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This article mainly shows you the "JSP how to achieve file upload function", the content is easy to understand, clear, hope to help you solve your doubts, the following let the editor lead you to study and learn "JSP how to achieve file upload function" this article.

I. preparation part

Need Apache's fileupload.jar and io.jar package to complete together. You can continue after you finish building the path.

Resource address

Second, the part of the page student number: name: upload photo:

Note:

1. Files must be uploaded using post to avoid using the get method to transfer more than the maximum number of characters that the search box can hold.

two。 The enctype= "multipart.form-data" field must be added

3. The file office needs to use "file".

III. Servlet partial package webtest; import java.io.File;import java.io.IOException;import java.util.Iterator;import java.util.List; import javax.servlet.ServletException;import javax.servlet.annotation.WebServlet;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.FileItemFactory;import org.apache.commons.fileupload.FileUploadBase;import org.apache.commons.fileupload.FileUploadException Import org.apache.commons.fileupload.disk.DiskFileItemFactory;import org.apache.commons.fileupload.servlet.ServletFileUpload; / * Servlet implementation class UploadServlet * / @ WebServlet ("/ UploadServlet") public class UploadServlet extends HttpServlet {private static final long serialVersionUID = 1L; protected void doGet (HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {request.setCharacterEncoding ("utf-8"); / / request encoding processing, response.setCharacterEncoding ("utf-8") during transmission / / response coding processing, response.setContentType ("utf-8") when transmitting; / / response coding processing, boolean isMultipart = ServletFileUpload.isMultipartContent (request) when displayed; / / judging whether there is entype= "multipart/form-data" part if (isMultipart) {try {FileItemFactory factory = new DiskFileItemFactory (); ServletFileUpload upload = new ServletFileUpload (factory) / / sets the memory buffer size when uploading, and writes temporary file 10kb ((DiskFileItemFactory) factory) .setSizeThreshold (10240) when it is exceeded; / / unit byte / / sets temporary file directory to prevent system space from running out of space ((DiskFileItemFactory) factory) .setRepository (new File (request.getSession () .getServletContext () .setRepository ("Uploadtemp") / / dynamically obtain the location of the Uploadtemp folder in the project / / Control the maximum value of the upload list file 20kb upload.setSizeMax (20480); / / Unit byte List items = upload.parseRequest (request); / / parse all the request fields in form and save them in item Iterator iter = items.iterator () While (iter.hasNext ()) {/ / parses without order, so you need to look up FileItem item = iter.next (); if (item.isFormField ()) {/ / non-file data String itemName = item.getFieldName (); / / get the non-file range data name if (itemName.equals ("sno")) {int sno =-1 Sno = Integer.parseInt (item.getString ("utf-8"));} else if (itemName.equals ("sname")) {String sname = null; sname = item.getString ("utf-8");} else {System.out.println ("other fields...");} else {/ / File upload String fileName = item.getName () / / get file scope data. Path and its name / / determine the file type String ext = fileName.substring (fileName.indexOf (".") + 1); if (! (ext.equals ("png") | | ext.equals ("gif") | | ext.equals ("jpg")) {System.out.println ("only png.gif,jpg type files are supported"); return;} String path = request.getSession (). GetServletContext (). GetRealPath ("Upload") / / dynamically obtain the location of the Upload folder in the project File file = new File (path,fileName); item.write (file); / / define the upload path, mostly the server path System.out.println (fileName+ "uploaded successfully");} item.delete (); / / delete the temporary directory files}} catch (FileUploadBase.SizeLimitExceededException e) {System.out.println ("maximum 20KB") } catch (FileUploadException e) {/ / TODO Auto-generated catch block e.printStackTrace ();} catch (Exception e) {/ / TODO Auto-generated catch block e.printStackTrace ();} / * @ see HttpServlet#doPost (HttpServletRequest request, HttpServletResponse * response) * / protected void doPost (HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {/ / TODO Auto-generated method stub doGet (request, response);}}

Note:

1. If the package is marked red and the package is not found after hovering over the mouse, you can use the "alt" + "/" key combination to select the first class in the figure below to import.

two。 Because if the Upload and Uploadtemp files are stored under the project corresponding to tomcat, every time the code is updated through eclipse, the code under eclipse will be directly overwritten, so the two folders will be overwritten directly. You can create a new one in eclipse or set it in another folder through an absolute / relative path.

3. The data in the temporary file will be retained for a short period of time, so adding sleep allows the program to hibernate and may be visible. Even without item.delete (), temporary files are deleted after the entire session is complete.

4. If you report an error and can't find the file, please try using a browser if Google does it, instead of using Eclipse.

The above is all the contents of the article "how to upload files in JSP". Thank you for reading! I believe we all have a certain understanding, hope to share the content to help you, if you want to learn more knowledge, welcome to follow the industry information channel!

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