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Unique key auto generated in Spring Boot Entity

I have a primary key in my entity table which is autogenerated but now I want unique keys to be auto generated so how to do it
Please help me out.
#Entity
#Table(name = "director")
public class Director {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
#Column(name = "id")
private long id;
//how to make this field auto generated like above one
#Column(name = "subid", unique=true)
private long sub_id;
My database table picture is here please refer

You can use timestamp or static AtomicLong counter as sub_id value. Try to define method with annotation #PrePersist in your entity class and your JPA provider will execute it before persisting an object.
Note: using timestamp in concurrent environment may lead to collisions and values won't be unique.
private final static AtomicLong subIdCounter = new AtomicLong(System.nanoTime());
#PrePersist
void sub_id() {
this.sub_id = subIdCounter.incrementAndGet();
}

After a short study it seems that that Hibernate supports the feature of generated values only with fields annotated with #Id. With #Id and default #generatedValue Hibernate creates - depending on the database and dialect used - appropriate way to generate the value of id field. usually this is something like creating a sequence and setting the column definition like (examples are from Postgres 12):
id bigint not null nextval('director_id_seq'::regclass)
Interesting thing is that this is done by issuing create statement like this:
create table director (id bigserial not null, primary key (id))
So, the column type bigserial actually generates sequence that is used to insert default value to the id column.
There are two options it you want to generate the value for column sub_id as it is generated to the column id. Both are database dependent.
Just create the sequence manually to the database and alter column sub_id to fetch the default value from the sequence.
OR
Change your column definition to use appropriate column type, like:
#Column(name = "subid", insertable = false,
nullable = false, unique = true, columnDefinition = "bigserial")
private long sub_id;
This will cause Hibernate to generate table like:
create table director (id bigserial not null, subid bigserial not null, primary key (id))
and result to a column like:
subid bigint not null nextval('director_subid_seq'::regclass)
But again: this is database specific stuff.
Also note: that JPA is aware only of the value that is stored to the id field. The subid is inserted to the database table but the sub_id field is not populated until entity is refreshed in its persistence context.

JPA/Hibernate: Update Parent column value before inserting child column value

This is my scenario. I have a Parent table Files_Info and a child table Files_Versions.
create table files_info(
id bigint primary key,
name varchar(255) not null,
description varchar(255) not null,
last_modified TIMESTAMP,
latest_version integer default 0 not null
);
create table files_versions(
id bigint primary key,
file_id bigint references files_info(id),
version integer not null,
location text not null,
created TIMESTAMP,
unique(file_id, version)
);
This is mainly to track a file and its various versions. When the user initiates a new file creation (not yet uploaded any version of the file), an entry is made to the files_info table with basic info like name, description. The latest_version will be 0 initially.
Then when the user uploads the first version, an entry is created in the files_versions table for that file_id and the version
value is set as parent's latest_version + 1. Parent's latest_version is now set to 1.
The user can also upload an initial version of the file when he/she initiates a new file creation. In that case, parent record
will be created with latest_version as 1 and also the corresponding version 1 child record.
I do not know how to design this using JPA / Hibernate.
I wrote my Entity and Repository classes and the save methods seem to work independently. But I do not know how to do the simultaneously latest_version updates.
Can this be done using JPA / Hibernate? Or should it be a database trigger?

A trigger is a valid option, but It can be done using JPA/Hibernate.
I'll suggest to use #PrePersist annotation on some method defined at the files_versions entity ... This method will be called by JPA when you execute: EntityManager.persist(FileVersion); and it can be use to update entity's derivative attributes ... In your case, will be the sum of the file last_version + 1 ... Example:
#Entity
#Table(name = "files_info")
public class FileInfo {
}
#Entity
#Table(name = files_versions)
public class FileVersion {
... //some attributes
#Column(name = "version")
private int version;
#ManyToOne
#JoinColumn(name = "file_id")
private FileInfo fileInfo;
... //some getters and setters
#PrePersist
private void setupVersion() {
// fileInfo should be set before of calling persist()!
// fileInfo should increase its lastest Version before of calling persist()!
this.version = this.fileInfo.getLastVersion();
}
}

