The second method of file upload in form form is implemented by fileitem class, servletfileupload class and diskfileitemfactory class.

Use commons-fileupload-1.4-bin.zip To get a file with a file stream form The form data .

Problem analysis ：

Current end form When the form transfers data to the back end , There will be a very difficult problem ： Is there any file data in the data ？？ Because there is a different way to deal with it . Design the front-end and use it now Ajax Application Technology , The back end automatically judges when receiving the request form Whether the form data has file data , If there is file data, it is necessary to process the file stream and save it to the specified path .

So how to judge form Does the data from the form contain a file stream ？ The ideas and tools used here are FileItem class 、ServletFileUpload class 、DiskFileItemFactory class .

Using these three tools, you can put the front end form All the data in the form is divided into one by one FileItem object , Every data is an object , In this way, we can use the loop to judge whether each data is file data , I'm going to use it directly here if Conditional statements implement , If it is a file, the data should be saved to the path , If it's not file data, use the function fileItem.getFieldName() hold name Save the name of to the database statement sql Field name string in strfiestr1 in ; Use fileItem.getString("utf-8") Save data to database statement sql Medium value in , I named this string strvalSTR1. This is a parameter to prepare for the later modular insertion of data into the database . That is to say , Every time you take one, put fileItem.getFieldName() Value as sql Field name of the command string , hold fileItem.getString The value of sql Command string value Internal value .

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FileItem class

It is mainly used to process the data from the front end

ServletFileUpload class

It is mainly used to judge whether the front-end data is mime By way of agreement

DiskFileItemFactory class

It is mainly used to limit the size of uploaded files

union ServletFileUpload Generate file factory , And save to FileItem Type of List in , In this way, you can judge whether it is file data one by one .

DiskFileItemFactory factory1=new DiskFileItemFactory();// originate ：commons-fileupload-1.4.jar
factory1.setSizeThreshold(1024*1024*20);// Set the number of bytes used in memory 
ServletFileUpload uploadf1=new ServletFileUpload(factory1); // Create a file factory 
uploadf1.setHeaderEncoding("utf-8");// It can only solve the garbled Chinese characters in the file name or path 	   
java.util.List<FileItem> fileItemList;	 
fileItemList = uploadf1.parseRequest(request);
for(FileItem fileItem :fileItemList ){

}

One 、 FileItem The five most important methods of class

fileItem.isFormField() Method for judgment FileItem Class object encapsulates the data as a plain text form field , Or a file form field , If it is a normal form field, it returns true, Otherwise return to false.

fileItem.getName() Method is used to obtain the file path name of the uploaded file , We have to deal with the name later .

fileItem.getFieldName Method to get input Labeled name value .

fileItem.getString() Method is used to get the data value of the current object , namely input What the user enters in the tag .

fileItem.writer() Method is used to write the uploaded file to disk .

Two 、ServletFileUpload class

ServletFileUpload.isMultipartContent(request) Method is used to judge whether the data transmitted from the front end is mime agreement , That is to judge whether the data transmitted this time contains file data .enctype="multipart/form-data"

3、 ... and 、DiskFileItemFactory class

factory1.setSizeThreshold(1024*1024*20);// Set the number of bytes used in memory

Four 、 Combining the above technologies , The front end can be realized automatically form Form data can be saved to the database whether it contains files or not .

Tool class code ：

package com.jdbc.utils;
import java.io.File;
import java.io.IOException;
import java.io.PrintWriter;
import java.io.UnsupportedEncodingException;
import java.sql.SQLException;
import java.sql.Statement;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.apache.commons.fileupload.FileItem;
import org.apache.commons.fileupload.FileUploadException;
import org.apache.commons.fileupload.disk.DiskFileItemFactory;
import org.apache.commons.fileupload.servlet.ServletFileUpload;
import com.alibaba.fastjson.JSONArray;
import com.alibaba.fastjson.JSONObject;
import com.mysql.jdbc.Connection;
public class FormPostUtil {
	public void getparm(HttpServletRequest request,HttpServletResponse response, String path1, JSONArray jsonarr1,JSONObject jsonob1,String tablname1) {
		 String fname1=""; // Reserved file name , Whether or not to use it later , If a file is uploaded , It has value ; No file transfer , It's a null value 
		// If it is MIME To upload files 
		 try {
			request.setCharacterEncoding("UTF-8");  
		} catch (UnsupportedEncodingException e1) {
			// TODO Auto-generated catch block
			e1.printStackTrace();
		}
		  response.setContentType("text/html;Charset=UTF-8");
		 String sqlfiestr1=""; This string is used to save sql Of insert Field column name in command , One click 
		  String sqlvalSTR1=""; // This string is used to save sql Of insert In the command vlaue value  
		 DiskFileItemFactory factory1=new DiskFileItemFactory();// originate ：commons-fileupload-1.4.jar
		 factory1.setSizeThreshold(1024*1024*20);// Set the number of bytes used in memory 
		 ServletFileUpload uploadf1=new ServletFileUpload(factory1); // Create a file factory 
		 uploadf1.setHeaderEncoding("utf-8");// It can only solve the garbled Chinese characters in the file name or path 	   
		 java.util.List<FileItem> fileItemList;	 
		 try {
			fileItemList = uploadf1.parseRequest(request);
			
			for(FileItem fileItem :fileItemList )
			 {if(fileItem.isFormField())  // Indicates that it is a normal parameter , It's not a document . The following is a patchwork sql command insert Prepare the string 
			   {  sqlfiestr1=sqlfiestr1+fileItem.getFieldName()+",";
			      try {
					sqlvalSTR1=sqlvalSTR1+"'"+fileItem.getString("utf-8")+"',";
				} catch (UnsupportedEncodingException e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				}	 // Code it , Otherwise, the Chinese characters taken out may be garbled 	   
			 
