Multi-file uploads with Ajax and Servlet implementations

Build the Environment

Here, use Maven to import the jar package:

<dependencies>
  <!--file Upload--
  <dependency>
      <groupid>commons-fileupload</ groupid>
      <artifactId>commons-fileupload</artifactId>
      <version>1.3.2</version >
  </dependency>
  <dependency>
      <groupId>org.apache.commons</groupId>
      <artifactId>commons-io</artifactId>
      <version>1.3.2</version>
  </dependency >
  <!--json-->
  <dependency>
      <groupId>org.json</groupId>
      < artifactid>json</artifactid>
      <version>20160810</version>
  </dependency>

</dependencies>

Three main jar packages, which will also use jquery and submit forms asynchronously, so jquery and Jquery.form files are required
JSP page

<%--Created by IntelliJ idea. USER:WQH DATE:2017/5/26 time:9:46 To change this template use File | Settings |
File Templates. --%> <%@ page contenttype= "Text/html;charset=utf-8" language= "java"%>  
servlet Code

File upload test, upload files will not be saved to the local L. Returns the file name directly to the page and returns the JSON format.

 Req.setcharacterencoding ("Utf-8");

        Resp.setcharacterencoding ("Utf-8");
        list<string> fileName = new arraylist<> ();
        Boolean ismultipartcontent = Servletfileupload.ismultipartcontent (req);
            Determine if the file is uploaded if (ismultipartcontent) {Diskfileitemfactory factory = new Diskfileitemfactory ();
            Servletfileupload fileUpload = new Servletfileupload (factory);
                try {list<fileitem> fileitems = fileupload.parserequest (req);
                        for (Fileitem fileitem:fileitems) {//To determine the type of field if (Fileitem.isformfield ()) {
                        Working with normal fields} else{//file fields, processing the upload field, this will not save the file locally.
                    Filename.add (Fileitem.getname ());
            }}} catch (Fileuploadexception e) {e.printstacktrace ();
            }//Convert list to JSONint index = 1;
            Jsonarray Jsonarray = new Jsonarray ();
                for (String s:filename) {jsonobject jsonobject = new Jsonobject ();
                Jsonobject.put ("file", s);
            Jsonarray.put (Jsonobject);
        } resp.getwriter (). print (Jsonarray);
 }
 
Test 
Select the uploaded file


File upload test and return JSON format file name successfully: