Product and ProductTag form a one-to-many relationship, as shown below.
#Entity
public class Product {
#Id
Long id;
#OneToMan(mappedBy = "product")
List<ProductTag> productTags;
}
#Entity
public class ProductTag {
#Id
Long id;
String content;
#ManyToOne(fetch = FetchType.LAZY)
#JoinColumn(name = "product_id")
Product product;
}
Now I have an API that searches products, then returns them with their tags. Every time I call product.getProductTags(), Hibernate will fire an SQL query. Since the MySQL server is far away from the app server, I would like to cache product.getProductTags() call. How do I achieve that?
Use a specific query to fetch the tags and store them in a cache:
public TagRepository extends JpaRepository<Tag, Long> {
#Cacheable("tagsByProducts")
#Query("Select t from ProductTag t where t.product = ?product")
List<Tag> findByProduct(Product product);
}
somewhere you need some method to evict the cache: annotated by#CacheEvict("tagsByProducts")
But to be honest: I doubt that is a good idea to store JPA Entities in a cache! I think this would lead to many many strange problems. So better query just for the tag names (or content) instead of the tag-entities.
public TagRepository extends JpaRepository<Tag, Long> {
#Cacheable("tagsByProducts")
#Query("Select t.content from ProductTag t where t.product = ?product")
List<String> findTagContentByProduct(Product product);
}
#Entity
public class Product {
#Id
Long product_id;
#OneToMany(casacade=CascadeType.ALL,
fetch=FetchType.Eager,mappedBy = "product")
#JsonManagedReference(value="product-tag")
List<ProductTag> productTags;
}
#Entity
public class ProductTag {
#Id
Long id;
String content;
#ManyToOne(fetch = FetchType.LAZY)
#JoinColumn(name = "product_id")
#JsonBackReference(value="product-tag")
Product product;
}
Related
this is my order entity,
#Data
#NoArgsConstructor
#AllArgsConstructor
#ToString
#Entity
#Table(name = "ordertab")
public class Order {
#Id
private int orderId;
private String orderDate;
#ManyToMany(targetEntity = Medicine.class,cascade = CascadeType.ALL)
#JoinTable(name="ord_med",
joinColumns = {#JoinColumn(name="ord_id")},
inverseJoinColumns = {#JoinColumn(name="med_id")})
private List<Medicine> medicineList;
private String dispatchDate;
private float totalCost;
#ManyToOne(targetEntity = Customer.class,cascade = CascadeType.ALL)
#JoinColumn(name= "custord_fk",referencedColumnName = "customerId")
private Customer customer;
private String status;
}
and this is my medicine entity,
#Data
#NoArgsConstructor
#AllArgsConstructor
#ToString
#Entity
public class Medicine {
#Id
private String medicineId;
private String medicineName;
private float medicineCost;
private LocalDate mfd;
private LocalDate expiryDate;
**#ManyToMany(cascade = CascadeType.ALL, mappedBy = "medicineList")
private List<Order> orderList;** //order/ medicine many to many mapping
// OneToOne Mapping
#OneToOne(cascade = CascadeType.ALL)
#JoinColumn(name = "categoryId", referencedColumnName = "categoryId")
private Category category;
in my order service interface i have a method,
List showAllOrder(string medId);
I have to fetch all orders that has the matching med id.
this many to many mapping have created a additional table ord_med with two columns named ord_id,med_id(type foreign keys).In addition to that due to this bidirectional mapping(i believe it is) while creating object of medicine entity its asking me to add orderlist ,how to approach this method or how exactly should i solve this. thankyou.
in your OrderRepository you can implements this method
findByMedicineId(String id);
if i go for findByMedicineId(String id);
it gives error saying no property medicineId is found in Order entity,cuz the property medicineId is in Medicine entity,while defining custom method in repository follows rules, refer https://docs.spring.io/spring-data/jpa/docs/current/reference/html/#jpa.query-methods.query-creation
anyway I have found the solution for this,
public List<Order> getOrderListBasedOnMedicineId(String medicineid) {
Optional<Medicine> med=medicineRepo.findById(medicineid);//find if medicine is present in database with the id.
if(med.isEmpty()) {
return null;
}
List<Order> orders = medicineServ.getOrderList(); //getorderlist defined in service implementation of medicine.
