I have entity with two Lists of children entities. When calling EntityManager.find() it returns duplicates based on multiplication of two lists.
I'm using Spring, Jackson and JPA with Hibernate and SQL Server.
When testing with parent that has N elements of first and M of second child entity it always returns N*M elements of both entities.
For example below there are 3 tasks and 5 comments and JPA returns 15 for both lists. (5 copies of task list, and 3 copies of comment list)
Output from controller is:
Comments 15
Tasks 15
And the rest of the code is below.
controller.java
#RequestMapping(method = RequestMethod.GET)
public String listAll(Model model) {
Goal goal = new Goal();
goal = service.getGoalById(25);
System.out.println("Comments " + goal.getComments().size());
System.out.println("Tasks " + goal.getTasks().size());
return "home";
}
service.java
#Transactional
public Goal getGoalById(int goalId) {
Goal goal = em.find(Goal.class, goalId);
return goal;
}
goal.java
#Entity
#Table(name = "goal")
public class Goal {
#Id
#GeneratedValue
private int id;
#JsonManagedReference
#OneToMany(mappedBy = "tasksGoal", cascade = CascadeType.PERSIST, fetch = FetchType.EAGER)
private List<Task> projectTasks = new ArrayList<Task>();
#JsonManagedReference
#OneToMany(mappedBy = "commentsGoal", cascade = CascadeType.PERSIST, fetch = FetchType.EAGER)
private List<Comment> goalComments = new ArrayList<Comment>();
...
}
task.java
#Entity
#Table(name="projectTask")
public class Task {
#Id
#GeneratedValue
private int id;
#JsonBackReference
#ManyToOne (fetch = FetchType.LAZY)
#JoinColumn(name = "task_goal_id")
private Goal tasksGoal;
...
}
comment.java
#Entity
#Table (name="goalComment")
public class Comment {
#Id
#GeneratedValue
private int id;
#JsonBackReference
#ManyToOne (fetch = FetchType.LAZY)
#JoinColumn(name = "goal_id")
private Goal commentsGoal;
...
}
persistence.xml
<persistence xmlns="http://java.sun.com/xml/ns/persistence"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" version="2.0"
xsi:schemaLocation="http://java.sun.com/xml/ns/persistence http://java.sun.com/xml/ns/persistence/persistence_2_0.xsd">
<persistence-unit name="persistenceUnit"
transaction-type="RESOURCE_LOCAL">
<provider>org.hibernate.ejb.HibernatePersistence</provider>
<properties>
<property name="hibernate.dialect" value="org.hibernate.dialect.SQLServer2008Dialect" />
<property name="hibernate.hbm2ddl.auto" value="update" />
<property name="hibernate.ejb.naming_strategy" value="org.hibernate.cfg.ImprovedNamingStrategy" />
<property name="hibernate.connection.charSet" value="UTF-8" />
<!-- Hibernate prints SQL -->
<property name="hibernate.show_sql" value="true" />
</properties>
</persistence-unit>
This is because of your fetch = FetchType.EAGER.
he Hibernate tries to get everything in one shot, i.e. using one single query for each entry of element linked to a "master" object.
Hibernate creates JOINs and tries to get all your collections with one query.
This problem can be successfully solved at a cost of N+1 query, if you add the #Fetch (FetchMode.SELECT) annotation to your collection.
If you really need FetchType.EAGER and don't want to replace your collection with Set you can use #Fetch (FetchMode.SELECT) annotation for your collection:
#JsonManagedReference
#OneToMany(mappedBy = "tasksGoal", cascade = CascadeType.PERSIST, fetch = FetchType.EAGER)
#Fetch (FetchMode.SELECT)
private List projectTasks = new ArrayList();
#JsonManagedReference
#OneToMany(mappedBy = "commentsGoal", cascade = CascadeType.PERSIST, fetch = FetchType.EAGER)
#Fetch (FetchMode.SELECT)
private List<Comment> goalComments = new ArrayList<Comment>();
#Fetch (FetchMode.SELECT)
can help you. it is the default fetching strategy. it enabled the lazy loading of all it’s related collections.
