下载程序运行两次，第一次必然报错：getOutputStream() has already been called for this response java下载报错：getOutputStream() has...
\u6c42\u89e3\uff01\uff01\uff01JSF\u5b9e\u73b0\u4e0b\u8f7d\u529f\u80fd\u8001\u662f\u62a5\u8fd9\u4e2a\u9519\uff0cgetOutputStream() has already been called for this response\u3002\u95ee\u9898\uff1a\u4f60\u9700\u8981\u6e05\u7a7a\u5e76\u4e14\u5173\u95ed\u6d41\u5bf9\u8c61\u3002
\u6211\u63d0\u4f9b\u4e24\u79cd\u89e3\u51b3\u65b9\u6848\uff0c\u5e76\u4e14\u89e3\u51b3\u4e86\u4e2d\u6587\u6587\u4ef6\u540d\u4e71\u7801\u95ee\u9898\uff0c\u517c\u5bb9IE\u548c\u706b\u72d0\u4e24\u79cd\u6d4f\u89c8\u5668\u3002
\u4f60\u53ef\u4ee5\u9009\u62e9\u3002
\u65b9\u6848\u4e00\uff1a\u4ee3\u7801\u5199\u5728\u4e00\u4e2a.jsp\u6587\u4ef6\u4e2d\u3002
\u4e0b\u8f7d\u8bf7\u6c42\u9875\u9762\u4f20\u9012\u8fc7\u6765\u7684\u53c2\u6570\uff08\u5f53\u7136\u5177\u4f53\u770b\u4f60\u8981\u51e0\u4e2a\u53c2\u6570\uff09
file.jsp \u6587\u4ef6\u4ee3\u7801\uff1a
<%response.reset();
String ATTACHMENTSTOREPATH = \u5df2\u7ecf\u4e0a\u4f20\u4e86\u7684\u9644\u4ef6\u7684\u8def\u5f84\uff0c\u81ea\u5df1\u5e94\u8be5\u77e5\u9053\uff1f
int docId = 0;
int revNo = -1;
int attachmentNo = 0;
String filename = null;
String storageName = null;
try {
docId = Integer.parseInt(request.getParameter("docId"));
revNo = Integer.parseInt(request.getParameter("revNo"));
attachmentNo = Integer.parseInt(request.getParameter("attachmentNo"));
//\u5728\u706b\u72d0\u6d4f\u89c8\u5668\u4e0b\u8f7d\uff0c\u542b\u7a7a\u683c\u7684\u6587\u4ef6\u540d\u4f1a\u51fa\u73b0\u5f02\u5e38\uff0c\u4e8e\u662f\u5c06\u7a7a\u683c\u7528\u4e0b\u5212\u7ebf\u4ee3\u66ff
filename = (new String(request.getParameter("filename").
getBytes("ISO-8859-1"),"UTF-8")).replace(" ", "_");
//\u5c06\u7a7a\u683c\u8f6c\u5316\u4e3a\u4e0b\u5212\u7ebf\u540e\u91cd\u65b0\u5bf9\u6587\u4ef6\u540d\u8fdb\u884cUTF-8\u7f16\u7801
filename = java.net.URLEncoder.encode(filename, "UTF-8"); storageName = request.getParameter("storageName");
} catch (NumberFormatException nfe) {
}
if (docId >= 0 && revNo > -1 && attachmentNo >= 0) {
String filePath = null;
filePath = ATTACHMENTSTOREPATH + File.separator + storageName;
response.setContentType("application/octet-stream");
//\u56e0\u4e3a\u6d4f\u89c8\u5668\u4f1a\u5c06\u5b57\u7b26GBK\u7f16\u7801\uff0c\u6240\u4ee5\u4ece\u6570\u636e\u5e93\u83b7\u5f97\u7684UTF-8\u9700\u8981\u8f6c\u6362\u6210GBK
//UTF-8\u4e00\u4e2a\u6c49\u5b5724\u4f4d\uff0cGBK\u4e00\u4e2a\u6c49\u5b5716\u4f4d
//Start UTF-8 to GBK(\u76f8\u5bf9\u4ee5\u524d\u7684\u7a0b\u5e8f\u4e3b\u8981\u5c31\u662f\u4fee\u6539\u4e86\u8fd9\u91cc\uff09
String str=filename;
StringBuffer sb = new StringBuffer();
for(int i=0; i<str.length(); i++) {
char c = str.charAt(i);
switch (c) {
case '+':
sb.append(' ');
break;
case '%':
try {
sb.append((char)Integer.parseInt(
str.substring(i+1,i+3),16));
}
catch (NumberFormatException e) {
throw new IllegalArgumentException();
}
i += 2;
break;
default:
sb.append(c);
break;
}
}
String result = sb.toString();
result= new String(result.getBytes("ISO-8859-1"),"UTF-8");
