I have a question about usage of nested list projection interface. I have two entity (Parent and child) (they have Unidirectional association)
Parent =>
#Table(name = "parent")
#Entity
public class ParentEntity {
#GeneratedValue(strategy = GenerationType.AUTO)
private long id;
private String name;
// other fields........
}
Child =>
#Table(name = "child")
#Entity
public class ChildEntity {
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
private long id;
#NonNull
private String name;
#NonNull
#ManyToOne(fetch = FetchType.LAZY)
private ParentEntity parent;
// other fields........
}
I have two projection interface for select specific columns.
ParentProjection =>
public interface ParentProjection {
String getName();
Set<ChildProjection> getChild();
}
ChildProjection =>
public interface ChildProjection {
String getId();
String getName();
}
I want to take list of ParentProjection which includes with list of ChildProjection.
Repository query like that =>
#Query("select p.name as name, c as child from ParentEntity p left join ChildEntity as c on p.id = c.parent.id")
List<ParentProjection> getParentProjectionList();
This query works, but it selects all columns of ChildEntity, and map only id, name propeties to ChildProjection. (generated query selects all columns, but i want to select only id and name columns)
How can i select only id and name columns (select specific columns for nested list projection interface) and map to ChildProjection fields (using with #Query) ?
Note: I don't need to use class type projection.
You need to add the OneToMany relation to ParentEntity and annotate with Lazy.
Hope it helps (i have tried this).
Related
I have an issue trying to generate multiple relationship in JPA with three Entities.
Order
Product
Modifier
I have an Entity to handle the relationship many to many.
OrderProducts (order_id and product_id)
Contains the relationship of one order can have multiple products
OrderDetails (order_products_id and modifier_id)
Contains the id of the previous relationship Order-Products and the Id of the modifier which is a set of multiple values that can affect the price of the product.
Not quite sure how to handle this kind of relationship in JPA as I'm new to it.
You need a join entity with a composite key. You will need to research it further.
Your entities:
#Entity
#Table(name = "ordertable")
#Data
public class Order {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
#OneToMany(mappedBy = "order")
#EqualsAndHashCode.Exclude
private Set<OrderProductModifier> products;
}
#Entity
#Table(name = "product")
#Data
public class Product {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
#EqualsAndHashCode.Exclude
private BigDecimal unitPrice;
}
#Entity
#Table(name = "modifier")
#Data
public class Modifier {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
#EqualsAndHashCode.Exclude
private BigDecimal modifier;
}
And the entity that ties it all together will need to have the foreign keys for each of the above entities, as you have noted.
#Entity
#Table(name = "orderproductmodifier")
#Data
public class OrderProductModifier {
#EmbeddedId
private OrderProductModifierId id;
#MapsId("orderId")
#ManyToOne
#EqualsAndHashCode.Exclude
#ToString.Exclude
private Order order;
#MapsId("productId")
#ManyToOne
#EqualsAndHashCode.Exclude
private Product product;
#MapsId("modifierId")
#ManyToOne
#EqualsAndHashCode.Exclude
private Modifier modifier;
}
#SuppressWarnings("serial")
#Embeddable
#Data
public class OrderProductModifierId implements Serializable {
private Long orderId;
private Long productId;
private Long modifierId;
}
This is pretty simple to use:
private void run() {
EntityManagerFactory factory = Persistence.createEntityManagerFactory("UsersDB");
EntityManager em = factory.createEntityManager();
em.getTransaction().begin();
Product product = new Product();
product.setUnitPrice(BigDecimal.TEN);
em.persist(product);
Modifier modifier = new Modifier();
modifier.setModifier(new BigDecimal(".90"));
em.persist(modifier);
Order order = new Order();
em.persist(order);
OrderProductModifier opm = new OrderProductModifier();
opm.setId(new OrderProductModifierId());
opm.setOrder(order);
opm.setProduct(product);
opm.setModifier(modifier);
em.persist(opm);
em.getTransaction().commit();
em.clear();
Order o = em.createQuery("select o from Order o join fetch o.products where o.id = 1", Order.class).getSingleResult();
System.out.println("Order for " + o.getProducts());
System.out.println("Order cost " + o.getProducts().stream().map(p->p.getProduct().getUnitPrice().multiply(p.getModifier().getModifier()).doubleValue()).collect(Collectors.summingDouble(Double::doubleValue)));
}
The above query could be better, but that will give you something to work on.
Given this very simple DTO:
#Entity
public class Employee implements Serializable {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private long id;
private String name;
#OneToOne
private Employee boss;
}
I'd like to make a query that gathers all employee names and their boss' id, put in a nice clean POJO:
public class EmployeeInfo {
private String name;
private Long bossId;
public EmployeeInfo(String name, Long bossId) {
this.name = name;
this.bossId = bossId;
}
}
This query should be of use:
CriteriaBuilder cb = em.getCriteriaBuilder();
CriteriaQuery<EmployeeInfo> query = cb.createQuery(EmployeeInfo.class);
Root<Employee> root = query.from(Employee.class);
query.select(
cb.construct(EmployeeInfo.class,
root.get("name").as(String.class),
root.get("boss").get("id").as(Long.class)));
result = em.createQuery(query).getResultList();
When a bossId is present in the employee column this works just fine. But when no boss id is set the record will be completly ignored. So how do i treat this non existing boss relation as null or 0 for the construct/multiselect?
