By using the DistributedMap or DistributedObjectCache interfaces, Java Platform, Enterprise Edition (Java EE) applications and system components can cache and share Java objects by storing a reference to the object in the cache.
The DistributedMap and DistributedObjectCache interfaces are simple interfaces for the dynamic cache. Using these interfaces, Java EE applications and system components can cache and share Java objects by storing a reference to the object in the cache. The default dynamic cache instance is created if the dynamic cache service is enabled in the administrative console. This default instance is bound to the global Java Naming and Directory Interface (JNDI) namespace using the name services/cache/distributedmap.
Multiple instances of the DistributedMap and DistributedObjectCache interfaces on the same Java virtual machine (JVM) enable applications to separately configure cache instances as needed. Each instance of the DistributedMap interface has its own properties.
Place JAR files in a shared library when you deploy the application in a cluster with replication enabled. Simply turning on replication does not require a shared library; however, if you are using application-specific Java objects, such as cache key or cache value, those Java classes are required to be in the shared library.
The default servlet cache instance (JNDI name: services/cache/basecache) is created when the server starts , if servlet caching is enabled. The default object cache instance (JNDI name: services/cache/distributedmap) is always created when the server starts.
InitialContext ic = new InitialContext(); DistributedMap dm1 = (DistributedMap)ic.lookup("services/cache/instance_one"); DistributedMap dm2 = (DistributedMap)ic.lookup("services/cache/instance_two"); // or InitialContext ic = new InitialContext(); DistributedObjectCache dm1 = (DistributedObjectCache)ic.lookup("services/cache/instance_one"); DistributedObjectCache dm2 = (DistributedObjectCache)ic.lookup("services/cache/instance_two");
A servlet cache instance is a location, in addition to the default servlet cache, where dynamic cache can store, distribute, and share data. By using servlet cache instances, your applications have greater flexibility and better tuning of the cache resources. The Java™ Naming and Directory Interface (JNDI) name that is specified for the cache instance is mapped to the name attribute in the <cache instance> tag in the cachespec.xml configuration file.
An object cache instance is a location, in addition to the default object cache, where dynamic cache can store, distribute, and share data for Java™ Platform, Enterprise Edition (Java EE) applications. Use cache instances to give applications better flexibility and tuning of the cache resources. Use the DistributedObjectCache programming interface to access the cache instances. For more information about the DistributedObjectCache application programming interface, see the API documentation.
Create and configure the object cache instance, as follows:
InitialContext ic = new InitialContext(); DistributedMap dm1 = (DistributedMap)ic.lookup("services/cache/instance_one"); DistributedMap dm2 = (DistributedMap)ic.lookup("services/cache/instance_two"); // or InitialContext ic = new InitialContext(); DistributedObjectCache dm1 = (DistributedObjectCache)ic.lookup("services/cache/instance_one"); DistributedObjectCache dm2 = (DistributedObjectCache)ic.lookup("services/cache/instance_two");
You can create cache instances using the cacheinstances.properties file and package the file in your Enterprise Archive (EAR) file. Use the table information in the cacheinstances.properties file article as a reference of the names, values, and explanations.
cache.instance.x=InstanceName
cache.instance.x.customPropertyName=customPropertyValue
where: cache.instance.0=/services/cache/instance_one
cache.instance.0.cacheSize=1000
cache.instance.0.enableDiskOffload=true
cache.instance.0.diskOffloadLocation=${app_server_root}/diskOffload
cache.instance.0.flushToDiskOnStop=true
cache.instance.0.useListenerContext=true
cache.instance.0.enableCacheReplication=false
cache.instance.0.disableDependencyId=false
cache.instance.0.htodCleanupFrequency=60
cache.instance.1=/services/cache/instance_two
cache.instance.1.cacheSize=1500
cache.instance.1.enableDiskOffload=false
cache.instance.1.flushToDiskOnStop=false
cache.instance.1.useListenerContext=false
cache.instance.1.enableCacheReplication=true
cache.instance.1.replicationDomain=DynaCacheCluster
cache.instance.1.disableDependencyId=true
The preceding example creates two cache instances named instance_one and instance_two. Cache instance_one has a cache entry size of 1,000 and instance_two has a cache entry size of 1,500. Disk offload is enabled in instance_one and disabled in instance_two. Use listener context is enabled in instance_one and disabled in instance_two. Flush to disk on stop is enabled in instance_one and disabled in instance_two. Cache replication is enabled in instance_two and disabled in instance_one. The name of the data replication domain for instance_two is DynaCacheCluster. Dependency ID support is disabled in instance_two.
