I have this "Parent" class :
#Entity
#Table(name = "parent_table")
public class Parent {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
private String firstName;
private String lastName;
#OneToMany(fetch=FetchType.LAZY, mappedBy = "parent", cascade = {CascadeType.ALL})
List<Child> children;
}
And, I have the following child class :
#Entity
#Table(name = "children")
public class Child {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private Long childId;
#ManyToOne
#JoinColumn(name="parent_id")
private Parent parent;
private String name;
}
I am also sending this as my request body :
{
"firstName": "Test",
"lastName": "Parent",
"children":[{
"name":"jack"
},
{
"name":"jill"
}
]
}
The good news is that is that I can write these children to the database directly from the parent repository, however... when I do my GET, to get a parent, it comes back without the child entities (even though they are in the database, in their table)
SEMI-USEFUL UPDATE (MAYBE?) : I have noticed that the parent_id field in the database for the child records doesn't seem to be getting populated! No idea why!
You are creating the relationship with the wrong column names.
Your parent class has id column defined as:
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
That will generate a column id in your parent table.
Your child class has foreign key defined as:
#ManyToOne
#JoinColumn(name="parent_id")
private Parent parent;
You indicate to look for parent_id column within parent table to make a relationship. Such column does not exist.
If you wish to indicate foreign key column name must be parent_id you have to define it as:
#ManyToOne
#Column(name = "parent_id") // Your child field
#JoinColumn(name="id") // Your parent id field
private Parent parent;
Related
I am new to JPA. I have parent and several children. I am able to successfully save parent and associated child with Column Mapping using below code.
#Data
#Entity
#Table(name = "Parent")
public class Parent{
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
#Column(name = "ParentKey", nullable = false, length = 20)
private Long parentKey;
#Column(name = "ParentID", nullable = true, length = 60)
private String parentID;
#OneToMany(cascade = CascadeType.ALL)
#JoinColumn(name = "ParentKey", nullable = false)
private Set<Child> childSet = new HashSet<>(0);
}
#Data
#Entity
#Table(name = "Child")
public class Child {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private Long childKey;
private String ChildID;
}
I have a scenario where I receive only child records with parent ID. I lookup parent and want to use same child object and repository for saving additional child records. Since there is no reference for parent key, how can I achieve without duplicating child object.
Child Object does not have ParentKey. I do not want to make any changes to Parent when I am loading child records only.
I am using mySQL.
Thanks
First, you need a way to query DB that will get you Parent entity by parentID. If you are using spring data jpa module, you can add the following method to a ParentRepository
Optional<Parent> findByParentID(String parentID);
Assuming your service method looks like this, you first retrieve Parent from DB using parentID and then you can add children to that parent.
public void saveChildren(String parentID, Set<Child> children) {
Parent parent = parentRepository.findByParentID(parentID)
.orElseThrow(() -> <Your excp that says parent not found by parentID>);
// assuming you have filtered out duplicates, now you can save remaining as
parent.getChildSet().addAll(children);
parentRepository.save(parent);
}
Let's say I have the following "parent" pojo...
#Entity
#Table(name = "parent")
public class Parent{
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
#OneToMany(fetch=FetchType.LAZY, mappedBy = "parent", cascade = {CascadeType.ALL})
#JsonIgnoreProperties("parent")
List<Child> children;
}
and I have the following child POJO :
#Entity
#Table(name = "child")
public class Child{
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
#ManyToOne
#JoinColumn(name="parent_id")
private Parent parent;
}
The result of this will be that I have two tables, and my jpa repository will perform queries using the parent_id field within the child table.
However, What if I want it be like a lookup, where by there is a third table for the relationship, where I have the child id and the parent id as a row, and that would be the relationship? can I modify my spring - jpa / hibernate setup for that? If so, some help would be appreciated!
I cannot figure out how to simply relate a child entity to and existing parent.
#Entity
#Table(name = "parent")
#Document(indexName = "parent")
public class Parent implements Serializable {
#Id
#GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "sequenceGenerator")
#SequenceGenerator(name = "sequenceGenerator")
private Long id;
#Column(name = "name")
private String name;
#OneToOne(fetch = FetchType.EAGER, cascade = CascadeType.ALL)
#JoinColumn(unique = true)
private Child child;
//getters, setters
}
Child
#Entity
#Table(name = "child")
#Document(indexName = "child")
public class Child implements Serializable {
#Id
#GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "sequenceGenerator")
#SequenceGenerator(name = "sequenceGenerator")
private Long id;
#Column(name = "name")
private String name;
#OneToOne(mappedBy = "child")
private Parent parent;
//getters, setters
}
These are the two basic models.
