I have a spring boot JPA project with an entity called Customers and another one CustomerReports
#Entity
public class Customers {
#Id
#GeneratedValue(strategy= GenerationType.IDENTITY)
private int id;
private String Name;
#JsonIgnore
#OneToOne(cascade = CascadeType.ALL)
#JoinColumn(name = "customer_id", referencedColumnName = "id")
private Reports reports;
//getter and setters..etc
}
#Entity
public class CustomerReports {
#Id
#GeneratedValue(strategy= GenerationType.IDENTITY)
private int id;
private BigDecimal monthlyPayment;
//done
#JsonIgnore
#OneToOne(mappedBy = "reports")
private Customers customers;
//constructors, getters...etc.
}
I want whenever I insert a Customer, a report to also be generated for that customer. The column "monthlyPayment" in reports is also generated through a reference from another table so I don't want to insert those columns manually if that makes sense.
Is there a way to do that? I'm not sure what to google so it would be great if anyone can give me an idea
If I understand your question properly, you can derive CustomerReports entity based on Customers via simple java utility method & then call save if you are using jparepository :
CustomerReports customerReports=reportUtil(customerEntity);
jpaRepository.save(customerEntity);
jpaRepository.save(customerReports);
...
private CustomerReports reportUtil(Customers customerEntity){
/*Derive values for CustomerReports based on Customers & return*/
}
Or if you don't want to do by this way then check if your underlying database support triggers which you can use for inserting data into CustomerReports while doing insert to Customers
Related
I am using spring boot. I am loading test data through yml by defining spring.datasource.data=classpath:/test-data/sql_file_EntityOne.sql, classpath:/test-data/sql_file_EntityTwo.sql,...
For every single entity it works seamlessly but problem comes when EntityOne and EntityTwo have foreign key relationship and the corresponding insert statements are written in 2 different SQL files as depicted above.
I am using in memory h2 dB for local.
sql_file_EntityOne.sql
(Id_One, data_1,data_2) values(101, 'dat', 5)
sql_file_EntityTwo.sql
(Id_two, Id_Onethis is fk, data_3,data_4)
values(1,101, 'dat2', null, 5)
EntityOne
#Id
IdOne
....
#OneToMany(Cascade.All, mappedBy="entityOneRef")
List entityTwoRef
EntityTwo
#Id
IdTwo
....
#ManyToOne(Cascade.All)
#JoinColumn("entityTwoRef")
EntityOne entityOneRef
Can you please mention the error you are getting here?
You can use the following hibernate annotations for bidirectional relationship:
#OneToMany(mappedBy = ) on parent enity
#ManyToOne #JoinColumn(name = , nullable = false) on child entity
for example, let's take an example of Cart and Item as two entities with a Cart related as one to many with item:
//Cart
#Entity
#Data
public class Cart {
#Id
private Integer cartId;
#Column
private String data;
#OneToMany(mappedBy = "cart")
private Set<Item> items;
}
//Item
#Entity
#Data
public class Item {
#Id
private Integer itemId;
#Column
private String data;
#ManyToOne
#JoinColumn(name = "cart_id", nullable = false)
private Cart cart;
}
#Data is just lombok annotation for getters and setters. Scripts as below:
//Script1
INSERT INTO CART(cart_id,data) VALUES (101,'data1')
//Script2
INSERT INTO ITEM(item_id,cart_id,data) VALUES (1,101,'data2')
Then load the scripts in spring-boot in order:
spring.datasource.data=classpath:sql_script1.sql,classpath:sql_script2.sql
Hope it helps :)
In my application users can post articles. And other users can like these articles.
Article class :
#Entity
public class Article {
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
#Column(name = "article_id")
private int id;
#Column(name = "article_title")
private String articleTitle;
#OneToMany(mappedBy = "event")
private List<PeopleWhoLiked> peopleWhoLiked;
}
#Entity
public class PeopleWhoLiked {
#EmbeddedId
private PeopleWhoLiked id;
#ManyToOne #MapsId("articleId")
private Article article;
#ManyToOne #MapsId("userId")
private User user;
}
And there is category entity.Every article has one category.
public class Category {
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
#Column(name = "category_id")
private int id;
#NotEmpty
#Column(name = "categoryName")
private String categoryName;
#OneToMany(mappedBy = "article")
private List<Article> articleList;
}
My Like Table
Article_id User_id
x x
These are both foreign keys to related tables.
With
category.getArticleList(); function i can show articles to users.They can like articles.But the thing is the system doesn't know that if the article was liked by user already. So always like button is active.
Querying (select statement for every article on Like table) is looks like has huge time complexity and overload to the system.) Even if i do how can i post this into thymeleaf th:each statement with only Article object.
I think querying 10 article's like per time with one select statement sounds good .But again how can i pass this to thymeleaf with Article object.
Your problem with performance is caused by additional request for every row.
For 1 select returning 100 rows you make additionals 100 select to database.
If you need display complicated result build view and than map result of view to your #Entity class, which will used only for presentation purpose.
I have created two entities Book and Book_Category with one-to-many relationship. When I issued BookCategoryRepository.findAll(), I expected hibernate to use 'INNER JOIN' query. But it just issued query to take data from Book_Category.
What I am missing? What should I do to make hibernate issue JOIN query?
Book.java
#Entity
public class Book {
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
private int id;
private String name;
#ManyToOne
#JoinColumn(name = "book_category_id")
private BookCategory bookCategory;
}
BookCategory.java
#Entity
#Table(name = "book_category")
public class BookCategory {
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
private int id;
private String name;
#OneToMany(mappedBy = "bookCategory", fetch = FetchType.EAGER, cascade = CascadeType.ALL)
private Set<Book> books;
}
BookCategoryRepository.java
public interface BookCategoryRepository extends JpaRepository<BookCategory, Integer> {
}
bookCategoryRepository.findAll()
Hibernate uses by default a second query to retriev the child collection. One reason for this is a proper limit query. Otherwise, there would be more rows in the result set, than entities for the 1 side, if at least one has more than 1 child.
There exists an annotation to change this behaviour in hibernate which is ignored by the Spring Data Jpa Repositories. The annotation is #Fetch(FetchMode.JOIN). You might consider How does the FetchMode work in Spring Data JPA if you really need this behaviour.
I have the entity Project and entity Cluster.
A Project can have multiple Clusters.
I don't want a third table to save this relationship. Just the Project ID saved to the Cluster.
This is my project Entity:
#Entity
#Table(name = "Project")
public class Project {
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
private Integer id;
private String projectName;
#OneToMany
#JoinTable(name = "cluster")
private Set<Cluster> clusters;
}
This is my Cluster entity
#Entity
#Table(name = "Cluster")
public class Cluster {
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
private Integer id;
private String team;
private String concept;
}
This gives me the error: must have same number of columns as the referenced primary key .
How could I fix this? I don't see how to fix this.
Use #JoinColumn instead of #JoinTable
public class Project {
//...
#OneToMany
#JoinColumn(name="PROJECT_ID", referencedColumnName="id")
private Set<Cluster> clusters;
and add PROJECT_ID column to Cluster entity.
public class Cluster {
//...
#Column(name = "PROJECT_ID")
private Integer projectId;
Correct me if I'm wrong but, as far as I know about Software Engineering, what you want CAN'T be done: you can't store a relationship nowhere but in a third table. Lists, sets, maps, and so on MUST be stored that way.
Otherwise, and in your case, you'd have Project's properties replicated for each cluster of the relationship, and that's not desirable.
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.