Spring Boot
Spring Data
JPA Hibernate
Came across a requirement where JPA ManyToMany relationship table with an extra column. Have looked at StackOverflow and found several questions related to same requirement. Most of the answers on the forums ask for EmbeddedId field with a composite primary key with two columns. I tried the solutions from the forums, here is the code snippet.
#Data
#Entity
#Table (name = "TABLE_A")
public class TableA {
#Id
#Column (name = "table_a_id")
private Integer id;
...
#OneToMany (mappedBy = "pk.tableA")
private List<TableABMapping> mappingTable;
}
#Data
#Entity
#Table (name = "TABLE_B")
public class TableB {
#Id
#Column (name = "table_b_id")
private Integer id;
...
#OneToMany (mappedBy = "pk.tableB")
private List<TableABMapping> mappingTable;
}
#Data
#Entity
#Table (name = "TABLE_A_TABLE_B_MAPPING")
public class TableABMapping implements Serializable {
#EmbeddedId
private MappingKey pk = new MappingKey();
#Column(name = "addon_field")
private Double additionalField;
#Transient
public TableA getTableA() {
return getPk().getTableA();
}
public void setTableA(TableA tableA) {
getPk().setTableA(tableA);
}
#Transient
public TableB getTableB() {
return getPk().getTableB();
}
public void setTableB(TableB tableB) {
getPk().setTableB(tableB);
}
// equals() & hashCode() method override
}
#Data
#Embeddable
public class MappingKey implements Serializable {
#ManyToOne
#JoinColumn(name = "table_a_id", referencedColumnName = "table_a_id")
private TableA tableA;
#ManyToOne
#JoinColumn(name = "table_b_id", referencedColumnName = "table_b_id")
private TableB tableB;
// No argument constructor, two arguments constructor.
// equals() & hashCode() method override
}
Trying save operation from service class like this:
for (TableB tabB : tableA.getTableB()) {
TableABMapping abMapping = new TableABMapping();
abMapping.setTableA(tableA);
abMapping.setProduct(tabB);
abMapping.setAdditionalField(tabB.getAddonField());
if (tableA.getMappingTable() == null) {
tableA.setMappingTable(new ArrayList<TableABMapping>());
}
tableA.getMappingTable().add(abMapping);
}
TableA ta = tableARepository.save(tableA);
System.out.println("TableA.save(): " + ta);
Getting this error on save operation.
Unable to find TableABMapping with id MappingKey(tableA = TableA( ... ), tableB = TableB ( ... ))
Both the entities have proper ids at the time of saving the entity. But still it throws this error. Where I am making mistake?
Is it possible to join two entity cross schema with JPA.
Example:
#Entity
#Table(schema="department")
public class Department{
#Id
Integer departmentId;
String departmentName;
}
#Entity
#Table(schema="student")
public class Student{
#Id
Integer studentId;
String studentName;
#OneToOne
#MapsId("departmentId")
#JoinColumn(name = "departmentId")
Department department;
}
Please advise me how can I do that.
Thank you!
I am trying to create a simple CRUD application using Spring Boot with User, UserEntity, Post, Comment entities.
-> UserEntity is super class of Comment and Post.
-> Each comment has a ManyToOne relationship to a UserEntity (which can be a Post or another Comment)
UserEntity
|
#ManyToOne
createdBy - refers to user table (id)
|
--------------------
| |
| |
Post Comment
|
#ManytoOne
UserEntity - refers to PK(entity_id) of user_entity table as comment can be on post or reply to another comment
On trying to save a comment on post from the CommentService class,
//Controller
#PostMapping(path = "api/v1/addComment")
public void addComment(#RequestBody Comment comment){ commentService.addCommentOnPost(comment); }
//Service
public void addCommentOnEntity(Comment comment){ commentRepos.save(comment); }
the foreign key in comment table (parent_entity_id) referring to entity_id in user_entity table is not getting updated. The value is blank.
On the other hand UserEntity has a manytoone relationship with User -- createdBy -- which is updating foriegn key user_id in user_entity table properly
Can someone guide me what could be wrong, I have been trying since yesterday night but no luck. Have checked some other answers but could not get an answer for this case.
