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Trigger #OneToMany lazy fetch

I have an ExampleRequest entity that can optionally have one or more ExampleRequestYear. It's currently configured this way (unrelated fields and gettters/setters omitted for brevity, please let me know if you need anything else):
#Entity
#Table(name = "EXAMPLE_REQUEST")
#SequenceGenerator(name = "EXAMPLE_REQUEST_ID_SEQ", sequenceName = "EXAMPLE_REQUEST_ID_SEQ", allocationSize = 1)
#Cacheable(false)
public class ExampleRequest implements Serializable {
#Id
#GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "EXAMPLE_REQUEST_ID_SEQ")
#Column(name="EXAMPLE_REQUEST_ID", nullable = false)
private Long exampleRequestId;
#OneToMany(cascade = CascadeType.ALL, fetch = FetchType.LAZY, mappedBy = "exampleRequest")
private List<ExampleRequestYear> exampleRequestYearList;
public ExampleRequest() {
}
public List<ExampleRequestYear> getExampleRequestYearList() {
if(this.exampleRequestYearList == null){
this.exampleRequestYearList = new ArrayList<ExampleRequestYear>();
}
return this.exampleRequestYearList;
}
public void setExampleRequestYearList(List<ExampleRequestYear> exampleRequestYearList) {
this.exampleRequestYearList = exampleRequestYearList;
}
public ExampleRequestYear addExampleRequestYear(ExampleRequestYear exampleRequestYear) {
getExampleRequestYearList().add(exampleRequestYear);
exampleRequestYear.setExampleRequest(this);
return exampleRequestYear;
}
public ExampleRequestYear removeExampleRequestYear(ExampleRequestYear exampleRequestYear) {
getExampleRequestYearList().remove(exampleRequestYear);
exampleRequestYear.setExampleRequest(null);
return exampleRequestYear;
}
}
#Entity
#Table(name = "EXAMPLE_REQUEST_YEAR")
#IdClass(ExampleRequestYearPK.class)
public class ExampleRequestYear implements Serializable {
#Id
#Column(nullable = false)
private Integer year;
#Id
#ManyToOne
#JoinColumn(name = "EXAMPLE_REQUEST_ID", referencedColumnName = "EXAMPLE_REQUEST_ID")
private ExampleRequest exampleRequest;
public ExampleRequestYear() {
}
public void setExampleRequest(ExampleRequest exampleRequest) {
this.exampleRequest = exampleRequest;
}
public ExampleRequest getExampleRequest() {
return exampleRequest;
}
}
Part of the code was auto-generated by the IDE and I'm still wrapping my head around JPA so there're probably design mistakes all around.
My app works (apparently) when I create a new ExampleRequest:
ExampleRequest exampleRequest = new ExampleRequest();
ExampleRequestYear exampleRequestYear = new ExampleRequestYear(2020);
request.addExampleRequestYear(exampleRequestYear);
However, I can't figure out how to edit an existing ExampleRequest because I'm unsure on how I'm meant to retrieve the linked entities. According to articles I've read, lazy fetching should be automatic, yet when I try this:
ExampleRequest exampleRequest = employeeRequestsController.getExampleRequestById(123);
System.out.println(exampleRequest.getExampleRequestYearList().size());
... I get a null pointer exception upon .size() because the getter runs but neither initialises an empty list, nor retrieves items from DB:
public List<ExampleRequestYear> getExampleRequestYearList() {
if(this.exampleRequestYearList == null){
// Field is null and conditional is entered
this.exampleRequestYearList = new ArrayList<ExampleRequestYear>();
// After initialisation, field is still null!
}
return this.exampleRequestYearList;
}
Also, switch to FetchType.EAGER solves this particular problem entirely. What am I missing?
Further details regarding app design. The Resource classes that handle HTTP requests interact with a set of Controller classes like this:
#Stateless(name = "ISomeActionController", mappedName = "ISomeActionController")
public class SomeActionController implements ISomeActionController {
#EJB
private IFooDAO fooDao;
#EJB
private IBarDAO barDao;
#Override
public ExampleRequest getExampleRequestById(Long exampleRequestId) {
return fooDao.getEntityById(exampleRequestId);
}
}
It's in the DAO classes where EntityManager is injected an used:
#Local
public interface IGenericDAO<T> {
public T persistEntity(T o);
public T persistEntityCommit(T o);
public void removeEntity(T o);
public void removeEntity(long id);
public T mergeEntity(T o);
public List<T> getEntitiesFindAll();
public List<T> getEntitiesFindAllActive();
public T getEntityById(Object id);
}
public interface IFooDAO extends IGenericDAO<ExampleRequest> {
public void flushDAO();
public ExampleRequest getExampleRequestById(Long exampleRequestId);
}
#Stateless(name = "IFooDAO", mappedName = "IFooDAO")
public class FooDAO extends GenericDAO<ExampleRequest> implements IFooDAO {
public FooDAO() {
super(ExampleRequest.class);
}
#Override
public void flushDAO(){
em.flush();
}
#Override
public ExampleRequest getExampleRequestById(Long exampleRequestId){
String sql = "...";
Query query = em.createNativeQuery(sql, ExampleRequest.class);
//...
}
}

