Micronaut FunctionInitializer override application properties

Question

@Singleton
public class TestFunction extends FunctionInitializer {
    Logger log = LoggerFactory.getLogger(TestFunction.class);

    public TestFunction() {
    }

    public String execute() {
        return "Hello";
    }

}

I want to override datasource properties in application.yml file programmatically, but without using bean created event listener. Is there a way to do that. Like creating a custom application context with properties.

I have used the below approach for Micronaut API gateway proxy.

public class StreamLambdaHandler implements RequestStreamHandler {
.......
public StreamLambdaHandler() {
        try {
            log.info("Initializing Lambda Container");
            this.dbCredentialService = new DBCredentialService();
            // Get updated database credential map
            Map<String, Object> props = this.dbCredentialService.getDbCredential();
            // Create application context builder with updated properties
            // i.e Override datasources properties in application.yml
            builder = ApplicationContext.build().properties(props);
            handler = new MicronautLambdaContainerHandler(builder);
      }....
    ........
}

Can we do something similar with FunctionInitializer?

Answer 1

If you plan to override only datasource credentials properties it could be done this way.

@Factory
public class HikariDataSourceFactory {

    @Bean
    @Primary
    public DataSource dataSource(DBCredentialService credentialService) throws URISyntaxException {

        Map<String, Object> credentials = this.dbCredentialService.getDbCredential();
        String username = "user";
        String password = credentials.get("username");  
        
        HikariConfig config = new HikariConfig();
        config.setJdbcUrl("jdbc:postgresql://localhost:5432/postgres");
        config.setUsername(username);
        config.setPassword(password);
        config.setDriverClassName("org.postgresql.Driver");

        return new HikariUrlDataSource(config);
    }
}