databuild/examples/basic_graph/GenerateExecute.java

package com.databuild.examples.basic_graph;

import java.io.FileWriter;
import java.io.IOException;
import java.nio.charset.StandardCharsets;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.Random;

/**
 * Execute class for generating a random number.
 * This class generates a random number based on the partition ref.
 */
public class GenerateExecute {
    public static String BASE_PATH = "/tmp/databuild/examples/basic_graph/";

    public static void main(String[] args) {
        if (args.length < 1) {
            System.err.println("Error: Partition ref (output path) is required");
            System.exit(1);
        }
        
        String partitionRef = args[0];
        
        try {
            // Create a hash of the partition ref to use as a seed
            MessageDigest md = MessageDigest.getInstance("MD5");
            byte[] hashBytes = md.digest(partitionRef.getBytes(StandardCharsets.UTF_8));
            
            // Convert the first 8 bytes of the hash to a long to use as a seed
            long seed = 0;
            for (int i = 0; i < Math.min(8, hashBytes.length); i++) {
                seed = (seed << 8) | (hashBytes[i] & 0xff);
            }
            
            // Create a random number generator with the seed
            Random random = new Random(seed);
            
            // Generate a random number
            int randomNumber = random.nextInt(100);
            
            // Write the random number to the output file
            // Ensure dir exists
            java.io.File parent = new java.io.File(partitionRef).getParentFile();
            if (parent != null) {
                parent.mkdirs();
            }
            try (FileWriter writer = new FileWriter(partitionRef)) {
                writer.write("Random number for partition " + partitionRef + ": " + randomNumber);
            }

            System.out.println("Generated random number " + randomNumber + " for partition " + partitionRef);

            // Write the random number to the output file
            String outputPath = partitionRef;
            System.out.println("Writing random number " + randomNumber + " to " + outputPath);
            // Ensure dir exists
            new java.io.File(outputPath).getParentFile().mkdirs();
            // Write number (overwrite)
            try (FileWriter writer = new FileWriter(outputPath)) {
                writer.write(String.valueOf(randomNumber));
            }

        } catch (NoSuchAlgorithmException | IOException e) {
            System.err.println("Error: " + e.getMessage());
            e.printStackTrace();
            System.exit(1);
        }
    }
}