EntityManager merge using specific column other than id

I'm currently using Spring and Hibernate framework, and have an entity with:
#Id
#GeneratedValue(strategy=GenerationType.IDENTITY)
#Column(name="ID")
private Long id;
#Column(name="ACC_ID")
private Long accId;
Now, in a specific case I'd like to merge an object in the database using column "ACC_ID" instead of "ID", however, I do not want to assign #Id to accId because I do not want to change the entity itself.
Is there anything I can do on the merge function? (But apparently merge takes no other parameter than an object)
entityManager.merge(entityObject)
Thanks in advance for any clue or help. =)

entityManager.merge(entityObject) can be used if it is your primary key based.
If it is another unique constraint you'd have to handle it by yourself. First try to find an entity with that value (with a query).
If a match is found, copy the primary key to your new entity before saving as normal.
For example:
public Entity save(Entity entity, boolean rollback) {
// look for a match, you'll have to implement your own method here
Entity match = getEntityByValue("column_name", entity.getMergeColumn());
if (match != null) {
// copy the primary key
entity.setId(match.getId());
}
// save the entity
save(entity, rollback);
}

Hibernate maps with discrimination column or class name as key

I've been pulling my hair out over this for the best part of a day now, and simply can't find any answers to this problem.
I've got a PostgreSQL schems that looks like this:
+---------+ 1-n +-------------+ 1-1 +------+
| Product |-------->| ProductSpec |-------->| Spec |
+---------+ +-------------+ +------+
This represents a one to many relationship between a Product and its list of Specifications (The reason I don't just use a foreign key in the specifications table into the products table is because specifications can belong to things that aren't in the product inheritance tree, those links are represented by other intersection tables).
Each Specification is a subclass of a Specification class (Weight, Length, NumberOfThings, and so on), with the name of the subclass in question being stored in the Spec table. Each product has a collection of specifications, but each subclass of specification can only appear once. A product can only have one weight (though if you need a weight for the actual product, and a shipping weight for the courier to calculate shipping charges, you can simply subclass ActualWeight and ShippingWeight from the Weight specification).
Using the simplest case, a Set in the Product class, I'm able to construct the object graph correctly from a Hibernate query of the products table. I want to use a Map instead, however, so I can address specific specifications directly. The plan was to use the class name as the key, but I'm having serious issues trying to get it to work. I'm unable to figure out how to use the Java class name as the key, and trying to use the class name as stored in the database as the map key is proving problematic.
As currently implemented, I'm able to query the specifications, and the products individually (if I comment out the code implementing the mapping between products and specifications). I can also query the products with the specifications embedded if I use a set, but if I use a map with the MapKey set to be the specifications class name, I get an exception.
Sep 01, 2013 1:25:55 AM org.hibernate.util.JDBCExceptionReporter
logExceptions WARNING: SQL Error: 0, SQLState: 42P01 Sep 01, 2013
1:25:55 AM org.hibernate.util.JDBCExceptionReporter logExceptions
SEVERE: ERROR: relation "specifications" does not exist Position: 424
I've annotated my (cut down) classes as follows. The product class:
#Entity
#Table (
name="products",
schema="sellable"
)
