Is it possible to use a DB sequence for some column that is not the identifier/is not part of a composite identifier?
I'm using hibernate as jpa provider, and I have a table that has some columns that are generated values (using a sequence), although they are not part of the identifier.
What I want is to use a sequence to create a new value for an entity, where the column for the sequence is NOT (part of) the primary key:
@Entity
@Table(name = "MyTable")
public class MyEntity {
//...
@Id //... etc
public Long getId() {
return id;
}
//note NO @Id here! but this doesn't work...
@GeneratedValue(strategy = GenerationType.AUTO, generator = "myGen")
@SequenceGenerator(name = "myGen", sequenceName = "MY_SEQUENCE")
@Column(name = "SEQ_VAL", unique = false, nullable = false, insertable = true, updatable = true)
public Long getMySequencedValue(){
return myVal;
}
}
Then when I do this:
em.persist(new MyEntity());
the id will be generated, but the mySequenceVal property will be also generated by my JPA provider.
Just to make things clear: I want Hibernate to generate the value for the mySequencedValue property. I know Hibernate can handle database-generated values, but I don't want to use a trigger or any other thing other than Hibernate itself to generate the value for my property. If Hibernate can generate values for primary keys, why can't it generate for a simple property?
If you have a column with UNIQUEIDENTIFIER type and default generation needed on insert but column is not PK
@Generated(GenerationTime.INSERT)
@Column(nullable = false , columnDefinition="UNIQUEIDENTIFIER")
private String uuidValue;
In db you will have
CREATE TABLE operation.Table1
(
Id INT IDENTITY (1,1) NOT NULL,
UuidValue UNIQUEIDENTIFIER DEFAULT NEWID() NOT NULL)
In this case you will not define generator for a value which you need (It will be automatically thanks to columnDefinition="UNIQUEIDENTIFIER"). The same you can try for other column types
Although this is an old thread I want to share my solution and hopefully get some feedback on this. Be warned that I only tested this solution with my local database in some JUnit testcase. So this is not a productive feature so far.
I solved that issue for my by introducing a custom annotation called Sequence with no property. It's just a marker for fields that should be assigned a value from an incremented sequence.
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.FIELD)
public @interface Sequence
{
}
Using this annotation i marked my entities.
public class Area extends BaseEntity implements ClientAware, IssuerAware
{
@Column(name = "areaNumber", updatable = false)
@Sequence
private Integer areaNumber;
....
}
To keep things database independent I introduced an entity called SequenceNumber which holds the sequence current value and the increment size. I chose the className as unique key so each entity class wil get its own sequence.
@Entity
@Table(name = "SequenceNumber", uniqueConstraints = { @UniqueConstraint(columnNames = { "className" }) })
public class SequenceNumber
{
@Id
@Column(name = "className", updatable = false)
private String className;
@Column(name = "nextValue")
private Integer nextValue = 1;
@Column(name = "incrementValue")
private Integer incrementValue = 10;
... some getters and setters ....
}
The last step and the most difficult is a PreInsertListener that handles the sequence number assignment. Note that I used spring as bean container.
@Component
public class SequenceListener implements PreInsertEventListener
{
private static final long serialVersionUID = 7946581162328559098L;
private final static Logger log = Logger.getLogger(SequenceListener.class);
@Autowired
private SessionFactoryImplementor sessionFactoryImpl;
private final Map<String, CacheEntry> cache = new HashMap<>();
@PostConstruct
public void selfRegister()
{
// As you might expect, an EventListenerRegistry is the place with which event listeners are registered
// It is a service so we look it up using the service registry
final EventListenerRegistry eventListenerRegistry = sessionFactoryImpl.getServiceRegistry().getService(EventListenerRegistry.class);
// add the listener to the end of the listener chain
eventListenerRegistry.appendListeners(EventType.PRE_INSERT, this);
}
@Override
public boolean onPreInsert(PreInsertEvent p_event)
{
updateSequenceValue(p_event.getEntity(), p_event.getState(), p_event.getPersister().getPropertyNames());
return false;
}
private void updateSequenceValue(Object p_entity, Object[] p_state, String[] p_propertyNames)
{
try
{
List<Field> fields = ReflectUtil.getFields(p_entity.getClass(), null, Sequence.class);
if (!fields.isEmpty())
{
if (log.isDebugEnabled())
{
log.debug("Intercepted custom sequence entity.");
