[spring-boot] Select datasource

[kamko]

Would it be possible to update the Spring auto-configuration so that the DataSource would be configurable, or at least specifically injectable?

Reference: DbSchedulerAutoConfiguration.java

The idea behind this is that I have two cases:

• I am using a routing DataSource and want to control where DbScheduler should connect.
• I have jobs that are not in the primary application database.

The implementation could be done by extending DbSchedulerCustomizer or, alternatively, by implementing a simple provider class specifically for the DataSource, like this:

public interface DbSchedulerDatasourceProvider {
    DataSource dataSource();
}

@Bean
@ConditionalOnMissingBean
@ConditionalOnBean(DataSource.class)
DbSchedulerDatasourceProvider dbSchedulerDatasourceProvider(DataSource dataSource) {
    return () -> dataSource;
}

and then

public DbSchedulerAutoConfiguration(
    DbSchedulerProperties dbSchedulerProperties,
    DbSchedulerDatasourceProvider dataSourceProvider,
    List<Task<?>> configuredTasks,
    List<SchedulerListener> schedulerListeners,
    List<ExecutionInterceptor> executionInterceptors) {
    
    this.config = Objects.requireNonNull(
        dbSchedulerProperties, "Can't configure db-scheduler without required configuration"
    );
    this.existingDataSource = Objects.requireNonNull(
        dataSourceProvider.dataSource(), "An existing javax.sql.DataSource is required"
    );
    this.configuredTasks = Objects.requireNonNull(
        configuredTasks, "At least one Task must be configured"
    );
    this.schedulerListeners = schedulerListeners;
    this.executionInterceptors = executionInterceptors;
}

If this approach is acceptable, I can implement it.

This is currently a blocker for me because I don't want to create my own auto-configuration, as I would prefer not to manage potential changes there. However, I also need some additional customization.

[kamko]

I'm using reflection as workaround for now.

public interface DbSchedulerDataSourceCustomizer {
    DataSource dataSource();
}
---

public class DbSchedulerDataSourceCustomizerPostProcessor implements BeanPostProcessor {

    private final ObjectProvider<DbSchedulerDataSourceCustomizer> dbSchedulerDataSourceCustomizerProvider;

    DbSchedulerDataSourceCustomizerPostProcessor(
            ObjectProvider<DbSchedulerDataSourceCustomizer> dbSchedulerDataSourceCustomizerProvider
    ) {
        this.dbSchedulerDataSourceCustomizerProvider = dbSchedulerDataSourceCustomizerProvider;
    }

    @Override
    public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
        if ("com.github.kagkarlsson.scheduler.boot.autoconfigure.DbSchedulerAutoConfiguration".equals(beanName)) {
            var field = ReflectionUtils.findField(
                    bean.getClass(), "existingDataSource");

            if (field == null) {
                throw new IllegalArgumentException(
                        "Something changed in DbSchedulerAutoConfiguration - code must be updated to handle this change.");
            }

            field.setAccessible(true);
            ReflectionUtils.setField(
                    field, bean, dbSchedulerDataSourceCustomizerProvider.getIfAvailable().dataSource());
            field.setAccessible(false);
        }

        return bean;
    }
}

[kagkarlsson]

Sure, I am open to such a change. Not sure how it is best done in Spring though, but feel free to open a PR for it.