I need to save two collections in my MongoDB using Java. Where one collection is Department and other collection is Employee . Where one Department can have many employees I want to save a collection like an employee unique ID has to mapped in my department employee list.
Example:
{
"_id" : ObjectId("598da19250aa4ad2413d4bc0"),
"_class" : "com.department",
"departmentName" : "SAQ-A",
"departmentNumber" : "3_2",
"employee" : [
"id" : "1",
"id" : "2",
"id" : "3"
]
}
Can I know what is the way I can achieve it in MongoDB using Java?
By the provided document and tags I assume you are using spring data to deal with mongodb. So here you may want to use DBRefs to bind employees into departments. Luckily Spring Data gives you @DBRef annotation.
Employee class:
import org.springframework.data.annotation.Id;
import org.springframework.data.mongodb.core.mapping.Document;
@Document
public class Employee {
@Id
private Integer id;
...
}
Department class:
import org.springframework.data.annotation.Id;
import org.springframework.data.mongodb.core.mapping.DBRef;
import org.springframework.data.mongodb.core.mapping.Document;
@Document
public class Department {
@Id
private String id;
@DBRef
private Collection<Employee> employees;
...
}
MongoDB document:
{
"_id" : ObjectId("598dc04ac4fdd0e29867ccbb"),
"_class" : "foo.bar.Department",
"employees" : [
{
"$ref" : "employee",
"$id" : 1
},
{
"$ref" : "employee",
"$id" : 2
}
]
}
Note: Employee instance must already exist in MongoDB. DBRef will not save Employees in cascade style. Look at this article about cascading .
If $id didn't work try just id like this
"employees" : [ { "$ref" : "employee", "id" : 1 }, { "$ref" : "employee", "id" : 2 } ]
The technical post webpages of this site follow the CC BY-SA 4.0 protocol. If you need to reprint, please indicate the site URL or the original address.Any question please contact:yoyou2525@163.com.