Skip to content
How-to Guides

Database Resolver

Database Resolver

DatabaseResolver controls which DataSource the JDBC store uses for upsert dialect detection. Override it when you use the multi-tenant SCHEMA strategy and need to route to a per-tenant DataSource.

Interface

public interface DatabaseResolver {
    String resolve(DataSource dataSource);
}

Returns a database product name string (e.g. "H2", "PostgreSQL", "MySQL", "Oracle", "Microsoft SQL Server"). The JDBC store uses this to pick the correct upsert SQL dialect.

When to Use

The default DatabaseResolver calls dataSource.getConnection().getMetaData().getDatabaseProductName(). Override it when:

  • You use a connection pool that does not reliably expose product metadata.
  • You know the database product at configuration time and want to avoid a metadata lookup.
  • You test with H2 but deploy on PostgreSQL and need separate dialect resolution per environment.

Step 1 — Implement DatabaseResolver

FixedDatabaseResolver.java
@Component
public class FixedDatabaseResolver implements DatabaseResolver {

    @Value("${failover.database-product:}")
    private String product;

    @Override
    public String resolve(DataSource dataSource) {
        if (!product.isBlank()) return product;
        try (Connection c = dataSource.getConnection()) {
            return c.getMetaData().getDatabaseProductName();
        } catch (SQLException e) {
            throw new FailoverStoreException("Cannot resolve database product", e);
        }
    }
}

Supported Product Names

Returned string Dialect used
H2 MERGE INTO ... KEY (...)
PostgreSQL INSERT ... ON CONFLICT DO UPDATE
MySQL / MariaDB INSERT ... ON DUPLICATE KEY UPDATE
Oracle MERGE INTO ... USING DUAL
Microsoft SQL Server MERGE INTO ... USING (VALUES ...) AS src

Next Steps