Related
I got a typical entity association of order and items. To make it possible to read only orders, the items set is default FetchType.LAZY. 2nd level and query cache is enabled. To read an order with associated items, I'm using a JPQL query. The query and the entities are cached by EHCache. But on the second call when accessing items, a LazyInitializationException was thrown, because items are not initialized (not restored from cache). Why? What's the best way to implement this requirement?
Order:
#Entity
#Cacheable
#NamedQueries({
#NamedQuery(name = Order.NQ_FIND_BY_ID_FETCH_ITEMS, query = "SELECT DISTINCT o FROM Order o JOIN FETCH o.items WHERE o.id = :id")
})
#Table(...)
public class Order extends ... {
...
#OneToMany(mappedBy = "order", cascade = CascadeType.ALL, orphanRemoval = true)
// #Cache(usage = CacheConcurrencyStrategy.READ_WRITE)
private Set<Item> items = new HashSet<Item>();
...
}
Item:
#Entity
#Cacheable
#Table(...)
public class Item extends ... {
#ManyToOne
#JoinColumn(name = "order_id", nullable = false)
private Order order;
...
}
DAO:
public class OrderDaoJpaImpl extends ... {
#Override
public Catalog findByIdFetchItems(Long id) {
TypedQuery<Order> query = entityManager.createNamedQuery(Order.NQ_FIND_BY_ID_FETCH_ITEMS, Order.class);
query.setParameter("id", id);
// query.setHint(QueryHints.HINT_CACHEABLE, Boolean.TRUE);
Order order = JPAUtil.singleResultOrNull(query);
return order;
}
Service:
#Service("orderService")
#Transactional(propagation = Propagation.SUPPORTS, readOnly = true)
public class OrderServiceImpl implements OrderService {
#Override
public Order getOrderWithItems(Long orderId) {
return orderDao.findByIdFetchItems(orderId);
}
}
persistence.xml:
<persistence ...>
<persistence-unit name="shop-persistence" transaction-type="RESOURCE_LOCAL">
<jar-file>shop-persistence.jar</jar-file>
<!-- Enable JPA 2 second level cache -->
<shared-cache-mode>ALL</shared-cache-mode>
<properties>
...
<property name="hibernate.cache.use_second_level_cache" value="true" />
<property name="hibernate.cache.use_query_cache" value="true" />
<property name="hibernate.cache.region.factory_class" value="org.hibernate.cache.ehcache.SingletonEhCacheRegionFactory"/>
</properties>
</persistence-unit>
</persistence>
Spring Framework 4.3.7.RELEASE and Hibernate 5.2.9.Final.
As you can see, I've tried to use Hibernate entity annotations and cache hints instead of JPA caching. I've also tried JPA entity graphs instead of JOIN FETCH. Always the same: Items are not initialized/restored on the second call of the order query.
The LazyInitializationException is thrown because of the HHH-12430 issue.
However, there are some issues with your code as well, and there is a workaround that you can use until the Hibernate HHH-12430 issue is fixed.
When you're using Hibernate, it's not enough to annotate your entity with #Cacheable.
You need to provide a CacheConcurrencyStrategy as well:
#Entity
#org.hibernate.annotations.Cache(usage = CacheConcurrencyStrategy.READ_WRITE)
The Query Cache only stores entity identifiers, and since you are only selecting the Order, the items association will not get cached as well.
What you can do is to change your query to this:
#NamedQuery(name = Order.NQ_FIND_BY_ID_FETCH_ITEMS, query = "SELECT DISTINCT o FROM Order o WHERE o.id = :id")
Then, activate the cache for collection:
#OneToMany(mappedBy = "order", cascade = CascadeType.ALL, orphanRemoval = true)
#Cache(usage = CacheConcurrencyStrategy.READ_WRITE)
private Set<Item> items = new HashSet<Item>();
And both the Order and the Item should use this:
#Entity
#org.hibernate.annotations.Cache(usage =
CacheConcurrencyStrategy.READ_WRITE)
since they need to be cacheable.