The parent already exists within the database, and I want to add a new child in relation.
Child childEntity = childRepository.save(child);
The child is populated as follows:
child.json
{
"name": "smallChild",
"parent": { "id" : "1" }
}
I want to be able to save the child, and have it automatically have a relation to the parent.
I did some really nasty code...
Save the Child without a parent for the ID
Query the database for the parent by ID
Set the child to the parent entity
Save the Parent with the new child
Set the Parent entity TO the child entity
Resave the child with the parent.
This ended up being 6-ish database queries.
I tried watching a few course videos from lynda.com, but it didn't help.
Thanks!
Either the Parent Primary Key or the complete entity is required.
If the parent's ID available, then the extra query for fetching parent object is not required if the goal is to just save.
If you have the parent's Id available with you then you can save the child entity as:
Child child = new Child();
//...
//Setters for child
//...
//Now just create a parent object and set the id to it
Parent p = new Parent();
p.SetId(parentId); // as the parentId is already vailable
child.setParent(p);
Child childEntity = childRepository.save(child);
Maybe a very obvious answer exists but I cant see it.
I have a parent table Parent and a child Table Child.
#Entity
#Table(name="PARENT")
public class Parent implements Serializable {
#Id #GeneratedValue(strategy=GenerationType.IDENTITY)
#Column(name="PARENT_ID")
private int parentId;
#JsonBackReference
#OneToMany(mappedBy="parent", cascade = CascadeType.ALL)
private List<Child> childs;
....
}
And the child entity.
#Entity
#Table(name="CHILD")
public class Child implements Serializable {
#EmbeddedId
private ChildPK id;
#ManyToOne
#JsonManagedReference
#JoinColumn(name="PARENT_ID",insertable = false, updatable = false, referencedColumnName = "PARENT_ID")
private Parent parent;
....
}
The composite primary key being:
#Embeddable
public class ChildPK implements Serializable {
#Column(name="CTGRY_ID", insertable=false, updatable=false)
private int ctgryId;
#Column(name="PARENT_ID", insertable=false, updatable=false)
private int parentId;
....
}
Now in my service method, i set the relation both ways
childItem.setParent(parent);
parent.setChilds(childItemList);
and call save on the entity:
parentDao.save(parent);
This creates a new entry for the PARENT table as expected with a pk generated by the table identity. Creates a new insert in the CHILD table as expected with a pk generated by the table identity.
However, the fk of the child entry should have been the parentId, but it comes as 0!
Am i missing something?
Although this problem is not unique, when I tried looking for similar issues online, few of the suggestions didn't appear to be relevant.
Please let me know in case you need more details.
Thanks!
You are making both id's entries not insertable (one must be insertable, or the JPA implementation wont know from where take the id):
#ManyToOne
#JsonManagedReference
#JoinColumn(name="PARENT_ID", insertable = false, updatable = false, referencedColumnName = "PARENT_ID")
private Parent parent;
And
#Column(name="PARENT_ID", insertable=false, updatable=false)
private int parentId;
You should remove the insertable = false from parent object (first example).
Other option is removing the insertable false from the second one and making it "by hand" in the #prepersist:
#PrePersist
protected setIdsBeforeSave() {
this.id = new ChildPK(parent.Id, categoryId);
}
Edit
Option 1
#Entity
#Table(name="CHILD")
public class Child implements Serializable {
#EmbeddedId
private ChildPK id;
#ManyToOne
#JsonManagedReference
#JoinColumn(name="PARENT_ID", referencedColumnName = "PARENT_ID")
private Parent parent;
....
}
And the other classes remain the same
Option 2
#Entity
#Table(name="CHILD")
public class Child implements Serializable {
#EmbeddedId
private ChildPK id;
....
#PrePersist
protected void setIdsBeforeSave() {
//You set the parent ID, so wont be null, idk what category means, that why i just put the 0
this.id = new ChildPK(parent.Id, 0);
}
}
Say I have a unidirectional #ManyToOne relationship like the following:
#Entity
public class Parent implements Serializable {
#Id
#GeneratedValue
private long id;
}
#Entity
public class Child implements Serializable {
#Id
#GeneratedValue
private long id;
#ManyToOne
#JoinColumn
private Parent parent;
}
If I have a parent P and children C1...Cn referencing back to P, is there a clean and pretty way in JPA to automatically remove the children C1...Cn when P is removed (i.e. entityManager.remove(P))?
