Apache FileUpload的两种上传方式介绍及应用

时间：2021-05-28

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

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