Recurrsive loop on method call, unsure if it is related to mapping

I'm having some issues with my entity mapping on these objects. I don't get an exception but it seems like it goes into a recursive loop
public class LabResult implements java.io.Serializable {
private Long labResultId;
private Customer customer;
private LabResultUnprocessed labResultUnprocessed;
public LabResult(){
}
public LabResult(Long labResultId) {
this.labResultId = labResultId;
}
public LabResult(Long labResultId, Customer customer, LabResultUnprocessed labResultUnprocessed) {
this.labResultId = labResultId;
this.customer = customer;
this.labResultUnprocessed = labResultUnprocessed;
}
#OneToOne(fetch=FetchType.LAZY, mappedBy="labResult")
#JoinColumn(name="lab_result_id")
public LabResultUnprocessed getLabResultUnprocessed(){
return labResultUnprocessed;
}
public void setLabResultUnprocessed(LabResultUnprocessed labResultUnprocessed) {
this.labResultUnprocessed = labResultUnprocessed;
}
The next domain is LabResultUnprocessed
#Entity
#Table(name="lab_result_unprocessed"
,schema="public"
)
public class LabResultUnprocessed implements java.io.Serializable {
private LabResult labResult;
private Boolean processedFlag;
public LabResultUnprocessed() {
}
public LabResultUnprocessed(LabResult labResult, Boolean processedFlag) {
this.labResult = labResult;
this.processedFlag = processedFlag;
}
#Id
#OneToOne(fetch=FetchType.LAZY)
#JoinColumn(name="lab_result_id")
public LabResult getLabResult() {
return labResult;
}
public void setLabResult(LabResult labResult) {
this.labResult = labResult;
}
Here is the LabResultUnprocessedRepository
public interface LabResultUnprocessedRepository extends CrudRepository<LabResult, String>{
#Query("select lru from LabResultUnprocessed lru "
+" join fetch lru.labResult lr "
+" where lru.labResult.labResultId = lr.labResultId "
+" and lru.processedFlag = false")
List<LabResultUnprocessed> findAllByProcessedFlag();
In my service when I call this method it seems like it goes into a recursive loop and never hits my breakpoint which is on the actual method call in this 2nd line.
List<LabResultUnprocessed> allUnprocessedResults = new ArrayList<LabResultUnprocessed>();
allUnprocessedResults = labResultUnprocessedRepository.findAllByProcessedFlag();
allUnprocessedResults.forEach(lru -> {
...////

You have two problems in this section:
#OneToOne(fetch=FetchType.LAZY, mappedBy="testResult")
#JoinColumn(name="test_result_id")
mappedBy and #JoinColumn don't go together. One end of the relationship should have one, and the other end should have the other. Neither end should have both. Remove #JoinColumn from this end to fix this.
The value of mappedBy needs to be the name of the field on the other end of the relationship - in this case, labResult.

