验证码！
这是一段获得验证码的代码:
<%@ page contentType= "image/jpeg " import= "java.awt.*,
java.awt.image.*,java.util.*,javax.imageio.*,java.io.OutputStream " %>
<%!
Color getRandColor(int fc,int bc)
{
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);
}
%>
<%
out.clear();//????????resin·????÷????????tomacat????????????
response.setHeader( "Pragma ", "No-cache ");
response.setHeader( "Cache-Control ", "no-cache ");
response.setDateHeader( "Expires ", 0);
int width=60, height=20;
BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
Graphics g = image.getGraphics();
Random random = new Random();
g.setColor(getRandColor(200,250));
g.fillRect(0, 0, width, height);
g.setFont(new Font( "Times New Roman ",Font.PLAIN,18));
g.setColor(getRandColor(160,200));
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);
}
String sRand= " ";
for (int i=0;i <4;i++){
String rand=String.valueOf(random.nextInt(10));
sRand+=rand;
g.setColor(new Color(20+random.nextInt(110),20+random.nextInt(110),20+random.nextInt(110)));
g.drawString(rand,13*i+6,16);
}
// ?????¤??????SESSION
session.setAttribute( "rand ",sRand);
g.dispose();
ImageIO.write(image, "JPEG ", response.getOutputStream());
%>
提示的错误是
java.lang.IllegalStateException: getOutputStream() has already been called for this response
该怎么解决？是什么原因引起的？
[解决办法]
做到servlet 里面去就不会有这个错了.
[解决办法]
JSP里默认调用了out输出方法，所以冲突了，你需要加这样几句out.clear();
out = pageContext.pushBody();，就加在最后，你再44：）