And make sure you initialize the items collection prior to returning the result set:
Order order = JPAUtil.singleResultOrNull(query);
if(order != null) {
order.getItems().size();
}
return order;
This way, the items will always be initialized and the collection will be fetched from the cache, not from the database.
I think the #Cacheable is not Hibernate cache, but Spring cache.
#Cache annotation is for Hibernate cache.
Besides of this, when I have troubles with this stuff, to get the JOIN FETCH result also usable with cache, I had to add Hibernate.initialize(...) to the Dao method to avoid LazyInitializationException.
I think im doing something wrong but i cant get working #any annotation on hibernate 4.2.2 with jpa2 1.0.1
The class works ok, but i cant get join.
My code is this:
#Entity(name = "conta")
public class Conta {
#Id
#GeneratedValue(strategy = GenerationType.AUTO)
private int id;
#Column(name = "empresa_id")
private int empresaId;
private String descricao;
#Any(metaColumn = #Column(name = "tipo"), fetch = FetchType.EAGER)
#AnyMetaDef(idType = "int", metaType = "string", metaValues = {
#MetaValue(value = "BANCO", targetEntity = Banco.class),
#MetaValue(value = "CIELO", targetEntity = Cielo.class)
})
#JoinColumn(name = "financeira_id")
private Financeira financeira;
//getters and setters
}
Financeira its an interface, Banco.class and Cielo.class implements Conta as well. When i try to fetch from DB i can get all records, but the join doesnt happen.
My code inspection on Intellij IDEA says for private Financeira financeira that "'Basic' attribute type should not be 'Financeira'". I know or i think i know that this message says that jpa dont have metamodel for #any annotation, but hibernate does, so, this should work right?
UPDATE
Got the problem solved by using hibernate native xml configuration.
Now i can persist my objects but i got another problem. I cant fetch the association, im using a factory to fetch de association on #postLoad event, but thats not the right way.
above my xml code.
<any id-type="java.lang.Integer" meta-type="string" name="tipo" cascade="all">
<meta-value value="BANCO" class="br.com.leaftecnologia.lfadmin.model.financeiro.BANCO" />
<meta-value value="PLAYSMS" class="br.com.leaftecnologia.lfadmin.model.financeiro.CIELO" />
<column name="tipo" />
<column name="financeira_id" /></any>
I am trying to make a relationship between 2 entities in different jar.
This is a first entity which is in main project:
#Entity(name = "StdyDtlLabelBean")
#Table(name = "STDY_DTL_LABEL")
public class StdyDtlLabelBean implements Serializable {
#EmbeddedId
private StdyDtlLabelBeanPk id;
#ManyToOne(targetEntity = StdyDtlSubject.class)
#JoinColumns({
#JoinColumn(name="STUDY_ID", insertable = false, updatable = false, referencedColumnName="STUDY_ID"),
#JoinColumn(name="SUBJECT_ID", insertable = false, updatable = false, referencedColumnName="SUBJECT_ID")
})
private StdyDtlSubject subject;
//getters and setters
}
This one is an entity which is in library project as a jar file:
#Entity
#Table(name = "STDY_DTL_SUBJECT")
public class StdyDtlSubject implements Serializable {
private static final long serialVersionUID = 2479124604L;
public StdyDtlSubject() {
}
#EmbeddedId
private StdyDtlSubjectPK key;
//getters and setters
}
#Embeddable
public class StdyDtlSubjectPK implements Serializable {
private static final long serialVersionUID = 6691432687933341920L;
#Column(name = "STUDY_ID")
private Integer studyId;
#Column(name = "SUBJECT_ID")
private String subjectId;
public StdyDtlSubjectPK() {
}
Here is the persistence unit:
<persistence-unit name="stdyPersistence" transaction-type="RESOURCE_LOCAL">
<jta-data-source>java:comp/env/jdbc/OraclePooledDS</jta-data-source>
<class>com.ctasc.ctpm.jpa.StdyDtlSubject</class>
<class>stdy.brms.beans.StdyDtlLabelBean</class>
<properties>
<property name="hibernate.dialect" value="org.hibernate.dialect.Oracle10gDialect" />
<property name="hibernate.show_sql" value="true" />
<property name="hibernate.format_sql" value="true" />
</properties>
</persistence-unit>
When I create an entity manager factory I gets following error:
#OneToOne or #ManyToOne on stdy.brms.beans.StdyDtlLabelBean.subject references an unknown entity: com.ctasc.ctpm.jpa.StdyDtlSubject
But if I remove a relationship annotation from StdyDtlLabelBean entity and create named queries on StdyDtlSubject entity. Those named queries work fine. Also, if I copy StdyDtlSubject class to my main project, it works fine. I gets this error only if I put relationship between them.