how to map Many to Many with composite key

I have the following tables
Trainingplan
TrainingplanID int(11) AI PK
Trainer int(11)
Client int(11)
validFrom date
validTo date
type int(11)
TrainingplanExercises
trainingplan int(11) PK
exercise int(11) PK
parameter int(11) PK
value varchar(45)
No I have problems connecting them with Hibernate. I did the following:
package beans;
#Entity
#Table(name = "Trainingplan")
public class Training {
private IntegerProperty id;
private ObjectProperty<Person> client;
private ObjectProperty<Person> trainer;
private ObjectProperty<Date> validFrom;
private ObjectProperty<Date> validTo;
private ObjectProperty<TrainingplanType> type;
private List<TrainingplanExercise> exercises;
public Training(int id, Person client, Person trainer, Date validFrom, Date validTo, TrainingplanType type) {
this.id = new SimpleIntegerProperty(id);
this.client = new SimpleObjectProperty<>(client);
this.trainer = new SimpleObjectProperty<>(trainer);
this.validFrom = new SimpleObjectProperty<>(validFrom);
this.validTo = new SimpleObjectProperty<>(validTo);
this.type = new SimpleObjectProperty<>(type);
exercises = FXCollections.observableArrayList();
}
public Training(Person client, Person trainer, Date validFrom, Date validTo, TrainingplanType type){
this(0, client, trainer, validFrom, validTo, type);
}
public Training(){
this(0, null,null,null,null, null);
}
#OneToOne
#JoinColumn(name = "client")
public Person getClient() {
return client.get();
}
public ObjectProperty<Person> clientProperty() {
return client;
}
public void setClient(Person client) {
this.client.set(client);
}
#OneToOne
#JoinColumn(name = "trainer")
public Person getTrainer() {
return trainer.get();
}
public ObjectProperty<Person> trainerProperty() {
return trainer;
}
public void setTrainer(Person trainer) {
this.trainer.set(trainer);
}
#Column
public Date getValidFrom() {
return validFrom.get();
}
public ObjectProperty<Date> validFromProperty() {
return validFrom;
}
public void setValidFrom(Date validFrom) {
this.validFrom.set(validFrom);
}
#Column
public Date getValidTo() {
return validTo.get();
}
public ObjectProperty<Date> validTillProperty() {
return validTo;
}
public void setValidTo(Date validTill) {
this.validTo.set(validTill);
}
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
#Column(name = "TrainingplanID")
public int getId() {
return id.get();
}
public IntegerProperty idProperty() {
return id;
}
public void setId(int id) {
this.id.set(id);
}
#OneToOne
#JoinColumn(name = "type")
public TrainingplanType getType() {
return type.get();
}
public ObjectProperty<TrainingplanType> typeProperty() {
return type;
}
public void setType(TrainingplanType type) {
this.type.set(type);
}
#ManyToMany()
#JoinTable(name="TrainingplanExercises",
joinColumns={#JoinColumn(name="trainingplan")},
inverseJoinColumns={#JoinColumn(name="trainingplan"), #JoinColumn(name="exercise"), #JoinColumn(name="parameter")})
public List<TrainingplanExercise> getExercises() {
return exercises;
}
public void setExercises(List<TrainingplanExercise> exercises) {
this.exercises = exercises;
}
#Override
public String toString() {
return "Training{" +
"id=" + getId() +
", client=" + getClient() +
", trainer=" + getTrainer() +
", validFrom=" + getValidFrom() +
", validTill=" + getValidTo() +
", type=" + getType() +
'}';
}
#Override
public boolean equals(Object o) {
if (this == o) return true;
if (o == null || getClass() != o.getClass()) return false;
Training training = (Training) o;
return id != null ? id.equals(training.id) : training.id == null;
}
#Override
public int hashCode() {
return id != null ? id.hashCode() : 0;
}
}
TrainingplanExercise.java
#Entity
#Table(name = "TrainingplanExercises")
#IdClass(TrainingplanExerciseId.class)
public class TrainingplanExercise {
private ObjectProperty<Exercise> exercise;
private ObjectProperty<Training> training;
private ObjectProperty<String> value;
private ObjectProperty<Parameter> parameter;