}
for (Field field : fields)
{
Integer value = getSequenceNumber(p_entity.getClass().getName());
field.setAccessible(true);
field.set(p_entity, value);
setPropertyState(p_state, p_propertyNames, field.getName(), value);
if (log.isDebugEnabled())
{
LogMF.debug(log, "Set {0} property to {1}.", new Object[] { field, value });
}
}
}
}
catch (Exception e)
{
log.error("Failed to set sequence property.", e);
}
}
private Integer getSequenceNumber(String p_className)
{
synchronized (cache)
{
CacheEntry current = cache.get(p_className);
// not in cache yet => load from database
if ((current == null) || current.isEmpty())
{
boolean insert = false;
StatelessSession session = sessionFactoryImpl.openStatelessSession();
session.beginTransaction();
SequenceNumber sequenceNumber = (SequenceNumber) session.get(SequenceNumber.class, p_className);
// not in database yet => create new sequence
if (sequenceNumber == null)
{
sequenceNumber = new SequenceNumber();
sequenceNumber.setClassName(p_className);
insert = true;
}
current = new CacheEntry(sequenceNumber.getNextValue() + sequenceNumber.getIncrementValue(), sequenceNumber.getNextValue());
cache.put(p_className, current);
sequenceNumber.setNextValue(sequenceNumber.getNextValue() + sequenceNumber.getIncrementValue());
if (insert)
{
session.insert(sequenceNumber);
}
else
{
session.update(sequenceNumber);
}
session.getTransaction().commit();
session.close();
}
return current.next();
}
}
private void setPropertyState(Object[] propertyStates, String[] propertyNames, String propertyName, Object propertyState)
{
for (int i = 0; i < propertyNames.length; i++)
{
if (propertyName.equals(propertyNames[i]))
{
propertyStates[i] = propertyState;
return;
}
}
}
private static class CacheEntry
{
private int current;
private final int limit;
public CacheEntry(final int p_limit, final int p_current)
{
current = p_current;
limit = p_limit;
}
public Integer next()
{
return current++;
}
public boolean isEmpty()
{
return current >= limit;
}
}
}
As you can see from the above code the listener used one SequenceNumber instance per entity class and reserves a couple of sequence numbers defined by the incrementValue of the SequenceNumber entity. If it runs out of sequence numbers it loads the SequenceNumber entity for the target class and reserves incrementValue values for the next calls. This way I do not need to query the database each time a sequence value is needed. Note the StatelessSession that is being opened for reserving the next set of sequence numbers. You cannot use the same session the target entity is currently persisted since this would lead to a ConcurrentModificationException in the EntityPersister.
Hope this helps someone.
I want to provide an alternative next to @Morten Berg's accepted solution, which worked better for me.
This approach allows to define the field with the actually desired Number type - Long in my use case - instead of GeneralSequenceNumber. This can be useful, e.g. for JSON (de-)serialization.
The downside is that it requires a little more database overhead.
First, we need an ActualEntity in which we want to auto-increment generated of type Long:
// ...
@Entity
public class ActualEntity {
@Id
// ...
Long id;
@Column(unique = true, updatable = false, nullable = false)
Long generated;
// ...
}
Next, we need a helper entity Generated. I placed it package-private next to ActualEntity, to keep it an implementation detail of the package:
@Entity
class Generated {
@Id
@GeneratedValue(strategy = SEQUENCE, generator = "seq")
@SequenceGenerator(name = "seq", initialValue = 1, allocationSize = 1)
Long id;
}
Finally, we need a place to hook in right before we save the ActualEntity. There, we create and persist aGenerated instance. This then provides a database-sequence generated id of type Long. We make use of this value by writing it to ActualEntity.generated.
In my use case, I implemented this using a Spring Data REST @RepositoryEventHandler, which get's called right before the ActualEntity get's persisted. It should demonstrate the principle:
@Component
@RepositoryEventHandler
public class ActualEntityHandler {
@Autowired
EntityManager entityManager;
@Transactional
@HandleBeforeCreate
public void generate(ActualEntity entity) {
Generated generated = new Generated();
entityManager.persist(generated);
entity.setGlobalId(generated.getId());
entityManager.remove(generated);
}
}
I didn't test it in a real-life application, so please enjoy with care.
Although this is an old thread I want to share my solution and hopefully get some feedback on this. Be warned that I only tested this solution with my local database in some JUnit testcase. So this is not a productive feature so far.