I've tried adding
<jar-file>ctpm.jar</jar-file>
<jar-file>lib/ctpm.jar</jar-file>
<exclude-unlisted-classes>false</exclude-unlisted-classes>
<property name="hibernate.archive.autodetection" value="class, hbm" />
<property name="packagesToScan" value="com.ctasc.ctpm.jpa" />
None of them helped me to solve this. Could you please suggest something to solve this problem?
Ensure that the jar which you want to relate to has a persisence.xml in it's META-INF with all entities in the jar enlisted.
I am using EclipseLink JPA as ORM and web logic 10.3 as an application server in my project. Everything working fine until i got a bug for data refresh. Here is the case one of my entity table row is updated to new value but my entity manager or JPA did not pick that value. For this we have lite rely re started the server. then it picked up the value.
Here is my persistence.xml file and here is the way i am using entity manager in my class.
<persistence-unit name="BasePersistenceUnit" transaction-type="JTA">
<provider>org.eclipse.persistence.jpa.PersistenceProvider</provider>
<jta-data-source>jdbc/CTH_DS</jta-data-source>
<class>org.test.partyrequest.model.dataobject.RqstTrc</class>
<exclude-unlisted-classes>true</exclude-unlisted-classes>
<properties>
<property name="eclipselink.target-server" value="WebLogic_10" />
<!-- Logging level is set to INFO, Need to change in Production -->
<property name="eclipselink.logging.level" value="FINE" />
<property name="eclipselink.persistence-context.flush-mode" value="COMMIT" />
<property name="eclipselink.persistence-context.close-on-commit" value="true" />
<property name="eclipselink.cache.shared.default" value="false" />
</properties>
</persistence-unit>
SPRING JPA XML FILE
<context:load-time-weaver aspectj-weaving="on" />
<bean id="entityManagerFactory" class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean">
<property name="persistenceUnitName" value="BasePersistenceUnit" />
</bean>
<bean id="jpaVendorAdapter" class="org.springframework.orm.jpa.vendor.EclipseLinkJpaVendorAdapter" />
<bean id="transactionManager" class="org.springframework.transaction.jta.WebLogicJtaTransactionManager" />
<!-- ========================= BUSINESS OBJECT DEFINITIONS ========================= -->
<!-- Instruct Spring to perform declarative transaction management automatically on annotated classes. -->
<tx:annotation-driven mode="aspectj" transaction-manager="transactionManager"/>
<!-- Post-processor to perform exception translation on #Repository classes
(from native exceptions such as JPA PersistenceExceptions to Spring's DataAccessException hierarchy).
