验证码在myeclipse控制台报异常问题

Question

一个彩色验证码的程序，我把它应用到具体的地方的运行该页面的时候，在myeclipse的控制台会打印如下异常：
Servlet.service() for servlet jsp threw exception
java.lang.IllegalStateException: getOutputStream() has already been called for this response
at org.apache.catalina.connector.Response.getWriter(Response.java:610)
at org.apache.catalina.connector.ResponseFacade.getWriter(ResponseFacade.java:198)
at org.apache.jasper.runtime.JspWriterImpl.initOut(JspWriterImpl.java:125)
at org.apache.jasper.runtime.JspWriterImpl.flushBuffer(JspWriterImpl.java:118)
at org.apache.jasper.runtime.PageContextImpl.release(PageContextImpl.java:188)
at org.apache.jasper.runtime.JspFactoryImpl.internalReleasePageContext(JspFactoryImpl.java:118)
at org.apache.jasper.runtime.JspFactoryImpl.releasePageContext(JspFactoryImpl.java:77)
at org.apache.jsp.makeCertPic_jsp._jspService(makeCertPic_jsp.java:79)
at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:374)
at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:342)
at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:267)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:128)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:286)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:845)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:583)
at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:447)
at java.lang.Thread.run(Thread.java:619)请问这个是什么意思呀？？？
     如果大家还需要详细点的代码的话，给我留言哈。
  谢谢大家啦

Answer 1

getOutputStream() has already been called for this response 你的代码的问题

Answer 2

java.lang.IllegalStateException: getOutputStream() has already been called for this response 无效的状态：getOutputStream() 方法中存在调用了response

Answer 3

源代码：
import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.io.OutputStream;
import java.util.Random;
import javax.imageio.ImageIO;public class CopyOfMakeCertPic {
    
    private char mapTable[]={
     'a','b','c','d','e','f',
     'g','h','i','j','k','l',
     'm','n','o','p','q','r',
     's','t','u','v','w','x',
     'y','z','0','1','2','3',
     '4','5','6','7','8','9'};
    
    public String getCertPic(int width, int height, OutputStream os) {
if(width<=0)width=60;
if(height<=0)height=20;
BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB); 
Graphics g = image.getGraphics(); 
g.setColor(new Color(0xDCDCDC)); 
g.fillRect(0, 0, width, height); 
g.setColor(Color.black); 
g.drawRect(0,0,width-1,height-1); 
String strEnsure = "";
for(int i=0; i<4; ++i) {
strEnsure += mapTable[(int)(mapTable.length*Math.random())];
}
g.setColor(Color.black); 
g.setFont(new Font("Atlantic Inline",Font.PLAIN,18)); 
String str = strEnsure.substring(0,1); 
g.drawString(str,8,17); 
str = strEnsure.substring(1,2); 
g.drawString(str,20,15); 
str = strEnsure.substring(2,3); 
g.drawString(str,35,18); 
str = strEnsure.substring(3,4); 
g.drawString(str,45,15); 
Random rand = new Random();
for (int i=0;i<10;i++) { 
int x = rand.nextInt(width); 
int y = rand.nextInt(height); 
g.drawOval(x,y,1,1); 
} 
g.dispose(); 
try {
ImageIO.write(image, "JPEG", os);
} catch (IOException e) {
return "";
}
return strEnsure;
}
}
一个jsp页面
<%@page contentType="image/jpeg" %>
<jsp:useBean id="image" scope="page" class="com.caipu.commons.MakeCertPic" />
<%
String str = image.getCertPic(0,0,response.getOutputStream());
session.setAttribute("certCode", str); 
%>
然后在另外一个页面调用能成功，就是每次刷新一次页面就会出现一个上面的异常
   大家都说是代码的问题
  就麻烦高人们找找看是什么地方的问题啦
   谢谢！