public TrainingplanExercise(Exercise exercise, Training training, String value, Parameter parameter){
this.exercise = new SimpleObjectProperty<>(exercise);
this.training = new SimpleObjectProperty<>(training);
this.value = new SimpleObjectProperty<>(value);
this.parameter = new SimpleObjectProperty<>(parameter);
}
public TrainingplanExercise(){
this(null,null,null,null);
}
#Id
#OneToOne
#JoinColumn(name = "parameter")
public Parameter getParameter() {
return parameter.get();
}
public ObjectProperty<Parameter> parameterProperty() {
return parameter;
}
public void setParameter(Parameter parameter) {
this.parameter.set(parameter);
}
#Id
#OneToOne
#JoinColumn(name = "exercise")
public Exercise getExercise() {
return exercise.get();
}
public ObjectProperty<Exercise> exerciseProperty() {
return exercise;
}
public void setExercise(Exercise exercise) {
this.exercise.set(exercise);
}
#Id
#OneToOne
#JoinColumn(name = "trainingplan")
public Training getTraining() {
return training.get();
}
public ObjectProperty<Training> trainingProperty() {
return training;
}
public void setTraining(Training training) {
this.training.set(training);
}
#Column(name = "value")
public String getValue(){
return value.get();
}
public ObjectProperty<String> valueProperty() {
return value;
}
public void setValue(String value) {
this.value.set(value);
}
#Override
public String toString() {
return "TrainingplanExercise{" + "exercise=" + exercise + ", training=" + training + ", value=" + value + '}';
}
}
class TrainingplanExerciseId implements Serializable{
protected ObjectProperty<Exercise> exercise;
protected ObjectProperty<Training> training;
protected ObjectProperty<Parameter> parameter;
public TrainingplanExerciseId() {
if(exercise == null)
exercise = new SimpleObjectProperty<>(null);
if(training == null)
training = new SimpleObjectProperty<>(null);
if(parameter == null)
parameter = new SimpleObjectProperty<>(null);
}
public TrainingplanExerciseId(ObjectProperty<Exercise> exercise, ObjectProperty<Training> training, ObjectProperty<Parameter> parameter) {
this.exercise = exercise;
this.training = training;
this.parameter = parameter;
}
#Override
public boolean equals(Object o) {
if (this == o) return true;
if (o == null || getClass() != o.getClass()) return false;
TrainingplanExerciseId that = (TrainingplanExerciseId) o;
if (exercise != null ? !exercise.equals(that.exercise) : that.exercise != null) return false;
if (training != null ? !training.equals(that.training) : that.training != null) return false;
return parameter != null ? parameter.equals(that.parameter) : that.parameter == null;
}
#Override
public int hashCode() {
int result = exercise != null ? exercise.hashCode() : 0;
result = 31 * result + (training != null ? training.hashCode() : 0);
result = 31 * result + (parameter != null ? parameter.hashCode() : 0);
return result;
}
public Exercise getExercise() {
return exercise.get();
}
public ObjectProperty<Exercise> exerciseProperty() {
return exercise;
}
public void setExercise(Exercise exercise) {
this.exercise.set(exercise);
}
public Training getTraining() {
return training.get();
}
public ObjectProperty<Training> trainingProperty() {
return training;
}
public void setTraining(Training training) {
this.training.set(training);
}
public Parameter getParameter() {
return parameter.get();
}
public ObjectProperty<Parameter> parameterProperty() {
return parameter;
}
public void setParameter(Parameter parameter) {
this.parameter.set(parameter);
}
}
Now when I want to save a new Training, I get this error:
Caused by: com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: Unknown column 'TrainingplanID' in 'field list'
Because of this SQL:
Hibernate: insert into TrainingplanExercises (TrainingplanID, trainingplan, exercise, parameter) values (?, ?, ?, ?)
How do I fix this?
If I change the joinColumn to "trainingplan" I get the error that there are two same columns. If I remove "trainingplan" from the reversed columns, I get an error that one is missing because the foreign constraint requires 3 columns