-->
<bean class="org.springframework.dao.annotation.PersistenceExceptionTranslationPostProcessor" />
My Entity calss
#Entity
#Table(name = "PRTY_RQST")
public class PrtyRqst implements Serializable {
private static final long serialVersionUID = -4679712398918736694L;
#Id
#GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "PRTY_RQST_PRTYRQSTID_GENERATOR")
#SequenceGenerator(name = "PRTY_RQST_PRTYRQSTID_GENERATOR", allocationSize = 1, sequenceName = "PRTY_RQST_SEQ")
#Column(name = "PRTY_RQST_ID")
private Long prtyRqstId;
#Column(name = "CHLD_RQST_IND")
private String chldRqstInd;
#Column(name = "PARNT_PRTY_RQST_ID")
private BigDecimal parntPrtyRqstId;
#Column(name = "PROCES_REFR")
private String procesRefr;
#Temporal(TemporalType.TIMESTAMP)
#Column(name = "RQST_DT_TM")
private Date rqstDtTm;
#Column(name = "UPDT_BY")
private String updtBy;
// bi-directional many-to-one association to PrtyKey
#OneToMany(mappedBy = "prtyRqst", fetch = FetchType.LAZY, cascade = CascadeType.ALL)
private List<PrtyKey> prtyKeys;
// bi-directional many-to-one association to PrtyRqstHist
#OneToMany(mappedBy = "prtyRqst", fetch = FetchType.LAZY, cascade = CascadeType.ALL)
#OrderBy("rqstDtTm DESC")
private List<PrtyRqstHist> prtyRqstHists;
#OneToOne(mappedBy = "prtyRqst", fetch = FetchType.LAZY, cascade = CascadeType.ALL)
private RqstPayload rqstPayload;
// bi-directional many-to-one association to RqstTrc
#OneToMany(mappedBy = "prtyRqst", fetch = FetchType.LAZY, cascade = CascadeType.ALL)
private List<RqstTrc> rqstTrcs;
// bi-directional many-to-one association to AddtnRqstInfo
#OneToMany(mappedBy = "prtyRqst", fetch = FetchType.LAZY, cascade = CascadeType.ALL)
private List<AddtnRqstInfo> addtnRqstInfos;
// bi-directional many-to-one association to BusnApplc
#ManyToOne(fetch = FetchType.LAZY, cascade = CascadeType.REFRESH)
#JoinColumn(name = "BUSN_APPLC_ID")
private BusnApplc busnApplc;
#ManyToOne(fetch = FetchType.LAZY, cascade = CascadeType.REFRESH)
#JoinColumn(name = "INTN_PROCES_TYP_ID")
private IntnProcesTyp intnProcesTyp;
#ManyToOne(fetch = FetchType.LAZY, cascade = CascadeType.REFRESH)
#JoinColumn(name = "INTN_STATS_ID")
private IntnStat intnStat;
#Column(name = "ORCHESTRATION_ID")
private String orchestrationId;
#ManyToOne(fetch = FetchType.LAZY, cascade = CascadeType.REFRESH)
#JoinColumn(name = "ALLW_CHNL_ID")
private AllwChnl allwChnl;
// bi-directional many-to-one association to RqstTyp
#ManyToOne(fetch = FetchType.LAZY, cascade = CascadeType.REFRESH)
#JoinColumn(name = "RQST_TYP_ID")
private RqstTyp rqstTyp;
#Column(name = "TRACK_RQST_IND")
private String trackRqstInd;
#Temporal(TemporalType.TIMESTAMP)
#Column(name = "SUBMIT_DT_TM")
private Date submitDtTm;
#Temporal(TemporalType.DATE)
#Column(name = "EFFECTIVE_DT")
private Date effectiveDt;
#Temporal(TemporalType.TIMESTAMP)
#Column(name = "RQST_CREATE_DT_TM")
private Date rqstCreateDtTm;
In my DAO IMPL class I have this.persist(prtyRqstDO);
#Transactional(readOnly = true, propagation=Propagation.REQUIRED)
private PartyRequestBO createRequest(PartyRequestBO partyRequestBO, boolean isParent) throws RuntimeException {
if (log.isDebugEnabled()) {
log.debug("Enter: PartyRequestsDAOImpl:createRequest()");
}
partyRequestBO.setOrchestrationID(generateOrchestrationId());
PrtyRqst prtyRqstDO = PartyRequestEntityMapper.partyRequestMapper(partyRequestBO, isParent, true);
try {
this.persist(prtyRqstDO);
partyRequestBO.setRequestIdentifier(prtyRqstDO.getPrtyRqstId());
} catch (Exception e) {
if(log.isDebugEnabled()) {
log.debug("PartyRequestsDAOImpl:createRequest : " + PartyRequestConstants.UNABLE_TO_INSERT, e);
}
throw new PartyRequestDataException(PartyRequestConstants.UNABLE_TO_INSERT, e);
}
if (log.isDebugEnabled()) {
log.debug("Exit: PartyRequestsDAOImpl:createRequest()");
}
return partyRequestBO;
}
#Transactional(readOnly = true, propagation=Propagation.REQUIRED)
public void persist(T entity) {
if (log.isDebugEnabled()) {
log.debug("Enter: BaseDAO:persist() : " + entity);
}
this.getEntityManager().persist(entity);
if (log.isDebugEnabled()) {
log.debug("Exit: BaseDAO:persist()");
}
}
public EntityManager getEntityManager() {
if (log.isDebugEnabled()) {
log.debug("Enter: BaseDAO:getEntityManager() : " + this.entityManager);
}
return this.entityManager;
}
Here the problem is, if i update the row in one of the table through back end my application container is not picking the change.