I solved that issue for my by introducing a custom annotation called Sequence with no property. It's just a marker for fields that should be assigned a value from an incremented sequence.
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.FIELD)
public @interface Sequence
{
}
Using this annotation i marked my entities.
public class Area extends BaseEntity implements ClientAware, IssuerAware
{
@Column(name = "areaNumber", updatable = false)
@Sequence
private Integer areaNumber;
....
}
To keep things database independent I introduced an entity called SequenceNumber which holds the sequence current value and the increment size. I chose the className as unique key so each entity class wil get its own sequence.
@Entity
@Table(name = "SequenceNumber", uniqueConstraints = { @UniqueConstraint(columnNames = { "className" }) })
public class SequenceNumber
{
@Id
@Column(name = "className", updatable = false)
private String className;
@Column(name = "nextValue")
private Integer nextValue = 1;
@Column(name = "incrementValue")
private Integer incrementValue = 10;
... some getters and setters ....
}
The last step and the most difficult is a PreInsertListener that handles the sequence number assignment. Note that I used spring as bean container.
@Component
public class SequenceListener implements PreInsertEventListener
{
private static final long serialVersionUID = 7946581162328559098L;
private final static Logger log = Logger.getLogger(SequenceListener.class);
@Autowired
private SessionFactoryImplementor sessionFactoryImpl;
private final Map<String, CacheEntry> cache = new HashMap<>();
@PostConstruct
public void selfRegister()
{
// As you might expect, an EventListenerRegistry is the place with which event listeners are registered
// It is a service so we look it up using the service registry
final EventListenerRegistry eventListenerRegistry = sessionFactoryImpl.getServiceRegistry().getService(EventListenerRegistry.class);
// add the listener to the end of the listener chain
eventListenerRegistry.appendListeners(EventType.PRE_INSERT, this);
}
@Override
public boolean onPreInsert(PreInsertEvent p_event)
{
updateSequenceValue(p_event.getEntity(), p_event.getState(), p_event.getPersister().getPropertyNames());
return false;
}
private void updateSequenceValue(Object p_entity, Object[] p_state, String[] p_propertyNames)
{
try
{
List<Field> fields = ReflectUtil.getFields(p_entity.getClass(), null, Sequence.class);
if (!fields.isEmpty())
{
if (log.isDebugEnabled())
{
log.debug("Intercepted custom sequence entity.");
}
for (Field field : fields)
{
Integer value = getSequenceNumber(p_entity.getClass().getName());
field.setAccessible(true);
field.set(p_entity, value);
setPropertyState(p_state, p_propertyNames, field.getName(), value);
if (log.isDebugEnabled())
{
LogMF.debug(log, "Set {0} property to {1}.", new Object[] { field, value });
}
}
}
}
catch (Exception e)
{
log.error("Failed to set sequence property.", e);
}
}
private Integer getSequenceNumber(String p_className)
{
synchronized (cache)
{
CacheEntry current = cache.get(p_className);
// not in cache yet => load from database
if ((current == null) || current.isEmpty())
{
boolean insert = false;
StatelessSession session = sessionFactoryImpl.openStatelessSession();
session.beginTransaction();
SequenceNumber sequenceNumber = (SequenceNumber) session.get(SequenceNumber.class, p_className);
// not in database yet => create new sequence
if (sequenceNumber == null)
{
sequenceNumber = new SequenceNumber();
sequenceNumber.setClassName(p_className);
insert = true;
}
current = new CacheEntry(sequenceNumber.getNextValue() + sequenceNumber.getIncrementValue(), sequenceNumber.getNextValue());
cache.put(p_className, current);
sequenceNumber.setNextValue(sequenceNumber.getNextValue() + sequenceNumber.getIncrementValue());
if (insert)
{
session.insert(sequenceNumber);
}
else
{
session.update(sequenceNumber);
}
session.getTransaction().commit();
session.close();
}
return current.next();
}
}
private void setPropertyState(Object[] propertyStates, String[] propertyNames, String propertyName, Object propertyState)
{
for (int i = 0; i < propertyNames.length; i++)
{
if (propertyName.equals(propertyNames[i]))
{
propertyStates[i] = propertyState;
return;
}
}
}
private static class CacheEntry
{
private int current;
private final int limit;
public CacheEntry(final int p_limit, final int p_current)
{
current = p_current;
limit = p_limit;
}
public Integer next()
{
return current++;
}
public boolean isEmpty()
{
return current >= limit;
}
}
}
As you can see from the above code the listener used one SequenceNumber instance per entity class and reserves a couple of sequence numbers defined by the incrementValue of the SequenceNumber entity. If it runs out of sequence numbers it loads the SequenceNumber entity for the target class and reserves incrementValue values for the next calls. This way I do not need to query the database each time a sequence value is needed. Note the StatelessSession that is being opened for reserving the next set of sequence numbers. You cannot use the same session the target entity is currently persisted since this would lead to a ConcurrentModificationException in the EntityPersister.
