Callback Data Decryption Implementation

import javax.servlet.http.HttpServletRequest;
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.util.Base64;

public APIResult handleFormData(HttpServletRequest request) {
    try {
        // 1. Read raw encrypted data from request input stream
        StringBuilder encryptedBuilder = new StringBuilder();
        try (BufferedReader reader = new BufferedReader(
            new InputStreamReader(request.getInputStream())
        )) {
            String line;
            while ((line = reader.readLine()) != null) {
                encryptedBuilder.append(line);
            }
        }
        String base64Encrypted = encryptedBuilder.toString();

        // 2. Base64 decode to obtain encrypted byte data
        byte[] encryptedBytes = Base64.decodeString(base64Encrypted);

        // 3. Get merchant public key (hardcoded in example; should be obtained from secure source in production)
        String merchantPublicKey = "-----BEGIN PUBLIC KEY-----\n"
            + "MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAuKcQ3Z+7wZ3nP1gX2tRl\n"
            + "Y7t6mGjRk1p0lK1q7e2k8X8jfQ1zW6qZ3d1VkKJyDkF2aE8m0J3bGxO2BQ7S7n5x7\n"
            + "d9XlJf6gKjq7cQb3t7pYjzQ0N8sQa4i5dLZzX9YyKt0P7o9UYxQ5yW极3mIj0hGpFq\n"
            + "yVg2GXv8sZ1F7Gd5jC5s0e3kZdJj3JkLwIDAQAB\n"
            + "-----END PUBLIC KEY-----";

        // 4. Decrypt data using merchant public key
        byte[] decryptedBytes = RSAUtils.decryptByPublicKey(
            encryptedBytes,
            merchantPublicKey
        );

        // 5. Convert decrypted data to string
        String jsonData = new String(decryptedBytes);

        // 6. Return decryption result
        return APIResult.newSuccessResult(jsonData);
    } catch (Exception e) {
        return APIResult.newErrorResult("DECRYPT_FAILED");
    }
}