Merge pull request #18086 from Michaelin007/nestprojection

https://jira.baeldung.com/browse/BAEL-8561

Author: Maiklins

persistence-modules/spring-data-jpa-simple/src/main/java/com/baeldung/jpa/projection/repository/AddressRepository.java

@@ -2,11 +2,23 @@
 
 import java.util.List;
 
+import com.baeldung.jpa.projection.view.AddressDto;
+import org.springframework.data.jpa.repository.Query;
 import org.springframework.data.repository.Repository;
 
 import com.baeldung.jpa.projection.model.Address;
 import com.baeldung.jpa.projection.view.AddressView;
+import org.springframework.data.repository.query.Param;
 
 public interface AddressRepository extends Repository<Address, Long> {
     List<AddressView> getAddressByState(String state);
+
+    @Query("SELECT c.zipCode as zipCode, c.person as person FROM Address c WHERE c.state = :state")
+    List<AddressView> getViewAddressByState(@Param("state") String state);
+
+    @Query("SELECT new com.baeldung.jpa.projection.view.AddressDto(a.zipCode," +
+           "new com.baeldung.jpa.projection.view.PersonDto(p.firstName, p.lastName)) " +
+           "FROM Address a JOIN a.person p WHERE a.state = :state")
+    List<AddressDto> findAddressByState(@Param("state") String state);
+
 }

persistence-modules/spring-data-jpa-simple/src/main/java/com/baeldung/jpa/projection/view/AddressDto.java

@@ -0,0 +1,20 @@
+package com.baeldung.jpa.projection.view;
+
+public class AddressDto {
+
+    private final String zipCode;
+    private final PersonDto person;
+
+    public AddressDto(String zipCode, PersonDto person) {
+        this.zipCode = zipCode;
+        this.person = person;
+    }
+
+    public String getZipCode() {
+        return zipCode;
+    }
+
+    public PersonDto getPerson() {
+        return person;
+    }
+}

persistence-modules/spring-data-jpa-simple/src/test/java/com/baeldung/jpa/projection/JpaProjectionIntegrationTest.java

@@ -6,12 +6,12 @@
 import java.util.Arrays;
 import java.util.List;
 
+import com.baeldung.jpa.projection.view.AddressDto;
 import org.junit.jupiter.api.Test;
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.boot.autoconfigure.AutoConfigurationPackage;
 import org.springframework.boot.test.autoconfigure.orm.jpa.DataJpaTest;
 import org.springframework.test.context.jdbc.Sql;
-
 import com.baeldung.jpa.projection.model.Person;
 import com.baeldung.jpa.projection.repository.AddressRepository;
 import com.baeldung.jpa.projection.repository.PersonRepository;
@@ -40,6 +40,16 @@ void whenUsingClosedProjections_thenViewWithRequiredPropertiesIsReturned() {
         assertThat(personView.getLastName()).isEqualTo("Doe");
     }
 
+    @Test
+    void whenUsingCustomQueryForNestedProjection_thenViewWithRequiredPropertiesIsReturned() {
+        AddressView addressView = addressRepository.getViewAddressByState("CA").get(0);
+        assertThat(addressView.getZipCode()).isEqualTo("90001");
+
+        PersonView personView = addressView.getPerson();
+        assertThat(personView.getFirstName()).isEqualTo("John");
+        assertThat(personView.getLastName()).isEqualTo("Doe");
+    }
+
     @Test
     void whenUsingOpenProjections_thenViewWithRequiredPropertiesIsReturned() {
         PersonView personView = personRepository.findByLastName("Doe");
@@ -70,4 +80,15 @@ void whenUsingDynamicProjections_thenObjectWithRequiredPropertiesIsReturned() {
         assertThat(personView.getFirstName()).isEqualTo("John");
         assertThat(personDto.firstName()).isEqualTo("John");
     }
+
+    @Test
+    void whenUsingDTOProjection_thenCorrectResultIsReturned() {
+        List<AddressDto> addresses = addressRepository.findAddressByState("CA");
+        AddressDto address = addresses.get(0);
+        assertThat(address.getZipCode()).isEqualTo("90001");
+
+        PersonDto person = address.getPerson();
+        assertThat(person.firstName()).isEqualTo("John");
+        assertThat(person.lastName()).isEqualTo("Doe");
+    }
 }