Opik Backend Patterns

// ✅ GOOD
@Path("/v1/private/traces")
public class TracesResource { }

// ✅ GOOD - DAO and Service use singular
public class TraceDAO { }
public class TraceService { }

// ✅ GOOD - test classes match plural resource name
public class TracesResourceTest { }

// ❌ BAD - singular test class
public class TraceResourceTest { }

// ❌ BAD - singular resource/URL
@Path("/v1/private/trace")
public class TraceResource { }

// ❌ BAD - plural DAO/Service
public class TracesDAO { }
public class TracesService { }

// ✅ GOOD - internal record, Lombok @NonNull
@Builder(toBuilder = true)
record MyData(@NonNull UUID id, @NonNull String name, String description) {}

MyData data = MyData.builder()
        .id(id)
        .name(name)
        .build();

// ✅ GOOD - request-body DTO, Jakarta validators only
@Builder(toBuilder = true)
public record MyRequest(
        @NotNull UUID id,
        @NotBlank String name,
        @NotNull @Size(min = 1, max = 1000) @Valid List<MyItem> items) {}

// ❌ BAD - plain constructor (positional mistakes, less readable)
new MyData(id, name, null);

// ❌ BAD - @Builder without toBuilder
@Builder
record MyData(UUID id, String name) {}

// ❌ BAD - stacking @NonNull and @NotNull on the same field
public record MyRequest(@NonNull @NotNull UUID id) {}

// ✅ GOOD
@RequiredArgsConstructor(onConstructor_ = @Inject)
public class MyService {
    private final @NonNull DependencyA depA;
    private final @NonNull DependencyB depB;
}

// ❌ BAD - boilerplate constructor
public class MyService {
    private final DependencyA depA;
    @Inject
    public MyService(DependencyA depA) {
        this.depA = depA;
    }
}

// ✅ GOOD
interface MyService {
    void process(String workspaceId, UUID promptId);
}

// ❌ BAD - validation on interface
interface MyService {
    void process(@NonNull String workspaceId, @NonNull UUID promptId);
}

// ✅ GOOD
var template = TemplateUtils.newST(QUERY);

// ❌ BAD - causes memory leak via STGroup singleton
var template = new ST(QUERY);

// ✅ GOOD
users.getFirst()
users.getLast()

// ❌ BAD
users.get(0)
users.get(users.size() - 1)

// ✅ GOOD - text block, values bound, structure via StringTemplate
@SqlQuery("""
        SELECT * FROM datasets
        WHERE workspace_id = :workspace_id
        <if(name)> AND name like concat('%', :name, '%') <endif>
        """)

// ❌ BAD - string concatenation
@SqlQuery("SELECT * FROM datasets " +
        "WHERE workspace_id = :workspace_id " +
        "<if(name)> AND name like concat('%', :name, '%') <endif> ")

// ❌ BAD - caller splices the predicate in
private static final String TOKEN_USAGE_NAMES_TEMPLATE = """
        SELECT DISTINCT name FROM (
            SELECT usage FROM spans FINAL
            WHERE workspace_id = :workspace_id
            AND %s
        ) ...
        """;

static String tokenUsageNames(String projectPredicate) {
    return TOKEN_USAGE_NAMES_TEMPLATE.formatted(projectPredicate);
}

// caller: tokenUsageNames("project_id IN :project_ids")

// ✅ GOOD - both shapes live in the template, the caller picks one
private static final String TOKEN_USAGE_NAMES = """
        SELECT DISTINCT name FROM (
            SELECT usage FROM spans FINAL
            WHERE workspace_id = :workspace_id
            <if(project_ids)> AND project_id IN :project_ids <endif>
            <if(project_id)> AND project_id = :project_id <endif>
        ) ...
        """;

var template = TemplateUtils.newST(TOKEN_USAGE_NAMES);
template.add("project_ids", true);
...
statement.bind("project_ids", projectIds.toArray(new UUID[0]));