Simple criteria API can be a reasonable alternative to Spring Data-like finder methods, if it enables at least filtering and ordering of the results. Possible solution may look like following:

Java model

public record Account(String firstName, LocalDate birthDate) {}

Generated code

public class AccountRepository implements Finder<AccountCriteria, Account> {

    public static class AccountCriteria implements Criteria<AccountCriteria, Account> {}

    public static StringCriteriaBuilder<AccountCriteria> firstName() {}
    public static TemporalCriteriaBuilder<AccountCriteria> birthDate() {}

    // restrict to specific types of conditions
   @Override
    public List<Account> findAll(AccountCriteria criteria) {
         var rs = jdbc.query("SELECT firstName, birthDate FROM Account WHERE " + criteria.toSQLTemplate(), criteria.params())
    }
}

User code

AccountRepository accounts;

@Get("/search-accounts")
public List<Accounts> find(LocalDate givenDate, String searchString) {
      return accounts.findAll(birthDate().before(givenDate)
                                           .and(firstName().containsIgnoreCase(searchString)));
}

As first PoC has shown viability of this approach, next step will be to implement the model for embedding entities and data type conversions. The model must support reasonably deep embedding hierarchies and chaining of custom and built-in conversions, e.g.:

Embedding Given following structure:

record A(@Embed B b) {}
record B(@Embed C c) {}
record C(@Embed D d) {}
record D(String value) {}

The following table could be mapped:

CREATE TABLE A (
  b_c_d_value VARCHAR(255)
);

Conversion Given the following record:

record A(@Map(using = MyTimestampToInstant.class) MyTimestamp value) {}

The following table could be mapped, assuming conversion path from MyTimestamp to Instant and further to javax.sql.Timestamp.

CREATE TABLE A (
  value TIMESTAMP NOT NULL
);