Apache FileUpload的两种上传方式介绍及应用

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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:

 
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> 
<html> 
<body> 
<form method="POST" enctype="multipart/form-data" action="traditionalapi.jsp"> 
File to upload: <input type="file" name="file" size="40"><br/> 
<input type="submit" value="Press"> to upload the file! 
</form> 
</body> 
</html> 

//traditionalapi.jsp

复制代码代码如下:

 
<%@page contentType="text/html;charset=UTF-8" pageEncoding="UTF-8" language="java"%> 
<%@page import="java.io.File"%> 
<%@page import="java.util.List"%> 
<%@page import="org.apache.commons.fileupload.*"%> 
<%@page import="org.apache.commons.fileupload.disk.DiskFileItemFactory"%> 
<%@page import="org.apache.commons.fileupload.servlet.ServletFileUpload"%> 
<% 
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<FileItem> items = upload.parseRequest(request); // FileUploadException 
for(FileItem item : items) 
{ 
if(item.isFormField()) //regular form field 
{ 
String name = item.getFieldName(); 
String value = item.getString(); 
%> 
<h1><%=name%> --> <%=value%></h1> 
<% 
} 
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); 
%> 
<h1>upload file <%=uploadedFile.getName()%> done!</h1> 
<% 
} 
} 
} 
%> 

Streaming API上传方式
//fileupload02.htm

复制代码代码如下:

 
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> 
<html> 
<body> 
<form method="POST" enctype="multipart/form-data" action="streamingapi.jsp"> 
File to upload: <input type="file" name="file" size="40"><br/> 
<input type="submit" value="Press"> to upload the file! 
</form> 
</body> 
</html> 

//streamingapi.jsp

复制代码代码如下:

 
<%@page contentType="text/html;charset=UTF-8" pageEncoding="UTF-8" language="java"%> 
<%@page import="java.io.*"%> 
<%@page import="java.util.List"%> 
<%@page import="org.apache.commons.fileupload.*"%> 
<%@page import="org.apache.commons.fileupload.util.Streams"%> 
<%@page import="org.apache.commons.fileupload.servlet.ServletFileUpload"%> 
<% 
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 
{ 
%> 
<!-- read a FileItemStream's content into a string. --> 
<h1><%=fieldName%> --> <%=Streams.asString(is)%></h1> 
<% 
} 
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); 
%> 
<h1>upload file <%=uploadedFile.getName()%> done!</h1> 
<% 
} 
} 
} 
%> 

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：
http://stackoverflow.com/questions/11620432/apache-commons-fileupload-streaming-api
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.
http://commons.apache.org/proper/commons-fileupload/using.html