wso2mi : How to intialize SecretResolver?

Question

In recently migrator from wso2esb to wso2mi and in Mediator class we are reading username/password and password is encrypted so we were using org.wso2.securevault.SecretResolver and code look like something like this

public static void main(String[] args) throws Exception {
        File registryXML = null;
        String secretAliasValue = "bss";
        String secretAliasName = "OM.endpoint.username";
        try {
            ReadResouceFile sdd = new ReadResouceFile();
            registryXML = sdd.readFile();
        } catch (Exception e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        FileInputStream fileInputStream = null;
        if (registryXML.exists()) {
            try {
                fileInputStream = new FileInputStream(registryXML);
                StAXOMBuilder builder = new StAXOMBuilder(fileInputStream);
                OMElement configElement = builder.getDocumentElement();
                // Initialize the SecretResolver providing the configuration element.
                SecretResolver secretResolver = SecretResolverFactory.create(configElement, false);

                // Resolved the secret alias key value.
                if (secretResolver != null && secretResolver.isInitialized()) {
                    
                    if (secretResolver.isTokenProtected(secretAliasName)) {
                        secretAliasValue = secretResolver.resolve(secretAliasName);
                    } else {
                        System.out.println("Something went Wrong");
                    }
                }
            } catch (XMLStreamException e) {
                throw new Exception("Unable to parse " + e.getMessage());
            } catch (IOException e) {
                throw new Exception("Unable to read "+ e.getMessage());
            } finally {
                if (fileInputStream != null) {
                    try {
                        fileInputStream.close();
                    } catch (IOException e) {
                        throw new Exception(
                                "Failed to close the FileInputStream, file : "  + ". " + e.getMessage());
                    }
                }
            }
        }
    }

But secretResolver.isInitialized() always coming false. Due to this i am not able to read the value and pass into the another API. Can someone please help me tell how to exactly initialize SecretResolver class?