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Posts Tagged ‘JPA’

Spring + JPA + Hibernate + Tomcat + EHCache

May 2nd, 2010 5 comments

Having @ManyToMany(fetch=FetchType.EAGER) attributes can slow down retrieval quite significantly (up to 40 times slower).

I recall reading somewhere that FetchType.EAGER is the default for @ManyToMany associations. Also, from experience I noticed that setting FetchType.LAZY caused a org.hibernate.LazyInitializationException thrown with exception message similar to, failed to lazily initialize a collection of role: com.xyz.domain.EntityOne.images, no session or session was closed.

So, it seemed that the only other way to quickly reduce the time it took (for the retrieval) was to look into the caching options such as query caching, second-level caching, both of which are supported by Hibernate (the webapp’s JPA provider). For more information on second-level caching, please refer to this article.

Integrating Spring + JPA + Hibernate + Tomcat + EHCache took me a few hours this afternoon, but the effort paid off. The retrieval is now 40 times faster!

This post is summarizing the setup involved in getting them all to work together.

Relevant Section Of persistence.xml:

<provider>org.hibernate.ejb.HibernatePersistence</provider>
<shared-cache-mode>ENABLE_SELECTIVE</shared-cache-mode>
<properties>
  <property name="hibernate.cache.provider_class" 
    value="org.hibernate.cache.SingletonEhCacheProvider" />
  <property name="hibernate.cache.provider_configuration" value="/ehcache.xml" />
  <property name="hibernate.cache.use_second_level_cache" value="true" />
  <property name="hibernate.cache.use_query_cache" value="true" />
</properties>

Notes:

  • The persistence.xml is located at {tomcat}/webapps/{your-webapp}/META-INF.
  • I used org.hibernate.cache.SingletonEhCacheProvider instead of org.hibernate.cache.EhCacheProvider. I was getting a WARN message if I used org.hibernate.cache.EhCacheProvider. I referred to this post for a fix.

Relevant Section Of ehcache.xml:

  <diskStore path="user.dir/mywebapp-special-cache-folder"/>
 
  <defaultCache eternal="false" overflowToDisk="false"
    maxElementsInMemory="1000" timeToIdleSeconds="30" timeToLiveSeconds="60"/>
 
  <cache name="com.xyz.domain.EntityTwo" eternal="false" overflowToDisk="true" 
    maxElementsInMemory="1000" timeToIdleSeconds="300" timeToLiveSeconds="600"
    diskPersistent="true" diskExpiryThreadIntervalSeconds="300"/>
 
  <cache name="com.xyz.domain.EntityOne" eternal="false" overflowToDisk="true" 
    maxElementsInMemory="1000" timeToIdleSeconds="300" timeToLiveSeconds="600" 
    diskPersistent="true" diskExpiryThreadIntervalSeconds="300"/>
 
  <cache name="com.xyz.domain.EntityOne.images" eternal="false" 
    overflowToDisk="true" 
    maxElementsInMemory="1000" timeToIdleSeconds="300" timeToLiveSeconds="600" 
    diskPersistent="true" diskExpiryThreadIntervalSeconds="300"/>

Notes:

  • The ehcache.xml is located at {tomcat}/webapps/{your-webapp}/WEB-INF/classes.
  • The diskStore element indicates where the files to be used for caching will be stored for the entities I wish to be made persistent to disk. In my web application, the files are stored under {tomcat}/bin/{mywebapp-special-cache-folder}
  • diskPersistent="true" indicates that the disk store (for the specific entity) is persistent between cache and VM restarts. Please refer to the EHCache documentation on disk storage for more information.

Relevant JARs: under {tomcat}/webapps/{your-webapp}/WEB-INF/lib

  • ehcache-core-2.0.1.jar
  • hibernate3.jar
  • hibernate-jpa-2.0-api-1.0.0.Final.jar
  • slf4j-api-1.5.8.jar
  • slf4j-log4j12-1.5.6.jar
  • Spring 3.0.2 JARs..