What I'm looking for is a functionality similar to ON DELETE CASCADE in SQL.
If you are using hibernate as your JPA provider you can use the annotation #OnDelete. This annotation will add to the relation the trigger ON DELETE CASCADE, which delegates the deletion of the children to the database.
Example:
public class Parent {
#Id
private long id;
}
public class Child {
#Id
private long id;
#ManyToOne
#OnDelete(action = OnDeleteAction.CASCADE)
private Parent parent;
}
With this solution a unidirectional relationship from the child to the parent is enough to automatically remove all children. This solution does not need any listeners etc. Also a JPQL query like DELETE FROM Parent WHERE id = 1 will remove the children.
Relationships in JPA are always unidirectional, unless you associate the parent with the child in both directions. Cascading REMOVE operations from the parent to the child will require a relation from the parent to the child (not just the opposite).
You'll therefore need to do this:
Either, change the unidirectional #ManyToOne relationship to a bi-directional #ManyToOne, or a unidirectional #OneToMany. You can then cascade REMOVE operations so that EntityManager.remove will remove the parent and the children. You can also specify orphanRemoval as true, to delete any orphaned children when the child entity in the parent collection is set to null, i.e. remove the child when it is not present in any parent's collection.
Or, specify the foreign key constraint in the child table as ON DELETE CASCADE. You'll need to invoke EntityManager.clear() after calling EntityManager.remove(parent) as the persistence context needs to be refreshed - the child entities are not supposed to exist in the persistence context after they've been deleted in the database.
Create a bi-directional relationship, like this:
#Entity
public class Parent implements Serializable {
#Id
#GeneratedValue
private long id;
#OneToMany(mappedBy = "parent", cascade = CascadeType.REMOVE)
private Set<Child> children;
}
I have seen in unidirectional #ManytoOne, delete don't work as expected.
When parent is deleted, ideally child should also be deleted, but only parent is deleted and child is NOT deleted and is left as orphan
Technology used are Spring Boot/Spring Data JPA/Hibernate
Sprint Boot : 2.1.2.RELEASE
Spring Data JPA/Hibernate is used to delete row .eg
parentRepository.delete(parent)
ParentRepository extends standard CRUD repository as shown below
ParentRepository extends CrudRepository<T, ID>
Following are my entity class
#Entity(name = “child”)
public class Child {
#Id
#GeneratedValue
private long id;
#ManyToOne( fetch = FetchType.LAZY, optional = false)
#JoinColumn(name = “parent_id", nullable = false)
#OnDelete(action = OnDeleteAction.CASCADE)
private Parent parent;
}
#Entity(name = “parent”)
public class Parent {
#Id
#GeneratedValue
private long id;
#Column(nullable = false, length = 50)
private String firstName;
}
Use this way to delete only one side
#ManyToOne(cascade=CascadeType.PERSIST, fetch = FetchType.LAZY)
// #JoinColumn(name = "qid")
#JoinColumn(name = "qid", referencedColumnName = "qid", foreignKey = #ForeignKey(name = "qid"), nullable = false)
// #JsonIgnore
#JsonBackReference
private QueueGroup queueGroup;
#Cascade(org.hibernate.annotations.CascadeType.DELETE_ORPHAN)
Given annotation worked for me. Can have a try
For Example :-
public class Parent{
#Id
#GeneratedValue(strategy=GenerationType.AUTO)
#Column(name="cct_id")
private Integer cct_id;
#OneToMany(cascade=CascadeType.REMOVE, fetch=FetchType.EAGER,mappedBy="clinicalCareTeam", orphanRemoval=true)
#Cascade(org.hibernate.annotations.CascadeType.DELETE_ORPHAN)
private List<Child> childs;
}
public class Child{
#ManyToOne(fetch=FetchType.EAGER)
#JoinColumn(name="cct_id")
private Parent parent;
}
You don't need to use bi-directional association instead of your code, you have just to add CascaType.Remove as a property to ManyToOne annotation, then use #OnDelete(action = OnDeleteAction.CASCADE), it's works fine for me.