The web is often used for file upload and download. In most cases, the user's request parameter on the form is a string, but if you set the form element to the "multipart/form-data" attribute, when a form is submitted, parameters are no longer submitted in the form of strings, but requests are submitted in binary format.
Enctype has the following attributes: application/x-www-form-urlencoded (default encoding, which processes only the value attribute values and URL encoding ); multipart/form-data (Processing form data using a binary stream will encapsulate the content of the file specified in the file field into the request parameters; the request cannot be used. getParameter method to obtain Request Parameters); text/plain (mainly used for Form Direct Mail ).
The upload framework is used to complete the upload. For java files, there are two Common upload frameworks: Common-FileUpload and COS, it is responsible for parsing all the fields in the HttpServletRequest request-whether it is a file field or a common form field.
Struts 2 File Upload
Struts 2 does not provide its own request parser. That is to say, struts 2 does not process multipart/form-data requests by itself. It needs to call other upload frameworks to parse binary request data. Struts 2 is further encapsulated on the basis of the original upload parser to further simplify file upload.
For example, upload an object.
The Code is as follows:
<Body> <form action = "upload. action "method =" post "enctype =" multipart/form-data "> file title: <input type = "text" name = "title"/> <br/> select a file: <input type = "file" name = "upload"/> <br/> <input value = "upload" type = "submit"/> </form> </body>
The Action of Struts 2 does not need to process the HttpServletRequest request. As described above, the Action of Struts 2 has been completely separated from the Servlet API. The Struts 2 framework is responsible for parsing parameters in the HttpServletRequest request, including File fields. Struts 2 uses the File type to encapsulate File fields. The following is the Action for processing the upload request:
UploadAction. java
Package Lee; import COM. opensymphony. xwork2.action; import Org. apache. struts2.servletactioncontext; import Java. io. file; import Java. io. *; import COM. opensymphony. xwork2.actionsupport; public class uploadaction extends actionsupport {// encapsulate the attribute private String title of the file title request parameter; // encapsulate the attribute private file upload of the uploaded file domain; // encapsulate the private string uploadcontenttype attribute of the upload file type; // encapsulate the private string uploadfilename attribute of the Upload File Name; // directly in struts. the attribute private string savepath configured in the XML file; // accept struts. XML file configuration value method public void setsavepath (string value) {This. savepath = value;} // returns the storage location of the uploaded file. Private string getsavepath () throws exception {return servletactioncontext. getrequest (). getrealpath (savepath);} // setter and getter methods of the file title Public void settitle (String title) {This. title = title;} Public String gettitle () {return (this. title);} // setter and getter methods of the file content corresponding to the uploaded file public void setupload (File Upload) {This. upload = upload;} public file getupload () {return (this. upload);} // setter and getter methods of the file type to be uploaded public void setuploadcontenttype (string uploadcontenttype) {This. uploadcontenttype = uploadcontenttype;} Public String getuploadcontenttype () {return (this. uploadcontenttype);} // setter and getter methods of the file name to be uploaded public void setuploadfilename (string uploadfilename) {This. uploadfilename = uploadfilename;} Public String getuploadfilename () {return (this. uploadfilename) ;}@ overridepublic string execute () throws exception {// create an upload file output stream fileoutputstream Fos = new fileoutputstream (getsavepath () with the server's file storage address and original file name () + "\" + getuploadfilename (); fileinputstream FCM = new fileinputstream (getupload (); byte [] buffer = new byte [1024]; int Len = 0; while (LEN = FCM. read (buffer)> 0) {FOS. write (buffer, 0, Len);} return success ;}}
Corresponding Struts. xml
<? Xml version = "1.0" encoding = "GBK"?> <! DOCTYPE struts PUBLIC "-// Apache Software Foundation // DTD Struts Configuration 2.1 // EN" "http://struts.apache.org/dtds/struts-2.1.dtd"> <struts> <! -- Specify the baseName of the international resource file as globalMessages --> <constant name = "struts. custom. i18n. resources" value = "globalMessages"/> <! -- Set the decoding set used by the Application --> <constant name = "struts. i18n. encoding "value =" GBK "/> <constant name =" struts. multipart. saveDir "value ="/tmp "/> <package name =" lee "extends =" struts-default "> <! -- Configure the Action for processing file uploads --> <action name = "upload" class = "lee. UploadAction"> <! -- Dynamically set the Action property value --> <param name = "savePath">/upload </param> <! -- Configure the default view page of Struts 2 --> <result>/succ. jsp </result> </action> <action name = ""> <result>. </result> </action> </package> </struts>
Succ. jsp
<Body> upload successful! <Br/> file title: <s: property value = "+ title"/> <br/> file: "/> <br/> </body>
Interface:
Struts can use list or array to upload multiple files:
<Form action = "upload. action "method =" post "enctype =" multipart/form-data "> file title: <input type = "text" name = "title"/> <br/> select the first file: <input type = "file" name = "upload"/> <br/> select the second file: <input type = "file" name = "upload"/> <br/> select the third file: <input type = "file" name = "upload"/> <br/> <input value = "upload" type = "submit"/> </form>
Action:
Public class uploadaction extends actionsupport {private String title; // use the File array to encapsulate the file content private file [] upload corresponding to multiple file domains; // use a string array to encapsulate the file type private string [] uploadcontenttype corresponding to multiple file domains; // use a string array to encapsulate the file name private string [] uploadfilename corresponding to multiple file domains; // Private string savepath, which accepts dependency injection; // setter and getter methods of the title attribute public void settitle (String title) {This. title = title;} Public String gettitle () {return this. title;} // setter and getter methods of the upload attribute public void setupload (file [] upload) {This. upload = upload;} public file [] getupload () {return this. upload;} // setter and getter methods of the uploadcontenttype attribute public void setuploadcontenttype (string [] uploadcontenttype) {This. uploadcontenttype = uploadcontenttype;} Public String [] getuploadcontenttype () {return this. uploadcontenttype;} // The setter and getter methods of the uploadfilename attribute are public void setuploadfilename (string [] uploadfilename) {This. uploadfilename = uploadfilename;} Public String [] getuploadfilename () {return this. uploadfilename;} // setter and getter methods of the savepath attribute public void setsavepath (string savepath) {This. savepath = savepath;} Public String getsavepath () {return servletactioncontext. getrequest (). getrealpath (savepath) ;}@ overridepublic string execute () throws exception {// get the file array to be uploaded file [] files = getupload (); // traverse each file to be uploaded for (INT I = 0; I <files. length; I ++) {// create an upload file output stream fileoutputstream Fos = new fileoutputstream (getsavepath () at the server's file storage address and original file name () + "\" + getuploadfilename () [I]); // create a file input stream fileinputstream (New fileinputstream (files [I]) for each file to be uploaded. // write each file to the corresponding file on the server. byte [] buffer = new byte [1024]; int Len = 0; while (LEN = FCM. read (buffer)> 0) {FOS. write (buffer, 0, Len);} FOS. close () ;}return success ;}}
The list method is similar.
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