Hope this helps someone.
I've been in a situation like you (JPA/Hibernate sequence for non @Id field) and I ended up creating a trigger in my db schema that add a unique sequence number on insert. I just never got it to work with JPA/Hibernate
If you have a column with UNIQUEIDENTIFIER type and default generation needed on insert but column is not PK
@Generated(GenerationTime.INSERT)
@Column(nullable = false , columnDefinition="UNIQUEIDENTIFIER")
private String uuidValue;
In db you will have
CREATE TABLE operation.Table1
(
Id INT IDENTITY (1,1) NOT NULL,
UuidValue UNIQUEIDENTIFIER DEFAULT NEWID() NOT NULL)
In this case you will not define generator for a value which you need (It will be automatically thanks to columnDefinition="UNIQUEIDENTIFIER"). The same you can try for other column types
I know this is a very old question, but it's showed firstly upon the results and jpa has changed a lot since the question.
The right way to do it now is with the @Generated annotation. You can define the sequence, set the default in the column to that sequence and then map the column as:
@Generated(GenerationTime.INSERT)
@Column(name = "column_name", insertable = false)
As a followup here's how I got it to work:
@Override public Long getNextExternalId() {
BigDecimal seq =
(BigDecimal)((List)em.createNativeQuery("select col_msd_external_id_seq.nextval from dual").getResultList()).get(0);
return seq.longValue();
}
"I don't want to use a trigger or any other thing other than Hibernate itself to generate the value for my property"
In that case, how about creating an implementation of UserType which generates the required value, and configuring the metadata to use that UserType for persistence of the mySequenceVal property?
I fixed the generation of UUID (or sequences) with Hibernate using @PrePersist annotation:
@PrePersist
public void initializeUUID() {
if (uuid == null) {
uuid = UUID.randomUUID().toString();
}
}
I've been in a situation like you (JPA/Hibernate sequence for non @Id field) and I ended up creating a trigger in my db schema that add a unique sequence number on insert. I just never got it to work with JPA/Hibernate
"I don't want to use a trigger or any other thing other than Hibernate itself to generate the value for my property"
In that case, how about creating an implementation of UserType which generates the required value, and configuring the metadata to use that UserType for persistence of the mySequenceVal property?
I run in the same situation like you and I also didn't find any serious answers if it is basically possible to generate non-id propertys with JPA or not.
My solution is to call the sequence with a native JPA query to set the property by hand before persisiting it.
This is not satisfying but it works as a workaround for the moment.
Mario
I was struggling with this today, was able to solve using this
@Generated(GenerationTime.INSERT)
@Column(name = "internal_id", columnDefinition = "serial", updatable = false)
private int internalId;
I've found this specific note in session 9.1.9 GeneratedValue Annotation from JPA specification: "[43] Portable applications should not use the GeneratedValue annotation on other persistent fields or properties." So, I presume that it is not possible to auto generate value for non primary key values at least using simply JPA.
Hibernate definitely supports this. From the docs:
"Generated properties are properties which have their values generated by the database. Typically, Hibernate applications needed to refresh objects which contain any properties for which the database was generating values. Marking properties as generated, however, lets the application delegate this responsibility to Hibernate. Essentially, whenever Hibernate issues an SQL INSERT or UPDATE for an entity which has defined generated properties, it immediately issues a select afterwards to retrieve the generated values."
For properties generated on insert only, your property mapping (.hbm.xml) would look like:
<property name="foo" generated="insert"/>
For properties generated on insert and update your property mapping (.hbm.xml) would look like:
<property name="foo" generated="always"/>
Unfortunately, I don't know JPA, so I don't know if this feature is exposed via JPA (I suspect possibly not)
Alternatively, you should be able to exclude the property from inserts and updates, and then "manually" call session.refresh( obj ); after you have inserted/updated it to load the generated value from the database.
This is how you would exclude the property from being used in insert and update statements:
<property name="foo" update="false" insert="false"/>
Again, I don't know if JPA exposes these Hibernate features, but Hibernate does support them.