Can any one Tell me? thank you in advance.
EDIT:
Thank you both of you. I have modified according to your comments added following lines of code.
this.entityManager.clear();
this.entityManager.close();
//this.getEntityManager().refresh(entityManager);
Here i could able to get the update value what i have done it through backend with out restarting server. But the problem is it hold all the changed values.
for example i have changed value to FulOrderWSA it was working. changed to FulorderWSB it was working again.Now i have tried for FulOrderWSZ it didn't work(DB values is FulorderWSB ).
Finally i tried here with old value that is FulorderWSA as per DB it should not work but it worked for me. what i noticed that it is holding all the DB changed values here.
How to get ride of this. I have used both clear and close for entityManager. can any one help me on this.
thank you.
Vijay.
You have turned off the EclipseLink shared cache (AKA second level cache), so the issue is likely that you are holding onto long lived EntityManagers. Once an entity becomes managed by the EM, JPA requires that EM to return that exact instance from every find/query operation as it was when first read and any changes your app might have made to it.
There are a number of options. The best is to look at your EntityManager lifecycle and only obtain an EntityManager when needed, and close it when done. Or, just call em.clear() at points to prevent them from filling up, which will detach all entities associated to the em. Make sure to flush changes though if you wish to keep the changes before calling clear.
If there is a specific entity you need to refresh, em.refresh(entity) will work. This will clear any changes the application might have made though, and can be dangerous with cascade refresh settings mixed with lazy access - so use carefully or you may unintentionally wipe out changes to a whole tree at a later time.
You have caching disabled, so you should see any database changes.
My guess is that you are hold onto a single EntityManager in your DAO. This is very bad, as an EntityManger should be created per transaction, or per request, not held for the duration of the application. It is also not thread safe, so holding onto a single one does not make sense, as it is a transactional object.
You seem to also be using Spring, so it might be proxying the EntityManager underneath and creating one per transaction, but perhaps you have not configured Spring or your transactions correctly.
Include the code the creating/configures the EntityManager.
Thanks,
for all your support. Basically we are not using Cache from EclipseLink. we had bean that handles all the metadata initialization as init method. what we have done is, used JDK Timer to reload the particular Bean to refresh the data. It was working fine.
I have checked the time taking to refresh the all the methods are less than 500 milliseconds. I can foresee only issue when this thread is executing and there is a request.since it is taking less than 500 millisecs its ok for us.
I hope this will be helpful if someone is not using cache you can try this approach.
Thank you.
I need help with lazy blob loading in Hibernate.
I have in my web application these servers and frameworks: MySQL, Tomcat, Spring and Hibernate.
The part of database config.
