文件下载

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<%@page contentType="text/html;charset=utf-8" %><%@page import="com.jspsmart.upload.*" %><%@page import="java.io.*"%><%@page import="java.io.File"%><%@page import="java.net.URLEncoder"%><%方法一：if(request.getAttribute("wenjian")!=null){String dizhi=request.getAttribute("wenjian").toString();String name = dizhi.split("/")[4];InputStream ins = new FileInputStream(dizhi);//加BufferedInputStream bins = new BufferedInputStream(ins);// OutputStream outs = response.getOutputStream();// BufferedOutputStream bouts = new BufferedOutputStream(outs); response.reset();response.setContentType("application/x-msdownload"); response.setHeader( "Content-Disposition", "attachment;filename=" + URLEncoder.encode(name, "UTF-8").replaceAll("\\+", "%20").replaceAll("%28", "\\(").replaceAll("%29", "\\)").replaceAll("%3B", ";").replaceAll("%40", "@").replaceAll("%23", "\\#").replaceAll("%26", "\\&")); //乱码处理int bytesRead = 0; byte[] buffer = new byte[8192]; // while ((bytesRead = bins.read(buffer, 0, 8192)) != -1) { bouts.write(buffer, 0, bytesRead); } bouts.flush();// out.clear(); out= pageContext.pushBody(); //解决错误 getOutputStream() has already been called for this response 原因如最下面ins.close(); bins.close(); outs.close(); bouts.close(); File file = new File(dizhi);//如果下载完了的文件不需要了 这里就可以将文件删除file.delete();方法二 jspsmartUpdate.jar下载/* SmartUpload su = new SmartUpload();su.initialize(pageContext);su.setContentDisposition(null); File file1=new File(dizhi);su.downloadFile(file1.getAbsolutePath()); File file=new File(dizhi);file.delete(); out.clear(); out = pageContext.pushBody(); */} %>

getOutputStream() has already been called for this response异常出现的原因和解决方法：

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：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

Java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，在使用完输出流以后调用以下两行代码即可：

Java代码  
out.clear();  
out = pageContext.pushBody();  

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