• Java Signature Generator
  • Signature.java
  • SignatureGenerator.java

#Java Signature Generator

#Signature.java

public class Signature {
    private final String hash;
    private final String salt;

    public Signature(String hash, String salt) {
        this.hash = hash;
        this.salt = salt;
    }

    public String getHash() {
        return hash;
    }

    public String getSalt() {
        return salt;
    }
}

#SignatureGenerator.java

import java.net.URL;
import java.nio.charset.StandardCharsets;
import java.security.MessageDigest;
import java.util.Arrays;
import java.util.Map;

public class SignatureGenerator {
    public Signature generate(String url, Map<String, ?> params, String secret, String salt) {
        String path = (new URL(url)).getPath();
    
        StringBuilder values = getValues(params);
        String toSign = path + values.toString() + (salt != null ? salt : "");
    
        String hmac = hmacSha256(toSign, secret);
    
        return new Signature(hmac, salt);
    }
    
    private StringBuilder getValues(Map<String, ?> obj) {
        StringBuilder values = new StringBuilder();
    
        obj.entrySet().stream()
            .sorted(Map.Entry.comparingByKey())
            .forEach(e -> {
                Object value = e.getValue();
    
                if (value instanceof Map || value instanceof Object[]) {
                    values.append(getValues((Map<String, ?>) value));
                    return;
                }
    
                if (value instanceof Boolean) {
                    values.append((Boolean) value ? "1" : "0");
                    return;
                }
    
                values.append(value != null ? value.toString() : "");
            });
    
        return values;
    }
    
    private String hmacSha256(String message, String secret) {
        try {
            Mac mac = Mac.getInstance("HmacSHA256");
            SecretKeySpec secretKeySpec = new SecretKeySpec(secret.getBytes(StandardCharsets.UTF_8), "HmacSHA256");
            mac.init(secretKeySpec);
            byte[] hash = mac.doFinal(message.getBytes(StandardCharsets.UTF_8));
            return Arrays.stream(hash)
                .map(b -> String.format("%02x", b))
                .collect(StringBuilder::new, StringBuilder::append, StringBuilder::append)
                .toString();
        } catch (Exception e) {
            throw new RuntimeException(e);
        }
    }
}