Get checksum of a jar file

Peter Penzov

I implemented this example of jar file which checks it's own checksum:

   File currentJavaJarFile = new File(MainApp.class.getProtectionDomain().getCodeSource().getLocation().getPath());
        String jarFile = currentJavaJarFile.getAbsolutePath();// + "jarChecksumTest-1.0.jar";

        byte[] data = Files.readAllBytes(Paths.get(jarFile));

        MessageDigest complete = MessageDigest.getInstance(data);

        MessageDigest md = MessageDigest.getInstance("SHA-256");
        md.update(complete.toString().getBytes());

        byte byteData[] = md.digest();

        // convert the byte to hex format
        StringBuilder sb = new StringBuilder();
        for (int i = 0; i < byteData.length; i++)
        {
            sb.append(Integer.toString((byteData[i] & 0xff) + 0x100, 16).substring(1));
        }

        if ("L9ThxnotKPzthJ7hu3bnORuT6xI=".equals(sb.toString()))
        {
            System.out.println("Success!!!");
        }

But then I run the file I get this message:

Caused by: java.security.NoSuchAlgorithmException: D:\.....\target\jarChecksumTest-1.0.jar MessageDigest not available

How I can solve this issue?

Java Programmer

Try this code, it is running fine. You may choose any algorithm whether it is SHA/MD5

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

public class Checksum 
{
    public static void main(String ar[])
    {
        File currentJavaJarFile = new File(Checksum.class.getProtectionDomain().getCodeSource().getLocation().getPath());
        String filepath = currentJavaJarFile.getAbsolutePath();
        StringBuilder sb = new StringBuilder();
        try
        {
            MessageDigest md = MessageDigest.getInstance("SHA-256");// MD5
            FileInputStream fis = new FileInputStream(filepath);
            byte[] dataBytes = new byte[1024];
            int nread = 0; 

            while((nread = fis.read(dataBytes)) != -1)  
                 md.update(dataBytes, 0, nread);

            byte[] mdbytes = md.digest();

            for(int i=0; i<mdbytes.length; i++)
            sb.append(Integer.toString((mdbytes[i] & 0xff) + 0x100 , 16).substring(1));  
        }
        catch(NoSuchAlgorithmException e)
        {
            e.printStackTrace();
        }
        catch(IOException e)
        {
            e.printStackTrace();
        }

        System.out.println("Checksum: "+sb);
    }
}

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