What are the alternatives to using ADCs to authenticate to AlloyDB from a Spring Boot Java app?

In this thread https://www.googlecloudcommunity.com/gc/Databases/AlloyDB-ORM-Support/m-p/537212 some engineer from Google said that AlloyDb doesn't have support to spring boot natively and open sourced.

So, I can not handle use Application Default Credentials (https://cloud.google.com/docs/authentication/provide-credentials-adc#local-user-cred) and impersonate the SA.

So, Can someone confirm if i need to generates pass/user (https://cloud.google.com/iam/docs/create-short-lived-credentials-direct) is only way to proceed (using JDBC dependencies)?

I was expecting use as cloud sql dependencies:

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-test</artifactId>
    <scope>test</scope>
</dependency>
<dependency>
    <groupId>com.google.cloud</groupId>
    <artifactId>spring-cloud-gcp-starter</artifactId>
</dependency>
<!-- Add CloudSQL Starter for PostgreSQL -->
<dependency>
    <groupId>com.google.cloud</groupId>
    <artifactId>spring-cloud-gcp-starter-sql-postgresql</artifactId>
</dependency>

I have a workaround: refresh a short lived SA password when is needed.

package br.com.xyzservices.cloudSA;


import com.google.auth.oauth2.AccessToken;
import com.google.auth.oauth2.GoogleCredentials;
import com.zaxxer.hikari.HikariConfig;
import com.zaxxer.hikari.HikariDataSource;

import java.io.IOException;

public class CloudSqlAutoIamAuthnDataSource extends HikariDataSource {

    public CloudSqlAutoIamAuthnDataSource(HikariConfig configuration) {
        super(configuration);
    }

    @Override
    public String getPassword() {
        GoogleCredentials credentials;
        try {
            credentials = GoogleCredentials.getApplicationDefault();

        } catch (IOException err) {
            throw new RuntimeException(
                    "Unable to obtain credentials to communicate with the Cloud SQL API", err);
        }

        // Scope the token to ensure it's scoped to logins only.
        GoogleCredentials scoped = credentials.createScoped(
                "https://www.googleapis.com/auth/sqlservice.login");

        try {
            scoped.refresh();
        } catch (IOException e) {
            throw new RuntimeException(e);
        }
        AccessToken accessToken = scoped.getAccessToken();
        return accessToken.getTokenValue();
    }
}

Source code: https://github.com/dedeco/spring-boot-app-sa-iam-based