public abstract class Product extends Sellable {
private Map <String, Specification> specifications = new HashMap <> ();
#OneToMany (fetch = FetchType.EAGER)
#Cascade (CascadeType.SAVE_UPDATE)
#JoinTable (
schema = "sellable",
name = "productspecifications",
joinColumns = {#JoinColumn (name = "sll_id")},
inverseJoinColumns = {#JoinColumn (name = "spc_id")})
#MapKey (name = "className")
private Map <String, Specification> getSpecifications () {
return this.specifications;
}
private Product setSpecifications (Map <String, Specification> specs) {
this.specifications = specs;
return this;
}
}
And the Specification class:
#Entity
#Table (
name="specifications",
schema="sellable",
uniqueConstraints = #UniqueConstraint (columnNames="spc_id")
)
#Inheritance (strategy = InheritanceType.SINGLE_TABLE)
#DiscriminatorColumn (name = "spc_classname", discriminatorType=DiscriminatorType.STRING)
public abstract class Specification implements Serializable {
private Integer specId = null;
private String className = null;
#Id
#Column (name="spc_id", unique=true, nullable=false)
#SequenceGenerator (name = "specifications_spc_id_seq", sequenceName = "sellable.specifications_spc_id_seq", allocationSize = 1)
#GeneratedValue (strategy = GenerationType.SEQUENCE, generator = "specifications_spc_id_seq")
public Integer getSpecId () {
return this.specId;
}
private Specification setSpecId (Integer specId) {
this.specId = specId;
return this;
}
#Column (name="spc_classname", insertable = false, updatable = false, nullable = false)
public String getClassName () {
return this.className;
}
private void setClassName (String className) {
this.className = className;
}
}
The DB schema looks like this:
CREATE TABLE sellable.sellables
(
sll_id serial NOT NULL, -- Sellable ID
sll_date_created timestamp with time zone NOT NULL DEFAULT now(), -- Date the item was created
sll_date_updated timestamp with time zone NOT NULL DEFAULT now(), -- Date the item was last updated
sll_title character varying(255) NOT NULL, -- Title of the item
sll_desc text NOT NULL, -- Textual description of the item
CONSTRAINT sellables_pkey PRIMARY KEY (sll_id)
)
CREATE TABLE sellable.products
(
sll_id integer NOT NULL, -- Sellable ID
mfr_id integer NOT NULL, -- ID of the product manufacturer
CONSTRAINT products_pkey PRIMARY KEY (sll_id),
CONSTRAINT products_mfr_id_fkey FOREIGN KEY (mfr_id)
REFERENCES sellable.manufacturers (mfr_id) MATCH SIMPLE
ON UPDATE NO ACTION ON DELETE NO ACTION,
CONSTRAINT products_sll_id_fkey FOREIGN KEY (sll_id)
REFERENCES sellable.sellables (sll_id) MATCH SIMPLE
ON UPDATE NO ACTION ON DELETE NO ACTION
)
CREATE TABLE sellable.specifications
(
spc_id serial NOT NULL, -- Specification ID
spc_classname character varying(127) NOT NULL, -- Specification subclass
CONSTRAINT specifications_pkey PRIMARY KEY (spc_id)
)
CREATE TABLE sellable.productspecifications
(
ps_id serial NOT NULL, -- Primary key
sll_id integer NOT NULL, -- Product the specification is linked to
spc_id integer NOT NULL, -- Specification the product is associated with
CONSTRAINT productspecifications_pkey PRIMARY KEY (ps_id),
CONSTRAINT productspecifications_sll_id_fkey FOREIGN KEY (sll_id)
REFERENCES sellable.products (sll_id) MATCH SIMPLE
ON UPDATE NO ACTION ON DELETE NO ACTION,
CONSTRAINT productspecifications_spc_id_fkey FOREIGN KEY (spc_id)
REFERENCES sellable.specifications (spc_id) MATCH SIMPLE
ON UPDATE NO ACTION ON DELETE NO ACTION,
CONSTRAINT productspecifications_spc_id_key UNIQUE (spc_id)
)
The query that Hibernate generates is listed below (I've not trimmed this the way I have the classes in case there's something in the unabridged query that is an issue). One obvious problem is that it's trying to query the specifications table without inserting the schema name.
select
bicycle0_.sll_id as sll1_0_3_,
bicycle0_2_.sll_date_created as sll2_0_3_,
