getOutputStream() has already been called for this response异常的原因和解决方法
来源:互联网 发布:win8.1网络连接不可用 编辑:程序博客网 时间:2024/04/30 06:32
转自http://blog.csdn.net/iron_wang/article/details/4204672
1.tomcat5下jsp出现getOutputStream() has already been called for this response异常的原因和解决方法在tomcat5下jsp中出现此错误一般都是在jsp中使用了输出流(如输出图片验证码,文件下载等),
没有妥善处理好的原因。
具体的原因就是
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();
最后这里是一个输出彩色验证码例子(这样的例子几乎随处可见)
imag.jsp
<%@ page import="java.awt.*,java.awt.image.*,java.util.*,javax.imageio.*" %>
<%@ page import="java.io.OutputStream" %>
<%!
Color getRandColor(int fc,int bc){
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);
}
%>
<%
try{
response.setHeader("Pragma","No-cache");
response.setHeader("Cache-Control","no-cache");
response.setDateHeader("Expires", 0);
int width=60, height=20;
BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
OutputStream os=response.getOutputStream();
Graphics g = image.getGraphics();
Random random = new Random();
g.setColor(getRandColor(200,250));
g.fillRect(0, 0, width, height);
g.setFont(new Font("Times New Roman",Font.PLAIN,18));
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);
}
String sRand="";
for (int j=0;j<4;j++){
String rand=String.valueOf(random.nextInt(10));
sRand+=rand;
g.setColor(new Color(20+random.nextInt(110),20+random.nextInt(110),20+random.nextInt(110)));
g.drawString(rand,13*j+6,16);
}
session.setAttribute("rand",sRand);
g.dispose();
ImageIO.write(image, "JPEG",os);
os.flush();
os.close();
os=null;
response.flushBuffer();
out.clear();
out = pageContext.pushBody();
}
catch(IllegalStateException e)
{
System.out.println(e.getMessage());
e.printStackTrace();
}%>
如有不足之处,欢迎斧正!
2
getOutputStream() has already been called for this response问题的解决
在jsp向页面输出图片的时候,使用response.getOutputStream()会有这样的提示:java.lang.IllegalStateException:getOutputStream() has already been called for this response,会抛出Exception
原因一:
JSP默认的输出流为PrintWriter ,即<% %>以外的东西所默认的输出方式,如果你尝试在JSP中使用ServletOutputStream就会引起错误.要嘛直接改用Servlet输出(复写service方法),要嘛删除除%><%中的任何东西
(包括HTML标签,空格,回车等东西)应该就可以。
对于这样的情况应该这样来解决,删除%><%之间的所有内容包括空格和换行符,最后也要消除空格和换行符,
最好再加上一句response.reset()。
原因二:
在J2EE的API参考里有这么个:
ServletResponse的getWriter()方法里会抛出这个异常,
IllegalStateException - if the getOutputStream method has already been called
for this response object
而它的getOutputStream()方法里会抛出这个异常.
IllegalStateException - if the getOutputStream method has already been called for this response object
并且两者的函数申明里都有这么样的一句
Either this method or getOutputStream() may be called to write the body, not both.
Either this method or getWriter() may be called to write the body, not both.
以上说明也解释了为什么在往页面中写入图片的时候要使用如下循环格式
OutputStream output=response.getOutputStream();
while((len=in.read(b)) >0)
{
output.write(b,0,len);
}
output.flush();
而不是把response.getOutputStream().write()放到循环体内
在页面中直接写:
<body bgcolor="#ffffff">
<h1>
<%
response.getOutputStream();
%>
</h1>
</body>
将会出现错误消息如下:
java.lang.IllegalStateException: getOutputStream() has already been called for this response
org.apache.catalina.connector.Response.getWriter(Response.java:604)
org.apache.catalina.connector.ResponseFacade.getWriter(ResponseFacade.java:198)
org.apache.jasper.runtime.JspWriterImpl.initOut(JspWriterImpl.java:125)
org.apache.jasper.runtime.JspWriterImpl.flushBuffer(JspWriterImpl.java:118)
- jsp出现getOutputStream() has already been called for this response异常的原因和解决方法
- getOutputStream() has already been called for this response异常的原因和解决方法
- 验证码 getOutputStream() has already been called for this response异常的原因和解决方法
- jsp出现getOutputStream() has already been called for this response异常的原因和解决方法
- jsp出现getOutputStream() has already been called for this response异常的原因和解决方法
- jsp出现getOutputStream() has already been called for this response异常的原因和解决方法
- getOutputStream() has already been called for this response异常的原因和解决方法
- getOutputStream() has already been called for this response异常出现的原因和解决方法
- getOutputStream() has already been called for this response异常的原因和解决方法
- 验证码 getOutputStream() has already been called for this response异常的原因和解决方法
- getOutputStream() has already been called for this response异常的原因和解决方法
- getOutputStream() has already been called for this response异常的原因和解决方法
- getOutputStream() has already been called for this response异常的原因和解决方法
- getOutputStream() has already been called for this response异常出现的原因和解决方法
- getOutputStream() has already been called for this response异常的原因和解决方法
- getOutputStream() has already been called for this response异常的原因和解决方法
- getOutputStream() has already been called for this response异常出现的原因和解决方法
- jsp出现getOutputStream() has already been called for this response异常的原因和解决方法
- struts2 s标签
- ARM体系结构与编程(杜春雷版)英文参考资料详解(一)
- 面向对象设计原则之开闭原则
- JS控制网页背景随窗口大小自动适应
- 应用程序无法正确启动,0x00000b
- getOutputStream() has already been called for this response异常的原因和解决方法
- 第十五章动态规划之“最优二叉查找树”
- android生命周期和状态方法调用时间点
- 安卓游戏开发------播放背景音乐和音效(MediaPlayer和SoundPool)
- WinSDK方式设置ListView控件指定位置数据
- <cocos2d-x for wp7>使用cocos2d-x制作基于Tile地图的游戏:不一样的战斗(回合制战斗)(四)
- 关闭135端口
- 二叉树中路径和为某整数的所有路径
- A very basic introduction about Java stack and heap