用jsp页面实现验证码出现getOutputStream() has already been called for this response

getOutputStream() has already been called for this response
java.lang.IllegalStateException: getOutputStream() has already been called for this response
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java.lang.IllegalStateException: getOutputStream() has already been called for this response
at org.apache.catalina.connector.Response.getWriter(Response.java:604)
at org.apache.catalina.connector.ResponseFacade.getWriter(ResponseFacade.java:198)
每次进入或刷新login页面都出现此错。
原因在于login.jsp页面，里面有此段生成验证码
<tr>
<td 验证码:
</td>
<td <input type="text" name="rand" />
*
<img alt="验证码" name="randImage" id="randImage" src="image.jsp"
width="60" height="20" border="1" align="middle">
</td>
</tr>
导致出错在于src="image.jsp"。
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image.jsp原文如下
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%@ page contentType="image/jpeg" import="java.awt.*,java.awt.image.*,java.util.*,javax.imageio.*" %>
<%!
Color getRandColor(int fc,int bc){//给定范围获得随机颜色
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));
//画边框
//g.setColor(new Color());
//g.drawRect(0,0,width-1,height-1);

// 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(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);
}
// 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=sRand.concat(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)));
g.drawString(rand,13*i+6,16);
}
// 将认证码存入SESSION
session.setAttribute("rand",sRand);

// 图象生效
g.dispose();
// 输出图象到页面
ImageIO.write(image, "JPEG", response.getOutputStream());
out.clear();//添加此语句,解决问题
out = pageContext.pushBody();

%>
------------------------------------
在末尾加入
out.clear();
out = pageContext.pushBody();
不再出错。