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Apache FileUpload的两种上传方式介绍及应用

环境
tomcat5.6
commmons-fileupload-1.3.jar
commmons-io-2.4.jar
JSP
编码:UTF-8
临时文件夹:fileupload/tmp相对于网站根目录
上传文件保存位置:fileupload
Traditional API上传方式
//fileload01.htm
复制代码 代码如下:

File to upload:

to upload the file!

//traditionalapi.jsp
复制代码 代码如下:

request.setCharacterEncoding(“UTF-8”);
// file less than 10kb will be store in memory, otherwise in file
system.
final int threshold = 10240;
final File tmpDir = new File(getServletContext().getRealPath(“/”) +
“fileupload” + File.separator + “tmp”);
final int maxRequestSize = 1024 * 1024 * 4; // 4MB
// Check that we have a file upload request
if(ServletFileUpload.isMultipartContent(request))
{
// Create a factory for disk-based file items.
FileItemFactory factory = new DiskFileItemFactory(threshold, tmpDir);

// Create a new file upload handler
ServletFileUpload upload = new ServletFileUpload(factory);
// Set overall request size constraint.
upload.setSizeMax(maxRequestSize);
List items = upload.parseRequest(request); // FileUploadException
for(FileItem item : items)
{
if(item.isFormField()) //regular form field
{
String name = item.getFieldName();
String value = item.getString();
%>

–>

}
else
{ //file upload
String fieldName = item.getFieldName();
String fileName = item.getName();
File uploadedFile = new File(getServletContext().getRealPath(“/”) +
“fileupload” + File.separator + fieldName + “_” + fileName);
item.write(uploadedFile);
%>

upload file done!

}
}
}
%>

Streaming API上传方式
//fileupload02.htm
复制代码 代码如下:

File to upload:

to upload the file!

//streamingapi.jsp
复制代码 代码如下:

request.setCharacterEncoding(“UTF-8”);
// Check that we have a file upload request
if(ServletFileUpload.isMultipartContent(request))
{
// Create a new file upload handler
ServletFileUpload upload = new ServletFileUpload();

// Parse the request
FileItemIterator iter = upload.getItemIterator(request);
while(iter.hasNext())
{
FileItemStream item = iter.next();
String fieldName = item.getFieldName();
InputStream is = item.openStream();
if(item.isFormField()) //regular form field
{
%>

–>

}
else
{ //file upload
String fileName = item.getName();
File uploadedFile = new File(getServletContext().getRealPath(“/”) +
“fileupload” + File.separator + fieldName + “_” + fileName);
OutputStream os = new FileOutputStream(uploadedFile);
// write file to disk and close outputstream.
Streams.copy(is, os, true);
%>

upload file done!

}
}
}
%>

Traditional API vs Streaming API
Streaming
API上传速度相对较快。因为它是利用内存保存上传的文件,节省了传统API将文件写入临时文件带来的开销。
可参考:

This page describes the traditional API of the commons fileupload
library. The traditional API is a convenient approach. However, for
ultimate performance, you might prefer the faster Streaming API.

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