本文通过实例来介绍如何使用commons-fileupload.jar，apache的commons-fileupload.jar可方便的实现文件的上传功能，具体内容如下
将apache的commons-fileupload.jar放在应用程序的web-inf\lib下，即可使用。下面举例介绍如何使用它的文件上传功能。
所使用的fileupload版本为1.2，环境为eclipse3.3+myeclipse6.0。fileupload 是基于 commons io的，所以在进入项目前先确定commons io的jar包（本文使用commons-io-1.3.2.jar）在web-inf\lib下。
此文作示例工程可在文章最后的附件中下载。
示例1
最简单的例子，通过servletfileupload静态类来解析request，工厂类fileitemfactory会对mulipart类的表单中的所有字段进行处理，不只是file字段。getname（）得到文件名，getstring（）得到表单数据内容，isformfield（）可判断是否为普通的表单项。
demo1.html
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<html>
<head>
<meta http-equiv="content-type" content="text/html; charset=gb18030">
<title>file upload</title>
</head>
<body>
//必须是multipart的表单数据。
<form name="myform" action="demo1.jsp" method="post"
enctype="multipart/form-data">
your name: <br>
<input type="text" name="name" size="15"><br>
file:<br>
<input type="file" name="myfile"><br>
<br>
<input type="submit" name="submit" value="commit">
</form>
</body>
</html>
demo1.jsp
<%@ page language="java" contenttype="text/html; charset=gb18030"
pageencoding="gb18030"%>
<%@ page import="org.apache.commons.fileupload.*"%>
<%@ page import="org.apache.commons.fileupload.servlet.*"%>
<%@ page import="org.apache.commons.fileupload.disk.*"%>
<%@ page import="java.util.*"%>
<!doctype html public "-//w3c//dtd html 4.01 transitional//en">
<%
boolean ismultipart = servletfileupload.ismultipartcontent(request);//检查输入请求是否为multipart表单数据。
if (ismultipart == true) {
fileitemfactory factory = new diskfileitemfactory();//为该请求创建一个diskfileitemfactory对象，通过它来解析请求。执行解析后，所有的表单项目都保存在一个list中。
servletfileupload upload = new servletfileupload(factory);
list<fileitem> items = upload.parserequest(request);
iterator<fileitem> itr = items.iterator();
while (itr.hasnext()) {
fileitem item = (fileitem) itr.next();
//检查当前项目是普通表单项目还是上传文件。
if (item.isformfield()) {//如果是普通表单项目，显示表单内容。
string fieldname = item.getfieldname();
if (fieldname.equals("name")) //对应demo1.html中type="text" name="name"
out.print("the field name is" + item.getstring());//显示表单内容。
out.print("<br>");
} else {//如果是上传文件，显示文件名。
out.print("the upload file name is" + item.getname());
out.print("<br>");
}
}
} else {
out.print("the enctype must be multipart/form-data");
}
%>
<html>
<head>
<meta http-equiv="content-type" content="text/html; charset=gb18030">
<title>file upload</title>
</head>
<body>
</body>
</html>
结果：
the field name isjeff
the upload file name isd:\c语言考试样题\作业题.rar
示例2
上传两个文件到指定的目录。
demo2.html
<html>
<head>
<meta http-equiv="content-type" content="text/html; charset=gb18030">
<title>file upload</title>
</head>
<body>
<form name="myform" action="demo2.jsp" method="post"
enctype="multipart/form-data">
file1:<br>
<input type="file" name="myfile"><br>
file2:<br>
<input type="file" name="myfile"><br>
<br>
<input type="submit" name="submit" value="commit">
</form>
</body>
</html>
demo2.jsp
<%@ page language="java" contenttype="text/html; charset=gb18030"
pageencoding="gb18030"%>
<%@ page import="org.apache.commons.fileupload.*"%>
<%@ page import="org.apache.commons.fileupload.servlet.*"%>
<%@ page import="org.apache.commons.fileupload.disk.*"%>
<%@ page import="java.util.*"%>
<%@ page import="java.io.*"%>
<!doctype html public "-//w3c//dtd html 4.01 transitional//en">
<%string uploadpath="d:\\temp";
boolean ismultipart = servletfileupload.ismultipartcontent(request);
if(ismultipart==true){
try{
fileitemfactory factory = new diskfileitemfactory();
servletfileupload upload = new servletfileupload(factory);
list<fileitem> items = upload.parserequest(request);//得到所有的文件
iterator<fileitem> itr = items.iterator();
while(itr.hasnext()){//依次处理每个文件
fileitem item=(fileitem)itr.next();
string filename=item.getname();//获得文件名，包括路径
if(filename!=null){
file fullfile=new file(item.getname());
file savedfile=new file(uploadpath,fullfile.getname());
item.write(savedfile);
}
}
out.print("upload succeed");
}
catch(exception e){
e.printstacktrace();
}
}
else{
out.println("the enctype must be multipart/form-data");
}
%>
<html>
<head>
<meta http-equiv="content-type" content="text/html; charset=gb18030">
<title>file upload</title>
</head>
<body>
</body>
</html>
结果：
upload succeed
此时，在"d:\temp"下可以看到你上传的两个文件。
示例3
上传一个文件到指定的目录，并限定文件大小。
demo3.html
<html>
<head>
<meta http-equiv="content-type" content="text/html; charset=gb18030">
<title>file upload</title>
</head>
<body>
<form name="myform" action="demo3.jsp" method="post"
