Use of the FileUpload component and Multifile upload

Use of the FileUpload component and Multifile upload
Significance of File Upload
Uploading files frequently in projects: uploading images via qq, uploading images through photo albums, sharing data ......

Steps for File Upload
1. specify the form type as a file upload form.
You must specify the form attribute enctype = "multipart/form-data"
<Form action = "" method = "post" enctype = "multipart/form-data>
<Input type = "file" name = "files"/>
2. The submission method must be post.
Process uploaded files manually
// Obtain the file in the form
// Obtain the input stream
InputStream in = request. getInputStream ();
// Convert the stream
InputStreamReader inReader = new InputStreamReader (in );
// Define the buffer stream
BufferedReader br = new BufferedReader (inReader );
Process data files
Content-Disposition: form-data; name = "files"; filename = "D: \ 01readme.txt"
Content-Type: text/plain
To process files, you must process Content-Disposition.

Use the File Upload Component During Development to upload files
The biggest feature of a good group: simplicity, ease of use, and security, followed by powerful functions
The fileupload component is usually used to upload the package to be introduced.
1. commons-fileupload-1.2.1.jar
2. commons-io-1.4.jar
// Create a file upload Project
FileItemFactory fileItemFactory = new DiskFileItemFactory ();
FileItemFactory encapsulates each form request object into a FileIteam object
Fac. serRepository (repository) sets the temporary directory for File Upload
The default is the temp directory of the server.
The maximum memory of a virtual machine is 1 GB in Windows and 16 GB in linux.

// Create a file first and upload the core Class Object
ServletFileUpload upload = new ServletFileUpload (fileItemFactory );
Purpose: obtain all FileItem objects.
Upload. parseRequest (request); Return Value Type List, get all file upload items
Boolean isMultipartContent (request) determines the form type
Upload. setFileSizeMax (fileSize) sets the maximum value for a single file
Upload. setSizeMax (fileSize) sets the maximum value of the uploaded file (all files)
Upload. setHeaderEncoding (encoding method); equivalent to request. setContentType (encoding method );
// Determine whether it is a file upload form
If (ServletFileUpload. isMultipartContent (request )){
// Convert the request data to a FileIteam object set
Try {
// Each upload item placed in the list
List <FileItem> list = upload. parseRequest (request );
// Traverse each upload item
For (FileItem fileItem: list ){
// Determine whether it is a normal form or a file upload item
If (fileItem. isFormField ()){
// Normal Form
String fileName = fileItem. getFieldName ();
// Text box Value
String str = fileItem. getString ();
} Else {
// File form
// Form element name
String fileName = fileItem. getFieldName ();
// File type
String contentType = fileItem. getContentType ();
// Obtain the file name
String name = fileItem. getName ();
// Obtain the value of the text box, that is, the file content.
String str = fileItem. getString ();

// Set the request encoding.
FileItem. getString ("encoding method ");
// Write the file to the specified directory
FileItem. write (new File ("specify directory "))
// Delete a temporary file
FileItem. delete ()
// File stream
InputStream in = fileItem. getInputStream ();
// File Size
Long size = fileItem. getSize ();
}
}
} Catch (FileUploadException e ){
// TODO Auto-generated catch block
E. printStackTrace ();
}
} Else {
System. out. println ("not a file upload form ");
}