Spring Data JPA also support count query derived methods. Instead of using 'find', we need to start our query method with 'count' keyword. For example:
public interface EmployeeRepository extends CrudRepository<Employee, Long> {
long countByDept(String deptName);
}
Calling above method:
long count = repo.countByDept("IT");
Example
Entity
@Entity
public class Employee {
private @Id
@GeneratedValue
Long id;
private String name;
private String dept;
private int salary;
.............
}
Repository
public interface EmployeeRepository extends CrudRepository<Employee, Long> {
long countByDept(String deptName);
long countBySalaryGreaterThanEqual(int salary);
long countByNameEndingWith(String endString);
long countByNameLike(String likeString);
}
Example Client
@Component
public class ExampleClient {
@Autowired
private EmployeeRepository repo;
public void run() {
List<Employee> employees = createEmployees();
repo.saveAll(employees);
System.out.println(" -- finding all employees --");
Iterable<Employee> all = repo.findAll();
all.forEach(System.out::println);
System.out.println(" -- finding the employee count in IT dept --");
long count = repo.countByDept("IT");
System.out.println(count);
System.out.println(" -- finding the employee count with salary greater or equal to 4000 --");
count = repo.countBySalaryGreaterThanEqual(4000);
System.out.println(count);
System.out.println(" -- finding the employee count with name ending with 'e' --");
count = repo.countByNameEndingWith("e");
System.out.println(count);
System.out.println(" -- finding the employee count with name like '%a_a' --");
count = repo.countByNameLike("%a_a");
System.out.println(count);
}
private List<Employee> createEmployees() {
return Arrays.asList(
Employee.create("Diana", "Admin", 3000),
Employee.create("Mike", "IT", 1000),
Employee.create("Rose", "IT", 4000),
Employee.create("Sara", "Admin", 3500),
Employee.create("Tanaka", "IT", 3000),
Employee.create("Charlie", "IT", 4500)
);
}
}
Main class
public class ExampleMain {
public static void main(String[] args) {
AnnotationConfigApplicationContext context =
new AnnotationConfigApplicationContext(AppConfig.class);
ExampleClient exampleClient = context.getBean(ExampleClient.class);
exampleClient.run();
EntityManagerFactory emf = context.getBean(EntityManagerFactory.class);
emf.close();
}
} -- finding all employees -- Employee{id=1, name='Diana', dept='Admin', salary=3000} Employee{id=2, name='Mike', dept='IT', salary=1000} Employee{id=3, name='Rose', dept='IT', salary=4000} Employee{id=4, name='Sara', dept='Admin', salary=3500} Employee{id=5, name='Tanaka', dept='IT', salary=3000} Employee{id=6, name='Charlie', dept='IT', salary=4500} -- finding the employee count in IT dept -- 4 -- finding the employee count with salary greater or equal to 4000 -- 2 -- finding the employee count with name ending with 'e' -- 3 -- finding the employee count with name like '%a_a' -- 3
Example ProjectDependencies and Technologies Used: - spring-data-jpa 2.0.9.RELEASE: Spring Data module for JPA repositories.
Uses org.springframework:spring-context version 5.0.8.RELEASE - hibernate-core 5.3.5.Final: Hibernate's core ORM functionality.
Implements javax.persistence:javax.persistence-api version 2.2 - h2 1.4.197: H2 Database Engine.
- JDK 1.8
- Maven 3.5.4
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