9‘,‘0‘,
‘A‘,‘Q‘,‘W‘,‘E‘,‘R‘,‘T‘,‘G‘,‘D‘,‘S‘,‘W‘,‘G‘,‘H‘};//随机字符的字典
public static Random random = new Random();//随机数
public static String getRandomString(){
//字符的缓存
StringBuffer buf= new StringBuffer();
for(int i=0;i<6;i++){//循环 六次
buf.append(CHARS[random.nextInt(CHARS.length)]);
}
return buf.toString();
}
public static Color getRandomColor(){
return new Color(random.nextInt(255),random.nextInt(255),random.nextInt(255));
}
public static Color getReverseColor(Color c){
return new Color(255-c.getRed(),255-c.getGreen(),255-c.getBlue());
}
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("image/jpeg");//设置输出的类型
String randomString =getRandomString();//得到返回的字符集
request.getSession(true).setAttribute("randomString", randomString);
int with=100;int hight=30;//生成图片的大小
Color color=getRandomColor();//用于背景色
Color reverse =getReverseColor(color);//用于前景色
BufferedImage bi = new BufferedImage(with, hight, BufferedImage.TYPE_INT_RGB);//创建一个彩色的图片
Graphics2D g = bi.createGraphics();//获取到绘图对象
g.setFont(new Font(Font.SANS_SERIF,Font.BOLD,16));//设置字体
g.setColor(color);//设置颜色
g.fillRect(0, 0, with, hight);//绘制背景
g.setColor(reverse);//设置颜色
g.drawString(randomString, 18, 20);//绘制随机字符
for(int i=0,n=random.nextInt(100);i<n;i++){//画最多100个噪音点
g.drawRect(random.nextInt(with), random.nextInt(hight), 1, 1);//随机噪音点
}
ServletOutputStream out =response.getOutputStream();
//转换图片格式
JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(out);
encoder.encode(bi);//对图片进行编码
out.flush();//输出
}
<script type="text/javascript">
function reloadImage(){
document.getElementByIdx_x_x("btn").disabled=false;
document.getElementByIdx_x_x("Identity").src=‘servlet/IdentityServlet?ts=‘+new Date().getTime();
}
</script>
<body>
<img src="servlet/IdentityServlet" id="Identity" />
<input type="button" id="btn" value="换个图片" onclick="reloadImage()"/>
</body>效果如下：
servlet生成验证码验证的实现,布布扣,bubuko.com
原文：http://blog.csdn.net/u012367513/article/details/25504977
