一个不会报错的jsp彩色验证码程序
一个不会报错的jsp彩色验证码程序一般的，会报servlet错误：
getOutputStream() has already been called for this response
但是这个程序不会报错，原因是把里面的空格都删除
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在tomcat中jsp编译成servlet之后在函数_jspService(HttpServletRequest request, HttpServletResponse response)的最后
有一段这样的代码
finally {
if (_jspxFactory != null) _jspxFactory.releasePageContext(_jspx_page_context);
}
这里是在释放在jsp中使用的对象，会调用response.getWriter(),因为这个方法是和
response.getOutputStream()相冲突的！所以会出现以上这个异常。然后当然是要提出解决的办法，其实挺简单的（并不是和某些朋友说的那样--
将jsp内的所有空格和回车符号所有都删除掉），
在使用完输出流以后调用以下两行代码即可：
out.clear();
out = pageContext.pushBody();
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分割线内为引用～
<div style="border-right: #cccccc 1px solid; padding-right: 5px; border-top: #cccccc 1px solid; padding-left: 4px; font-size: 13px; padding-bottom: 4px; border-left: #cccccc 1px solid; width: 98%; padding-top: 4px; border-bottom: #cccccc 1px solid; background-color: #eeeeee;"> 1http://www.blogjava.net/Images/OutliningIndicators/None.gif<%@ page import="java.awt.*,java.awt.image.*,java.util.*,javax.imageio.*" %>
2http://www.blogjava.net/Images/OutliningIndicators/None.gif<%@ page import="java.io.OutputStream" %>
3http://www.blogjava.net/Images/OutliningIndicators/None.gif<%!
4http://www.blogjava.net/Images/OutliningIndicators/ExpandedBlockStart.gifhttp://www.blogjava.net/Images/OutliningIndicators/ContractedBlock.gifColor getRandColor(int fc,int bc)http://www.blogjava.net/Images/dot.gif{
5http://www.blogjava.net/Images/OutliningIndicators/InBlock.gifRandom random = new Random();
6http://www.blogjava.net/Images/OutliningIndicators/InBlock.gifif(fc>255) fc=255;
7http://www.blogjava.net/Images/OutliningIndicators/InBlock.gifif(bc>255) bc=255;
8http://www.blogjava.net/Images/OutliningIndicators/InBlock.gifint r=fc+random.nextInt(bc-fc);
9http://www.blogjava.net/Images/OutliningIndicators/InBlock.gifint g=fc+random.nextInt(bc-fc);
10http://www.blogjava.net/Images/OutliningIndicators/InBlock.gifint b=fc+random.nextInt(bc-fc);
11http://www.blogjava.net/Images/OutliningIndicators/InBlock.gifreturn new Color(r,g,b);
12http://www.blogjava.net/Images/OutliningIndicators/ExpandedBlockEnd.gif}
13http://www.blogjava.net/Images/OutliningIndicators/None.gif%>
14http://www.blogjava.net/Images/OutliningIndicators/None.gif<%
15http://www.blogjava.net/Images/OutliningIndicators/ExpandedBlockStart.gifhttp://www.blogjava.net/Images/OutliningIndicators/ContractedBlock.giftryhttp://www.blogjava.net/Images/dot.gif{
16http://www.blogjava.net/Images/OutliningIndicators/InBlock.gifresponse.setHeader("Pragma","No-cache");
17http://www.blogjava.net/Images/OutliningIndicators/InBlock.gifresponse.setHeader("Cache-Control","no-cache");
18http://www.blogjava.net/Images/OutliningIndicators/InBlock.gifresponse.setDateHeader("Expires", 0);
19http://www.blogjava.net/Images/OutliningIndicators/InBlock.gifint width=60, height=20;
20http://www.blogjava.net/Images/OutliningIndicators/InBlock.gifBufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
21http://www.blogjava.net/Images/OutliningIndicators/InBlock.gifOutputStream os=response.getOutputStream();
22http://www.blogjava.net/Images/OutliningIndicators/InBlock.gifGraphics g = image.getGraphics();
23http://www.blogjava.net/Images/OutliningIndicators/InBlock.gifRandom random = new Random();
24http://www.blogjava.net/Images/OutliningIndicators/InBlock.gifg.setColor(getRandColor(200,250));
25http://www.blogjava.net/Images/OutliningIndicators/InBlock.gifg.fillRect(0, 0, width, height);