In pure SQL it is easy:
SELECT name, COALESCE(boss_id, 0) FROM EMPLOYEE;
But for the love of god i cannot make the criteria api do this.
cb.construct(EmployeeInfo.class,
root.get("name").as(String.class),
cb.coalesce(root.get("boss").get("id").as(Long.class), 0L)));
The problem is that root.get("boss") generate query with cross join like this from Employee employee, Employee boss where employee.boss.id=boss.id. So records where employee.boss.id is null are ignored.
To solve the problem you should use root.join("boss", JoinType.LEFT) instead of root.get("boss")
I am using springboot and springdata with Mysql.
I have 2 entities, Customer & Order:
#Entity
#Table(name = "customers")
public class Customer {
#Id
#GeneratedValue(strategy= GenerationType.IDENTITY)
#Column(name="id", nullable = false)
protected long id;
#Column(name = "name")
private String name;
}
#Entity
#Table(name = "orders")
public class Order {
#Id
#GeneratedValue(strategy= GenerationType.IDENTITY)
#Column(name="id", nullable = false)
protected long id;
#Column(name="customer_id")
private long customerId;
}
I also have a repository:
#Repository
public interface OrdersRepository extends JpaRepository<Order, Long> {
#Query("select o from Order o, Customer c where o.customerId = c.id")
Page<Order> searchOrders(final Pageable pageable);
}
The method has some more arguments for searching, but the problem is when I send a PageRequest object with sort that is a property of Customer.
e.g.
Sort sort = new Sort(Sort.Direction.ASC, "c.name");
ordersRepository.search(new PageRequest(x, y, sort));
However, sorting by a field of Order works well:
Sort sort = new Sort(Sort.Direction.ASC, "id");
ordersRepository.search(new PageRequest(x, y, sort));
The error I get is that c is not a property of Order (but since the query is a join of the entities I would expect it to work).
Caused by: org.hibernate.QueryException: could not resolve property c of Order
Do you have any idea how I can sort by a field of the joined entity?
Thank you
In JPA , the thing that you sort with must be something that is returned in the select statement, you can't sort with a property that is not returned
You got the error because the relationship is not modeled properly. In your case it is a ManyToOne relation. I can recomend the wikibooks to read further.
#Entity
#Table(name = "orders")
public class Order {
#Id
#GeneratedValue(strategy= GenerationType.IDENTITY)
#Column(name="id", nullable = false)
protected long id;
#ManyToOne
#JoinColumn(name="customer_id", referencedColumnName = "id")
private Customer customer;
}
The query is not needed anymore because the customer will be fetched.
#Repository
public interface OrdersRepository extends PagingAndSortingRepository<Order, Long> {
}
Now you can use nested properties.
Sort sort = new Sort(Sort.Direction.ASC, "customer.name");
ordersRepository.findAll(new PageRequest(x, y, sort));
I'm trying to find out the appropriate relationship to be used in order to model an JPA Entity Field which needs a Look-up table (Comboxbox equivalent on the UI) to select the value from. An example below:
#Entity
public class Employee {
#Id
private int employeeId;
private String name;
private Department department;
}
#Entity
public class Department {
#Id
private int id;
private String name;
}
The instances of Department could be as follows:
Id | Name
-----------------------
100 | Human Resources
101 | Sales
102 | Finances
For an employee, the department field should get a value from one of the above. What should be the JPA annotations for the corresponding fields in both the entities?
Thanks,
Sandeep Joseph
I think you are looking for a unidirectional ManyToOne relationship from Employee to Department, something like this:
#Entity
public class Employee {
#Id
private int employeeId;
private String name;
#ManyToOne
#JoinColumn(name = "department_id", nullable = false)
private Department department;
}
This means an employee must be associated to a single department and a department can be associated to many employees.
If you need to know the list of employees associated to a department then you can make the relationship bidirectional by adding this:
#Entity
public class Department {
#Id
private int id;
private String name;
#OneToMany(mappedBy = "department")
private Collection<Employee> employees;
}
i have two entities Customer and Order (trivial setters and getters excluded)
#Entity
public class Customer {
#GeneratedValue
#Id
private int id;
#OneToMany
List<Order> orderList;
}
#Entity
public class Order {
#GeneratedValue
#Id
private int id;
#ManyToOne
Customer customer;
private boolean paid;
public Order(Customer customer) {
this.customer = customer;
customer.getOrderList().add(this)
}
}
Now i want to set 'paid = true' for all the orders of a given customer
Below query seem to do the trick, but I get a feeling it is innefficient and the fact that i stored the reverse relationship in Customer.orderList hints that there should be some other way to do this.
UPDATE Order o SET o.paid = true WHERE EXISTS
(SELECT c.orderList FROM Customer c WHERE o MEMBER OF c.orderList AND c = :customer)
I'm using container managed transactions, glassfish and javaDb. But I'd prefer if improvements could be done in JPA/JPQL domain and not specific to container or db.
private id; ?? missed field type
Add to #OneToMany annotation,cascade = CascadeType.All
Customer entity = entityManager.find(Customer.class, id)
for (Order order : entity.getOrderList())
{
order.setPaid(true);
}
if you are using cantainer managed transaction then true will be saved to DB