Commons-fileupload-1.2.1.jar plugin upload and download

1: First write a text field on the page:

Import= "java.util.*" pageencoding= "UTF-8"%><! DOCTYPE HTML PUBLIC "-//w3c//dtd HTML 4.01 transitional//en" >        File:<input type= "file" name= "file"/>         Description:<input type= "text" name= "desc"/>        <input type= "Submit" value= "Submit"/>    </form>  </body>
<form action= "Uploadservlet" method= "post" enctype= "Multipart/form-data" >
File:<input type= "File" name= "file"/>
Description: <input type= "text" name= "desc"/>
<input type= "Submit" value= "Submit"/>
</form>
1). Request mode is post: <form action= "Uploadservlet" method= "POST" ... >
2). form fields using file: <input type= "file" name= "file"/>
3). Request encoding using Multipart/form-data: <form action= "Uploadservlet" method= "post" enctype= "Multipart/form-data" >
2: Get the information on the page using the FileUpload plugin
 PackageFileUpload;ImportJava.io.File;ImportJava.io.FileOutputStream;Importjava.io.IOException;ImportJava.io.InputStream;ImportJava.io.OutputStream;Importjava.util.List;Importjavax.servlet.ServletException;ImportJavax.servlet.http.HttpServlet;Importjavax.servlet.http.HttpServletRequest;ImportJavax.servlet.http.HttpServletResponse;ImportOrg.apache.commons.fileupload.FileItem;Importorg.apache.commons.fileupload.FileUploadException;Importorg.apache.commons.fileupload.disk.DiskFileItemFactory;ImportOrg.apache.commons.fileupload.servlet.ServletFileUpload; Public classUploadservletextendsHttpServlet {Private Static Final LongSerialversionuid = 1L; protected voidDoPost (httpservletrequest request, httpservletresponse response)throwsservletexception, IOException {//1. Get Fileitem's collection items//Create a factory for disk-based file itemsDiskfileitemfactory factory =Newdiskfileitemfactory (); //Set factory constraints setting factory information
Writes to a temporary file in excess of 500K
Factory.setsizethreshold (1024 * 500); File tempdirectory=NewFile ("E:\\beforeproject");        Factory.setrepository (tempdirectory); //Create A new file upload handlerServletfileupload upload =Newservletfileupload (Factory); //Set overall request size constraint setting the total sizeUpload.setsizemax (1024 * 1024 * 5); //Parse the request        Try{List<FileItem>/*Fileitem*/Items =upload.parserequest (Request); //2. Traverse Items:             for(Fileitem item:items) {//If you have a general form field, print the information                if(Item.isformfield ()) {String name=Item.getfieldname (); String value=item.getstring (); SYSTEM.OUT.PRINTLN (Name+ ": " +value); }                //If the file domain, save the file to the D:\\files directory.                Else{String FieldName=Item.getfieldname (); String FileName=Item.getname (); String ContentType=Item.getcontenttype (); LongsizeInBytes =item.getsize ();                    System.out.println (FieldName);                    System.out.println (FileName);                    System.out.println (ContentType);                    System.out.println (sizeInBytes); InputStream in=Item.getinputstream (); byte[] buffer =New byte[1024]; intLen = 0; FileName= "E:\\files\\" +FileName;                    System.out.println (FileName); OutputStream out=NewFileOutputStream (fileName);  while(len = in.read (buffer))! =-1) {out.write (buffer,0, Len);                    } out.close ();                In.close (); }            }        } Catch(fileuploadexception e) {e.printstacktrace (); }    }}
Ii. Basic Ideas:

> Commons-fileupload can parse the request and get a List of Fileitem objects
> commons-fileupload resolves all request information to a Fileitem object, whether it is a generic text field or a file field.
> can call Fileitem's Isformfield () method to determine whether it is a form field or not a table fields (then a file field)
> to get further information

if (Item.isformfield ()) {
String name = Item.getfieldname ();
String value = item.getstring ();
...
}

if (!item.isformfield ()) {
String fieldName = Item.getfieldname ();
String fileName = Item.getname ();
String ContentType = Item.getcontenttype ();
Boolean isinmemory = Item.isinmemory ();
Long sizeinbytes = Item.getsize ();
 
InputStream Uploadedstream = Item.getinputstream ();
...
Uploadedstream.close ();
}

Iii. how to get the List<fileitem> object.

> A simple way

Create a factory for disk-based file items
Fileitemfactory factory = new Diskfileitemfactory ();

Create a new file upload handler
Servletfileupload upload = new Servletfileupload (factory);

Parse the request
List/* Fileitem */items = upload.parserequest (request);

> Complex way: You can add some restrictions and other attributes to file uploads

Create a factory for disk-based file items
Diskfileitemfactory factory = new Diskfileitemfactory ();

Set the maximum size of the uploaded file in memory and write the file to a temporary folder if it is exceeded. In units of byte
Factory.setsizethreshold (yourmaxmemorysize);
Set the Temp folder
Factory.setrepository (yourtempdirectory);

Create a new file upload handler
Servletfileupload upload = new Servletfileupload (factory);

Sets the total size of the uploaded file. You can also set the size of a single file.
Upload.setsizemax (yourmaxrequestsize);

Parse the request
List/* Fileitem */items = upload.parserequest (request);
Commons-fileupload-1.2.1.jar plugin upload and download