Commons-fileupload-1.2.1 for File Upload

Many File Upload components are implemented in Java, such as jspsmartupload and commons-fileupload, but jspsmartupload is almost eliminated.
I found the usage related to Apache commons-fileupload on the Internet and called the program, which will be used directly later ..
Jar package used: (download it from www.apache.org)
Commons-fileupload-1.2.1.jar
Commons-io-1.4.jar
There are more detailed usage on the Internet:
Http://www.cnblogs.com/yyw84/archive/2007/06/27/797652.html
Because there are too many codes, you can refer to them if you are interested.

This is the simple code that I used on my machine. Put it below:
Web. xml <? XML version = "1.0" encoding = "UTF-8"?>
<Web-app version = "2.5"
Xmlns = "http://java.sun.com/xml/ns/javaee"
Xmlns: xsi = "http://www.w3.org/2001/XMLSchema-instance"
Xsi: schemalocation = "http://java.sun.com/xml/ns/javaee
Http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd>
<Servlet>
<Servlet-Name> fileupload </servlet-Name>
<Servlet-class> fileupload. fileuploadservlet </servlet-class>
</Servlet>
<Servlet-mapping>
<Servlet-Name> fileupload </servlet-Name>
<URL-pattern>/servlet/fileuploadservlet </url-pattern>
</Servlet-mapping>

<Welcome-file-List>
<Welcome-File> fileupload. jsp </welcome-File>
</Welcome-file-List>
</Web-app>

Fileupload. javapackage fileupload;
Import java. Io. file;
Import java. Io. ioexception;
Import java. Io. printwriter;
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. fileuploadexception;
Import org. Apache. commons. fileupload. fileuploadbase. sizelimitexceededexception;
Import org. Apache. commons. fileupload. disk. diskfileitemfactory;
Import org. Apache. commons. fileupload. servlet. servletfileupload;
Public class fileuploadservlet extends httpservlet {
Public fileuploadservlet (){
Super ();
}
Public void destroy (){
Super. Destroy (); // just puts "Destroy" string in log
// Put your code here
}
Public void doget (httpservletrequest request, httpservletresponse response)
Throws servletexception, ioexception {
Dopost (request, response );
}
Public void dopost (httpservletrequest request, httpservletresponse response)
Throws servletexception, ioexception {
Final string apprealpath = This. getservletcontext (). getrealpath ("/"); // obtain the physical path of the web app
Final long max_size = 3*1024*1024; // sets the maximum size of the uploaded file to 3 MB.
Final string [] allowedext = new string [] {"jpg", "Jpeg", "GIF", "TXT ",
"Doc", "docx", "MP3", "WMA", "m4a"}; // list of file formats that can be uploaded
Response. setcontenttype ("text/html ");
Response. setcharacterencoding ("UTF-8"); // set the character encoding to a UTF-8, which supports Chinese Character Display
// Instantiate a hard disk file factory to configure the Upload Component servletfileupload
Diskfileitemfactory dfif = new diskfileitemfactory ();
Dfif. setsizethreshold (4096); // set the memory size used to temporarily store files during file upload. Here, more than 4 kb will be temporarily stored on the hard disk.
Dfif. setrepository (new file (apprealpath + "imagesuploadtemp //"));
// Set the directory for storing temporary files, and the imagesuploadtemp directory under the web root directory
// Use the above factory to instantiate the Upload Component
Servletfileupload SFU = new servletfileupload (dfif );

SFU. setsizemax (max_size); // sets the maximum upload size.
Printwriter out = response. getwriter ();

// Obtain the list of all upload domains from the request
List filelist = NULL;
Try {
Filelist = SFU. parserequest (request );
} Catch (fileuploadexception e) {// handle an exception when the file size is too large
If (E instanceof sizelimitexceededexception ){
Out. println ("the file size exceeds the specified size:" + max_size + "bytes <p/> ");
Out. println ("<a href =/" "+ request. getcontextpath () + "/fileupload. JSP "+"/"target =/" _ top/"> return </a> ");
Return;
}
E. printstacktrace ();
}
// No file is uploaded
If (filelist = NULL | filelist. Size () = 0 ){
Out. println ("Select Upload File <p/> ");
Out. println ("<a href =/" "+ request. getcontextpath () + "/fileupload. JSP "+"/"target =/" _ top/"> return </a> ");
Return;
}
// Obtain all uploaded files
Iterator fileitr = filelist. iterator ();
// Process all objects cyclically
While (fileitr. hasnext ()){
Fileitem = NULL;
String Path = NULL;
Long size = 0;
// Obtain the current file
Fileitem = (fileitem) fileitr. Next ();
// Ignore the simple form field rather than the file field of the uploaded domain (<input type = "text"/>)
If (fileitem = NULL | fileitem. isformfield ()){
Continue;
}
// Obtain the complete file path
Path = fileitem. getname ();
// Get the file size
Size = fileitem. getsize ();
If ("". Equals (PATH) | size = 0 ){
Out. println ("Select Upload File <p/> ");
Out. println ("<a href =/" "+ request. getcontextpath () + "/fileupload. JSP "+"/"target =/" _ top/"> return </a> ");
Return;
}
// Get the name of the removed path
String t_name = path. substring (path. lastindexof ("//") + 1 );
// Get the file extension (the full name will be obtained if there is no extension)
String t_ext = t_name.substring (t_name.lastindexof (".") + 1 );
// Refuse to accept file types other than the specified file format
Int allowflag = 0;
Int allowedextcount = allowedext. length;
For (; allowflag <allowedextcount; allowflag ++ ){
If (allowedext [allowflag]. Equals (t_ext ))
Break;
}
If (allowflag = allowedextcount ){
Out. println ("please upload the following types of files <p/> ");
For (allowflag = 0; allowflag <allowedextcount; allowflag ++)
Out. println ("*." + allowedext [allowflag]
+ "& Nbsp ;");
Out
. Println ("<a href =/" "+ request. getcontextpath () + "/fileupload. JSP "+"/"target =/" _ top/"> return </a> ");
Return;
}
Long Now = system. currenttimemillis ();
// Generate the uploaded file name based on the system time.
String prefix = string. valueof (now );
// Complete path of the stored final file, saved in the imagesuploaded directory under the web root directory
String u_name = apprealpath + "imagesuploaded //"
+ Prefix + "." + t_ext;
Try {
// Save the file
Fileitem. Write (new file (u_name ));
Out. println ("File Uploaded successfully. Saved as:" + prefix + "." + t_ext
+ "& Nbsp; file size:" + size + "bytes <p/> ");
Out. println ("<a href =/" "+ request. getcontextpath () + "/fileupload. JSP "+"/"target =/" _ top/"> continue upload </a> ");
} Catch (exception e ){
E. printstacktrace ();
}
}
}
Public void Init () throws servletexception {
// Put your code here
}
}

Fileupload. jsp <% @ page Language = "Java" Import = "Java. util. *" pageencoding = "gb18030" %>
<! Doctype HTML public "-// W3C // dtd html 4.01 transitional // en">
<HTML>
<Head>
<Title> my JSP 'fileupload. jsp 'starting page </title>
</Head>

<Body>
<Form action = "<% = request. getcontextpath () %>/servlet/fileuploadservlet" method = "Post" enctype = "multipart/form-Data">
<Input type = "file" name = "fileupload"/>
<Input type = "Submit" value = "Upload"/>
</Form>
</Body>
</Html>

Remember to specify enctype = "multipart/form-Data" in the uploaded form. Read fileupload. Java for details.