The recently learned file upload in the web phase, I just want to record it, help myself review and help you learn. Generally, I will save the uploaded file under the web inf in the server, because the user will not directly access it, and the path we save to the database is generally the path. There is no demonstration of database upload path. Momentum upload path is very simple. You only need to insert the path and file name into a table in the database. When you want to find the file, you can find the path from the database. Needless to say, the upper code (for the servlet that uploads files, the foreground interface only needs to have an input tag of file type. If you want to select multiple uploads at one time, you can write more input or add multiple="multiple" attribute in the input tag, then you can write several files in one input):

  1 package practice;
  2 
  3 import java.io.File;
  4 import java.io.FileOutputStream;
  5 import java.io.IOException;
  6 import java.io.InputStream;
  7 import java.io.UnsupportedEncodingException;
  8 import java.util.List;
  9 import java.util.UUID;
 10 
 11 import javax.servlet.ServletException;
 12 import javax.servlet.http.HttpServlet;
 13 import javax.servlet.http.HttpServletRequest;
 14 import javax.servlet.http.HttpServletResponse;
 15 
 16 import org.apache.commons.fileupload.FileItem;
 17 import org.apache.commons.fileupload.FileUploadBase;
 18 import org.apache.commons.fileupload.FileUploadException;
 19 import org.apache.commons.fileupload.disk.DiskFileItemFactory;
 20 import org.apache.commons.fileupload.servlet.ServletFileUpload;
 21 import org.apache.commons.io.FilenameUtils;
 22 
 23 
 24 
 25 public class UploadServlet extends HttpServlet {
 26 
 27     public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
 28          //Determine whether the form upload method is multipart/form-data;
 29         boolean ismultipartContent = ServletFileUpload.isMultipartContent(request);
 30         if(!ismultipartContent){
 31             throw new RuntimeException("your form is not multipart/form-data");
 32         }
 33         //Create a DiskFileItemFactory Factory
 34         DiskFileItemFactory factory = new DiskFileItemFactory();
 35         //Create a directory for temporary file storage
 36         String tempPath = this.getServletContext().getRealPath("/WEB-INF/temp"); 
 37         File  tempFile = new File(tempPath);
 38         if(!tempFile.exists()){
 39             tempFile.mkdir();
 40         }
 41         factory.setRepository(tempFile);
 42         //Establish ServletFileUoload Core objects
 43         ServletFileUpload  sfu = new ServletFileUpload(factory);
 44         //Solve the problem of file upload garbled
 45         sfu.setHeaderEncoding("utf-8");
 46         try {
 47         sfu.setFileSizeMax(1024*1024*3);  //Single file size
 48         sfu.setSizeMax(1024*1024*6);      //Total file size
 49         //Traversing the form collection returns a List<FileItem>aggregate
 50         List<FileItem> fileItems = sfu.parseRequest(request);
 51         for(FileItem fileItem:fileItems){
 52             //Determine whether it is a normal form or an upload form
 53             if(fileItem.isFormField()){
 54                 //Process as normal form
 55                 processFormField(fileItem);
 56             }else{
 57                 //Process according to the upload form
 58                 processUploadField(fileItem);
 59             }
 60         }
 61         }catch(FileUploadBase.FileSizeLimitExceededException e){
 62             e.printStackTrace();
 63             request.setAttribute("message", "Single file exceeds maximum");
 64             request.getRequestDispatcher("/uploadSong.jsp").forward(request, response);
 65             return;
 66         }catch(FileUploadBase.SizeLimitExceededException e){
 67             e.printStackTrace();
 68             request.setAttribute("message", "The total size of the uploaded file exceeds the limit");
 69             request.getRequestDispatcher("/uploadSong.jsp").forward(request, response);
 70             return;            
 71         } 
 72         catch (FileUploadException e) {
 73             // TODO Auto-generated catch block
 74             e.printStackTrace();
 75         } //Traverse form item collection
 76         
 77         
 78     }
 79 
 80     
 81     
 82     //Functions for handling uploaded files
 83     private void processUploadField(FileItem fileItem) {
 84         //Get the name of the uploaded file
 85         String filename = fileItem.getName();
 86         //Get file input stream
 87         try {
 88             InputStream is = fileItem.getInputStream();
 89             //Save file on server
 90             String directoryRealPath =this.getServletContext().getRealPath("/WEB-INF/upload");//Path created
 91             File storeDirectory = new File(directoryRealPath);
 92             if(!storeDirectory.exists()){
 93                 storeDirectory.mkdir(); //Create a specified directory
 94             }
 95             //Process filename
 96             //filename =filename.substring(filename.lastIndexOf(File.separator)+1);
 97             if(filename!=null){
 98                 filename=FilenameUtils.getName(filename);
 99             }
100             //Do not duplicate file names
101             filename=UUID.randomUUID()+"_"+filename;
102             //Break up the catalogue
103             String childDirectory = makChildDirectory(storeDirectory,filename);
104             
105             //Build a complete file path
106             /*File file =new File(storeDirectory,childDirectory+File.separator+filename);
107             //Create a write stream and write the picture to the path
108             FileOutputStream fos = new FileOutputStream(file);
109             int len=0;
110             byte [] buf = new byte[1024];
111             while((len=is.read(buf))!=-1){
112                 fos.write(buf,0,len);
113             }
114             fos.close();
115             is.close();*/
116             //Using tool class to upload files
117             fileItem.write(new File(storeDirectory,childDirectory+File.separator+filename));
118             fileItem.delete();//Delete temporary files
119         } catch (Exception e) {
120             // TODO Auto-generated catch block
121             e.printStackTrace();
122         }
123     }
124     
125     
126     //Break up the catalogue
127     private String makChildDirectory(File storeDirectory, String filename) {
128         int hashcode = filename.hashCode();
129         //hold hashcode Convert to hex
130         String code = Integer.toHexString(hashcode);
131         String childDirectory = code.charAt(0)+File.separator+code.charAt(1);
132         File file = new File(storeDirectory,childDirectory);
133         if(!file.exists()){
134             file.mkdirs();
135         }
136         return childDirectory;
137     }
138 
139 
140 
141     //Functions for handling normal forms
142     private void processFormField(FileItem fileItem) {
143         //Solve the problem of file name scrambling
144         try {
145             String fieldName = fileItem.getFieldName(); //Get field name
146             //String fieldValue = fileItem.getString();   //Get value
147             String fieldValue  = fileItem.getString("utf-8");
148         } catch (UnsupportedEncodingException e) {
149             // TODO Auto-generated catch block
150             e.printStackTrace();
151         }
152     }
153 
154     
155     
156     
157     public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
158 
159         doGet(request, response);
160     }
161 
162 }