Relevant Section Of Spring Configuration:

<!-- there should be a way out of hardcoding the location of the properties file -->
<bean 
  class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
  <property name="location" value="/WEB-INF/spring-hes-db.properties" />
</bean>
 
<!-- ENTITY MANAGER FACTORY -->
<!-- LocalEntityManagerFactoryBean did not work for me -->
<bean id="emf-p" 
  class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean">
  <property name="persistenceUnitManager" ref="pum"/>
  <property name="persistenceUnitName" value="pu1"/>
  <property name="dataSource" ref="dataSource-p" />
  <property name="jpaVendorAdapter">
    <bean class="org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter">
      <property name="database" value="MYSQL" />
      <property name="showSql" value="true" />
      <property name="generateDdl" value="true" />
      <property name="databasePlatform" value="org.hibernate.dialect.MySQLDialect"/>
    </bean>
  </property>
</bean>
 
<!-- TRANSACTION MANAGER -->
<bean id="transactionManager" 
  class="org.springframework.orm.jpa.JpaTransactionManager">
  <property name="entityManagerFactory" ref="emf-p"/>
  <property name="dataSource" ref="dataSource-p"/>
</bean>
 
<!-- DATA SOURCES -->
<bean id="dataSource-p" 
    class="org.springframework.jdbc.datasource.DriverManagerDataSource">
  <property name="driverClassName" value="com.mysql.jdbc.Driver" />
  <property name="url" 
    value="jdbc:mysql://${db.host}:${db.port}/${db.name}"/>
  <property name="username" value="${db.username}" />
  <property name="password" value="${db.password}" />
</bean>
 
<!-- JPA TEMPLATE -->
<bean id="jpaTemplate" class="org.springframework.orm.jpa.JpaTemplate">
 <property name="entityManagerFactory" ref="emf-p" />
</bean>
 
<!-- DAOs -->
<bean id="entityOneDao" class="hes.db.impl.EntityOneDAOImpl">
  <property name="jpaTemplate" ref="jpaTemplate"/>
</bean>
 
<!-- PERSISTENCE UNIT -->
<bean id="pum" 
  class="org.springframework.orm.jpa.persistenceunit.DefaultPersistenceUnitManager">
  <property name="persistenceXmlLocations">
    <list>
      <value>META-INF/persistence.xml</value>
    </list>
  </property>
  <property name="dataSources">
    <map>
      <entry key="remoteDataSource" value-ref="dataSource-p" />
    </map>
  </property>
  <property name="defaultDataSource" ref="dataSource-p"/>
</bean>

Some of this may be redundant and will be cleaned up later.

If you have some better ideas, please do share. Thanks.

Categories: Java Tags: , , ,

AnnotationException : Entity X References An Unknown Entity Y

April 30th, 2010 No comments

Problem: I was getting an org.hibernate.AnnotationException when creating a bidirectional one-to-one relationship between 2 entities (EntityOne and EntityTwo).

Relevant Section Of StackTrace:
Caused by: org.hibernate.AnnotationException: @OneToOne or @ManyToOne on com.xyz.domain.EntityOne.anImage references an unknown entity: com.xyz.domain.EntityTwo
at org.hibernate.cfg.ToOneFkSecondPass.doSecondPass(ToOneFkSecondPass.java:103)
at org.hibernate.cfg.AnnotationConfiguration.processEndOfQueue(AnnotationConfiguration.java:541)
at org.hibernate.cfg.AnnotationConfiguration.processFkSecondPassInOrder(AnnotationConfiguration.java:523)
at org.hibernate.cfg.AnnotationConfiguration.secondPassCompile(AnnotationConfiguration.java:380)
at org.hibernate.cfg.Configuration.buildMappings(Configuration.java:1206)
at org.hibernate.ejb.Ejb3Configuration.buildMappings(Ejb3Configuration.java:1449)

Relevant Section Of EntityOne’s Code:

@Entity
@Table(name = "entity1")
public class EntityOne implements Serializable {
  @Id
  @GeneratedValue(strategy = GenerationType.AUTO)
  @Column(name = "e1_id")
  private Long id;
 
  @OneToOne(fetch = FetchType.LAZY, optional = true)
  @JoinTable(name = "entity1_entity2_map",
    joinColumns = @JoinColumn(name = "e1_id"),
    inverseJoinColumns = @JoinColumn(name = "e2_id"))
  private EntityTwo anImage;
 
  //Other code
}

Relevant Section Of EntityTwo’s Code:

@Entity
@Table(name = "entity2")
public class EntityTwo implements Serializable {
  @Id
  @GeneratedValue(strategy = GenerationType.AUTO)
  @Column(name = "e2_id")
  private Long id;
 
  @OneToOne(mappedBy = "anImage", optional = true)
  private EntityOne e1;
 
  //Other code
}

Solution That Worked For Me:
Check the persistence.xml to ensure that the 2 entities (EntityOne and EntityTwo) are listed. Previously I had not included EntityTwo, which is why I kept getting the message com.xyz.domain.EntityOne.anImage references an unknown entity: com.xyz.domain.EntityTwo

    com.xyz.domain.EntityOne
    com.xyz.domain.EntityTwo
    <!-- other configurations -->
Categories: Java Tags: ,