<bean id="dataSource" class="com.mchange.v2.c3p0.ComboPooledDataSource" destroy-method="close">
<property name="user" value="${jdbc.username}"/>
<property name="password" value="${jdbc.password}"/>
<property name="driverClass" value="${jdbc.driverClassName}"/>
<property name="jdbcUrl" value="${jdbc.url}"/>
<property name="initialPoolSize">
<value>${jdbc.initialPoolSize}</value>
</property>
<property name="minPoolSize">
<value>${jdbc.minPoolSize}</value>
</property>
<property name="maxPoolSize">
<value>${jdbc.maxPoolSize}</value>
</property>
<property name="acquireRetryAttempts">
<value>${jdbc.acquireRetryAttempts}</value>
</property>
<property name="acquireIncrement">
<value>${jdbc.acquireIncrement}</value>
</property>
<property name="idleConnectionTestPeriod">
<value>${jdbc.idleConnectionTestPeriod}</value>
</property>
<property name="maxIdleTime">
<value>${jdbc.maxIdleTime}</value>
</property>
<property name="maxConnectionAge">
<value>${jdbc.maxConnectionAge}</value>
</property>
<property name="preferredTestQuery">
<value>${jdbc.preferredTestQuery}</value>
</property>
<property name="testConnectionOnCheckin">
<value>${jdbc.testConnectionOnCheckin}</value>
</property>
</bean>
<bean id="lobHandler" class="org.springframework.jdbc.support.lob.DefaultLobHandler" />
<bean id="sessionFactory" class="org.springframework.orm.hibernate3.LocalSessionFactoryBean">
<property name="dataSource" ref="dataSource" />
<property name="configLocation" value="/WEB-INF/hibernate.cfg.xml" />
<property name="configurationClass" value="org.hibernate.cfg.AnnotationConfiguration" />
<property name="hibernateProperties">
<props>
<prop key="hibernate.dialect">${hibernate.dialect}</prop>
</props>
</property>
<property name="lobHandler" ref="lobHandler" />
</bean>
<tx:annotation-driven transaction-manager="txManager" />
<bean id="txManager" class="org.springframework.orm.hibernate3.HibernateTransactionManager">
<property name="sessionFactory" ref="sessionFactory" />
</bean>
The part of entity class
#Lob
#Basic(fetch=FetchType.LAZY)
#Column(name = "BlobField", columnDefinition = "LONGBLOB")
#Type(type = "org.springframework.orm.hibernate3.support.BlobByteArrayType")
private byte[] blobField;
The problem description. I'm trying to display on a web page database records related to files, which was saved in MySQL database. All works fine if a volume of data is small. But the volume of data is big I'm recieving an error java.lang.OutOfMemoryError: Java heap space
I've tried to write in blobFields null values on each row of table. In this case, application works fine, memory doesn't go out of. I have a conclusion that the blob field which is marked as lazy (#Basic(fetch=FetchType.LAZY)) isn't lazy, actually!
I'm confused. Emmanuel Bernard wrote in ANN-418 that #Lob are lazy by default (i.e. you don't even need to use the #Basic(fetch = FetchType.LAZY) annotation).
Some users report that lazy loading of a #Lob doesn't work with all drivers/database.
Some users report that it works when using bytecode instrumentation (javassit? cglib?).
But I can't find any clear reference of all this in the documentation.
At the end, the recommended workaround is to use a "fake" one-to-one mappings instead of properties. Remove the LOB fields from your existing class, create new classes referring to the same table, same primary key, and only the necessary LOB fields as properties. Specify the mappings as one-to-one, fetch="select", lazy="true". So long as your parent object is still in your session, you should get exactly what you want. (just transpose this to annotations).
I would suggest you to use inheritance to handle this scenario. Have a base class without the blob and a derived class containing the byte array. You would use the derived class only when you need to display the blob on the UI.
Of course you could extract that value and put it into a new table with a "#OneToOne" relation that is lazy, however in our application the LOBs are loaded lazily on demand using just this configuration
#Lob
#Fetch(FetchMode.SELECT)
#Type(type="org.hibernate.type.PrimitiveByteArrayBlobType")
byte[] myBlob;
This is tested in our project simultaneously on PostgreSQL, MySQL, SQLServer and Oracle, so it should work for u
Lazy property loading requires buildtime bytecode instrumentation.
Hibernate docs: Using lazy property fetching
If you want to avoid bytecode instrumentation one option is to to create two entities that use same table, one with the blob one without. Then only use the entity with blob when you need the blob.