EDIT:
Try something from the comments. I did try OneToMany/ManyToOne:
#Id
#ManyToOne(fetch = FetchType.EAGER)
#JoinColumn(name = "trainingplan", nullable = false)
public Training getTraining() {
return training.get();
}
#OneToMany(fetch = FetchType.EAGER, mappedBy = "training")
public List<TrainingplanExercise> getExercises() {
return exercises;
}
If I try saving a training to the DB now, it works.
Let's say I want to get a Trainingplan from the database, and add new TrainingplanExercises. I would use this code:
Exercise ex = (Exercise) db.getAll(Exercise.class).get(1);
Training t = (Training) db.getAll(Training.class).get(0);
TrainingplanExercise te = new TrainingplanExercise(ex, t, "asdf", ex.getParameters().get(0));
TrainingplanExercise te1 = new TrainingplanExercise(ex, t, "asdf", ex.getParameters().get(1));
TrainingplanExercise te2 = new TrainingplanExercise(ex, t, "asdf", ex.getParameters().get(2));
TrainingplanExercise te3 = new TrainingplanExercise(ex, t, "asdf", ex.getParameters().get(3));
t.getExercises().clear();
t.getExercises().add(te);
t.getExercises().add(te1);
t.getExercises().add(te2);
t.getExercises().add(te3);
db.updateObj(t);
I get this exception:
Exception in thread "main" org.hibernate.exception.LockTimeoutException: could not execute statement
at org.hibernate.dialect.MySQLDialect$1.convert(MySQLDialect.java:447)
at org.hibernate.exception.internal.StandardSQLExceptionConverter.convert(StandardSQLExceptionConverter.java:49)
at org.hibernate.engine.jdbc.spi.SqlExceptionHelper.convert(SqlExceptionHelper.java:126)
at org.hibernate.engine.jdbc.spi.SqlExceptionHelper.convert(SqlExceptionHelper.java:112)
at org.hibernate.engine.jdbc.internal.ResultSetReturnImpl.executeUpdate(ResultSetReturnImpl.java:211)
at org.hibernate.engine.jdbc.batch.internal.NonBatchingBatch.addToBatch(NonBatchingBatch.java:62)
at org.hibernate.persister.entity.AbstractEntityPersister.insert(AbstractEntityPersister.java:3124)
at org.hibernate.persister.entity.AbstractEntityPersister.insert(AbstractEntityPersister.java:3581)
at org.hibernate.action.internal.EntityInsertAction.execute(EntityInsertAction.java:104)
at org.hibernate.engine.spi.ActionQueue.executeActions(ActionQueue.java:465)
at org.hibernate.engine.spi.ActionQueue.executeActions(ActionQueue.java:351)
at org.hibernate.event.internal.AbstractFlushingEventListener.performExecutions(AbstractFlushingEventListener.java:350)
at org.hibernate.event.internal.DefaultFlushEventListener.onFlush(DefaultFlushEventListener.java:56)
at org.hibernate.internal.SessionImpl.flush(SessionImpl.java:1258)
at org.hibernate.internal.SessionImpl.managedFlush(SessionImpl.java:425)
at org.hibernate.engine.transaction.internal.jdbc.JdbcTransaction.beforeTransactionCommit(JdbcTransaction.java:101)
at org.hibernate.engine.transaction.spi.AbstractTransactionImpl.commit(AbstractTransactionImpl.java:177)
at db.Database.updateObj(Database.java:100)
at db.Database.main(Database.java:171)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:497)
at com.intellij.rt.execution.application.AppMain.main(AppMain.java:144)
Caused by: java.sql.SQLException: Lock wait timeout exceeded; try restarting transaction
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:998)
at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3835)
at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3771)
at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:2435)
at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:2582)
at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2535)
at com.mysql.jdbc.PreparedStatement.executeInternal(PreparedStatement.java:1911)
at com.mysql.jdbc.PreparedStatement.executeUpdate(PreparedStatement.java:2145)
at com.mysql.jdbc.PreparedStatement.executeUpdate(PreparedStatement.java:2081)
at com.mysql.jdbc.PreparedStatement.executeUpdate(PreparedStatement.java:2066)
at org.hibernate.engine.jdbc.internal.ResultSetReturnImpl.executeUpdate(ResultSetReturnImpl.java:208)
... 19 more

