JDBC tool class jdbcfiledateutil uploads files and date format conversion, including the latest, simplest and easiest way to upload single files and multiple files

This document introduces the processing method of file upload , Including current end form The coding type of the form is enctype="multipart/form-data" How to deal with ？ And the old way to get the name of the uploaded file , The new method uses a function to get the name of the uploaded file . Finally, it explains the difference and code between uploading one file and uploading multiple files .

One 、 File upload considerations

Current end form The form contains the file upload , Have the following knowledge points ：

1.form The data coding type in the form should be written  enctype="multipart/form-data" To upload files , This encoding type will upload data in binary form .

2. The problem is coming. , When the encoding type is multipart/form-data when , Backstage through   request.getParameter(NAME) Will not be able to get the value of text type .

Two 、 Realize file upload and solve the problem that the value cannot be obtained in the background

The core ：servlet3.0 Of Part Interface

adopt @MultipartConfig annotation and HttpServletRequest Of Two new methods getPart() and getParts() Mutual assistance To reach the current end form Form use  enctype="multipart/form-data" The function of uploading file and text data .

1. Use @MultipartConfig Annotation can not only make the back-end request.getParameter(NAME) Can get the value of text data , You can also use servlet3 Newly added part Interface , There are two new methods in this interface, which can directly obtain the file data and write it to the save path . So it's very convenient and concise .

2.HttpServletRequest Two new methods getPart() and getParts() To receive the front end form File data transmitted from the form ,getPart() Only one file can be received ,getParts() Can receive multiple files .

3、 ... and 、@MultipartConfig Annotation has four attribute values to specify some attributes of the file .

fileSizeThreshold: Integer value setting , The default value is 0, If the size of the uploaded file exceeds this value , Will first write to the cache file .

location: Save path to upload file .

maxFileSize: Limit file upload size . The default value is -1L, It means unlimited size .

maxRequestSize: Limit multipart/form-data Request format , The default value is -1L, Indicates that there is no limit on the number of .

Point four 、 The whole source code of the old method of file upload

package com.jdbc.utils;
import java.io.IOException;
import java.sql.Date;
import java.sql.SQLException;
/*  The date data of the form is converted to sql Date format  dataTrans(String sr0)  
	1、 Convert the date in string format of the form to java Date format for 
	2、 take java The date format of is converted to sql Date format for 
	
	 Save the uploaded image to the specified storage path savaFile()
*/
import java.text.ParseException;
import java.text.SimpleDateFormat;

import javax.imageio.IIOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.Part;

import com.sun.org.apache.bcel.internal.generic.NEW;

public class JdbcFileDateUtil {
	public static java.sql.Date dataTrans(String sr0) {
		SimpleDateFormat  sdf = new SimpleDateFormat("yyyy-MM-dd");// Construct the object according to the string pattern specified by the parameter . Realize the relevant conversion between date type and string 
		java.util.Date sr1 =new java.util.Date();
		try {
			sr1=sdf.parse(sr0);// Is used to String Type conversion to Date type 
		} catch (ParseException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		return new java.sql.Date((sr1.getTime()));//getTime Gets the distance of the current object 1970 year 1 month 1 Japan 0 when 0 branch 0 Milliseconds in seconds 
	}
	
//	 Save the file selected for form upload to the upload file path specified by the server 
//	 It is applicable to both cases whether there are uploaded files or not 
	public static String savaFile(String MyFile,HttpServletRequest request) throws ServletException,SQLException, IOException {
		String savaPath = "D:\\Web Back end development technology \\uploadFile";
		Part part =request.getPart(MyFile);//MyFile The value is html in input Labeled name value 
		String header=part.getHeader("Content-Disposition");
		int start=header.lastIndexOf("=");
		filename=header.substring(start+1);
		if (filename.length()>2) {
			filename=filename.substring(filename.lastIndexOf('\\')+1);
			filename=filename.substring(0,filename.length()-1);// Remove the last quotation mark  ”
			String temp= new SimpleDateFormat("yyyyMMddHHmmssSSSS").format(new java.util.Date().getTime());// Time stamp , Add before file name , Used to prevent duplicate file names 
			filename=temp+"."+filename;
			part.write(savaPath+"\\"+filename);// Upload the file and write the path to save 
		}
		return filename;	
	}
}

Optimize the code ：  Take out the file name processing process separately and modularize it into a method getFileName(Part part).

（ One ） How to upload a file ： Use getPart(name)

public static String savaFile(String MyFile,HttpServletRequest request) throws ServletException,SQLException, IOException {
		String savaPath = "D:\\Web Back end development technology \\uploadFile";
	    Part part = request.getPart("MyFile");
        String filename = getFileName(part);
        part.write(savaPath+"\\"+filename);write() Method . You can directly write the uploaded file to disk 
		return filename;	 // To return , Used to store in the database 
	}
	
public static String getFileName(Part part) {
		String header = part.getHeader("Content-Disposition");
        int start=header.lastIndexOf("=");
        filename=header.substring(start+1);
        if (filename.length()>2) {
	            filename=filename.substring(filename.lastIndexOf('\\')+1);
			    filename=filename.substring(0,filename.length()-1);// Remove the last quotation mark  ”
			    String temp= new SimpleDateFormat("yyyyMMddHHmmssSSSS").format(new java.util.Date().getTime());// Time stamp , Add before file name , Used to prevent duplicate file names 
		    	filename=temp+"."+filename;
                return filename;
		}
		 return filename;// If the uploaded file is empty , Then the file name is empty 
}

