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Apache FileUpload的两种上传方式介绍及应用

2017年12月12日  | 移动技术网IT编程  | 我要评论

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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

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