03 JDBC

Question 1

@ Tabelle

Answer 1

@Entity

Question 2

@ Tabelle hat in Datenbank anderen Namen

Answer 2

@Table(name = “echterName”)

Question 3

@ Über Primärschlüssel

Answer 3

@Id

Question 4

@ nach Primärschlüssel wenn Id automatisch erstellt werden soll

Answer 4

@GeneratedValue

Question 5

@ 1 zu n

Answer 5

MUSS IN n DB SEIN

@ManyToOne
@JoinedColumn( name=”NameDesFremdschluessels”)

Question 6

// EntityManager erzeugen (Name der Persistence Unit: uni)

Answer 6

entityManagerFactory= Persistance.createEntityManagerFactory("uni");
entityManager = entityManagerFactory.createEntityManager()

Question 7

// Studiengang mit ID 5 aus Datenbank laden

Answer 7

entityManager.getTransaction().begin();
Studiengang studiengang = entityManager.find(Studiengang.class,5);
entityManager.getTransaction().commit();
System.out.println(studiengang.toString());

Question 8

// alle Studenten, die den Studiengang "IBAIT" studieren,
// aus Datenbank laden

Answer 8

TypedQuery tp = entityManager.createQuery(“SELECT s FROM Student s WHERE s.studiengang.name = ‘IBAIT’ “ , Student.class);

Question 9

List ibaitStudenten =

Answer 9

List ibaitStudenten = tp.getResultList();

for (Student s : ibaitStudenten){
System.out.println(s);
}

Question 10

// neue Studentin speichern
// Vorname: Petra, Nachname: Schmidt,
// Matrikelnr.: 1234, Studiengang-ID: 5

Answer 10

entityManager.getTransaction().begin();

Student neueStudentin = new Student();
neueStudentin.vorname = "Petra";
neueStudentin.nachname = "Schmidt";
neueStudentin.matrikelnr = 1234;
neueStudentin.studiengang.setId(5);
entityManager.persist(neueStudentin);

entityManager.getTransaction().commit();

Question 11

} finally {
// Ressourcen schließen

Answer 11

if (entityManager ! = null) {
    entityManager.close();
}
if (entityManagerFactory ! = null) {
    entityManagerFactory.close();}

Question 12

@ n:m

Answer 12

@ManyToMany
@JoinTable(
name= “HilfsDatenbankname”,
joinColumns = {@JoinColumn (name = “FremdschlusselEigenerDatenbank”)},
inverseJoinColumns = {@JoinColumn (name = “FremdschlusselAndereDB”)}
)

private Set <
andererTablename > neuertext;

Question 13

@ 1:1

Answer 13

@OneToOne

@JoinColumn (name=”andererFS”)

Question 14

Speichern (neu erzeugtes Object )

Answer 14

em.persist(kunde);