Ebean @ManyToOne, finder is not fetching all data of related object
I am using Ebean for my object mapping and I made SQL tables this way
create table company (
id int auto_increment not null primary key,
name varchar(100)
);
create table employee (
id int auto_increment not null primary key,
name varchar(100) not null,
company_id int not null,
constraint foreign key (company_id) references company (id)
on delete restrict on update restrict
);
This is the Ebean model
import javax.persistence.Entity;
import javax.persistence.Id;
import com.avaje.ebean.Model;
@Entity
public class Company extends Model
{
@Id
public Integer id;
public String name;
}
And the employee model
@Entity
public class Employee extends Model
{
@Id
public Integer id;
public String name;
@ManyToOne
public Company company;
public static Finder<Long, Employee> find = new Finder<Long, Employee>(Long.class, Employee.class);
}
When I run next
Company company = new Company();
company.name = "Microsoft";
company.save();
Employee employee = new Employee();
employee.name = "Mr John";
employee.company = company;
employee.save();
Employee mrJohn = Employee.find.where().eq("id", 1).findUnique();
System.out.println(mrJohn.company.id);
System.out.println(mrJohn.company.name);
The first System.out.println gives 1 (which is the correct company ID assigned to the employee), but the second shows null (which I expected should be "Microsoft"), with the result being
1
null
So the question is, why is only the company model ID being retrieved and not other related data?
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-
You can use fetch () to eagerly fetch other parts of the graph. In this case, enter the name of the company, for example:
Employee.find.fetch ("company", "name"), where () eq ("Identifier", 1) .findUnique (); ..
-
In the short field, the access cannot be intercepted (unless you activate the caller). Thus, using the accessor field for company.name meant that customer.name was a GETFIELD operation and that Ebean was not intercepted and therefore no lazy loading was invoked (and therefore null was returned).
Changing to using getters / setters meant that calling customer.getName () was lazy loading.
Java does not support properties (hance the getters and setters). You can look at other JVM languages that are really similar to Groovy and Kotlin.
Groovy maintains properties, example using Groovy with @CompileStatic: https://github.com/ebean-orm/avaje-ebeanorm-examples/blob/master/e-groovy https://github.com/ebean-orm/avaje -ebeanorm-examples / blob / master / e-groovy / src / main / groovy / org / example / domain / Customer.groovy
Kotlin supports properties, for example: https://github.com/ebean-orm/avaje-ebeanorm-examples/tree/master/e-kotlin-maven
Cheers, Rob.
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I ran into this problem today and I found out why it is not being called lazily when accessing a public variable.
The ribbon can be called lazily by calling the attributes method getter
. So I need to create getter
model selections in my data using the method getter
.
@Entity
public class Company extends Model
{
@Id
public Integer id;
public String name;
public Integer getId() {
return id;
}
public String getName() {
return name;
}
}
Then select a company:
System.out.println(mrJohn.company.getName());
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