bicycle0_2_.sll_date_updated as sll3_0_3_,
bicycle0_2_.sll_desc as sll4_0_3_,
bicycle0_2_.sll_title as sll5_0_3_,
bicycle0_1_.mfr_id as mfr2_1_3_,
bicycle0_.btp_id as btp2_2_3_,
manufactur1_.mfr_id as mfr1_4_0_,
manufactur1_.mfr_name as mfr2_4_0_,
specificat2_.sll_id as sll1_5_,
specificat3_.spc_id as spc2_5_,
(select
a9.spc_classname
from
specifications a9
where
a9.spc_id=specificat2_.spc_id) as formula0_5_,
specificat3_.spc_id as spc2_5_1_,
specificat3_.spc_classname as spc1_5_1_,
specificat3_1_.dec_value as dec1_6_1_,
specificat3_2_.bol_value as bol1_7_1_,
specificat3_3_.int_value as int1_8_1_,
specificat3_4_.str_value as str1_9_1_,
bicycletyp4_.btp_id as btp1_3_2_,
bicycletyp4_.btp_name as btp2_3_2_
from
sellable.bicycles bicycle0_
inner join
sellable.products bicycle0_1_
on bicycle0_.sll_id=bicycle0_1_.sll_id
inner join
sellable.sellables bicycle0_2_
on bicycle0_.sll_id=bicycle0_2_.sll_id
left outer join
sellable.manufacturers manufactur1_
on bicycle0_1_.mfr_id=manufactur1_.mfr_id
left outer join
sellable.productspecifications specificat2_
on bicycle0_.sll_id=specificat2_.sll_id
left outer join
sellable.specifications specificat3_
on specificat2_.spc_id=specificat3_.spc_id
left outer join
sellable.specdecimalvalues specificat3_1_
on specificat3_.spc_id=specificat3_1_.spc_id
left outer join
sellable.specbooleanvalues specificat3_2_
on specificat3_.spc_id=specificat3_2_.spc_id
left outer join
sellable.specintegervalues specificat3_3_
on specificat3_.spc_id=specificat3_3_.spc_id
left outer join
sellable.specstringvalues specificat3_4_
on specificat3_.spc_id=specificat3_4_.spc_id
left outer join
sellable.bicycletypes bicycletyp4_
on bicycle0_.btp_id=bicycletyp4_.btp_id
where
bicycle0_.sll_id=?
The problem is in the sub-query, which isn't getting a schema prepended to the specifications table name.
If anyone knows how to either get the query to be correct, or of using the class name directly as the Java map key, I'd appreciate being told.
EDIT: The reason I want to use a map instead of a set is because I want to directly address items in the specifications collection. If I use sets, the queries generated by Hibernate work, but I don't have an index to access the elements by. The API of the Product object hides the fact that the specifications are stored in a collection and provides getters and setters for each individual specification.
If I make the specifications a set, I have to implement the getters and setters like this:
#Transient
public BigDecimal getActualWeight () {
BigDecimal found = null;
for (Specification spec : this.specifications) {
if (spec instanceof ActualWeightSpec) {
found = ((ActualWeightSpec) spec).getValue ();
break;
}
}
return found;
}
public Product setActualWeight (Number value) {
ActualWeightSpec newWeight = new ActualWeightSpec ();
newWeight.setValue (value);
for (Specification spec : this.specifications) {
if (spec instanceof ActualWeightSpec) {
((ActualWeightSpec) spec).setValue (value);
return this;
}
}
this.specifications.add (newWeight);
return this;
}
Having to iterate over a set to get individual specification records seems a really bad way of accessing those records directly.
I did try maintaining a hashmap internally, and having the getter and setter for the specifications accept and return sets with a conversion taking place in the getter and setter. That way I'd only have to take the hit of iterating the specifications once.
private Product setSpecifications (Set <Specification> specs) {
HashMap <String, Specification> specsMap = new HashMap <> ();
for (Specification spec : specs) {
specsMap.put(spec.getClassName (), spec);
}
this.specifications = specsMap;
return this;
}
This didn't work either, causing Hibernate to throw an exception.
SEVERE: illegal access to loading collection