response.addHeader("Content-Disposition", "attachment; filename=" + new String(result.getBytes("GBK"),"ISO-8859-1"));
//End UTF-8 to GBK
BufferedOutputStream bos = null;
BufferedInputStream bis = null;
try {
bos = new BufferedOutputStream(response.getOutputStream());
bis = new BufferedInputStream(new FileInputStream(filePath));
byte[] buffer = new byte[1024];
int n = -1;
while ((n = bis.read(buffer)) > -1) {
bos.write(buffer, 0, n);
}
} catch (Exception e) {
e.printStackTrace();
} finally {
if (bis != null)
bis.close();
if (bos != null){
out.clear(); out = pageContext.pushBody(); bos.close(); } bis = null;
bos = null;
}
}
%>
\u6b64\u65b9\u6848\u4e2d\u5982\u679c\u4f60\u53bb\u6389\uff1aout.clear();
out = pageContext.pushBody();
\u62a5\u7684\u9519\u5c06\u548c\u4f60\u7684\u4e00\u6a21\u4e00\u6837\uff0c\u4e0d\u4fe1\u4f60\u8bd5\u8bd5\uff1f
\u65b9\u6848\u4e8c\uff1a\u7528Servlet\u4e0b\u8f7d\uff0c\u548c\u4f60\u7684\u662f\u4e00\u6837\u7684\u3002
\u8fd8\u662f\u9875\u9762\u8fc7\u6765\u7684\u53c2\u6570\uff1a \u5176\u4e2d/***/***\u662f\u4f60\u8c03\u7528\u7684Servlet
public class PrFileServlet extends HttpServlet {
//stauts\u5224\u65ad\u4f7f\u7528\u54ea\u4e2a\u8def\u5f84
private String UPLOAD_TEMP_PATH = "\u4e34\u65f6\u8def\u5f84\uff08\u8fd8\u6ca1\u6709\u4fdd\u5b58\uff09";
private String UPLOAD_PATH = "\u6587\u4ef6\u8def\u5f84\uff08\u5df2\u7ecf\u4fdd\u5b58\u4e86\u6587\u4ef6\uff09";
protected void doGet(HttpServletRequest request, HttpServletResponse response)throws IOException{
String storageName =
(request.getParameter("storage")==null?"":request.getParameter("storage"));
//\u5728\u706b\u72d0\u6d4f\u89c8\u5668\u4e0b\u8f7d\uff0c\u542b\u7a7a\u683c\u7684\u6587\u4ef6\u540d\u4f1a\u51fa\u73b0\u5f02\u5e38\uff0c\u4e8e\u662f\u5c06\u7a7a\u683c\u7528\u4e0b\u5212\u7ebf\u4ee3\u66ff
String displayName =new String(request.getParameter("display").getBytes("ISO-8859-1"),"UTF8").replace(" ", "_");
//\u5c06\u7a7a\u683c\u8f6c\u5316\u4e3a\u4e0b\u5212\u7ebf\u540e\u91cd\u65b0\u5bf9\u6587\u4ef6\u540d\u8fdb\u884cUTF-8\u7f16\u7801
displayName = java.net.URLEncoder.encode(displayName, "UTF-8");
String status = (request.getParameter("status")==null?"":request.getParameter("status"));
String code = (request.getParameter("code")==null?"":request.getParameter("code"));
String filePath = "";
if (status.equals("N")) {
filePath = UPLOAD_PATH + "//" + storageName.substring(0, 6);
} else if (status.equals("T")) {
filePath = UPLOAD_TEMP_PATH;
}
File file = new File(filePath, storageName);
if (file == null) {
response.sendRedirect("/weberp/workflow/pr/fileNotFound.jsp");
return;
}
if (!file.exists()) {
response.sendRedirect("/weberp/workflow/pr/fileNotFound.jsp");
return;
}
String contentType = getServletContext().getMimeType(storageName);
if (contentType == null) {
contentType = "application/octet-stream";
}
BufferedInputStream input = null;
BufferedOutputStream output = null;
try {
input = new BufferedInputStream(new FileInputStream(file));
int contentLength = input.available();
// Init servlet response.
