2007-10-5 20:48:28 org.apache.catalina.core.StandardWrapperValve invoke
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:606)
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:191)
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(org.apache.jsp.code_jsp:123)
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:332)
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 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$Http11ConnectionHandler.processConnection(Http11BaseProtocol.java:667)
at org.apache.tomcat.util.net.PoolTcpEndpoint.processSocket(PoolTcpEndpoint.java:527)
at org.apache.tomcat.util.net.LeaderFollowerWorkerThread.runIt(LeaderFollowerWorkerThread.java:80)
at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:684)
代码如下:
<%@ page language="java" pageEncoding="UTF-8"%>
<%@ page import="java.awt.*,java.awt.image.*,java.util.*,javax.imageio.*"%>
<%!
//给定范围,获得随机颜色
Color getRandColor(int fc,int bc)
{
Random random = new Random();
//颜色的RGB取值不能超过255
if(fc > 255)
fc = 255;
if(bc > 255)
bc = 255;
//随机产生三元色
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);
//在内存中创建图像
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();
//设置背景色
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155条干扰线,使图像中的验证码不易被其他程序探测到
g.setColor(getRandColor(160,200));
for(int i = 0; i < 155; i ++)
{
int x = random.nextInt(width);
int y = random.nextInt(height);
int x1 = random.nextInt(12);
int y1 = random.nextInt(12);
g.drawLine(x,y,x+x1,y+y1);
}
//取随机产生的验证码(4位数字)
String sRand = "";
for(int i = 0; i < 4; i ++)
{
String rand = String.valueOf(random.nextInt(10));
sRand += rand;
//将验证码显示到图像中
g.setColor(new Color(20 + random.nextInt(110),20 + random.nextInt(110),20 + random.nextInt(110)));
//函数调用出来的颜色相同,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);
}
//将验证码存入Session
session.setAttribute("rand",sRand);
//图像生效
g.dispose();
//输出图像到页面
ImageIO.write(image,"JPEG",response.getOutputStream());
