first draft

persistence-modules/spring-boot-persistence-mongodb-2/src/main/java/com/baeldung/boot/count/SpringBootCountApplication.java

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+package com.baeldung.boot.count;
+
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+import org.springframework.data.mongodb.repository.config.EnableMongoRepositories;
+
+@SpringBootApplication
+@EnableMongoRepositories(basePackages = { "com.baeldung.boot.count" })
+public class SpringBootCountApplication {
+    public static void main(String... args) {
+        SpringApplication.run(SpringBootCountApplication.class, args);
+    }
+}

persistence-modules/spring-boot-persistence-mongodb-2/src/main/java/com/baeldung/boot/count/dao/CarRepository.java

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+package com.baeldung.boot.count.dao;
+
+import org.springframework.data.mongodb.repository.MongoRepository;
+import org.springframework.data.mongodb.repository.Query;
+
+import com.baeldung.boot.count.data.Car;
+
+public interface CarRepository extends MongoRepository<Car, String> {
+    @Query(value = "{brand: ?0}", count = true)
+    public long countBrand(String brand);
+
+    Long countByBrand(String brand);
+
+    @Query(value = "{}", count = true)
+    Long countWithAnnotation();
+}

persistence-modules/spring-boot-persistence-mongodb-2/src/main/java/com/baeldung/boot/count/data/Car.java

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+package com.baeldung.boot.count.data;
+
+import org.springframework.data.mongodb.core.mapping.Document;
+@Document
+public class Car {
+    private String name;
+
+    private String brand;
+
+    public Car() {
+    }
+
+    public Car(String brand) {
+        this.brand = brand;
+    }
+
+    public String getBrand() {
+        return brand;
+    }
+
+    public void setBrand(String brand) {
+        this.brand = brand;
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    public void setName(String name) {
+        this.name = name;
+    }
+}

persistence-modules/spring-boot-persistence-mongodb-2/src/main/java/com/baeldung/boot/count/service/CountCarService.java

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+package com.baeldung.boot.count.service;
+
+import java.util.List;
+import java.util.Optional;
+
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.data.domain.Example;
+import org.springframework.data.mongodb.core.MongoTemplate;
+import org.springframework.data.mongodb.core.query.Criteria;
+import org.springframework.data.mongodb.core.query.Query;
+import org.springframework.stereotype.Service;
+
+import com.baeldung.boot.count.dao.CarRepository;
+import com.baeldung.boot.count.data.Car;
+
+@Service
+public class CountCarService {
+
+    @Autowired
+    private CarRepository repo;
+
+    @Autowired
+    private MongoTemplate mongo;
+
+    public List<Car> findCars() {
+        return repo.findAll();
+    }
+
+    public Optional<Car> findCar(String id) {
+        return repo.findById(id);
+    }
+
+    public Car insertCar(Car item) {
+        return repo.insert(item);
+    }
+
+    public long getCountWithQueryAnnotation() {
+        return repo.countWithAnnotation();
+    }
+
+    public long getCountWithCrudRepository() {
+        return repo.count();
+    }
+
+    public long getCountBrandWithQueryMethod(String brand) {
+        return repo.countByBrand(brand);
+    }
+
+    public long getCountWithExample(Car item) {
+        return repo.count(Example.of(item));
+    }
+
+    public long getCountWithExampleCriteria(Car item) {
+        Query query = new Query();
+        query.addCriteria(Criteria.byExample(item));
+        return mongo.count(query, Car.class);
+    }
+
+    public long getCountBrandWithQueryAnnotation(String brand) {
+        return repo.countBrand(brand);
+    }
+
+    public long getCountBrandWithCriteria(String brand) {
+        Query query = new Query();
+        query.addCriteria(Criteria.where("brand")
+            .is(brand));
+        return mongo.count(query, Car.class);
+    }
+}

persistence-modules/spring-boot-persistence-mongodb-2/src/main/java/com/baeldung/boot/count/web/CarController.java

