Checking Last Modification of a File on the Server in Java

Last Modification of a File

Many computer programs rely on the critical aspect of accessing and modifying files on a server in today's digital age. Yet, in order to guarantee the utilization of the latest information, it is frequently imperative to determine the last modification time of a file. Several strategies exist in Java for confirming the last modification of a file on a server, all of which have their benefits and drawbacks.

Method 1: (Using file.lastModified)

Accessing various file properties in Java can be done using the File class, including checking the last modification of a server file. Through utilizing the lastModified() method, the last modification time can be easily accessed once a File object that represents the server file is created. Using the Date class, the time in milliseconds since the epoch can be converted to a more readable format with this method.

Example

// Java Program to get last modification time of the file
import java.io.File;
import java.text.SimpleDateFormat;

public class Sample_Article {

   public static void main(String[] args) {
      // path of the file
      String fileName = "C:/Users/aashi/Desktop/File.txt";

      File file = new File(fileName);

      // getting the last modified time of the file in the
      // raw format I.e long value of milliseconds
      System.out.println("Before Format : "+ file.lastModified());

      // getting the last modified time of the file in
      // terms of time and date
      SimpleDateFormat sdf
         = new SimpleDateFormat("MM/dd/yyyy HH:mm:ss");

      System.out.println(
         "The Date and Time at which the file was last modified is "
         + sdf.format(file.lastModified()));
   }
}

Output

Before Format : 0
The Date and Time at which the file was last modified is 01/01/1970 00:00:00

Method 2: (Using BasicFile Attributes)

Another method for checking the last modification of a file on a server in Java is using basic file attributes. By Using java.nio.*, one can conveniently view both a file's metadata and various attributes, such as creation time, last access time, and last modified time.

Example

// Java Program to get last modification time of the file
import java.io.IOException;
import java.net.HttpURLConnection;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.nio.file.attribute.BasicFileAttributes;

public class Sample_Article {
   public static void main(String args[]) {
      // storing the path of the file in the string
      String fileName = "C:/Users/aashi/Desktop/File.txt";

      // used exception handling in order to catch the
      // exception
      // which may occur if there is no such file is
      // present at specified location
      // or the path of the file provided by the user is
      // incorrect
      try {
         // getting the path of the file
         Path file = Paths.get(fileName);
			
         // reading the attributes of the file
         BasicFileAttributes attr = Files.readAttributes(
            file, BasicFileAttributes.class);

         // getting the last modification time of the
         // file
         System.out.println(
            "lastModifiedTime of File Is : "+ attr.lastModifiedTime());
      }
      catch (IOException e) {
         e.printStackTrace();
      }
   }
}

Output

LastModifiedTime of a file is: 2023-05-02 T: 13:25:20

Method 3: (Using URL Class)

The third method for checking the last modification of a file on a server in Java is through the use of the URL Class. This provides a method for retrieving the last modification time of an uploaded file and retrieving the file's timestamp. This method requires authentication to access the server.

Example

// Java Program to get last modification time of the file
import java.net.URL;
import java.net.URLConnection;
import java.util.Calendar;
import java.util.Date;

public class Sample_Article {
   public static void main(String[] args) throws Exception{
      // resource url
      URL u = new URL(
         "https://www.waytoclass.org/file-handling-java-using-filewriter-filereader/");
      URLConnection uc = u.openConnection();
      uc.setUseCaches(false);
		
      // getting the last modified time of the file
      // uploaded on the server
      long timestamp = uc.getLastModified();
      System.out.println("The last modification time of java.bmp is:"
         + timestamp);
   }
}

Output

The last modification time of java.bmp is:0

Conclusion

There are various approaches, each with advantages and disadvantages, for determining when a file on a server was last modified in Java. The BasicFile Attributes function enables remote access to the retrieval of file information, while the file class offers a basic and easy to use approach for retrieving file properties. Although it requires authentication, the URL Class method offers a more secure way of viewing and editing files on a remote server. The strategy used will rely on the program's particular requirements and available resources.