I found that @Column(columnDefinition="serial") works perfect but only for PostgreSQL. For me this was perfect solution, because second entity is "ugly" option.
A call to saveAndFlush on the entity is also necessary, and save won't be enough to populate the value from the DB.
After spending hours, this neatly helped me to solve my problem:
For Oracle 12c:
ID NUMBER GENERATED as IDENTITY
For H2:
ID BIGINT GENERATED as auto_increment
Also make:
@Column(insertable = false)
This is not the same as using a sequence. When using a sequence, you are not inserting or updating anything. You are simply retrieving the next sequence value. It looks like hibernate does not support it.
I've found this specific note in session 9.1.9 GeneratedValue Annotation from JPA specification: "[43] Portable applications should not use the GeneratedValue annotation on other persistent fields or properties." So, I presume that it is not possible to auto generate value for non primary key values at least using simply JPA.
This is not the same as using a sequence. When using a sequence, you are not inserting or updating anything. You are simply retrieving the next sequence value. It looks like hibernate does not support it.
I run in the same situation like you and I also didn't find any serious answers if it is basically possible to generate non-id propertys with JPA or not.
My solution is to call the sequence with a native JPA query to set the property by hand before persisiting it.
This is not satisfying but it works as a workaround for the moment.
Mario
I was struggling with this today, was able to solve using this
@Generated(GenerationTime.INSERT)
@Column(name = "internal_id", columnDefinition = "serial", updatable = false)
private int internalId;
I've been in a situation like you (JPA/Hibernate sequence for non @Id field) and I ended up creating a trigger in my db schema that add a unique sequence number on insert. I just never got it to work with JPA/Hibernate
I have found a workaround for this on MySql databases using @PostConstruct and JdbcTemplate in a Spring application. It may be doable with other databases but the use case that I will present is based on my experience with MySql, as it uses auto_increment.
First, I had tried defining a column as auto_increment using the ColumnDefinition property of the @Column annotation, but it was not working as the column needed to be an key in order to be auto incremental, but apparently the column wouldn't be defined as an index until after it was defined, causing a deadlock.
Here is where I came with the idea of creating the column without the auto_increment definition, and adding it after the database was created. This is possible using the @PostConstruct annotation, which causes a method to be invoked right after the application has initialized the beans, coupled with JdbcTemplate's update method.
The code is as follows:
In My Entity:
@Entity
@Table(name = "MyTable", indexes = { @Index(name = "my_index", columnList = "mySequencedValue") })
public class MyEntity {
//...
@Column(columnDefinition = "integer unsigned", nullable = false, updatable = false, insertable = false)
private Long mySequencedValue;
//...
}
In a PostConstructComponent class:
@Component
public class PostConstructComponent {
@Autowired
private JdbcTemplate jdbcTemplate;
@PostConstruct
public void makeMyEntityMySequencedValueAutoIncremental() {
jdbcTemplate.update("alter table MyTable modify mySequencedValue int unsigned auto_increment");
}
}
"I don't want to use a trigger or any other thing other than Hibernate itself to generate the value for my property"
In that case, how about creating an implementation of UserType which generates the required value, and configuring the metadata to use that UserType for persistence of the mySequenceVal property?
As a followup here's how I got it to work:
@Override public Long getNextExternalId() {
BigDecimal seq =
(BigDecimal)((List)em.createNativeQuery("select col_msd_external_id_seq.nextval from dual").getResultList()).get(0);
return seq.longValue();
}
I have found a workaround for this on MySql databases using @PostConstruct and JdbcTemplate in a Spring application. It may be doable with other databases but the use case that I will present is based on my experience with MySql, as it uses auto_increment.
First, I had tried defining a column as auto_increment using the ColumnDefinition property of the @Column annotation, but it was not working as the column needed to be an key in order to be auto incremental, but apparently the column wouldn't be defined as an index until after it was defined, causing a deadlock.
Here is where I came with the idea of creating the column without the auto_increment definition, and adding it after the database was created. This is possible using the @PostConstruct annotation, which causes a method to be invoked right after the application has initialized the beans, coupled with JdbcTemplate's update method.
The code is as follows:
In My Entity:
@Entity
@Table(name = "MyTable", indexes = { @Index(name = "my_index", columnList = "mySequencedValue") })
public class MyEntity {
//...
@Column(columnDefinition = "integer unsigned", nullable = false, updatable = false, insertable = false)
private Long mySequencedValue;
//...