			   }
			 else // No fileItem.isFormField()), Then the next item is file flow （ Pay attention to the above program structure , Put the file at the end of the form , Otherwise, you will call the processing file to save in the above loop   Independent functions 
			 { 	 fname1=fileItem.getName();// Take out the file name in advance , When saving to the database later, use 
				 savafile(fileItem, path1);// Write the uploaded file into the save path 
			 }			 
			 }
			// Ready to insert the above data into the database ;  call  inserttable() function 
			inserttable("xs", sqlfiestr1, sqlvalSTR1, fname1,tablname1);// To the specified table , Insert the specified field name , Specify the value , Whether to bring files （ If fname1 If it is empty, insert an empty string into the table 
		    PrintWriter out1;
			try {
				out1 = response.getWriter();
				out1.println(jsonob1);
				out1.flush();
				out1.close();
			} catch (IOException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
			
			
		} catch (FileUploadException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} 
		
	}
	// Modular file saving 
	private void savafile(FileItem fileItem,String path1) {
		String  fname1; 
		fname1=fileItem.getName();
			// System.out.println(fname1);
			 // Remove the previous path , As long as it is followed by a clean file name .
			 int po=fname1.lastIndexOf("\\");
			 if(po!=-1)// Indicates that the right slash was found \
			 { fname1=fname1.substring(po+1);}
			// System.out.println(fname1);
			 System.out.println(fileItem.getSize());
			 if(fileItem.getSize()>1024*1024*20) // The file is too big , Refuse to upload 
			 {return;  }
			 if(fname1==null||fname1.equals("")||fileItem.getSize()==0)
			 {// That means no files have been uploaded , This kind of treatment   The advantage is , Users can transfer or not transfer files , It doesn't matter 
				 				 
			 }
			 else {
				
				File savefile1=new File(path1,fname1);
				try {
					fileItem.write(savefile1);// Let's solve the problem of the same name of existing files by ourselves , You can use the system time number , There is little possibility of conflict 
				} catch (Exception e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				}
			}
		
	}
	private  void  inserttable(String tablename, String sqlfiestr1,String  sqlvalSTR1,String fname1 ,String tablname1) {
		if(sqlfiestr1.length()<1||sqlvalSTR1.length()<1) // That means there is no data upload 
			;
		else { // It indicates that there is data upload in the form  , In this way, it is necessary to write to the database .  The classmates , This laziness   The premise of the method is HMTL Controls in the form name It must be the same as the column name of the database table .
		String sqlstr1="";
		if(fname1==""||fname1.equals(""))// It means that no file has been uploaded 
		{	// To remove the last comma in the field name string 
			sqlfiestr1=sqlfiestr1.substring(0,sqlfiestr1.length()-1);
			sqlvalSTR1=sqlvalSTR1.substring(0,sqlvalSTR1.length()-1);
			sqlstr1="insert into "+tablename+"("+sqlfiestr1+")values("+sqlvalSTR1+")";
		 
		}
		else // It means that there are documents coming up , File name is not empty  . adjustment insert String photo parameters 
		{  sqlfiestr1=sqlfiestr1+"photo";
		  int po=fname1.lastIndexOf("\\"); // Keep only the following file names , Don't go ahead 
		 if(po!=-1)// Indicates that the right slash was found \
		 { fname1=fname1.substring(po+1);}
		  sqlvalSTR1=sqlvalSTR1+"'"+fname1+"'";  
		   sqlstr1="insert into "+tablename+"("+sqlfiestr1+")values("+sqlvalSTR1+")";
		}
		   
		System.out.println(sqlstr1);
		Connection con1=(Connection) JdbcConUtil.getConnection();
		Statement st1;
		try {
			st1 = con1.createStatement();
			  st1.execute(sqlstr1);
			  JdbcConUtil.close(st1, con1);
		} catch (SQLException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		}
	}
	
	
	
}

Need to use json Of jar package 、commons-fileupload Of jar package

https://pan.baidu.com/s/1-xj4pgv61_D5v637FKMd4g?pwd=6666 
Extraction code ：6666

https://pan.baidu.com/s/1pjVKYmID4edb_mdggMeZzw?pwd=6666 
Extraction code ：6666

servlet Test code ：

protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException 
	{  
      JSONArray jsonarr1=new JSONArray();
	  JSONObject jsonob1=new JSONObject();	 
	  String path1="C:\\JAVA3\\uploadfile";	 // Specify the server location where the uploaded file is saved 
	  String tablname1="xs";// Specify the name of the table to operate on 
	 if(ServletFileUpload.isMultipartContent(request))// Judgment is not mime By the way 
	  { 
            new FormPostUtil.getparm(request, response, path1, jsonarr1, jsonob1,tablname1);		
	    }
	else { 
            // Here we deal with data without files , Here is another tool class for inserting data InsertObject Method 
          BeanUtils.populate(tempCourse, request.getParameterMap());
          String sql1 = "insert into course(cno,cname,tno) values(?,?,?)";
		  JdbcCRUDUtil.InsertObject(sql1, tempCourse);
	}