Today’s content:
File upload------commons-fileupload
The essence of file upload and download: copy of file
File upload: copy from local to server disk The client needs to write a file upload form---- >The server needs to write code to accept uploaded files
File download: copy from the server disk to the local disk You need to write server-side code, and the client's download work is solved by the browser kernel
(1) Need to write a file upload form
(2) Write server-side code with For receiving uploaded files
3, the server accepts the form for file upload Data
Principle of file upload and reception
Easy and quick to use File upload tool---Apache Commons-fileupload.jar
(1) Download the jar package for file upload fileuplaod with the help of commons-io.jar
(2) Use the API in the fileupload tool Encoding
4, the three core objects in the FileUpload tool
DiskFileItemFactory: Disk file item factory--some related configuration settings The size of the cache and the location of the temporary directory
ServletFileUplaod: A core class for file upload
FileItem: Represents each form item
6, Detailed explanation of file upload API
Set the cache size: factory.setSizeThreshold() in bytes
Set the directory of temporary files: factory.setRepository(File)
Determine whether it is a file upload form: ServletFileUpload.isMultipartContent(request);
Parse request to obtain a collection of form items: upload.parseRequest(request);
Set the encoding method of the uploaded file name: upload.setHeaderEncoding("UTF- 8");
Determine whether it is a normal form item ：item.isFormField();
Get the name attribute value of the form: item.getFieldName();
Get the value value of the form: item.getString("UTF-8") --- UTF-8 represents the encoding when obtaining Chinese
Get the name of the uploaded file: item.getName()
Get uploaded files: item.getInputStream();
Delete temporary files: item.delete();
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