This article shows how to quickly enable Ehcache on Openxava applications and thus improving performance.

When viewing an entity and its graph, relationships are loaded. Adding a second-level cache fasten the retrieval of associated elements, since already loaded elements are retrieved from cache and not database.

Eventually this page explains how minuteproject treats this aspect with keeping its promise: write nothing.
As an example, we will take the Lazuly minuteproject showcase.

Openxava-Ehcache integration

In Openxava, you describe your model in the manner of Java annotated POJO.The annotations come from the standard JPA2 ORM and Openxava specific ones.
But nothing prevents you to add others. This is what is done to add caching. There are also couple of configurations to undertake to enable caching.

List of actions

1. Add ehcache.xml config file at the root of your sources
2. Modify persistence.xml to include second level cache
3. Add caching annotation (alongside JPA2)

Openxava comes with the ehcache.jar so there is no need to add a dependency.

Detailed actions

Add ehcache.xml

In /persistence place ehcache.xml file

<ehcache>
 <defaultCache
 maxElementsInMemory="1000"
 eternal="false"
 timeToIdleSeconds="300"
 timeToLiveSeconds="300"
 overflowToDisk="false"
 diskPersistent="false"
 diskExpiryThreadIntervalSeconds="300"
 memoryStoreEvictionPolicy="LRU"
 />
 <cache
 name="your.domain.object"
 maxElementsInMemory="5000"
 eternal="false"
 timeToIdleSeconds="300"
 timeToLiveSeconds="600"
 overflowToDisk="false"
 />
</ehcache>

Modify persistence.xml

Persistence.xml file contains information related to the persitence unit such as connection pool info,
class or configuration to load. ‘persistence.xml’ is located in /persistence/META-INF

We will append properties for L2 cache.

<properties>
 <property name="hibernate.dialect" value="org.hibernate.dialect.MySQLDialect"/>
 <property name="hibernate.cache.provider_class" value="net.sf.ehcache.hibernate.SingletonEhCacheProvider" />
 <property name="net.sf.ehcache.configurationResourceName" value="/ehcache.xml" />
 <property name="hibernate.cache.use_query_cache" value="true" />
 <property name="hibernate.cache.use_second_level_cache" value="true" />
 <property name="hibernate.generate_statistics" value="true" /> 

 </properties>

Add cache annotation

Here the hibernate annotation is used instead of the standard one (Cacheable in fact seems not to work)
Place Cache annotation at class level of your domain object.

@org.hibernate.annotations.Cache(usage = org.hibernate.annotations.CacheConcurrencyStrategy.READ_WRITE)

Example

Lazuly application

Lazuly is a sample database holding conference information used for MinuteProject showcase purpose.
Minuteproject generates a comprehensive set of artefacts to speedup the release of OX application.
Further information can be found in Minuteproject 4 Openxava Lazuly showcase.
On this part we focus on the artefacts generated for the caching specific.
Minuteproject for the generation base itself on a configuration file, where we define the datamodel to reverse engineer. In this configuration there is an enrichement part where you can add information.
One of this information deals with the type of content is held in an entity. There are 4 possibilities (reference-data, master-data, pseudo-static-data, live-business-data)
If you enrich your entity with the content-type=”master-data” or “reference-data” MinuteProject 4 Openxava will generate associated caching.

This is done here for the entity Country.

<entity name="COUNTRY" content-type="reference-data">

ehcache.xml

<ehcache>

 <!--
 Sets the path to the directory where cache files are created.

 If the path is a Java System Property it is replaced by its value in the
 running VM.

 The following properties are translated:
 * user.home - User's home directory
 * user.dir - User's current working directory
 * java.io.tmpdir - Default temp file path

 Subdirectories can be specified below the property e.g. java.io.tmpdir/one
 -->
<!--MP-MANAGED-UPDATABLE-BEGINNING-DISABLE @ehcache-main-config-conference@-->
 <diskStore path="java.io.tmpdir"/>

 <!--
 Mandatory Default Cache configuration. These settings will be applied to caches
 created programmtically using CacheManager.add(String cacheName)
 -->
 <defaultCache
 maxElementsInMemory="1000"
 eternal="false"
 timeToIdleSeconds="300"
 timeToLiveSeconds="300"
 overflowToDisk="false"
 diskPersistent="false"
 diskExpiryThreadIntervalSeconds="300"
 memoryStoreEvictionPolicy="LRU"
 />
<!-- The unnamed query cache -->
 <cache
 name="org.hibernate.cache.StandardQueryCache"
 maxElementsInMemory="1000"
 eternal="false"
 timeToLiveSeconds="300"
 overflowToDisk="false"
 />
<!--MP-MANAGED-UPDATABLE-ENDING-->

