I have following relationship b.w two entities given below ,when I get OutletProductVariety object from repository ,the price is coming in PersistentBag and not as a List even after using fetchtype Eager.
#Entity
public class OutletProductVariety {
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
Long id;
#ManyToOne
#JoinColumn(name = "varietyId")
Variety variety;
#OneToMany(mappedBy = "outletVariety", fetch = FetchType.EAGER)
List<Price> price;
}
And
#Entity
public class Price {
#Id
#GeneratedValue(strategy=GenerationType.AUTO)
Long Id;
#ManyToOne
#JoinColumn(name="outletVareityId")
private OutletProductVariety outletVariety;
private Double price;
}
How can I get a List of prices rather then PersistentBag?
Have a look at Hibernates PersistentBag
An unordered, unkeyed collection that can contain the same element
multiple times. The Java collections API, curiously, has no
Bag. Most developers seem to use Lists to represent
bag semantics, so Hibernate follows this practice.
public class PersistentBag extends AbstractPersistentCollection implements List
protected List bag;
It implements java.util.List; so it is basically a List and wraps your List internally
It is just Hibernates way to represent your List.
Related
I've a question about One to One unidirectional Mapping in Spring Boot.
I've a Customer class with a One to One unidirectional mapping to an Address class.
But when I try to associate a new customer with an existing Address, the database is updated.
So two Customers are now associated with the one Address.
As I understand it only one Customer should be associated with one unique Address. Do I understand the concept correctly, or am I doing something wrong in Spring Boot/ Spring Data JPA/ Hibernate?
Customer
#Entity
public class Customer {
#Id
private Long cId;
private String cName;
#OneToOne(cascade = CascadeType.ALL)
#JoinColumn(name="aid")
private Address cAddr;
:
}
Address
#Entity
public class Address {
#Id
private Long aid;
private String town;
private String county;
:
}
data.sql
insert into address values (100, "New York", "NY");
insert into customer values (1, "John Smith", 100);
Application.java
#Override
public void run(String... args) throws Exception {
Customer c1 = new Customer((long)5, "Mr. Men");
Optional<Address> a100 = ar.findById((long)100);
c1.setcAddr(a100.get());
cr.save(c1);
}
Database
There are 2 options on how to make #OneToOne relation: unidirectional and bidirectional: see hibernate doc.
When you scroll down a little bit you will find the following:
When using a bidirectional #OneToOne association, Hibernate enforces the unique constraint upon fetching the child-side. If there are more than one children associated with the same parent, Hibernate will throw a org.hibernate.exception.ConstraintViolationException
It means that you'll have the exception only on fetching and when you have a bidirectional association. Because Hibernate will make an additional query to find the dependent entities, will find 2 of them, which doesn't fit #OneToOne relation and will have to throw an exception.
One way to "fix" uniqueness for your entities, is to make cAddr unique:
#OneToOne(cascade = CascadeType.ALL)
#JoinColumn(name="aid", unique=true)
private Address cAddr;
If you create your db tables, by setting hbm2ddl property this will add a unique constraint to the aid column.
I really recommend to read the following:
#OneToOne javadoc itself provides examples of how to do everything correctly (for you Examples 1 and 2 are the most useful)
Check Vlad's blog about #OneToOne. It must be the best you can find. At least jump to the chapter "The most efficient mapping" and implement it bidirectional and sharing the PK, using #MapsId.
Also maybe you will come up to the idea to use #ManyToOne option (at least i can imagine that customer can have multiple addresses)
This is not One-to-Many relation. It's One-to-Many as One object has multiple related objects. Checkout this article.
Example:
Post.java
#Getter
#Setter
#AllArgsConstructor
#NoArgsConstructor
#Entity
#Table
public class Post {
#Id
#GeneratedValue
#Column(name = "post_id")
private Long id;
#Column
private String postHeader;
#OneToMany(
cascade = CascadeType.ALL,
orphanRemoval = true
)
private List<Comment> comments = new ArrayList<>();
public void addComment(Comment comment) {
comments.add(comment);
}
public void removeComment(Comment comment) {
comments.remove(comment);
}
// equals() and hashCode()
}
Comment:
#Getter
#Setter
#AllArgsConstructor
#NoArgsConstructor
#Entity
#Table
public class Comment {
#Id
#GeneratedValue
#Column(name = "postcom_id")
private Long id;
#Column
private String text;
// equals() and hashCode()
}
Check out step "3. Uni-directional one-to-one mapping demonstration" at this site basically carbon copy of what you're trying to do.
I have a rare scenario where i have to maintain two tables say
Student_failed and Student_passed. both have exactly same schema.
#Entity
#Table(name = "student_failed")
public class StudentFailed {
#Id
#Column(name="id")
private String id;
#Column(name="student_name")
private String studentName;
#Column(name="home_town")
private String homeTown;
...
}
and
#Entity
#Table(name = "student_passed")
public class StudentPassed {
#Id
#Column(name="id")
private String id;
#Column(name="student_name")
private String studentName;
#Column(name="home_town")
private String homeTown;
...
}
as both entities are same i want to use single entity for both table. I have two different controllers that do crud operations on either of the tables.
Can i use single entity and map it to both the tables? I came across #SecondaryTables annotation but i am not sure it if will work.
PS: i know its a bad approach to keep two different tables with same fields but due to some specific requirement i am not allowed to do that).