Place the cacheinstances.properties file in either your application server or application class path. For example, you can use your application WAR file, WEB-INF\classes directory or server_root\classes directory. The first entry in the properties file (cache.instance.0) specifies the JNDI name for the cache instance in the global namespace.
InitialContext ic = new InitialContext();
DistributedMap dm1 =
(DistributedMap)ic.lookup("services/cache/instance_one");
DistributedMap dm2 =
(DistributedMap)ic.lookup("services/cache/instance_two");
// or
InitialContext ic = new InitialContext();
DistributedObjectCache dm1 = (DistributedObjectCache)ic.lookup("services/cache/instance_one");
DistributedObjectCache dm2 = (DistributedObjectCache)ic.lookup("services/cache/instance_two");
<resource-ref id="ResourceRef_1">
<res-ref-name>dmap/LayoutCache</res-ref-name>
<res-type>com.ibm.websphere.cache.DistributedMap</res-type>
<res-auth>Container</res-auth>
<res-sharing-scope>Shareable</res-sharing-scope>
</resource-ref>
<resource-ref id="ResourceRef_2">
<res-ref-name>dmap/UserCache</res-ref-name>
<res-type>com.ibm.websphere.cache.DistributedMap</res-type>
<res-sharing-scope>Shareable</res-sharing-scope>
</resource-ref>
<?xml version="1.0" encoding="UTF-8"?>
<webappbnd:WebAppBinding xmi:version="2.0" xmlns:xmi="http://www.omg.org/XMI"
xmlns:webappbnd="webappbnd.xmi"
xmlns:webapplication="webapplication.xmi" xmlns:commonbnd="commonbnd.xmi"
xmlns:common="common.xmi"
xmi:id="WebApp_ID_Bnd" virtualHostName="default_host">
<webapp href="WEB-INF/web.xml#WebApp_ID"/>
<resRefBindings xmi:id="ResourceRefBinding_1"
jndiName="services/cache/instance_one">
<bindingResourceRef href="WEB-INF/web.xml#ResourceRef_1"/>
</resRefBindings>
<resRefBindings xmi:id="ResourceRefBinding_2"
jndiName="services/cache/instance_two">
<bindingResourceRef href="WEB-INF/web.xml#ResourceRef_2"/>
</resRefBindings>
</webappbnd:WebAppBinding>
However, a Java EE 5 or later module can exist within an application that includes pre-Java EE 5 files and uses the .xmi file name extension.
The ibm-webservices-ext.xmi, ibm-webservices-bnd.xmi, ibm-webservicesclient-bnd.xmi, ibm-webservicesclient-ext.xmi, and ibm-portlet-ext.xmi files continue to use the .xmi file extensions.
sptcfgInitialContext ic = new InitialContext();
DistributedMap dm1a =(DistributedMap)ic.lookup("java:comp/env/dmap/LayoutCache");
DistributedMap dm2a =(DistributedMap)ic.lookup("java:comp/env/dmap/UserCache");
// or
DistributedObjectCache dm1a =(DistributedObjectCache)ic.lookup("java:comp/env/dmap/LayoutCache");
DistributedObjectCache dm2a =(DistributedObjectCache)ic.lookup("java:comp/env/dmap/UserCache");
The previous resource-ref example maps java:comp/env/dmap/LayoutCache to /services/cache/instance_one and java:comp/env/dmap/UserCache to /services/cache/instance_two. In the examples, DistributedMap dm1 and dm1a are the same object. DistributedMap dm2 and dm2a are the same object.
You can set the custom properties globally to affect all cache instances. This overwrites the settings in method 1, method 2 and method 3, but not method 4 (cacheinstances.properties). Configure the cache instance globally, as follows: