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。
采用方法很简单.在使用OutputStream输出流完成后,调用下面2个方法即可解决该问题:
out.clear();
out = pageContext.pushBody();
示例代码:
OutputStream os=response.getOutputStream();
os.write(new String("true "+"nowNum=" + nowNum+"===").getBytes());
os.flush();
os.close();
out.clear();
out = pageContext.pushBody();
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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
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.
while((len=in.read(b)) >0)
{
output.write(b,0,len);
}
output.flush();