Performante Java Enterprise Applikationen trotz O/R-Mapping

1. PERFORMANTE
JAVA ENTERPRISE APPLIKATIONEN
TROTZ O/R-MAPPING
Simon Martinelli, simas GmbH
@simas_ch | about.me/simas_ch
https://github.com/simasch/orders

2. DAS PROBLEM

3. DAS MODELL

4. N+1 SELECT PROBLEM
• Orders und OrderItems = FetchType.LAZY
@OneToMany(mappedBy = "customer", cascade = CascadeType.ALL, orphanRemoval =
true)
private Set<Order> orders;
@OneToMany(mappedBy = "order", cascade = CascadeType.ALL, orphanRemoval = true)
private List<OrderItem> items;
• Ein Query für alle Customers
• Pro Customer 1 Query für die Orders
• Pro Order 1 Query für die OrderItems

5. LÖSUNGSANSÄTZE
• FetchType.EAGER oder EntityGraph (JPA 2.1)
– Nur ein Hinweis für JPA
– != SQL JOIN
– Hibernate erlaubt nur eine List mit
FetchType.EAGER pro Entity
org.hibernate.HibernateException: cannot simultaneously fetch
multiple bags
• JOIN FETCH
– Achtung vor kartesischen Produkten

6. DTO
Quelle: Martin Fowler, http://martinfowler.com/eaaCatalog/dataTransferObject.html

7. CustomerInfoDTO
public class CustomerInfoDTO {
private final Long id;
private final String lastname;
private final String firstname;
private final double revenue;
public CustomerInfoDTO(Long id, String lastname, String firstname,
double revenue) {
this.id = id;
this.lastname = lastname;
this.firstname = firstname;
this.revenue = revenue;
}
...

8. CONSTRUCTOR EXPRESSION
Query q = em.createQuery(
"SELECT " +
"NEW control.CustomerInfoDTO(c.id, c.lastname, c.firstname," +
"SUM(i.product.price)) " +
"FROM Customer c " +
"JOIN c.orders o " +
"JOIN o.items i " +
"GROUP BY c.lastnamem, c.firstname" +
"ORDER BY c.lastname, c.firstname");
List<CustomerInfoDTO> list = q.getResultList();

9. DAS DATENMODELL IM ZENTRUM
• Ein 1-1 Abbild der Datenbank in Entities oft
unnötig
X

10. WAS IST MIT JPQL OHNE DIE
BEZIEHUNG CUSTOMER->ORDER?
NEU IN JPA 2.1
Query q = em.createQuery(
"SELECT " +
"NEW control.CustomerInfoDTO(c.id, c.lastname, c.firstname, " +
"SUM(i.product.price)) " +
"FROM Customer c " +
"JOIN c.orders o ON o.customerId = c.id " +
"JOIN o.items i " +
"GROUP BY c.lastname, c.firstname" +
"ORDER BY c.lastname, c.firstname");
List<CustomerInfoDTO> list = q.getResultList();

11. ORM FÜR ALLES?
Just because you're using Hibernate, doesn't
mean you have to use it for everything.
A point I've been making for about ten years
now.
Gavin King, 10.12.2013

12. SQL?
• VORTEILE
– Testbar mit SQL Developer/TOAD/IDE
– Optimierbar (Execution Plan)
• ABER SQL VON HAND? NEIN!
– JPA 2.1 ConstructorResult
– QLRM
– jOOQ

13. JPA 2.1 CONSTRUCTOR RESULT
Query q = em.createNativeQuery(
"SELECT C.ID, C.LASTNAME, C.FIRSTNAME, SUM(P.PRICE) AS REVENUE" +
"FROM CUSTOMERS C " +
"JOIN ORDERS O ON O.CUSTOMER_ID = C.ID " +
"JOIN ORDERITEMS I ON I.ORDER_ID = O.ID " +
"JOIN PRODUCTS P ON P.ID = I.PRODUCT_ID " +
"GROUP BY C.ID, C.LASTNAME, C.FIRSTNAME " +
"ORDER BY C.LASTNAME, C.FIRSTNAME", "CustomerInfoDTO");
@SqlResultSetMapping(name="CustomerInfoDTO",
classes={
@ConstructorResult(targetClass=CustomerInfoDTO.class,
columns={@ColumnResult(name="ID"),
@ColumnResult(name="LASTNAME"),
@ColumnResult(name="FIRSTNAME"),
@ColumnResult(name="REVENUE", type=Double.class)})
})

14. QLRM
Query q = em.createNativeQuery(
"SELECT C.ID, C.LASTNAME, C.FIRSTNAME, SUM(P.PRICE) AS REVENUE" +
"FROM CUSTOMERS C " +
"JOIN ORDERS O ON O.CUSTOMER_ID = C.ID " +
"JOIN ORDERITEMS I ON I.ORDER_ID = O.ID " +
"JOIN PRODUCTS P ON P.ID = I.PRODUCT_ID " +
"GROUP BY C.ID, C.LASTNAME, C.FIRSTNAME " +
"ORDER BY C.LASTNAME, C.FIRSTNAME");
JpaResultMapper mapper = new JpaResultMapper();
List<CustomerInfoDTO> list =
jpaResultMapper.list(q, CustomerInfoDTO.class);
QLRM: https://github.com/simasch/qlrm

15. jOOQ
List<CustomersInfoDTO> list = create.
select(CUSTOMERS.ID, CUSTOMERS.LASTNAME, CUSTOMERS.FIRSTNAME,
sum(PRODUCTS.PRICE)).
from(CUSTOMERS).
join(ORDERS).on(ORDERS.CUSTOMER_ID.eq(CUSTOMERS.ID)).
join(ORDERITEMS).on(ORDERITEMS.ORDER_ID.eq(ORDERS.ID)).
join(PRODUCTS).on(PRODUCTS.ID.eq(ORDERITEMS.PRODUCT_ID)).
groupBy(CUSTOMERS.ID, CUSTOMERS.NAME).
orderBy(CUSTOMERS.NAME).
fetchInto(CustomersInfoDTO.class);
jOOQ: http://www.jooq.org

16. CQRS
Quelle: Martin Fowler, http://martinfowler.com/bliki/CQRS.html

17. CQRS IM KLEINEN
• QUERIES
– JPA Constructor Expression
– JPA ConstructorResult
– QLRM
– jOOQ
• COMMANDS
– JPA Entities

18. EMPFEHLUNGEN
• Entities zum Erstellen und Ändern der Daten
• DTO für lesende Zugriffe
– Constructor Expression
– SQL mit QLRM oder jOOQ

19. BONUS MATERIAL

20. RANDOM-DATA-GENERATOR
RandomDataGenerator randomDataGenerator = new RandomDataGenerator();
List<Customer> customers = randomDataGenerator.generateList(
400,
new GenConfig()
.name(Name.Firstname, "firstname")
.name(Name.Lastname, "lastname"),
Customer.class);

21. LOG4JDBC
Anpassungen im META-INF/persistence.xml
<property name="javax.persistence.jdbc.url"
value="jdbc:log4jdbc:derby://localhost:1527/orders"/>
<property name="javax.persistence.jdbc.driver"
value="net.sf.log4jdbc.sql.jdbcapi.DriverSpy"/>
log4jdbc-log4j2: https://code.google.com/p/log4jdbc-log4j2/