jsp页面has already been called for this response错误解决方法。

创建验证码的jsp页面提示错误：has already been called for this response

<%@ page contentType="image/jpeg" %>
<%@ page import="java.awt.*,java.awt.image.*,java.util.*,javax.imageio.*"%>
<%!
Color getRandColor(int fc,int bc){ //在确定的范围中获得随机颜色
Random random = 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);
}
%>
<% //设置页面不缓存
response.setHeader("Pragma","No-cache");
response.setHeader("Cache-Control","no-cache");
response.setDateHeader("Expires", 0);
//在内存中创建图象
int width=60, height=20;
BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
//获取图形上下文
Graphics g = image.getGraphics();
//生成随机类
Random random = 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("Times New Roman",Font.PLAIN,18));
//随机产生50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(160,200));
for (int i=0;i<50;i++){
int x = random.nextInt(width);
int y = random.nextInt(height);
int xl = random.nextInt(width);
int yl = random.nextInt(height);
g.drawLine(x,y,x+xl,y+yl);
}
//取随机产生的认证码(4位数字)
String sRand="";
for (int i=0;i<4;i++){
String rand=String.valueOf(random.nextInt(10));
sRand+=rand;
//将认证码显示到图象中
g.setColor(new Color(20+random.nextInt(110),20+random.nextInt(110),20+random.nextInt(110)));
//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(rand,13*i+6,16);
}
//将认证码存入SESSION
session.setAttribute("rand",sRand);
//图象生效
g.dispose();
response.reset(); //输出图象到页面
ImageIO.write(image, "JPEG", response.getOutputStream());

%>

解决方法：

在ImageIO.Write()方法后面添加

out.clear(); 
out = pageContext.pushBody();

问题解决。

参考资料

http://zhidao.baidu.com/link?url=WuIcu5XLaQpqPNlT-ouZkYQ_sFvooU5f4EQkRR4Wb6u-nHMU0u70PjxRFHA4zt3ic-4gW4k6d6rprgCBfOdaxZZ_tqWjVeMUE2K4IuVXOUm

http://blog.sina.com.cn/s/blog_4f92b1870100w2fg.html