I'm trying to add a order with equipment list, here's my entities:
the order entity
#Entity #Table(name = "orders") public class Order extends Ticket{
#OneToMany(mappedBy = "order", cascade = CascadeType.ALL)
private Set<OrderEquipment> orderEquipments = new HashSet<>();}
the equipment entity
#Entity #Table(name = "equipments") public class Equipment extends DateAudit {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
#NotBlank
#Size(max = 30)
private String name;
#NotNull
private Long nbr_piece ;
#OneToMany(mappedBy = "equipment", cascade = CascadeType.ALL, orphanRemoval = true)
private Set<OrderEquipment> orderEquipments = new HashSet<>();}
and the order_equipment entity
#Entity #Table(name = "order_equipment") public class OrderEquipment extends DateAudit { #Id
#ManyToOne
#JoinColumn(name = "order_id")
private Order order;
#Id
#ManyToOne
#JoinColumn(name = "equipment_id")
private Equipment equipment;
#NotBlank
#Column(name = "quantity")
private Long quantity;}
here is the add function in the orderController
#PostMapping("/orders")
public Order createOrder(#Valid #RequestBody Order Order){
Order.setObservateurEmail(Order.getObservateurEmail());
Order.setObject(Order.getObject());
Order.setDescription(Order.getDescription());
return orderRepository.save(Order);
}
I have seen a mistakes there, lemme try to help you. Since you issue is not clear, please lemme know if it does/does not work:
You have two bidirectional mappings there:
Order (with ALL cascade) <-> OrderEquipment
Equipment (with ALL cascade) <-> OrderEquipment
You are using #JoinColumn for both of them, even though they are bidirectional. Please take a look at this. You should always use the mappedBy attribute when defining bidirectional relationships.
Now, you are receiving an Order object from a POST request, making changes to 3 attributes and then saving it. Since the mapping between the Order and OrderEquipment have the CascadeType.ALL attribute, any save on the Order object will save all OrderEquipment children associated. If the Order object you are receiving already have OrderEquipment children, your method will also save/update them.
Your POST mapping looks good to me, just take care with your table relationship definitions.
Take a look at this answer to check how a lits of entities should be formatted on a JSON POST.
I have the following POJOs'
Filter ----> Filter Components
#Entity
public class Filter {
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
private int id;
private String name;
//Setters and getters are not shown
And I have the following child class
#Entity
public class FilterComponents {
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
private int id;
private int component_id;
private int component_type;
#ManyToOne
#JoinColumn(name = "filter_id")
private Filter filter;
//Setters and getters are not shown
I created a repository to query for Filters
public interface FilterRepository extends JpaRepository <Filter, Long> {}
I am calling the findAll() function to get all Filters. The function is working fine; however, it only returns the name and id of each filter.
Is there a way to return the corresponding Filter Components as well? I assume I can write a join query, but I have a feeling that there is a cleaner way to do it!
Thank you
Make Filter to FilterComponents a OneToMany unidirectional mapping. So, you will be managing child FilterComponents inside its parent.
#Entity
public class Filter {
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
private int id;
private String name;
#OneToMany
#JoinColumn(name = "filter_id")
private List<FilterComponents> filterComponenets;
}
#Entity
public class FilterComponents {
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
private int id;
private int component_id;
private int component_type;
// Removed mapping
}
What you probably missing is a filterComponents field for a Filter e.g.
public class Filter {
...
#OneToMany(mappedBy="cart")
private List< FilterComponents> filterComponents;
You can define eager or lazy fetching depending on your needs here
Your Filter entity does not have any explicit association with FilterComponent entity. In this case you would need to do another request to select all filter components with the given filter id.
On the other hand you can declare the following field in the Filter entity:
#OneToMany(mappedBy = "filter", fetch = FetchType.EAGER)
private List<FilterComponent> filterComponents;
and always load filter components eagerly.
If eager loading does not fit you you can use custom query with left join fetch:
select distinct f from Filter f left join fetch f.filterComponents c
I have two pojo classes with one-to-many relationship in hibernate
CustomerAccountEnduserOrderDetails.class
#Entity #Table(name="customer_account_enduser_order_details")
public class CustomerAccountEnduserOrderDetails implements Serializable{
private static final long serialVersionUID = 1L;
#Id
#GeneratedValue(strategy=GenerationType.AUTO)
#Column(name="id")
private Long id;
#ManyToOne(fetch=FetchType.EAGER)
#JoinColumn(name = "product_id", insertable = false, updatable = false)
private CustomerCmsProduct customerCmsProduct;
}
Second is CustomerCmsProduct.class
#Entity
#Table(name="customer_cms_product")
#JsonIgnoreProperties(ignoreUnknown = true)
public class CustomerCmsProduct {
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
#Column(name="id")
private Long id;
#Column(name="name")
private String name;
#Column(name="offer_price")
private String offerPrice;
#Column(name="original_price")
private String originalPrice;
#Column(name="discount")
private String discount;
}
Here if I fetch the object of CustomerAccountEnduserOrderDetails class,then i will get the CustomerCmsProduct class also , my problem is that here i want the specific column of CustomerCmsProduct table (not all by default i am getting all) like only id and originalPrice.
How i can do like that projection here?
In the service layer or at a webservice layer( if this is a web project) Create two different classes other than #Entity as DTO(Data Transfer Objects) which helps is data transfer from one layer to the other.
public class CustomerAccountEnduserOrderDetailsPojo {
private List<CustomerCmsProductPojo> productPojoList = new ArrayList<> ();
// getter and setter
}
public class CustomerCmsProductPojo {}
Follow the below steps
Retrieve the #Entity class data by executing the query from service layer.
Iterate over all the fields and copy only required fields to pojo layer
Expose the data to other layers using service method.
This way, we can avoid changing the custom hibernate behavior as it is linked with many parameters like cache, one to many queries that are fired per iteration.
And also, do any customization that you want in this layer. Hope this is multi layered project where you have different layers which servers different purpose.