（ Two ） How to upload multiple files ： Use getParts()

public static String savaFiles(String MyFile,HttpServletRequest request) throws ServletException,SQLException, IOException {
		String savaPath = "D:\\Web Back end development technology \\uploadFile";
	  	//  From the front end form Get all file data in and store it in a list in 
		List<Part> parts = (List<Part>) request.getParts();

// Loop through the file , Each loop gets the name of a file and writes the file data to disk 
//  Get current part Point to the input Labeled name, Only name In order to MyFile Can enter the operation of getting file name only if it starts with the value of ,
//  Or jump to the next part, there part.getName().startsWith(MyFile) The key point is to understand and combine the front-end input Of name Value understanding 
//  startsWith() The parameter of is the corresponding to the upload folder input Labeled name name 

        for(Part part : parts) {
         if (part.getName().startsWith(MyFile)) {
        	  String filename = getFileName(part);
        	  if (filename.length()>2) {   		
	      			String temp= new SimpleDateFormat("yyyyMMddHHmmssSSSS").format(new java.util.Date().getTime());
	      			filename=temp+"."+filename;
	      			part.write(savaPath+"\\"+filename);//write() Method . You can directly write the uploaded file to disk 
        	  	}
               filenames+=filename+"/";// Multiple files , The filenames Save all file names and store them in the database 
			}
        }
		return filenames;	 // To return , Used to store in the database 
	}

Focus on the multi file upload process ：

chart 1 The file name and... Selected by the front end input Labeled name name , There are three name=photo Of , There is one name=pic In the middle .

 

chart 2 Printed in the process of background processing files head Information and file name , Only found name=photo Your file was received .

Through this case, I think Key points Yes. , Only the back-end   part.getName().startsWith(MyFile) Satisfaction is input Labeled name Named part Will accept the data .

Heavy focus, little five 、 The latest method of uploading single file and multiple files

tomcat8 Use servlet3.0 Upload files , There's a way getSubmittedFileName() Get the file name directly , There's no need to intercept so much trouble .

/* 
 	 One 、 The date data of the form is converted to sql Date format  dataTrans(String sr0)  
		1、 Convert the date in string format of the form to java Date format for 
		2、 take java The date format of is converted to sql Date format for 
	
	 Two 、 Save the uploaded image to the specified storage path savaFile(), Here is a single file upload 
*/
package com.jdbc.utils;
import java.io.IOException;
import java.sql.Date;
import java.sql.SQLException;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.List;

import javax.imageio.IIOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.Part;

import com.sun.org.apache.bcel.internal.generic.NEW;

public class JdbcFileDateUtil {
	
// Date format conversion tool 
	public static java.sql.Date dataTrans(String sr0) {
		
		// Construct the object according to the string pattern specified by the parameter . Realize the relevant conversion between date type and string 
		SimpleDateFormat  sdf = new SimpleDateFormat("yyyy-MM-dd");
		java.util.Date sr1 =new java.util.Date();
		try {
			sr1=sdf.parse(sr0);// Is used to String Type conversion to Date type 
		} catch (ParseException e) {
			e.printStackTrace();
		}
		//getTime Gets the distance of the current object 1970 year 1 month 1 Japan 0 when 0 branch 0 Milliseconds in seconds 
		return new java.sql.Date((sr1.getTime()));
	}
	
//	 Save the file selected for form upload to the upload file path specified by the server 
//	 It is applicable to both cases whether there are uploaded files or not , If the file is not uploaded, it will be empty .
	//1. Single file upload 
	public static String savaFile(String MyFile,HttpServletRequest request) throws ServletException,SQLException, IOException {
		String savaPath = "D:\\【1】 School professional courses \\ Junior year \\Web Back end development technology \\uploadFile";
		Part part =request.getPart(MyFile);
		//tomcat8 Use servlet3.0 Upload files , There's a way getSubmittedFileName Get the file name directly , There's no need to intercept so much trouble 
		String filename = part.getSubmittedFileName();
		if (filename.length()>2) {
			// Add a timestamp to the file name , Prevent duplicate files .
			String temp= new SimpleDateFormat("yyyyMMddHHmmssSSSS").format(new java.util.Date().getTime());
			filename=temp+"."+filename;
			part.write(savaPath+"\\"+filename);//write() Method . You can directly write the uploaded file to disk 
		}
		System.out.println(filename);
		return filename;	
	}
	
	
	//2. Upload multiple files 
	public static String savaFiles(String MyFile,HttpServletRequest request) throws ServletException,SQLException, IOException {
		String savaPath = "D:\\【1】 School professional courses \\ Junior year \\Web Back end development technology \\uploadFile";
//  From the front end form Get all file data in and store it in a list in 
		List<Part> parts = (List<Part>) request.getParts();
		String filenames ="";
// Loop through the file , Each loop gets the name of a file and writes the file data to disk 
        for(Part part : parts) {
//  Get current part Point to the input Labeled name, Only name In order to MyFile Can enter the operation of getting file name only if it starts with the value of ,
//  Or jump to the next part, there part.getName().startsWith(MyFile) The key point is to understand and combine the front-end input Of name Value understanding 
//        	startsWith() The parameter of is the corresponding to the upload folder input Labeled name name 
        if (part.getName().startsWith(MyFile)) {
        	  String filename = part.getSubmittedFileName();// Get the current part The file name that points to 
        	  if (filename.length()>2) {   		
	      			String temp= new SimpleDateFormat("yyyyMMddHHmmssSSSS").format(new java.util.Date().getTime());
	      			filename=temp+"."+filename;
	      			part.write(savaPath+"\\"+filename);//write() Method . You can directly write the uploaded file to disk 
        	  	}
               filenames+=filename+"/";// Multiple files , The filenames Save all file names and store them in the database 
			}
        }
		return filenames;	 // To return , Used to store in the database 
	}

}