}
In a PostConstructComponent class:
@Component
public class PostConstructComponent {
@Autowired
private JdbcTemplate jdbcTemplate;
@PostConstruct
public void makeMyEntityMySequencedValueAutoIncremental() {
jdbcTemplate.update("alter table MyTable modify mySequencedValue int unsigned auto_increment");
}
}
I fixed the generation of UUID (or sequences) with Hibernate using @PrePersist annotation:
@PrePersist
public void initializeUUID() {
if (uuid == null) {
uuid = UUID.randomUUID().toString();
}
}
I want to provide an alternative next to @Morten Berg's accepted solution, which worked better for me.
This approach allows to define the field with the actually desired Number type - Long in my use case - instead of GeneralSequenceNumber. This can be useful, e.g. for JSON (de-)serialization.
The downside is that it requires a little more database overhead.
First, we need an ActualEntity in which we want to auto-increment generated of type Long:
// ...
@Entity
public class ActualEntity {
@Id
// ...
Long id;
@Column(unique = true, updatable = false, nullable = false)
Long generated;
// ...
}
Next, we need a helper entity Generated. I placed it package-private next to ActualEntity, to keep it an implementation detail of the package:
@Entity
class Generated {
@Id
@GeneratedValue(strategy = SEQUENCE, generator = "seq")
@SequenceGenerator(name = "seq", initialValue = 1, allocationSize = 1)
Long id;
}
Finally, we need a place to hook in right before we save the ActualEntity. There, we create and persist aGenerated instance. This then provides a database-sequence generated id of type Long. We make use of this value by writing it to ActualEntity.generated.
In my use case, I implemented this using a Spring Data REST @RepositoryEventHandler, which get's called right before the ActualEntity get's persisted. It should demonstrate the principle:
@Component
@RepositoryEventHandler
public class ActualEntityHandler {
@Autowired
EntityManager entityManager;
@Transactional
@HandleBeforeCreate
public void generate(ActualEntity entity) {
Generated generated = new Generated();
entityManager.persist(generated);
entity.setGlobalId(generated.getId());
entityManager.remove(generated);
}
}
I didn't test it in a real-life application, so please enjoy with care.
Hibernate definitely supports this. From the docs:
"Generated properties are properties which have their values generated by the database. Typically, Hibernate applications needed to refresh objects which contain any properties for which the database was generating values. Marking properties as generated, however, lets the application delegate this responsibility to Hibernate. Essentially, whenever Hibernate issues an SQL INSERT or UPDATE for an entity which has defined generated properties, it immediately issues a select afterwards to retrieve the generated values."
For properties generated on insert only, your property mapping (.hbm.xml) would look like:
<property name="foo" generated="insert"/>
For properties generated on insert and update your property mapping (.hbm.xml) would look like:
<property name="foo" generated="always"/>
Unfortunately, I don't know JPA, so I don't know if this feature is exposed via JPA (I suspect possibly not)
Alternatively, you should be able to exclude the property from inserts and updates, and then "manually" call session.refresh( obj ); after you have inserted/updated it to load the generated value from the database.
This is how you would exclude the property from being used in insert and update statements:
<property name="foo" update="false" insert="false"/>
Again, I don't know if JPA exposes these Hibernate features, but Hibernate does support them.
"I don't want to use a trigger or any other thing other than Hibernate itself to generate the value for my property"
In that case, how about creating an implementation of UserType which generates the required value, and configuring the metadata to use that UserType for persistence of the mySequenceVal property?
Hibernate definitely supports this. From the docs:
"Generated properties are properties which have their values generated by the database. Typically, Hibernate applications needed to refresh objects which contain any properties for which the database was generating values. Marking properties as generated, however, lets the application delegate this responsibility to Hibernate. Essentially, whenever Hibernate issues an SQL INSERT or UPDATE for an entity which has defined generated properties, it immediately issues a select afterwards to retrieve the generated values."
For properties generated on insert only, your property mapping (.hbm.xml) would look like:
<property name="foo" generated="insert"/>
For properties generated on insert and update your property mapping (.hbm.xml) would look like:
<property name="foo" generated="always"/>
Unfortunately, I don't know JPA, so I don't know if this feature is exposed via JPA (I suspect possibly not)
Alternatively, you should be able to exclude the property from inserts and updates, and then "manually" call session.refresh( obj ); after you have inserted/updated it to load the generated value from the database.