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+package com.baeldung.boot.count.web;
+
+import java.util.Optional;
+
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.data.domain.Example;
+import org.springframework.data.mongodb.core.MongoTemplate;
+import org.springframework.data.mongodb.core.query.Criteria;
+import org.springframework.data.mongodb.core.query.Query;
+import org.springframework.web.bind.annotation.GetMapping;
+import org.springframework.web.bind.annotation.PathVariable;
+import org.springframework.web.bind.annotation.PostMapping;
+import org.springframework.web.bind.annotation.RequestBody;
+import org.springframework.web.bind.annotation.RequestMapping;
+import org.springframework.web.bind.annotation.RestController;
+
+import com.baeldung.boot.count.dao.CarRepository;
+import com.baeldung.boot.count.data.Car;
+
+@RestController
+@RequestMapping("/car")
+public class CarController {
+    @Autowired
+    private CarRepository carRepo;
+
+    @Autowired
+    private MongoTemplate mongo;
+
+    @GetMapping("/{id}")
+    public Optional<Car> getCar(@PathVariable String id) {
+        return carRepo.findById(id);
+    }
+
+    @PostMapping
+    public Car postCar(@RequestBody Car item) {
+        return carRepo.insert(item);
+    }
+
+    @GetMapping("/count/{brand}")
+    public Long getCountCarBrand(@PathVariable String brand) {
+        return carRepo.countByBrand(brand);
+    }
+
+    @GetMapping("/count2/{brand}")
+    public Long getCountCarBrand2(@PathVariable String brand) {
+        return carRepo.countBrand(brand);
+    }
+
+    @GetMapping("/count")
+    public Long getCountCar() {
+        return carRepo.countWithAnnotation();
+    }
+
+    @GetMapping("/count2")
+    public Long getCountCar2() {
+        // default do repo
+        return carRepo.count();
+    }
+
+    @PostMapping("/count")
+    public Long postCount(@RequestBody Car item) {
+        return carRepo.count(Example.of(item));
+    }
+
+    @PostMapping("/count/criteria")
+    public Long postCountCriteria(@RequestBody Car item) {
+        Query query = new Query();
+        query.addCriteria(Criteria.byExample(item));
+        return mongo.count(query, Car.class);
+    }
+
+    @GetMapping("/count/criteria/{brand}")
+    public Long getCountCarCriteria(@PathVariable String brand) {
+        Query query = new Query();
+        query.addCriteria(Criteria.where("brand")
+            .is(brand));
+        return mongo.count(query, Car.class);
+    }
+}

persistence-modules/spring-boot-persistence-mongodb-2/src/test/java/com/baeldung/boot/count/service/CountCarServiceIntegrationTest.java

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+package com.baeldung.boot.count.service;
+
+import static org.junit.Assert.assertEquals;
+
+import java.util.List;
+
+import org.junit.Before;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.test.annotation.DirtiesContext;
+import org.springframework.test.context.junit4.SpringRunner;
+
+import com.baeldung.boot.count.data.Car;
+
+@SpringBootTest
+@DirtiesContext
+@RunWith(SpringRunner.class)
+public class CountCarServiceIntegrationTest {
+    @Autowired
+    private CountCarService service;
+
+    Car car1 = new Car("B-A");
+
+    @Before
+    public void init() {
+        service.insertCar(car1);
+        service.insertCar(new Car("B-B"));
+        service.insertCar(new Car("B-C"));
+    }
+
+    @Test
+    public void givenAllDocs_whenQueryAnnotationCount_thenCountEqualsSize() {
+        List<Car> all = service.findCars();
+
+        long count = service.getCountWithQueryAnnotation();
+
+        assertEquals(count, all.size());
+    }
+
+    @Test
+    public void givenAllDocs_whenCrudRepositoryCount_thenCountEqualsSize() {
+        List<Car> all = service.findCars();
+
+        long count = service.getCountWithCrudRepository();
+
+        assertEquals(count, all.size());
+    }
+
+    @Test
+    public void givenFilteredDocs_whenCriteriaCountByBrand_thenCountEqualsSize() {
+        String filter = "B-A";
+        long all = service.findCars()
+            .stream()
+            .filter(car -> car.getBrand()
+                .equals(filter))
+            .count();
+
+        long count = service.getCountBrandWithCriteria(filter);
+
+        assertEquals(count, all);
+    }
+
+    @Test
+    public void givenQueryAnnotation_whenCountingByBrand_thenCountEqualsSize() {
+        String filter = "B-A";
+        long all = service.findCars()
+            .stream()
+            .filter(car -> car.getBrand()
+                .equals(filter))
+            .count();
+
+        long count = service.getCountBrandWithQueryAnnotation(filter);
+
+        assertEquals(count, all);
+    }
+
+    @Test
+    public void givenFilteredDocs_whenQueryMethodCountByBrand_thenCountEqualsSize() {
+        String filter = "B-A";
+        long all = service.findCars()
+            .stream()
+            .filter(car -> car.getBrand()
+                .equals(filter))
+            .count();
+
+        long count = service.getCountBrandWithQueryMethod(filter);
+
+        assertEquals(count, all);
+    }
+
+    @Test
+    public void givenFilteredDocs_whenExampleCount_thenCountEqualsSize() {
+        long all = service.findCars()
+            .stream()
+            .filter(car -> car.getBrand()
+                .equals(car1.getBrand()))
+            .count();
+
+        long count = service.getCountWithExample(car1);
+
+        assertEquals(count, all);
+    }
+
+    @Test
+    public void givenFilteredDocs_whenExampleCriteriaCount_thenCountEqualsSize() {
+        long all = service.findCars()
+            .stream()
+            .filter(car -> car.getBrand()
+                .equals(car1.getBrand()))
+            .count();
+
+        long count = service.getCountWithExampleCriteria(car1);
+
+        assertEquals(count, all);
+    }
+}