You could use a internal map of specifications, not bothering the database with the map. Do not initialize the map in getters or setters Hibernate uses, but check in your getters (e.g. getActualWeight) if your transient map has been initialized already. If not, iterate the specs once and build the map. Btw, if there are not too many specs, iterating each time should not hurt too much.

JPA Mapping Multi-Rows with ElementCollection

I'm trying to follow the JPA tutorial and using ElementCollection to record employee phone numbers:
PHONE (table)
OWNER_ID TYPE NUMBER
1 home 792-0001
1 work 494-1234
2 work 892-0005
Short version
What I need is a class like this:
#Entity
#Table(name="Phones")
public class PhoneId {
#Id
#Column(name="owner_id")
long owner_id;
#Embedded
List<Phone> phones;
}
that stores each person's phone numbers in a collection.
Long version
I follow the tutorial code:
#Entity
#Table(name="Phones")
public class PhoneId {
#Id
#Column(name="owner_id")
long owner_id;
#ElementCollection
#CollectionTable(
name="Phones",
joinColumns=#JoinColumn(name="owner_id")
)
List<Phone> phones = new ArrayList<Phone>();
}
#Embeddable
class Phone {
#Column(name="type")
String type = "";
#Column(name="number")
String number = "";
public Phone () {}
public Phone (String type, String number)
{ this.type = type; this.number = number; }
}
with a slight difference that I only keep one table. I tried to use the following code to add records to this table:
public static void main (String[] args) {
EntityManagerFactory entityFactory =
Persistence.createEntityManagerFactory("Tutorial");
EntityManager entityManager = entityFactory.createEntityManager();
// Create new entity
entityManager.getTransaction().begin();
Phone ph = new Phone("home", "001-010-0100");
PhoneId phid = new PhoneId();
phid.phones.add(ph);
entityManager.persist(phid);
entityManager.getTransaction().commit();
entityManager.close();
}
but it keeps throwing exceptions
Internal Exception: org.postgresql.util.PSQLException: ERROR: null
value in column "type" violates not-null constraint Detail: Failing
row contains (0, null, null). Error Code: 0 Call: INSERT INTO Phones
(owner_id) VALUES (?) bind => [1 parameter bound] Query:
InsertObjectQuery(tutorial.Phone1#162e295)
What did I do wrong?

Sadly, i think the slight difference that you only keep one table is the problem here.
Look at the declaration of the PhoneId class (which i would suggest is better called PhoneOwner or something like that):
#Entity
#Table(name="Phones")
public class PhoneId {
When you declare that a class is an entity mapped to a certain table, you are making a set of assertions, of which two are particularly important here. Firstly, that there is one row in the table for each instance of the entity, and vice versa. Secondly, that there is one column in the table for each scalar field of the entity, and vice versa. Both of these are at the heart of the idea of object-relational mapping.
However, in your schema, neither of these assertions hold. In the data you gave:
OWNER_ID TYPE NUMBER
1 home 792-0001
1 work 494-1234
2 work 892-0005
There are two rows corresponding to the entity with owner_id 1, violating the first assertion. There are columns TYPE and NUMBER which are not mapped to fields in the entity, violating the second assertion.
(To be clear, there is nothing wrong with your declaration of the Phone class or the phones field - just the PhoneId entity)
As a result, when your JPA provider tries to insert an instance of PhoneId into the database, it runs into trouble. Because there are no mappings for the TYPE and NUMBER columns in PhoneId, when it generates the SQL for the insert, it does not include values for them. This is why you get the error you see - the provider writes INSERT INTO Phones (owner_id) VALUES (?), which PostgreSQL treats as INSERT INTO Phones (owner_id, type, number) VALUES (?, null, null), which is rejected.
Even if you did manage to insert a row into this table, you would then run into trouble on retrieving an object from it. Say you asked for the instance of PhoneId with owner_id 1. The provider would write SQL amounting to select * from Phones where owner_id = 1, and it would expect that to find exactly one row, which it can map to an object. But it will find two rows!
The solution, i'm afraid, is to use two tables, one for PhoneId, and one for Phone. The table for PhoneId will be trivially simple, but it is necessary for the correct operation of the JPA machinery.
Assuming you rename PhoneId to PhoneOwner, the tables need to look like:
create table PhoneOwner (
owner_id integer primary key
)
create table Phone (
owner_id integer not null references PhoneOwner,
type varchar(255) not null,
number varchar(255) not null,
primary key (owner_id, number)
)
(I've made (owner_id, number) the primary key for Phone, on the assumption that one owner might have more than one number of a given type, but will never have one number recorded under two types. You might prefer (owner_id, type) if that better reflects your domain.)
The entities are then:
#Entity
#Table(name="PhoneOwner")
public class PhoneOwner {
#Id
#Column(name="owner_id")
long id;
#ElementCollection
#CollectionTable(name = "Phone", joinColumns = #JoinColumn(name = "owner_id"))
List<Phone> phones = new ArrayList<Phone>();
}
#Embeddable
class Phone {
#Column(name="type", nullable = false)
String type;
#Column(name="number", nullable = false)
String number;
}
Now, if you really don't want to introduce a table for the PhoneOwner, then you might be able to get out of it using a view. Like this:
create view PhoneOwner as select distinct owner_id from Phone;
As far as the JPA provider can tell, this is a table, and it will support the queries it needs to do to read data.
However, it won't support inserts. If you ever needed to add a phone for an owner who is not currently in the database, you would need to go round the back and insert a row directly into Phone. Not very nice.