This is how you would exclude the property from being used in insert and update statements:
<property name="foo" update="false" insert="false"/>
Again, I don't know if JPA exposes these Hibernate features, but Hibernate does support them.
Looks like thread is old, I just wanted to add my solution here(Using AspectJ - AOP in spring).
Solution is to create a custom annotation @InjectSequenceValue as follows.
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.FIELD)
public @interface InjectSequenceValue {
String sequencename();
}
Now you can annotate any field in entity, so that the underlying field (Long/Integer) value will be injected at runtime using the nextvalue of the sequence.
Annotate like this.
//serialNumber will be injected dynamically, with the next value of the serialnum_sequence.
@InjectSequenceValue(sequencename = "serialnum_sequence")
Long serialNumber;
So far we have marked the field we need to inject the sequence value.So we will look how to inject the sequence value to the marked fields, this is done by creating the point cut in AspectJ.
We will trigger the injection just before the save/persist method is being executed.This is done in the below class.
@Aspect
@Configuration
public class AspectDefinition {
@Autowired
JdbcTemplate jdbcTemplate;
//@Before("execution(* org.hibernate.session.save(..))") Use this for Hibernate.(also include session.save())
@Before("execution(* org.springframework.data.repository.CrudRepository.save(..))") //This is for JPA.
public void generateSequence(JoinPoint joinPoint){
Object [] aragumentList=joinPoint.getArgs(); //Getting all arguments of the save
for (Object arg :aragumentList ) {
if (arg.getClass().isAnnotationPresent(Entity.class)){ // getting the Entity class
Field[] fields = arg.getClass().getDeclaredFields();
for (Field field : fields) {
if (field.isAnnotationPresent(InjectSequenceValue.class)) { //getting annotated fields
field.setAccessible(true);
try {
if (field.get(arg) == null){ // Setting the next value
String sequenceName=field.getAnnotation(InjectSequenceValue.class).sequencename();
long nextval=getNextValue(sequenceName);
System.out.println("Next value :"+nextval); //TODO remove sout.
field.set(arg, nextval);
}
} catch (Exception e) {
e.printStackTrace();
}
}
}
}
}
}
/**
* This method fetches the next value from sequence
* @param sequence
* @return
*/
public long getNextValue(String sequence){
long sequenceNextVal=0L;
SqlRowSet sqlRowSet= jdbcTemplate.queryForRowSet("SELECT "+sequence+".NEXTVAL as value FROM DUAL");
while (sqlRowSet.next()){
sequenceNextVal=sqlRowSet.getLong("value");
}
return sequenceNextVal;
}
}
Now you can annotate any Entity as below.
@Entity
@Table(name = "T_USER")
public class UserEntity {
@Id
@SequenceGenerator(sequenceName = "userid_sequence",name = "this_seq")
@GeneratedValue(strategy = GenerationType.SEQUENCE,generator = "this_seq")
Long id;
String userName;
String password;
@InjectSequenceValue(sequencename = "serialnum_sequence") // this will be injected at the time of saving.
Long serialNumber;
String name;
}
I run in the same situation like you and I also didn't find any serious answers if it is basically possible to generate non-id propertys with JPA or not.
My solution is to call the sequence with a native JPA query to set the property by hand before persisiting it.
This is not satisfying but it works as a workaround for the moment.
Mario
After spending hours, this neatly helped me to solve my problem:
For Oracle 12c:
ID NUMBER GENERATED as IDENTITY
For H2:
ID BIGINT GENERATED as auto_increment
Also make:
@Column(insertable = false)
Looks like thread is old, I just wanted to add my solution here(Using AspectJ - AOP in spring).
Solution is to create a custom annotation @InjectSequenceValue as follows.
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.FIELD)
public @interface InjectSequenceValue {
String sequencename();
}
Now you can annotate any field in entity, so that the underlying field (Long/Integer) value will be injected at runtime using the nextvalue of the sequence.
Annotate like this.
//serialNumber will be injected dynamically, with the next value of the serialnum_sequence.
@InjectSequenceValue(sequencename = "serialnum_sequence")
Long serialNumber;
So far we have marked the field we need to inject the sequence value.So we will look how to inject the sequence value to the marked fields, this is done by creating the point cut in AspectJ.
We will trigger the injection just before the save/persist method is being executed.This is done in the below class.