enctype="multipart/form-data">
file:<br>
<input type="file" name="myfile"><br>
<br>
<input type="submit" name="submit" value="commit">
</form>
</body>
</html>
demo3.jsp
<%@ page language="java" contenttype="text/html; charset=gb18030"
pageencoding="gb18030"%>
<%@ page import="org.apache.commons.fileupload.*"%>
<%@ page import="org.apache.commons.fileupload.servlet.*"%>
<%@ page import="org.apache.commons.fileupload.disk.*"%>
<%@ page import="java.util.*"%>
<%@ page import="java.io.*"%>
<!doctype html public "-//w3c//dtd html 4.01 transitional//en">
<%
file uploadpath = new file("d:\\temp");//上传文件目录
if (!uploadpath.exists()) {
uploadpath.mkdirs();
}
// 临时文件目录
file temppathfile = new file("d:\\temp\\buffer\\");
if (!temppathfile.exists()) {
temppathfile.mkdirs();
}
try {
// create a factory for disk-based file items
diskfileitemfactory factory = new diskfileitemfactory();
// set factory constraints
factory.setsizethreshold(4096); // 设置缓冲区大小，这里是4kb
factory.setrepository(temppathfile);//设置缓冲区目录
// create a new file upload handler
servletfileupload upload = new servletfileupload(factory);
// set overall request size constraint
upload.setsizemax(4194304); // 设置最大文件尺寸，这里是4mb
list<fileitem> items = upload.parserequest(request);//得到所有的文件
iterator<fileitem> i = items.iterator();
while (i.hasnext()) {
fileitem fi = (fileitem) i.next();
string filename = fi.getname();
if (filename != null) {
file fullfile = new file(fi.getname());
file savedfile = new file(uploadpath, fullfile
.getname());
fi.write(savedfile);
}
}
out.print("upload succeed");
} catch (exception e) {
e.printstacktrace();
}
%>
<html>
<head>
<meta http-equiv="content-type" content="text/html; charset=gb18030">
<title>file upload</title>
</head>
<body>
</body>
</html>
示例4
利用servlet来实现文件上传。
upload.java
package com.zj.sample;
import java.io.file;
import java.io.ioexception;
import java.util.iterator;
import java.util.list;
import javax.servlet.servletexception;
import javax.servlet.http.httpservlet;
import javax.servlet.http.httpservletrequest;
import javax.servlet.http.httpservletresponse;
import org.apache.commons.fileupload.fileitem;
import org.apache.commons.fileupload.disk.diskfileitemfactory;
import org.apache.commons.fileupload.servlet.servletfileupload;
@suppresswarnings("serial")
public class upload extends httpservlet {
private string uploadpath = "d:\\temp"; // 上传文件的目录
private string temppath = "d:\\temp\\buffer\\"; // 临时文件目录
file temppathfile;
@suppresswarnings("unchecked")
public void dopost(httpservletrequest request, httpservletresponse response)
throws ioexception, servletexception {
try {
// create a factory for disk-based file items
diskfileitemfactory factory = new diskfileitemfactory();
// set factory constraints
factory.setsizethreshold(4096); // 设置缓冲区大小，这里是4kb
factory.setrepository(temppathfile);// 设置缓冲区目录
// create a new file upload handler
servletfileupload upload = new servletfileupload(factory);
// set overall request size constraint
upload.setsizemax(4194304); // 设置最大文件尺寸，这里是4mb
list<fileitem> items = upload.parserequest(request);// 得到所有的文件
iterator<fileitem> i = items.iterator();
while (i.hasnext()) {
fileitem fi = (fileitem) i.next();
string filename = fi.getname();
if (filename != null) {
file fullfile = new file(fi.getname());
file savedfile = new file(uploadpath, fullfile.getname());
fi.write(savedfile);
}
}
system.out.print("upload succeed");
} catch (exception e) {
// 可以跳转出错页面
e.printstacktrace();
}
}
public void init() throws servletexception {
file uploadfile = new file(uploadpath);
if (!uploadfile.exists()) {
uploadfile.mkdirs();
}
file temppathfile = new file(temppath);
if (!temppathfile.exists()) {
temppathfile.mkdirs();
}
}
}
demo4.html
<html>
<head>
<meta http-equiv="content-type" content="text/html; charset=gb18030">
<title>file upload</title>
</head>
<body>
// action="fileupload"对应web.xml中<servlet-mapping>中<url-pattern>的设置.
<form name="myform" action="fileupload" method="post"
enctype="multipart/form-data">
file:<br>
<input type="file" name="myfile"><br>
<br>
<input type="submit" name="submit" value="commit">
</form>
</body>
</html>
web.xml
<servlet> <servlet-name>upload</servlet-name> <servlet-class>com.zj.sample.upload</servlet-class> </servlet> <servlet-mapping> <servlet-name>upload</servlet-name> <url-pattern>/fileupload</url-pattern> </servlet-mapping>
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