Projections (Select)

Use Querity.advancedQuery() with selectBy to retrieve only specific fields instead of full entities.

AdvancedQuery query = Querity.advancedQuery()
    .select(selectBy("firstName", "lastName", "address.city"))
    .filter(filterBy("lastName", EQUALS, "Skywalker"))
    .build();
List<Map<String, Object>> results = querity.findAllProjected(Person.class, query);
// Each map contains only: {firstName: "...", lastName: "...", city: "..."}

Supports nested properties with dot notation (e.g., address.city).

Query vs AdvancedQuery

Querity provides two query types:

• Query - For simple entity queries. Use with findAll() to retrieve full entities.
• AdvancedQuery - For projection queries with selectBy, groupBy, having. Use with findAllProjected() to retrieve Map<String, Object> results.

// Simple entity query
Query query = Querity.query()
    .filter(filterBy("lastName", EQUALS, "Skywalker"))
    .build();
List<Person> entities = querity.findAll(Person.class, query);

// Projection query
AdvancedQuery advQuery = Querity.advancedQuery()
    .select(selectBy("firstName", "lastName"))
    .filter(filterBy("lastName", EQUALS, "Skywalker"))
    .build();
List<Map<String, Object>> projections = querity.findAllProjected(Person.class, advQuery);

Native select expressions (JPA only)

For advanced use cases, JPA modules support native expressions using CriteriaBuilder:

// Select concatenated full name using native expression
SelectionSpecification<Person> fullNameSpec = AliasedSelectionSpecification.of(
    (root, cb) -> cb.concat(cb.concat(root.get("firstName"), " "), root.get("lastName")),
    "fullName"
);
AdvancedQuery query = Querity.advancedQuery()
    .select(selectByNative(fullNameSpec))
    .build();
List<Map<String, Object>> results = querity.findAllProjected(Person.class, query);
// Each map contains: {fullName: "Luke Skywalker"}

Native select expressions are only available for JPA.