response.reset();
response.setContentType(contentType);
response.setContentLength(contentLength);
//\u56e0\u4e3a\u6d4f\u89c8\u5668\u4f1a\u5c06\u5b57\u7b26GBK\u7f16\u7801\uff0c\u6240\u4ee5\u4ece\u6570\u636e\u5e93\u83b7\u5f97\u7684UTF-8\u9700\u8981\u8f6c\u6362\u6210GBK
//UTF-8\u4e00\u4e2a\u6c49\u5b5724\u4f4d\uff0cGBK\u4e00\u4e2a\u6c49\u5b5716\u4f4d
//Start UTF-8 to GBK(\u76f8\u5bf9\u4ee5\u524d\u7684\u7a0b\u5e8f\u4e3b\u8981\u5c31\u662f\u4fee\u6539\u4e86\u8fd9\u91cc\uff09
String str=displayName;
StringBuffer sb = new StringBuffer();
for(int i=0; i<str.length(); i++) {
char c = str.charAt(i);
switch (c) {
case '+':
sb.append(' ');
break;
case '%':
try {
sb.append((char)Integer.parseInt(
str.substring(i+1,i+3),16));
}
catch (NumberFormatException e) {
throw new IllegalArgumentException();
}
i += 2;
break;
default:
sb.append(c);
break;
}
}
String result = sb.toString();
result= new String(result.getBytes("ISO-8859-1"),"UTF-8");
response.setHeader("Content-Disposition", "attachment; filename=" + new String(result.getBytes("GBK"),"ISO-8859-1"));
//End UTF-8 to GBK
output = new BufferedOutputStream(response.getOutputStream());
// Write file contents to response.
for (int data; (data = input.read()) != -1;) {
output.write(data);
}
// Finalize task.
output.flush();
} catch (IOException e) {
// Something went wrong?
e.printStackTrace();
} finally {
// Gently close streams.
close(output);
close(input);
}
}
private static void close(Closeable resource) {
if (resource != null) {
try {
resource.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
\u597d\u597d\u770b\u61c2\uff0c\u8981\u6709\u8010\u5fc3\u3002\u5e0c\u671b\u5bf9\u4f60\u6709\u6240\u5e2e\u52a9\u3002
\u3000\u3000\u51fa\u73b0getOutputStream() has already been called for this response\u5f02\u5e38\u7684\u539f\u56e0\u548c\u89e3\u51b3\u65b9\u6cd5\uff1a
\u3000\u3000\u51fa\u73b0\u6b64\u9519\u8bef\u4e00\u822c\u90fd\u662f\u5728jsp\u4e2d\u4f7f\u7528\u4e86\u8f93\u51fa\u6d41\uff08\u5982\u8f93\u51fa\u56fe\u7247\u9a8c\u8bc1\u7801\uff0c\u6587\u4ef6\u4e0b\u8f7d\u7b49\uff09\uff0c\u6ca1\u6709\u59a5\u5584\u5904\u7406\u597d\u7684\u539f\u56e0\u3002
\u3000\u3000\u89e3\u51b3\u7684\u529e\u6cd5\uff0c\u5728\u4f7f\u7528\u5b8c\u8f93\u51fa\u6d41\u4ee5\u540e\u8c03\u7528\u4ee5\u4e0b\u4e24\u884c\u4ee3\u7801\u5373\u53ef\uff1a
\u3000
\u3000 out.clear();
\u3000\u3000out = pageContext.pushBody();
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 收藏代码
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：
out.clear();
out = pageContext.pushBody();
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