Okay, look. What you have is a design problem, not really a general problem. First, as I understand it, you want to make a set of unique TrainingplanExercise's. For that, you have this Entity:
#Entity
public class TrainingplanExercise implements Serializable {
#EmbeddedId private TrainingplanExerciseId trainingplanExerciseId;
public TrainingplanExercise() {}
public TrainingplanExercise(TrainingplanExerciseId trainingplanExerciseId) {
this.trainingplanExerciseId = trainingplanExerciseId;
}
... other fields ...
}
The difference between the above Entity and your original Entity is that I have made the ID an EmbeddableId. In order to insure that only unique exercises are put into the TrainingplanExercise's, you have a compositeKey that was defined as a separate class:
#Embeddable
public class TrainingplanExerciseId implements Serializable {
private String exercise;
private String parameter;
public TrainingplanExerciseId() {}
public TrainingplanExerciseId(String exercise, String parameter) {
this.exercise = exercise;
this.parameter = parameter;
}
... getters, setters, hashCode, and equals
}
Here, I have made the class Embeddable so that it can be used as an ID. The way you were trying to declare a compositeKey didn't make any sense; you were trying to declare each individual field in the TrainingplanExercise Entity as an ID, but you can only have one ID.
What is different in this model is that the TrainingplanExerciseId compositeKey does not include a reference back to a TrainingPlan. If you are trying to get a list of TrainingPlan's that use any specific TrainingplanExercise, then you would need a Bidirectional instead of a Unidirectional relationship, but that's a different issue. Otherwise, I don't know why you want to refer back to a TrainingPlan from a TrainingplanExercise. Further, you were putting a reference to the TrainingPlan into the TrainingplanExerciseId compositeKey, which would require the TrainingPlan to be serialized, which really wouldn't work as a unique Id.
Now you can put individual exercises into the table:
public TrainingplanExercise createExercise(String exercise, String parameter) {
TrainingplanExercise trainingplanExercise = new TrainingplanExercise(new TrainingplanExerciseId(exercise, parameter));
em.persist( trainingplanExercise );
return trainingplanExercise;
}
After that, you want to have any number of TrainingPlan's that use the possible TrainingplanExercise's, which you do with this Entity:
#Entity
public class TrainingPlan implements Serializable {
#Id
#GeneratedValue(strategy=GenerationType.AUTO)
private Long id;
#ManyToMany(fetch=FetchType.EAGER)
private List<TrainingplanExercise> trainingplanExercises = new ArrayList<TrainingplanExercise>();
... getters, setters,
}
You have a ManyToMany relationship because a TrainingPlan refers to many TrainingplanExercise's and a TrainingplanExercise is used by many TrainingPlan's. You don't need any special annotation besides ManyToMany, the JPA provider will create a link table, putting the key from each Entity into a row, like this:
create table TrainingPlan_TrainingplanExercise (
TrainingPlan_id bigint not null,
trainingplanExercises_exercise varchar(255) not null,
trainingplanExercises_parameter varchar(255) not null
);
If you declare it as a OneToMany relationship, then the JPA provider will put an additional constraint on the link table insuring that a TrainingplanExercise cannot be linked to more than one TrainingPlan, so you don't want that. Just for example's sake, this is what the constraint would look like.
alter table TrainingPlan_TrainingplanExercise
add constraint UK_t0ku26ydvjkrme5ycrnlechgi unique (trainingplanExercises_exercise, trainingplanExercises_parameter);
Creating and updating TrainingPlans is straight forward:
public TrainingPlan createTrainingPlan() {
TrainingPlan trainingPlan = new TrainingPlan();
em.persist(trainingPlan);
return trainingPlan;
}
public TrainingPlan updateTrainingPlan(TrainingPlan trainingPlan) {
return em.merge(trainingPlan);
}
Now, you can create TrainingplanExercises and TrainingPlans, and add the exercises to the training plans and update them.
TrainingplanExercise squats20 = trainingService.createExercise("Squats", "20");
TrainingplanExercise lifts10 = trainingService.createExercise("Lifts", "10");
TrainingplanExercise crunches50 = trainingService.createExercise("Crunches", "50");
TrainingPlan trainingPlan = trainingService.createTrainingPlan();
trainingPlan.getTrainingplanExercises().add( squats20 );
trainingPlan.getTrainingplanExercises().add( lifts10 );
trainingService.updateTrainingPlan(trainingPlan);
trainingPlan = trainingService.createTrainingPlan();
trainingPlan.getTrainingplanExercises().add( lifts10 );
trainingPlan.getTrainingplanExercises().add( crunches50 );
trainingService.updateTrainingPlan(trainingPlan);
Also note that your application has the challenge of insuring that only unique TrainingplanExercises are created by users. If a TrainingplanExercise with a duplicate exercise and parameter is attempted to be created you will get a Unique index or primary key violation exception and the transaction will be rolled back.
EDIT: For reading the TrainingPlans, something like this can be used:
public List<TrainingPlan> listTrainingPlans() {
CriteriaQuery<TrainingPlan> criteria = em.getCriteriaBuilder().createQuery(TrainingPlan.class);
criteria.select(criteria.from(TrainingPlan.class));
List<TrainingPlan> trainingPlans = em.createQuery(criteria).getResultList();
return trainingPlans;
}
Note that since the List<TrainingplanExercise> trainingplanExercises is set to FetchType.EAGER this particular query will pull in the entire database. FetchType.EAGER probably isn't a problem for reading a single TrainingPlan, but if you only wanted a list of the TrainingPlan's without getting all of the details, then you would need to work out how FetchType.LAZY should be implemented.