I had the same issue and this was my fix:
My Entity:
#Entity
#Table(name = "file")
public class FileEntity {
#Id
#GeneratedValue
private UUID id;
#NotNull
private String filename;
#NotNull
#Lob #Basic(fetch = FetchType.LAZY)
private byte[] content;
...
Added plugin to pom.xml:
<plugin>
<groupId>org.hibernate.orm.tooling</groupId>
<artifactId>hibernate-enhance-maven-plugin</artifactId>
<executions>
<execution>
<phase>compile</phase>
<configuration>
<failOnError>true</failOnError>
<enableLazyInitialization>true</enableLazyInitialization>
</configuration>
<goals>
<goal>enhance</goal>
</goals>
</execution>
</executions>
</plugin>
For me lazy load only worked by compiling and then running it, didn't work on eclipse or intellij for example.
I'm using gradle then I did the following to get it working
Annotate entity
Setup Hibernate gradle plugin
build.gradle
buildscript {
repositories {
mavenCentral()
}
dependencies {
classpath "org.hibernate:hibernate-gradle-plugin:5.4.0.Final"
}
}
apply plugin: 'java'
apply plugin: 'application'
apply plugin: 'org.hibernate.orm'
hibernate {
enhance {
enableLazyInitialization = true
enableDirtyTracking = true
enableAssociationManagement = true
}
}
Entity.java
#Entity
public class Person {
#Id
#GeneratedValue
private Integer id;
#Lob
#Basic(fetch = FetchType.LAZY)
#Column(length = 255, nullable = false)
private String name;
Testing
./gradlew run
Full working example
Lazy loading works for me if I use Blob type instead of byte[].
#Column(name = "BlobField", nullable = false)
#Lob
#Basic(fetch = FetchType.LAZY)
private Blob blobField;
This one gets lazily loaded and if you need to retrieve its value access this field:
String value = IOUtils.toByteArray(entity.getBlobField().getBinaryStream());
A simple workarround using #OneTone notation based on the response of #MohammadReza Alagheband (Why does #Basic(fetch=lazy) doesn't work in my case?) but without the requirement of create a new table for each required lazy attribute is the following:
#Getter
#Setter
#Entity
#Table(name = "document")
#AllArgsConstructor
#NoArgsConstructor
public class DocumentBody implements java.io.Serializable{
#Column(name = "id", insertable = false)
#ReadOnlyProperty
#Id
#PrimaryKeyJoinColumn
private Integer id;
#Column(name = "body", unique = true, nullable = false, length = 254)
#JsonView({JSONViews.Simple.class, JSONViews.Complete.class})
private String content;
}
#Getter
#Entity
#Setter
#Table(name = "document")
#AllArgsConstructor
#NoArgsConstructor
public class DocumentTitle implements java.io.Serializable{
#Column(name = "id", insertable = false)
#ReadOnlyProperty
#Id
private Integer id;
#Column(name = "title", unique = true, nullable = false, length = 254)
#JsonView({JSONViews.Simple.class, JSONViews.Complete.class})
private String content;
}
public class Document implements java.io.Serializable {
#Id
#GeneratedValue(strategy = IDENTITY)
#Column(name = "id", unique = true, nullable = false)
#JsonView({JSONViews.Simple.class, JSONViews.Complete.class})
private Integer id;
//Also it is posssible to prove with #ManyToOne
#OneToOne(fetch = FetchType.LAZY, optional = false, cascade = {CascadeType.MERGE, CascadeType.PERSIST, CascadeType.REFRESH})
#JoinColumn(name = "id", referencedColumnName = "id", nullable = false)
#JsonView({JSONViews.Simple.class, JSONViews.Complete.class})
private DocumentTitle title;
#OneToOne(fetch = FetchType.LAZY, optional = false, cascade = {CascadeType.MERGE, CascadeType.PERSIST, CascadeType.REFRESH})
#JoinColumn(name = "id", referencedColumnName = "id", nullable = false)
#JsonView({JSONViews.Simple.class, JSONViews.Complete.class})
private DocumentBody body;
}