<!--MP-MANAGED-UPDATABLE-BEGINNING-DISABLE @cache-entity-country-conference@-->
 <cache
 name="net.sf.mp.demo.conference.domain.admin.Country"
 maxElementsInMemory="5000"
 eternal="false"
 timeToIdleSeconds="300"
 timeToLiveSeconds="600"
 overflowToDisk="false"
 />
<!--MP-MANAGED-UPDATABLE-ENDING-->

<!--MP-MANAGED-ADDED-AREA-BEGINNING @custom-cache-definition@-->
<!--MP-MANAGED-ADDED-AREA-ENDING @custom-cache-definition@-->

</ehcache>

Persistence.xml

<persistence xmlns="http://java.sun.com/xml/ns/persistence"
 xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
 xsi:schemaLocation="http://java.sun.com/xml/ns/persistence http://java.sun.com/xml/ns/persistence/persistence_1_0.xsd"
 version="1.0">
 
 <!-- Tomcat + Hypersonic -->
 <persistence-unit name="default">
 <non-jta-data-source>java:comp/env/jdbc/conferenceDS</non-jta-data-source>
 <class>org.openxava.session.GalleryImage</class>
 <properties>
 <property name="hibernate.dialect" value="org.hibernate.dialect.MySQLDialect"/>
 <property name="hibernate.cache.provider_class" value="net.sf.ehcache.hibernate.SingletonEhCacheProvider" />
 <property name="net.sf.ehcache.configurationResourceName" value="/ehcache.xml" />
 <property name="hibernate.cache.use_query_cache" value="true" />
 <property name="hibernate.cache.use_second_level_cache" value="true" />
 <property name="hibernate.generate_statistics" value="true" /> 
<!--MP-MANAGED-ADDED-AREA-BEGINNING @properties@-->
<!--MP-MANAGED-ADDED-AREA-ENDING @properties@-->
 </properties>
<!--MP-MANAGED-ADDED-AREA-BEGINNING @persistence-unit@-->
<!--MP-MANAGED-ADDED-AREA-ENDING @persistence-unit@-->
 </persistence-unit> 

<!--MP-MANAGED-ADDED-AREA-BEGINNING @persistence@-->
<!--MP-MANAGED-ADDED-AREA-ENDING @persistence@-->

</persistence>

Class annotation

@org.hibernate.annotations.Cache(usage = org.hibernate.annotations.CacheConcurrencyStrategy.READ_WRITE)
//MP-MANAGED-ADDED-AREA-BEGINNING @class-annotation@
//MP-MANAGED-ADDED-AREA-ENDING @class-annotation@
public class Country {

 @Hidden @Id @Column(name="id" )
 @GeneratedValue(strategy = GenerationType.AUTO)
 private Integer id; 
...

The generated code has markers inside file extension comment.

Within MP-MANAGED-ADDED-AREA-BEGINNING and  MP-MANAGED-ADDED-AREA-ENDING you can place customized code
Within MP-MANAGED-UPDATABLE-BEGINNING-DISABLE and  MP-MANAGED-UPDATABLE-ENDING you can alter the code. To keep your modifications please change MP-MANAGED-UPDATABLE-BEGINNING-DISABLE into MP-MANAGED-UPDATABLE-BEGINNING-ENABLE.
Updatable code prevent you to lose your customisation over consecutive generations.

For more information on updatable code see Minuteproject updatable code.

Generation

• Place the following file mp-config-LAZULY-OPENXAVA.xml in /mywork/config
• on a prompt execute mp-model-generation(.sh/cmd) mp-config-LAZULY-OPENXAVA.xml 
• the resulting artefacts in /DEV/output/openxava/conference 

To generate use the updated version of mp-config-LAZULY-OPENXAVA.xml

<!DOCTYPE root>
<generator-config>
 <configuration>
 <conventions>
 <target-convention type="enable-updatable-code-feature" />
 </conventions> 
 <model name="conference" version="1.0" package-root="net.sf.mp.demo">
 <data-model>
 <driver name="mysql" version="5.1.16" groupId="mysql" artifactId="mysql-connector-java"></driver>
 <dataSource>
 <driverClassName>org.gjt.mm.mysql.Driver</driverClassName>
 <url>jdbc:mysql://127.0.0.1:3306/conference</url>
 <username>root</username>
 <password>mysql</password>
 </dataSource>
 <!--
 for Oracle and DB2 please set the schema <schema> </schema>
 -->
 <primaryKeyPolicy oneGlobal="true">
 <primaryKeyPolicyPattern name="autoincrementPattern"></primaryKeyPolicyPattern>
 </primaryKeyPolicy>
 </data-model>
 <business-model>
 <!--
 <generation-condition> <condition type="exclude"
 startsWith="DUAL"></condition> </generation-condition>
 -->
 <business-package default="conference">
 <condition type="package" startsWith="STAT" result="statistics"></condition>
 <condition type="package" startsWith="COUNTRY" result="admin"></condition>
 <condition type="package" startsWith="ROLE" result="admin"></condition> 
 </business-package>
 <enrichment>
 <conventions>
 <column-naming-convention type="apply-strip-column-name-suffix"
 pattern-to-strip="_ID" />
 <reference-naming-convention
 type="apply-referenced-alias-when-no-ambiguity" is-to-plurialize="true" />
 </conventions>