Did you tried using many-to-one mapping instead because it's what you have with a foreign key anyway. You could then try something like:
#Id
#ManyToOne( cascade = {CascadeType.PERSIST}, targetEntity=Trainingplan.class )
#JoinColumn(name = "trainingplan")
public Training getTraining() {}

OUT OF MEMORY in hibernate

Hi I have created many to one relationship in hibernate.
Following is the code for that.
there are thousands of records present in B table which is link to single record of table A. When i used getBList() method it will returns thousands of record and JAVA goes OUT OF MEMORY.
So how can i solve this problem.
#Entity
#Table(name = "A")
public class A {
private int Id;
private String aName;
private List<MksReleaseInfo> bList;
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
#Column(name = "id")
public int getId() {
return releaseId;
}
public void setId(final int Id) {
this.Id = Id;
}
#Column(name = "aname", unique = true)
public String getAName() {
return aName;
}
public void setAName(final String aName) {
this.aName = aName;
}
#OneToMany(mappedBy = "aName")
public List<MksReleaseInfo> getBList() {
return bList;
}
public void setBList(final List<B> bList) {
this.bList = bList;
}
}
#Entity
#Table(name = "B")
public class B {
private int bIndex;
private int bpriority;
private A aName;
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
#Column(name = "id")
protected int getBIndex() {
return mksReleaseInfoIndex;
}
protected void setBIndex(final int bIndex) {
this.bIndex = bIndex;
}
#Column(name = "priority")
public int getBPriority() {
return bpriority;
}
public void setBPriority(final int bpriority) {
this.bpriority = bpriority;
}
#ManyToOne
#JoinColumn(name = "Id")
public A getAName() {
return aName;
}
public void setAName(final A aName) {
this.aName = aName;
}
}
after all the comments i have implemented the following code. but again it gives OUT OF MEMORY. Should i have to flush the memory explicitly and how?
public List<B> getList(String name, int offset, int limit) throws DAOException {
try {
String hql = "from B where name = :name";
begin();
Query query = getSession().createQuery(hql);
query.setString("name", name);
if(offset > 0){
query.setFirstResult(offset);
}
if(limit > 0){
query.setMaxResults(limit);
query.setFetchSize(limit);
}
commit();
return query.list();
} catch (HibernateException e) {
rollback();
}
}
public Long countB(String name) throws DAOException {
try {
String hql = "select count(*) from B where name = :name";
begin();
Query query = getSession().createQuery(hql);
query.setString("name", name);
commit();
return (Long)query.uniqueResult();
} catch (HibernateException e) {
rollback();
}
}
long count = countB(name);
int counter = (int) (count / 200);
if(count%200 > 0){
counter++;
}
for(int j = 0;j<counter;j++){
lists = getList(name, j*200, 200);
for(B count1 : lists){
System.out.println(count1);
}
}

You could introduce a DAO in order to retrieve the records from B given a A object in a paged way.
For example:
public interface BDao {
Page findByA(A a, PageRequest pageRequest);
}
Maybe you could take an idea from approach taked in Spring Data

Set MaxResults property of datasource, it will set limit on number of records you are getting.
Also, you can increase java heap memory size using -Xmx256m. This will set maximum heap allocation size to 256MB. You can set it as you need.

You can use query with paging for this purpose. In Query class you can find setFirstResult and setMaxResults methods which can help you to iterate over records. If you need to load all B objects and store them you can adjust memory settings of java by setting -Xmx option. Also you can try to declare some kind of reduced class B (for example ReducedB), which contains only required fields, and use iterating with converting B to ReducedB to reduce memory usage.
Also you can check this question. I think that it is close enought to what you want.
P.S. Final solution would depend on particular issue that you want to solve.

I had the same issue. I looked at my code and server space but nothing helped. Later I looked into data and realized wrongly placed data was making application use lot of processing power. Make sure you do not have duplicated data in child class.

How to get Hibernate JPA to manage list index automagically?

How do I setup a basic OneToMany relationship using a List and get Hibernate JPA to manage the sequence index number of the list automagically? Can this be done?
This is my test case (more or less);
#Table(name="Policy_Root")
public class PolicyRoot extends BaseDomainModel {
private List<Policy> policyList = new ArrayList<Policy>();
#OneToMany(targetEntity=Policy.class, mappedBy="policyRoot", cascade=CascadeType.ALL)
#IndexColumn(name="policy_sequence", base=0, nullable=false)
public List<Policy> getPolicyList() {
return policyList;
}
public void setPolicyList(List<Policy> policyList) {
this.policyList = policyList;
}
public void addPolicy(Policy policy) {
policyList.add(policy);
policy.setPolicyRoot(this);
}
public void addPolicy(int sequence, Policy policy) {
policyList.add(sequence, policy);
policy.setPolicyRoot(this);
}
}
#Entity()
#Table(name="Policy")
public class Policy extends BaseDomainModel {
/** The position of this policy record within the list of policy's belong to the parent PolicyRoot */
private int policySequence;
/** Birectional pointer to parent */
private PolicyRoot policyRoot;
#Column(name="policy_sequence")
public int getPolicySequence() {
return policySequence;
}
public void setPolicySequence(int policySequence) {
this.policySequence = policySequence;
}
#ManyToOne
#JoinColumn(name="policy_root_oid", nullable=false)
public PolicyRoot getPolicyRoot() {
return policyRoot;
}
public void setPolicyRoot(PolicyRoot policyRoot) {
this.policyRoot = policyRoot;
}
}
#Test
public void testCreation() {
Policy policy1 = new Policy();
Policy policy2 = new Policy();
// Uncomment the following and the test case works - but I don't want to manage the sequence numbers
//policy2.setPolicySequence(1);
PolicyRoot policyRoot = new PolicyRoot();
policyRoot.addPolicy(policy1);
policyRoot.addPolicy(policy2);
ServiceImplFacade.getPersistenceFacade().persistSingleItem(policyRoot);
Long oid = policyRoot.getOid();
PolicyRoot policyRootFromDB = ServiceImplFacade.getPersistenceFacade().getEntityManager().find(PolicyRoot.class, oid);
assertEquals(2, policyRootFromDB.getPolicyList().size());
}
If I uncomment the policy2.setPolicySequence(1); line then the test case passes, but I don't think I need to do this. I want Hibernate to do this for me. My understanding is that it can, but if it can't then knowing that it can't would be a good answer as well.
I've tried various combinations of setting nullable, insertable and updateable but I may have missed one.
Is this possible? - If so how?

