奇怪的问题?拿分啦

zhouzongxi 2008-07-10 11:11:35

我用自定义标签写了个类作为验证码，这几天都写的很顺利
今天又自己练习一遍出现一个异常：

严重: 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:599)

	at org.apache.catalina.connector.ResponseFacade.getWriter(ResponseFacade.java:195)

	at org.apache.jasper.runtime.JspWriterImpl.initOut(JspWriterImpl.java:124)

	at org.apache.jasper.runtime.JspWriterImpl.flushBuffer(JspWriterImpl.java:117)

	at org.apache.jasper.runtime.PageContextImpl.release(PageContextImpl.java:182)

	at org.apache.jasper.runtime.JspFactoryImpl.internalReleasePageContext(JspFactoryImpl.java:115)

	at org.apache.jasper.runtime.JspFactoryImpl.releasePageContext(JspFactoryImpl.java:75)

	at org.apache.jsp.code_jsp._jspService(code_jsp.java:70)

	at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:97)

	at javax.servlet.http.HttpServlet.service(HttpServlet.java:802)

	at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:334)

	at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:314)

	at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:264)

	at javax.servlet.http.HttpServlet.service(HttpServlet.java:802)

	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:252)

	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173)

	at com.zzx.filters.ChineseFilter.doFilter(ChineseFilter.java:29)

	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:202)

	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173)

	at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:213)

	at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:178)

	at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:126)

	at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:105)

	at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:107)

	at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:148)

	at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:869)

	at org.apache.coyote.http11.Http11BaseProtocol$Http11ConnectionHandler.processConnection(Http11BaseProtocol.java:664)

	at org.apache.tomcat.util.net.PoolTcpEndpoint.processSocket(PoolTcpEndpoint.java:527)

	at org.apache.tomcat.util.net.LeaderFollowerWorkerThread.runIt(LeaderFollowerWorkerThread.java:80)

	at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:684)

	at java.lang.Thread.run(Thread.java:595)

2008-7-10 15:06:58 org.apache.catalina.startup.HostConfig checkResources

拿着这段代码去别的机器上好好的有谁知道怎么回事么？
我的做验证码的代码：

package com.zzx.tags;



import java.awt.BufferCapabilities;

import java.awt.Color;

import java.awt.Font;

import java.awt.Graphics;

import java.awt.image.BufferedImage;

import java.io.IOException;

import java.io.PrintWriter;

import java.util.Random;



import javax.imageio.ImageIO;

import javax.servlet.ServletOutputStream;

import javax.servlet.ServletResponse;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

import javax.servlet.jsp.JspException;

import javax.servlet.jsp.tagext.BodyTagSupport;



public class ValidateTag extends BodyTagSupport {



	@Override

	public int doAfterBody() throws JspException {

		// TODO Auto-generated method stub

		return super.doAfterBody();

	}



	@Override

	public int doEndTag() throws JspException {

		// TODO Auto-generated method stub

		ServletResponse response = (ServletResponse) pageContext.getResponse();

		response.setContentType("image/jpeg");

		BufferedImage img = new BufferedImage(60, 20, 1);

		Graphics g = img.getGraphics();

		g.setColor(Color.blue);

		g.fillRect(0, 0, 60, 20);

		g.setFont(new Font("宋体", 1, 20));

		g.setColor(Color.cyan);

		char x[] = this.getChars();

		pageContext.getSession().setAttribute("code", new String(x));

		g.drawString("" + x[0], 12, 16);

		g.drawString("" + x[1], 24, 18);

		g.drawString("" + x[2], 36, 15);

		g.drawString("" + x[3], 48, 18);



		try {

			ImageIO.write(img, "JPEG", response.getOutputStream());

		} catch (IOException e) {

			// TODO Auto-generated catch block

			e.printStackTrace();

		}



		return super.EVAL_PAGE;

	}



	@Override

	public int doStartTag() throws JspException {

		// TODO Auto-generated method stub

		return super.doStartTag();

	}



	// 生成四个随机验证码的方法

	public char[] getChars() {

		String str = "abcdefghijkmnpqrstuvwxy123456789ABCDEFGHJKLMNPQRSTUVWXY";

		char[] x = new char[4];

		for (int i = 0; i < x.length; i++) {

			x[i] = str.charAt(new Random().nextInt(str.length()));

		}

		return x;

	}



}