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SESSIONsession.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
转载于:https://www.cnblogs.com/superroshan/p/4699834.html