Found the answer, - it was around getting the right combinations of nullable and insertable. Also had to make the "child index" at Integer so that it could be nullable, and there's also an "optional" flag in the following as well.
public class PolicyRoot extends BordereauxBaseDomainModel {
private List<Policy> policyList = new ArrayList<Policy>();
#OneToMany(cascade=CascadeType.ALL)
#IndexColumn(name="policy_sequence", nullable=false, base=0)
#JoinColumn(name="policy_root_oid", nullable=false)
public List<Policy> getPolicyList() {
return policyList;
}
public void setPolicyList(List<Policy> policyList) {
this.policyList = policyList;
}
}
public class Policy extends BordereauxBaseDomainModel {
/** The position of this policy record within the list of policy's belong to the parent PolicyRoot */
private Integer policySequence;
/** Birectional pointer to parent */
private PolicyRoot policyRoot;
#Column(name="policy_sequence", insertable=false, updatable=false)
public Integer getPolicySequence() {
return policySequence;
}
public void setPolicySequence(Integer policySequence) {
this.policySequence = policySequence;
}
#ManyToOne(optional=false)
#JoinColumn(name="policy_root_oid", insertable=false, updatable=false, nullable=false)
public PolicyRoot getPolicyRoot() {
return policyRoot;
}
public void setPolicyRoot(PolicyRoot policyRoot) {
this.policyRoot = policyRoot;
}
}
Found the answers on the following page after searching Google for a while.
http://opensource.atlassian.com/projects/hibernate/browse/HHH-4390

Do something like this:
#Entity
class Parent {
#OneToMany
#IndexColumn(name = "index_column")
List<Child> children;
}
#Entity
class Child {
#ManyToOne
Parent parent;
#Column(name = "index_column")
Integer index;
#PrePersist
#PreUpdate
private void prepareIndex() {
if (parent != null) {
index = parent.children.indexOf(this);
}
}
}

I'm going to post this answer since I recently had the same issue and this question, although outdated, keeps coming up in the researches.
The #IndexColumn annotation has been deprecated a long time ago and in its place it is best recommended using the #OrderColumn annotation. The second annotation not only simplifies its syntax without having to specify the base attribute, but it also avoids declaring an extra field in the detail class, in this case the policySequence field within the Policy class.
Here is the updated version of the previous snippet:
#Table(name="Policy_Root")
public class PolicyRoot extends BaseDomainModel {
private List<Policy> policyList = new ArrayList<Policy>();
#OneToMany(targetEntity=Policy.class, mappedBy="policyRoot", cascade=CascadeType.ALL)
#OrderColumn(name="policy_sequence", nullable=false)
public List<Policy> getPolicyList() {
return policyList;
}
public void setPolicyList(List<Policy> policyList) {
this.policyList = policyList;
}
public void addPolicy(Policy policy) {
policyList.add(policy);
policy.setPolicyRoot(this);
}
public void addPolicy(int sequence, Policy policy) {
policyList.add(sequence, policy);
policy.setPolicyRoot(this);
}
}
#Entity()
#Table(name="Policy")
public class Policy extends BaseDomainModel {
//No need to declare the policySequence field
/** Birectional pointer to parent */
private PolicyRoot policyRoot;
#Column(name="policy_sequence")
public int getPolicySequence() {
return policySequence;
}
public void setPolicySequence(int policySequence) {
this.policySequence = policySequence;
}
#ManyToOne
#JoinColumn(name="policy_root_oid", nullable=false)
public PolicyRoot getPolicyRoot() {
return policyRoot;
}
public void setPolicyRoot(PolicyRoot policyRoot) {
this.policyRoot = policyRoot;
}
}