Replace placeholders of the dropwizard yml file with values fetched from azure worker role configuration settings at the dw service startup

AzureYamlConfigurator.java

public class AzureYamlConfigurator
{
    final static Charset ENCODING = StandardCharsets.UTF_8;

    String configureYaml(String fileName) throws IOException
    {
        if (RoleEnvironment.isAvailable())
        {
            Map<String, String> propMap = RoleEnvironment.getConfigurationSettings();
            configureYaml(fileName, propMap);
            return fileName + YML_POST_FIX;
        }
        else
        {
            return fileName;
        }
    }

    void configureYaml(String fileName, Map<String, String> propMap) throws IOException
    {
        List<String> lines = new ArrayList<String>();
        for(String line : readYamlFile(fileName))
        {
            lines.add(replacePlaceHolders(line, propMap));
        }

        writeYamlFile(lines, fileName);
    }

    String replacePlaceHolders(String text, Map<String, String> props)
    {
        Scanner scanner = new Scanner(text);
        Pattern pattern = Pattern.compile("\\&([a-z].+)");
        StringBuffer stringBuffer = new StringBuffer();
        while (scanner.hasNextLine())
        {
            String line = scanner.nextLine();
            Matcher matcher = pattern.matcher(line);
            while (matcher.find())
            {
                String key = matcher.group(1);
                String replacement = props.get(key);
                if (replacement == null)
                {
                    // Not a recognized token that can be replaced.  Is that an error?  Maybe.
                    // We can throw an exception, log it, or just put back the original matched expression:
                    replacement = matcher.group();
                }
                matcher.appendReplacement(stringBuffer, replacement);
            }
            matcher.appendTail(stringBuffer);
        }
        scanner.close();

        return stringBuffer.toString();
    }

    private List<String> readYamlFile(String fileName) throws IOException
    {
        Path path = Paths.get(fileName);
        return Files.readAllLines(path, ENCODING);
    }

    private void writeYamlFile(List<String> lines, String fileName) throws IOException
    {
        Path path = Paths.get(fileName + YML_POST_FIX);
        Files.write(path, lines, ENCODING);
    }

}

DropwizardApplication.java

public class DropwizardApplication extends Application<AppConfiguration>
{
    public static void main(final String[] args)
    throws Exception                            // NOPMD: SignatureDeclareThrowsException
    {
        args[1] = new AzureYamlConfigurator().configureYaml(args[1]);
        new DropwizardApplication().run(args);
    }

    @Override
    public void initialize(final Bootstrap<AppConfiguration> bootstrap)
    {
        bootstrap.addBundle(new AssetsBundle("/assets", "/"));
        bootstrap.addBundle(new AssetsBundle("/assets"));
    }

    @Override
    public String getName()
    {
        return "iam-provisioning-service";
    }

    @Override
    public void run(final AppConfiguration configuration, final Environment environment)
    throws SecurityConfigurationException
    {
  

dropwizardService.yml

server:
  applicationConnectors:
    - type: https
      port: 8080
      keyStoreType: Windows-MY
      certAlias: &ssl.cert.alias
      validateCerts: false
  adminConnectors:
    - type: http
      port: 8081
  requestLog:
    appenders:
      - type: console
        threshold: OFF
      - type: syslog
        threshold: OFF
      - type: file
        currentLogFilename: ./logs/provisioningService-requestLog.log
        archivedLogFilenamePattern: ./logs/provisioningService-requestLog-%d.log.gz
        archivedFileCount: 5
        timeZone: UTC

rootPath: /rest/*

keyStore:
    secureCredentialsKeyAlias: &secure.credentials.key.alias

# Logging settings.
logging:
  # The default level of all loggers. Can be OFF, ERROR, WARN, INFO, DEBUG, TRACE, or ALL.
  level: &log.level
  # Uncomment to enable ContextRetrievalFilter to trace every request
  # loggers:
    # "com.prosrm.iam.provisioning.service.filter.ContextRetrievalFilter": DEBUG

  appenders:
    - type: file
      threshold: &log.level
      currentLogFilename: ./logs/provisioningService.log
      archivedLogFilenamePattern: ./logs/provisioningService-%d.log.gz
      archivedFileCount: 5
      timeZone: UTC
      logFormat: "|%date{ISO8601,UTC}|%-5level|%mdc{pros-request-id:-na}|%logger{40}|%mdc{pros-request-id}|%message|%n%rootException"

ServiceConfiguration.cscfg

    ...
    <ConfigurationSettings>
      ...
      <Setting name="ssl.cert.alias" value="sslCertAliasValue" />
      <Setting name="secure.credentials.key.alias" value="KeyAlias" />
      <Setting name="log.level" value="INFO" />
      <Setting name="security.config.application.secret.encrypted" value="BlaBla" />
    </ConfigurationSettings>
    ...