Spring Data JPA

Configuration

// FOR JPA
spring:
  datasource:
    url: jdbc:postgresql://[host]:[port]/[db name]
    username: username
    password: [password]

  jpa:
   hibernate.ddl-auto: update
   show-sql: true
   properties:
     hibernate:
       dialect: org.hibernate.dialect.PostgreSQLDialect

Embedded

@Embedded
private AnotherClass anotherClass;

// another class

@AttributeOverrides({
        @AttributeOverride(name = "something [in db]", 
        column = @Column(name = "something_field")),
})
public class AnotherClass {
    private String somethingField;
}

OneToOne

// example : class course one to one with courseMaterial
// course model
@OneToOne(mappedBy = "course")
private CourseMaterial courseMaterial;

// courseMaterial model
@OneToOne(
    cascade = CascadeType.ALL,
    fetch = FetchType.LAZY
)
@JoinColumn(
    name = "course_id",
    referencedColumnName = "courseId"
)
private Course course;

OneToMany & ManyToOne

// one teacher can teach many course
// one course can be taught by many teachers

// teacher class
@OneToMany(cascade = CascadeType.ALL)
@JoinColumn(name = "teacher_id", referencedColumnName = "teacherId")
private List<Course> courses;

// course class
@ManyToOne(cascade = CascadeType.ALL)
@JoinColumn(name = "teacher_id", referencedColumnName = "teacherId")
private Teacher teacher;

ManyToMany

// many students can take many courses

@ManyToMany(
    cascade = CascadeType.ALL
)
@JoinTable(
    name = "student_course_map", 
    joinColumns = @JoinColumn(
        name = "course_id", 
        referencedColumnName = "courseId"
    ), 
    inverseJoinColumns = @JoinColumn(
        name = "student_id", 
        referencedColumnName = "studentId"
    )
)
private List<Student> students;

@Qualifier("")

• You can mark a component with name, ex : @Component("fakedao") and when performing dependency injection, you can specifies which component to exactly inject, ex : @Qualifier("fakedao")

@Autowired
public PersonService(@Qualifier("fakeDao") PersonDao personDao) {
    this.personDao = personDao;
}

Repository Interface

@Repository
public interface TRepository extends JpaRepository<T, Long> {

}

Example Repository

@Repository
public interface StudentRepository extends JpaRepository<Student, Long> {

    List<Student> findByFirstName(String firstName);

    // JPQL-native
    @Query(value = "select * from tbl_student s where s.email_address = ?1", nativeQuery = true)
    Student getStudentByEmailAddressNative(String emailId);

    // JPQL
    @Query("select s from Student s where s.emailId = ?1")
    Student findStudentByEmail(String emailId);

    // Native Named Param
    @Query (
        value = "select * from tbl_student s where s.email_address = :emailId",
        nativeQuery = true
    )
    Student getStudentByEmailAddressNativeNamed(@Param("emailId") String emailId);

    @Modifying
    @Transactional
    @Query (
        value = "update tbl_student set first_name = ?1 where email_address = ?2",
        nativeQuery = true
    )
    Integer updatStudentEmailIdByFirstName(String firstName, String emailId);
}

Pagination and Sorting Repo

@Repository
public interface PersonPageRepository extends PagingAndSortingRepository<Person, Integer> {
}


public Page<Person> findAll(@RequestParam int page, @RequestParam int size) {
    PageRequest pr = PageRequest.of(page,size);
    return repository.findAll(pr);
}