@Aspect
@Configuration
public class AspectDefinition {
@Autowired
JdbcTemplate jdbcTemplate;
//@Before("execution(* org.hibernate.session.save(..))") Use this for Hibernate.(also include session.save())
@Before("execution(* org.springframework.data.repository.CrudRepository.save(..))") //This is for JPA.
public void generateSequence(JoinPoint joinPoint){
Object [] aragumentList=joinPoint.getArgs(); //Getting all arguments of the save
for (Object arg :aragumentList ) {
if (arg.getClass().isAnnotationPresent(Entity.class)){ // getting the Entity class
Field[] fields = arg.getClass().getDeclaredFields();
for (Field field : fields) {
if (field.isAnnotationPresent(InjectSequenceValue.class)) { //getting annotated fields
field.setAccessible(true);
try {
if (field.get(arg) == null){ // Setting the next value
String sequenceName=field.getAnnotation(InjectSequenceValue.class).sequencename();
long nextval=getNextValue(sequenceName);
System.out.println("Next value :"+nextval); //TODO remove sout.
field.set(arg, nextval);
}
} catch (Exception e) {
e.printStackTrace();
}
}
}
}
}
}
/**
* This method fetches the next value from sequence
* @param sequence
* @return
*/
public long getNextValue(String sequence){
long sequenceNextVal=0L;
SqlRowSet sqlRowSet= jdbcTemplate.queryForRowSet("SELECT "+sequence+".NEXTVAL as value FROM DUAL");
while (sqlRowSet.next()){
sequenceNextVal=sqlRowSet.getLong("value");
}
return sequenceNextVal;
}
}
Now you can annotate any Entity as below.
@Entity
@Table(name = "T_USER")
public class UserEntity {
@Id
@SequenceGenerator(sequenceName = "userid_sequence",name = "this_seq")
@GeneratedValue(strategy = GenerationType.SEQUENCE,generator = "this_seq")
Long id;
String userName;
String password;
@InjectSequenceValue(sequencename = "serialnum_sequence") // this will be injected at the time of saving.
Long serialNumber;
String name;
}
If you are using postgresql
And i'm using in spring boot 1.5.6
@Column(columnDefinition = "serial")
@Generated(GenerationTime.INSERT)
private Integer orderID;
Hibernate definitely supports this. From the docs:
"Generated properties are properties which have their values generated by the database. Typically, Hibernate applications needed to refresh objects which contain any properties for which the database was generating values. Marking properties as generated, however, lets the application delegate this responsibility to Hibernate. Essentially, whenever Hibernate issues an SQL INSERT or UPDATE for an entity which has defined generated properties, it immediately issues a select afterwards to retrieve the generated values."
For properties generated on insert only, your property mapping (.hbm.xml) would look like:
<property name="foo" generated="insert"/>
For properties generated on insert and update your property mapping (.hbm.xml) would look like:
<property name="foo" generated="always"/>
Unfortunately, I don't know JPA, so I don't know if this feature is exposed via JPA (I suspect possibly not)
Alternatively, you should be able to exclude the property from inserts and updates, and then "manually" call session.refresh( obj ); after you have inserted/updated it to load the generated value from the database.
This is how you would exclude the property from being used in insert and update statements:
<property name="foo" update="false" insert="false"/>
Again, I don't know if JPA exposes these Hibernate features, but Hibernate does support them.
I run in the same situation like you and I also didn't find any serious answers if it is basically possible to generate non-id propertys with JPA or not.
My solution is to call the sequence with a native JPA query to set the property by hand before persisiting it.
This is not satisfying but it works as a workaround for the moment.
Mario
I've been in a situation like you (JPA/Hibernate sequence for non @Id field) and I ended up creating a trigger in my db schema that add a unique sequence number on insert. I just never got it to work with JPA/Hibernate
I know this is a very old question, but it's showed firstly upon the results and jpa has changed a lot since the question.
The right way to do it now is with the @Generated annotation. You can define the sequence, set the default in the column to that sequence and then map the column as:
@Generated(GenerationTime.INSERT)
@Column(name = "column_name", insertable = false)
If you are using postgresql
And i'm using in spring boot 1.5.6
@Column(columnDefinition = "serial")
@Generated(GenerationTime.INSERT)
private Integer orderID;
I found that @Column(columnDefinition="serial") works perfect but only for PostgreSQL. For me this was perfect solution, because second entity is "ugly" option.
A call to saveAndFlush on the entity is also necessary, and save won't be enough to populate the value from the DB.
Source: Stackoverflow.com