 <entity name="COUNTRY" content-type="reference-data">
 <semantic-reference>
 <sql-path path="NAME" />
 </semantic-reference>
 </entity>
 <entity name="CONFERENCE_MEMBER">
 <semantic-reference>
 <sql-path path="FIRST_NAME" />
 <sql-path path="LAST_NAME" />
 </semantic-reference>
 <field name="STATUS">
 <property tag="checkconstraint" alias="conference_member_status">
 <property name="PENDING" value="PENDING" />
 <property name="ACTIVE" value="ACTIVE" />
 </property>
 </field>
 <field name="EMAIL">
 <stereotype stereotype="EMAIL" />
 </field>
 </entity>
 <entity name="SPEAKER">
 <field name="BIO">
 <stereotype stereotype="HTML_TEXT" />
 </field>
 <field name="PHOTO">
 <stereotype stereotype="PHOTO" />
 </field>
 <field name="WEB_SITE_URL">
 <stereotype stereotype="WEBURL" />
 </field>
 </entity>
 <entity name="PRESENTATION">
 <field name="STATUS">
 <property tag="checkconstraint" alias="presentation_status">
 <property name="PROPOSAL" value="PROPOSAL" />
 <property name="ACTIVE" value="ACTIVE" />
 </property>
 </field>
 </entity>
 <entity name="SPONSOR">
 <field name="STATUS">
 <property tag="checkconstraint" alias="sponsor_status">
 <property name="PENDING" value="PENDING" />
 <property name="ACTIVE" value="ACTIVE" />
 </property>
 </field>
 <field name="PRIVILEGE_TYPE">
 <property tag="checkconstraint" alias="sponsor_privilege">
 <property name="GOLDEN" value="Golden" />
 <property name="SILVER" value="Silver" />
 <property name="BRONZE" value="Bronze" />
 </property>
 </field>
 </entity>
 <!-- views -->
 <entity name="stat_mb_per_ctry_conf" alias="MEMBER_PER_COUNTRY_AND_CONFERENCE">
 <virtual-primary-key isRealPrimaryKey="true">
 <property name="virtualPrimaryKey" value="ID" />
 </virtual-primary-key>
 </entity>
 <entity name="stat_mb_by_role" alias="MEMBER_PER_ROLE_COUNTRY_AND_CONFERENCE">
 <virtual-primary-key isRealPrimaryKey="true">
 <property name="virtualPrimaryKey" value="id" />
 </virtual-primary-key>
 <field name="stat_mb_per_ctry_conf_ID" linkToTargetEntity="stat_mb_per_ctry_conf"
 linkToTargetField="id"></field>
 </entity>
 </enrichment>
 </business-model>
 </model>
 <targets>
 <!-- openxava -->
 <target refname="OpenXava" name="OpenXava"
 fileName="mp-template-config-openxava-last-features.xml"
 outputdir-root="../../DEV/output/openxava/conference"
 templatedir-root="../../template/framework/openxava">
 </target>

 <target refname="JPA2-LIB" fileName="mp-template-config-JPA2-LIB.xml"
 templatedir-root="../../template/framework/jpa">
 </target>
 
 <target refname="BSLA-LIB" fileName="mp-template-config-bsla-LIB-features.xml"
 templatedir-root="../../template/framework/bsla">
 </target>

 <target refname="CACHE-LIB" 
 fileName="mp-template-config-CACHE-LIB.xml" 
 templatedir-root="../../template/framework/cache">
 </target>
 
 </targets>
 </configuration>
</generator-config>

Test
To ensure that the caching is working properly:

• Enable hibernate logging. Add the following snippet as extra properties in persistence.xml.

<property name="hibernate.show_sql" value="true" />
 <property name="hibernate.format_sql" value="true" />

• navigate to an entity that reference country (example Address)
• When you view the detail of this entity you will notice that there is a load of the associated entity ‘country’
• But the second time you access to the details of this entity (or another entity referencing the same country instance), the country is not loaded twice from the database.

Reference: Adding Ehcache to Openxava application from our JCG partner Florian Adler at the minuteproject blog.