How can we assign a field of user table say id that is primary key, to another table as a primary key? using hibernate - sql

Question

See I dont want any mapping but what I want is just a simple thing that is....
I have two Entity
Tasks(taskid,taskname.....,userId)
User_Credentials(userId,password)
So What I want is userId of User Credentials used as a foreign key in Task table.
So when I fire an api to save the task I have to also pass the all details of user Credentials That I dont want.
{
"taskName": "Test",
"taskStatus": "Open",
"taskDueDate": "2022-04-15",
"taskCreatedDate": "2022-04-10",
"taskDescription": "Demo",
"taskPriority": "High",
"isTaskActive": "Yes",
"userCredentials":{
"associateId":"108",
"password":"something#9122"
}
}
What I want is
{
"taskName": "Test",
"taskStatus": "Open",
"taskDueDate": "2022-04-15",
"taskCreatedDate": "2022-04-10",
"taskDescription": "Demo",
"taskPriority": "High",
"isTaskActive": "Yes",
"userCredentials":"108"
}
That I want to post and if userCredentials id 108 is not in User Credentials Table so it pop up an error and if it is there it will save just like a foreign key concept.
So please tell me ho to do that.

Answer 1

You can use ElementCollection to achieve this.
In Tasks entity
#Id
#Column(name = "task_id")
private Integer id;
#ElementCollection
#CollectionTable(name = "task_user", joinColumns = #JoinColumn(name = "task_id", nullable = false))
#Column(name = "user_id", nullable = false)
private List<Integer> userCredentials;
In UserCredentials entity
#Id
#Column(name = "user_id")
private Integer id;
UserCredentials is an independent entity with no mapping with Tasks. You will now be able to pass UserCredentials like this userCredentials: [108] in the Tasks.
Add the following in your application.yml to generate the create.sql script with ddl commands for all the entities. ddl-auto: validate will restrict hibernate from creating the tables on its own.
spring:
jpa:
hibernate:
ddl-auto: validate
properties:
javax:
persistence:
schema-generation:
create-source: metadata
scripts:
action: create
create-target: create.sql
generate-ddl: true
The following is the ddl command to add foreign key constraints for tables user_credentials and tasks. Execute it alongwith the create.sql in any DB client.
CREATE TABLE "task_user"
( "user_id" integer ,
"task_id" integer,
PRIMARY KEY ("user_id","task_id"),
CONSTRAINT user_id_fkey
FOREIGN KEY ("user_id") REFERENCES "user_credentials" ("user_id"),
CONSTRAINT task_id_fkey
FOREIGN KEY ("task_id") REFERENCES "tasks" ("task_id")
);
Note: The create.sql already has a task_user create command but it needs to be replaced with the above command.