User.java
#Entity
#Table(name="[user]")
public class User {
#Id
#SequenceGenerator(name="student_sequence",
sequenceName = "student_sequence",
allocationSize = 1)
#GeneratedValue(strategy = GenerationType.SEQUENCE,
generator = "student_sequence")
private long id;
private String name;
private String email;
private int age;
private LocalDate DOB;
//Setters and Getters and default constructor
}
UserEntity.java
#Entity
#Inheritance(strategy = InheritanceType.JOINED)
public abstract class UserEntity {
#Id
#SequenceGenerator(sequenceName = "entity_sequence", name="entity_sequence", allocationSize = 1)
#GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "post_sequence")
private long entityId;
private char entityType;
private LocalDate createdOn;
private LocalDate modifiedOn;
#ManyToOne
#JoinColumn(name = "user_id", referencedColumnName = "id")
private User createdBy;
//Setters and Getters and default constructor
}
Post.java
#Entity
public class Post extends UserEntity{
private String postHeading;
private String postBody;
//Setters and Getters and default constructor
}
Comment.java
#Entity
public class Comment extends UserEntity{
private String comment;
#ManyToOne
#JoinColumn(name="parent_entity_id", referencedColumnName = "entityId")
private UserEntity parentEntity;
//Setters and Getters and default constructor
}
and their repositories
#NoRepositoryBean
public interface UserEntityBaseRepos<T extends UserEntity> extends JpaRepository<T, Long>{
Optional<List<T>> findByCreatedBy_Id(Long user_id);
Optional<List<T>> findByEntityId(Long entity_id);
}
#Repository
public interface UserRespository extends JpaRepository<User, Long> {
Optional<User> findUserByEmail(String email);
Optional<User> findUserByName(String name);
}
#Repository
public interface PostRepos extends UserEntityBaseRepos<Post>, JpaRepository<Post, Long> {
}
#Repository
public interface CommentRepos extends UserEntityBaseRepos<Comment>, JpaRepository<Comment, Long> {
}
Json for postComment service
{
"entityType" : "C",
"createdOn" : "2020-02-05",
"createdBy" : {
"id" : 1
},
"comment": "I am the comment",
"parentEntity" : {
"entityId" : 1
}
}
//User with id = 1 and UserEntity(Post) with entityId = 1 available in database.
Here createdBy.id (user id) is getting updated in the user_entity table, but userEntity.entityId is not getting updated in the comment table
You have very complex entity relationships, it seems to me...
Anyway, I found that you added a generator property to the UserEntity entity with a post_sequence value, but I can't find any relationship to the Post entity in your database. This is probably the reason of the breakdown. You have to connect UserEntity to Post as shown on your diagram or change the generator value.
I was able to solve the problem. The issue was in the following piece of code in Comment concrete class
#ManyToOne
#JoinColumn(name="parent_entity_id", referencedColumnName = "entityId")
private UserEntity parentEntity;
and this Json input
"parentEntity" : {
"entityId" : 1
}
It seems the parentEntity in json input was not being parsed. This was solved on placing JsonProperty("parentEntity") above parentEntity in the Json input was being parsed correctly.
However there was another issue. The parentEntity was not being deserialized to UserEntity as UserEntity is an abstract class. I had to use JacksonPolymorphicDeserialization by introducing a new field parentType("P" for post, "C" for comment) along with some Annotations like below to deserialize parentEntity to corresponding concrete class object.
public class Comment extends UserEntity{
private String comment;
#Transient
#JsonProperty("parentType")
private char parentType;
#ManyToOne
#JoinColumn(name="parent_entity_id", referencedColumnName = "entity_id", foreignKey = #ForeignKey(value=ConstraintMode.CONSTRAINT))
#JsonProperty("parentEntity")
#JsonTypeInfo(use = JsonTypeInfo.Id.NAME , property = "parentType", include = JsonTypeInfo.As.EXTERNAL_PROPERTY)
#JsonSubTypes(value = {
#JsonSubTypes.Type(value = Comment.class, name = "C"),
#JsonSubTypes.Type(value = Post.class, name = "P")
})
private UserEntity parentEntity;
reference - Jackson Polymorphic Deserialization via field. I am not really sure how this works. Will try to make sense of it and update the answer.
If anyone knows a better way to deserialize json, do mention it in the comments or as a new answer.
Unable to update entity for optional one to one relationship using spring data jpa(2.1.2.RELEASE) and spring boot(2.1.2.RELEASE)
Getting the error attempted to assign null one-to-one property
#Entity
#Table(name = "table_a")
public class EntityA {
#Id
String id;
String aa;
int bbb;
#Nullable
#OneToOne(mappedBy = "inv", optional = true,cascade = CascadeType.ALL)
EntityB bEntity;
}
#Entity
public class EntityB{
#Id
String id;
String aaa;
String nnnn;
#OneToOne
#MapsId
#JoinColumn(name = "id")
EntityA aEntity;
}
DAO Code as below
Optional eA = entARepo.findById("1234");
EntityA entA= null;
if (eA.isPresent()) {
entA= eA.get();
}
EntityB eB = entA.getBEntity();
if (Objects.isNull(eB)) {
eB= new EntityB();
eB.setAAA("12121");
eB.setAEntity(entA);
entA.setBEntity(entB);
}
repository.save(entA);
}``
I resolved this by using a join table instead of a shared primary key approach. would still to know how to make the shared primary key approach work for optional one to one relationship
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.