List<Order> ordersWithMedId = new ArrayList();//new list to add all orders that has atleast one medicineId that matches.
for(int i=0;i<orders.size();i++) {
List<Medicine> medicines= orders.get(i).getMedicineList();
for(int j=0;j<medicines.size();j++) {
ordersWithMedId.add(orders.get(i));
}
}
return ordersWithMedId;//returning the list of orders.
}
#Override
public List<Order> getOrderList() {//medicine service implementation
return orderRepo.findAll();
}
//OrderController
#GetMapping("/orders/list/{id}")
public ResponseEntity<List<Order>> getOrderListBasedOnMedicineId(#PathVariable("id") String id) {
List<Order> ord= orderService.getOrderListBasedOnMedicineId(id);
if(ord==null) {
throw new OrderNotFoundException("Order not found with medicine id:"+id);
}
return new ResponseEntity<List<Order>>(orderService.getOrderListBasedOnMedicineId(id),HttpStatus.OK);
}
I'm trying to have Spring Data JPA issue one query using joins to eagerly get a graph of entities:
#Entity
#NamedEntityGraph(name = "PositionKey.all",
attributeNodes = {#NamedAttributeNode("positionKey.account"),
#NamedAttributeNode("positionKey.product")
})
#Data
public class Position {
#EmbeddedId
private PositionKey positionKey;
}
#Embeddable
#Data
public class PositionKey implements Serializable {
#ManyToOne
#JoinColumn(name = "accountId")
private Account account;
#ManyToOne
#JoinColumn(name = "productId")
private Product product;
}
Here's my Spring Data repo:
public interface PositionRepository extends JpaRepository<Position, PositionKey> {
#EntityGraph(value = "PositionKey.all", type = EntityGraphType.LOAD)
List<Position> findByPositionKeyAccountIn(Set<Account> accounts);
}
This produces the following exception:
java.lang.IllegalArgumentException: Unable to locate Attribute with the the given name [positionKey.account] on this ManagedType
I want all of the accounts and products to be retrieved in one join statement with the positions. How can I do this / reference the embedded ID properties?
I would suggest refactoring the entity this way if it possible
#Entity
#NamedEntityGraph(name = "PositionKey.all",
attributeNodes = {#NamedAttributeNode("account"),
#NamedAttributeNode("product")
})
#Data
public class Position {
#EmbeddedId
private PositionKey positionKey;
#MapsId("accountId")
#ManyToOne
#JoinColumn(name = "accountId")
private Account account;
#MapsId("productId")
#ManyToOne
#JoinColumn(name = "productId")
private Product product;
}
#Embeddable
#Data
public class PositionKey implements Serializable {
#Column(name = "accountId")
private Long accountId;
#Column(name = "productId")
private Long productId;
}
Such an EmbeddedId is much easier to use. For instance, when you are trying to get an entity by id, you do not need to create a complex key containing two entities.
This is my Product entity class:
public class Product extends BaseEntity {
#Column
#ManyToMany()
private List<Customer> customers = new ArrayList<>();
#ManyToOne
private Supplier supplier;
}
And this is my Customer entity class:
public class Customer extends BaseEntity {
//Enum type to String type in database '_'
#Enumerated(EnumType.STRING)
#Column
private Type type;
#Column
#ManyToMany(targetEntity = Product.class)
private List<Product> products = new ArrayList<>();
}
When I run my Spring boot project, it creates 2 separate tables in my database(Mysql): product_customer and customer_product but I need only one. What can I do to solve this?
Update your classes as follows:
public class Product {
#ManyToMany
#JoinTable(name="product_customer"
joinColumns=#JoinColumn(name="product_id"),
inverseJoinColumns=#JoinColumn(name="customer_id")
)
private List<Customer> customers = new ArrayList<>();
...
}
public class Customer extends BaseEntity {
#ManyToMany
#JoinTable(name="product_customer"
joinColumns=#JoinColumn(name="customer_id"),
inverseJoinColumns=#JoinColumn(name="product_id")
)
private List<Product> products = new ArrayList<>();
...
}
Take a look to the following link to know how to map a ManyToMany relation in a suitable way. But basically, you can do:
public class Product {
...
#ManyToMany(cascade = {
CascadeType.PERSIST,
CascadeType.MERGE
})
#JoinTable(name="product_customer"
joinColumns=#JoinColumn(name="product_id"),
inverseJoinColumns=#JoinColumn(name="customer_id")
)
private Set<Customer> customers = new LinkedHashSet<>();
...
}
And:
public class Customer extends BaseEntity {
...