26http://www.blogjava.net/Images/OutliningIndicators/InBlock.gif
27http://www.blogjava.net/Images/OutliningIndicators/InBlock.gifg.setFont(new Font("Times New Roman",Font.PLAIN,18));
28http://www.blogjava.net/Images/OutliningIndicators/InBlock.gifg.setColor(getRandColor(160,200));
29http://www.blogjava.net/Images/OutliningIndicators/InBlock.giffor (int i=0;i<155;i++)
30http://www.blogjava.net/Images/OutliningIndicators/ExpandedSubBlockStart.gifhttp://www.blogjava.net/Images/OutliningIndicators/ContractedSubBlock.gifhttp://www.blogjava.net/Images/dot.gif{
31http://www.blogjava.net/Images/OutliningIndicators/InBlock.gifint x = random.nextInt(width);
32http://www.blogjava.net/Images/OutliningIndicators/InBlock.gifint y = random.nextInt(height);
33http://www.blogjava.net/Images/OutliningIndicators/InBlock.gifint xl = random.nextInt(12);
34http://www.blogjava.net/Images/OutliningIndicators/InBlock.gifint yl = random.nextInt(12);
35http://www.blogjava.net/Images/OutliningIndicators/InBlock.gifg.drawLine(x,y,x+xl,y+yl);
36http://www.blogjava.net/Images/OutliningIndicators/ExpandedSubBlockEnd.gif}
37http://www.blogjava.net/Images/OutliningIndicators/InBlock.gifString sRand="";
38http://www.blogjava.net/Images/OutliningIndicators/ExpandedSubBlockStart.gifhttp://www.blogjava.net/Images/OutliningIndicators/ContractedSubBlock.giffor (int i=0;i<4;i++)http://www.blogjava.net/Images/dot.gif{
39http://www.blogjava.net/Images/OutliningIndicators/InBlock.gifString rand=String.valueOf(random.nextInt(10));
40http://www.blogjava.net/Images/OutliningIndicators/InBlock.gifsRand+=rand;
41http://www.blogjava.net/Images/OutliningIndicators/InBlock.gifg.setColor(new Color(20+random.nextInt(110),20+random.nextInt(110),20+random.nextInt(110)));
42http://www.blogjava.net/Images/OutliningIndicators/InBlock.gifg.drawString(rand,13*i+6,16);
43http://www.blogjava.net/Images/OutliningIndicators/ExpandedSubBlockEnd.gif}
44http://www.blogjava.net/Images/OutliningIndicators/InBlock.gifsession.setAttribute("rand",sRand);
45http://www.blogjava.net/Images/OutliningIndicators/InBlock.gifg.dispose();
46http://www.blogjava.net/Images/OutliningIndicators/InBlock.gif
47http://www.blogjava.net/Images/OutliningIndicators/InBlock.gifImageIO.write(image, "JPEG",os);
48http://www.blogjava.net/Images/OutliningIndicators/InBlock.gifos.flush();
49http://www.blogjava.net/Images/OutliningIndicators/InBlock.gifos.close();
50http://www.blogjava.net/Images/OutliningIndicators/InBlock.gifos=null;
51http://www.blogjava.net/Images/OutliningIndicators/InBlock.gifresponse.flushBuffer();
52http://www.blogjava.net/Images/OutliningIndicators/InBlock.gifout.clear();
53http://www.blogjava.net/Images/OutliningIndicators/InBlock.gifout = pageContext.pushBody();
54http://www.blogjava.net/Images/OutliningIndicators/ExpandedBlockEnd.gif}
55http://www.blogjava.net/Images/OutliningIndicators/None.gifcatch(IllegalStateException e)
56http://www.blogjava.net/Images/OutliningIndicators/ExpandedBlockStart.gifhttp://www.blogjava.net/Images/OutliningIndicators/ContractedBlock.gifhttp://www.blogjava.net/Images/dot.gif{
57http://www.blogjava.net/Images/OutliningIndicators/InBlock.gifSystem.out.println(e.getMessage());
58http://www.blogjava.net/Images/OutliningIndicators/InBlock.gife.printStackTrace();
59http://www.blogjava.net/Images/OutliningIndicators/ExpandedBlockEnd.gif}%>
60http://www.blogjava.net/Images/OutliningIndicators/None.gif
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