#ManyToMany(mappedBy = "customers")
private Set<Product> products = new LinkedHashSet<>();
...
}
As #Kavithakaran mentioned in a comment of his answer, you can use #ManyToMany(mappedBy = ... once you identify the "owner of the relation".
If you mean that you don't want to create the third table then you can read the following link below:-
Hibernate Many to Many without third table
Otherwise, you can do this with #jointable annotation.
I'm writing 3 tables in the following relation:
Club class:
#Setter
#Getter
#Entity
#Table(name = "Club")
public class Club {
#Id
#GeneratedValue
private Long id;
private String name;
private String type;
private String mainPage;
private String logo;
#OneToMany(mappedBy="clubProductKey.club", cascade = CascadeType.ALL)
#JsonIgnoreProperties(value = "clubProductKey.club", allowSetters=true)
private Set<ClubProduct> clubProducts;
...
Product class:
#Setter
#Getter
#Entity
#Table(name = "Product")
public class Product {
#Id
#GeneratedValue
private Long id;
#OneToMany(mappedBy="clubProductKey.product", cascade = CascadeType.ALL)
#JsonIgnoreProperties(value = "clubProductKey.product", allowSetters=true)
private Set<ClubProduct> clubProducts;
...
ClubProduct class:
#Setter
#Getter
#Entity
#Table(name = "ClubProduct")
public class ClubProduct {
#EmbeddedId
private ClubProductKey clubProductKey;
...
ClubProductKey class:
#Setter
#Getter
#Embeddable
public class ClubProductKey implements Serializable {
#ManyToOne(cascade = {CascadeType.MERGE,CascadeType.REFRESH })
#JoinColumn(name = "club_id", referencedColumnName = "id")
#JsonIgnoreProperties(value = "clubProducts", allowSetters=true)
private Club club;
#ManyToOne(cascade = {CascadeType.MERGE,CascadeType.REFRESH })
#JoinColumn(name = "product_id", referencedColumnName = "id")
#JsonIgnoreProperties(value = "clubProducts", allowSetters=true)
private Product product;
...
ClubProductRepository class:
public interface ClubProductRepository extends JpaRepository<ClubProduct, ClubProductKey> {
public List<ClubProduct> findByClubProductKeyClub(Club club);
public List<ClubProduct> findByClubProductKeyProduct(Product product);
}
I try to save clubProduct like this:
#Service
public class ClubProductServiceImp implements ClubProductService {
#Autowired
private ClubProductRepository clubProductRepository;
...
ClubProduct savedClubProduct = clubProductRepository.save(clubProduct);
return savedClubProduct;
}
However I find that the clubProduct is not saved in the clubProducts list in the club or product entity, the list is null. Must I add lines like club.getClubProducts.add(clubProduct) or is there any other way to make it added automatically?
Thank you.
The #OnetoMany mapping in your Club class uses the attribute mappedby which means that it represents the owning side of the relation responsible for handling the mapping. However, we still need to have both sides in sync as otherwise, we break the Domain Model relationship consistency, and the entity state transitions are not guaranteed to work unless both sides are properly synchronized.
The answer is yes, you have to manage the java relations yourself so that the clubProducts gets persisted. You are using an instance of the repository class club to persist the data so , you should add a setter method like :
public void addClubProduct(ClubProduct clubProduct) {
if (clubProduct!= null) {
if (clubProduct== null) {
clubProduct= new ArrayList<ClubProduct>();
}
clubProducts.add(clubProduct);
clubProduct.setClubProduct(this);
}
}
also a method to remove it from the list and use these method in your code to set the values to the list properly before initiating save . Read related article
I had entities User, BlockUnit, Block and Unit as Follows.
User has ManyToMany relation with blockunit.
#Entity
public class User {
#ManyToMany
private Set<BlockUnit> blockUnits;
}
#Entity
public class BlockUnit {
#Id
private Long id;
#OneToOne(targetEntity = Block.class)
#JoinColumn(name = "block_id")
private Block block;
#OneToOne(targetEntity = Unit.class)
#JoinColumn(name = "unit_id")
private Unit unit;
#ManyToMany(fetch = FetchType.LAZY)
private Set<User> users = new HashSet<>();
}
BlockUnit has OneToOne relation with Block and Unit.
#Entity
public class Block {
#Id
private Long id;
}
#Entity
public class Unit {
#Id
private Long id;
}
How should I create the JPA criteria specification for above in order to select user's having Block ID and Unit ID?
Thank you very much in advance!